22 changed files with 2115 additions and 2326 deletions
--- a/.github/FUNDING.yml
+++ b/.github/FUNDING.yml
@ -1,3 +0,0 @@
 # These are supported funding model platforms
 custom: ['https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=WFQSSCD9GNM4S', 'https://btc.com/19DYtoEepxBmn9ZPspJGZrhCtySKCxPcP1']
--- a/.github/workflows/codespell.yml
+++ b/.github/workflows/codespell.yml
@ -1,26 +0,0 @@
 ---
 name: Codespell
 on:
  push:
    branches: [master]
  pull_request:
    branches: [master]
 permissions:
  contents: read
 jobs:
  codespell:
    name: Check for spelling errors
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v3
      - name: Codespell
        uses: codespell-project/actions-codespell@v2
        with:
          check_filenames: true
          skip: ".git,*.pdf,*.svg"
          ignore_words_list: uptodate
--- a/84
+++ b/84
@ -1,87 +1,9 @@
 btrbk-0.32.6
  * Fix backup of unrelated (by parent_uuid) snapshots (close #339).
  * Remove echo -e for portability (close #506).
  * Support btrfs send protocol v2 (send_protocol and
    send_compressed_data config options).
  * Add bzip3 support.
  * Convert ssh_filter_btrbk.sh to POSIX sh, and harden it.
  * Slight change in ssh_filter_btrbk.sh logging output.
  * Minor bugfixes, stability and documentation improvements.
 btrbk-0.32.5
  * Correct handling of zero-size raw info file (close #491).
 btrbk-0.32.4
  * Fix regression: wrong deprecation warnings in some cases.
 btrbk-0.32.3
  * Fix deletion of many subvolumes at once (close #476).
  * Allow disabling ssh_identity and ssh_user options.
  * Minor bugfixes and documentation improvements.
 btrbk-0.32.2
  * Fix regression: archive on missing target directories.
  * Fix action "config print".
  * Print version and help message to stdout (close #452).
  * Check results of filesystem usage (close #469).
  * Add "compat ignore_receive_errors" option (close #383).
  * Support multiple gpg recipients (close #471).
  * Fix changelog: remove "compat missing_otime" item in v0.32.1.
  * Fix changelog: correct "warn_unknown_targets" item in v0.31.3.
  * Minor bugfixes and framework improvements.
 btrbk-0.32.1
  * Fix regression: correctly read mountinfo (close #445).
  * Fix regression: filter paths for "lsbtr" (action "ls").
  * Add backend btrfs-progs-doas (close #444).
  * Allow directory traversal for local command line arguments.
  * Display all source subvolumes in "usage" action.
  * Handle errors from btrfs filesystem usage.
 btrbk-0.32.0
  * MIGRATION
    - If timestamp_format is not configured, explicitly set
      "timestamp_format short" to revert old behavior.
    - Update ssh_filter_btrbk.sh on remote hosts.
  * Change default for timestamp_format to "long".
  * Optional "volume" config section.
  * Use "volume" section only for grouping and relative paths.
  * Allow absolute path for "subvolume" and "snapshot_dir"
    (close #407, #121).
  * Support subvolume names with UTF-8 characters (close #392, #213,
    #120). Add "safe_commands" option for paranoid people.
  * Add "incremental_prefs" configuration option (close #387).
  * Change incremental prefs policy, giving snapshots created by btrbk
    higher preference than the global ones resolved by parent-uuid.
  * Change "incremental_clones" option to boolean.
  * Drop support of deprecated raw file format (btrbk < 0.26.0).
  * Drop support of deprecated "-r, --resume-only" cmdline option.
  * Fix ambiguous naming in --format=raw output of "list" actions.
  * Accept quoted values in config.
  * Use single quotes for raw table output.
 btrbk-0.31.3
  * Add "warn_unknown_targets" configuration option (close #393).
  * Add -1,--single-column command-line option for listing actions.
  * Allow relative path command line argument for all actions.
  * Add support for zstd adaptive compression (close #397).
  * Add contrib/tools/btrbk_restore_raw.py (close #401).
  * Minor bugfixes and framework improvements.
 btrbk-0.31.2
  * MIGRATION
    - Update ssh_filter_btrbk.sh on remote hosts.
  * ssh_filter_btrbk.sh: Fix security vulnerability.
-    Specially crafted commands may be executed without being properly
+    Specialy crafted commands may be executed without being propely
    checked. Applies to remote hosts filtering ssh commands using
    ssh_filter_btrbk.sh in authorized_keys.
  * Warn if no subvolume defined in config (close #378).
@ -248,7 +170,7 @@ btrbk-0.27.0
    - Allow snapshot_dir to be a mountpoint.
    - Search complete target tree for correlated subvolumes.
    - Include snapshots from all mountpoints as candidates (disabled
-      due to upstream bug: github.com/kdave/btrfs-progs/issues/96).
+      due to uptream bug: github.com/kdave/btrfs-progs/issues/96).
    - Read /proc/self/mountinfo instead of /proc/self/mounts.
    - Always read /proc/self/mountinfo.
    - Resolve realpath using readlink(1).
@ -319,7 +241,7 @@ btrbk-0.25.0
  * Allow trailing comments in btrbk.conf (close #129).
  * Bugfix: rate limiting must be done after compression (close #134).
  * raw_target_encrypt: Always set "gpg --no-random-seed-file":
-    prevents creation of "~/.gnupg/random_seed" with slight performance
+    prevents creation of "~/.gnupg/random_seed" with slight perfomance
    penalty.
 btrbk-0.24.0
--- a/3
+++ b/3
@ -17,8 +17,7 @@ SCRIPTS     = ssh_filter_btrbk.sh \
              contrib/cron/btrbk-mail \
              contrib/cron/btrbk-verify \
              contrib/migration/raw_suffix2sidecar \
-              contrib/crypt/kdf_pbkdf2.py \
+              contrib/crypt/kdf_pbkdf2.py
              contrib/tools/btrbk_restore_raw.py
 PN          = btrbk
 PREFIX     ?= /usr
--- a/README.md
+++ b/README.md
@ -9,7 +9,7 @@ The source and target locations are specified in a config file, which
 allows to easily configure simple scenarios like "laptop with locally
 attached backup disks", as well as more complex ones, e.g. "server
 receiving backups from several hosts via ssh, with different retention
-policies".
+policy".
 Key Features:
@ -18,8 +18,7 @@ Key Features:
  * Flexible retention policy
  * Backups to multiple destinations
  * Transfer via ssh
-  * Robust recovery from interrupted backups (for removable and mobile
+  * Resume backups (for removable and mobile devices)
    devices)
  * Archive to offline storage
  * Encrypted backups to non-btrfs storage
  * Wildcard subvolumes (useful for docker and lxc containers)
@ -60,7 +59,7 @@ For more information, read the [installation documentation].
  [btrfs-progs]: https://www.kernel.org/pub/linux/kernel/people/kdave/btrfs-progs/
  [Perl interpreter]: https://www.perl.org
-  [OpenSSH]: https://www.openssh.com
+  [OpenSSH]: https://www.openssh.org
  [mbuffer]: https://www.maier-komor.de/mbuffer.html
@ -73,8 +72,8 @@ a full description of the command line options.
  [btrbk(1)]: https://digint.ch/btrbk/doc/btrbk.1.html
-Configuration
+Configuration File
-=============
+==================
 Before running `btrbk`, you will need to create a configuration
 file. You might want to take a look at `btrbk.conf.example` provided
@ -82,37 +81,21 @@ with this package. For a detailed description, please consult the
 [btrbk.conf(5)] man-page.
 After a configuration change, it is highly recommended to check it by
-running btrbk with the `-n,--dry-run` option:
+running btrbk with the `-n,--dryrun` option:
-    # btrbk -c /path/to/myconfig -v -n run
+    btrbk -c /path/to/myconfig -v -n run
 This will read all btrfs information on the source/target filesystems
 and show what actions would be performed (without writing anything to
 the disks).
 The examples below assume that the btrfs subvolume containing `home`
 and `rootfs` is mounted at `/mnt/btr_pool`. This is usually the btrfs
 root subvolume, which always has `subvolid=5`.
 Mounting `subvolid=5` is *recommended* (mandatory for btrbk < v0.32.0)
 if you want to backup your root filesystem `/`.
 /etc/fstab:
    /dev/sda1  /mnt/btr_pool  btrfs  subvolid=5,noatime  0 0
 Note that some default btrfs installations (e.g. Ubuntu) use subvolume
 names `@` for rootfs (mounted at `/`) and `@home` for `/home`, as a
 naming convention. If this is the case on your file system, replace
 the `subvolume` declarations in the examples accordingly.
  [btrbk.conf(5)]: https://digint.ch/btrbk/doc/btrbk.conf.5.html
 Example: Local Regular Snapshots (time-machine)
 -----------------------------------------------
-The simplest use case is to only create snapshots of your data. This
+The simpliest use case is to only create snapshots of your data. This
 will obviously not protect it against hardware failure, but can be
 useful for:
@ -138,32 +121,15 @@ manage snapshots located on the same volume in `snapshot_dir`. Btrbk
 does not create subdirs by default, the snapshot directory must first
 be created manually:
-    # mkdir /mnt/btr_pool/btrbk_snapshots
+    sudo mkdir /mnt/btr_pool/btrbk_snapshots
-The "volume" section is merely used as a specifier for a base
+Start a dry run:
 directory, and can be skipped if you prefer to configure everything
 using absolute paths. The above configuration can also be written as:
-    snapshot_dir /mnt/btr_pool/btrbk_snapshots
+    sudo btrbk run -n
    subvolume    /mnt/btr_pool/home
 If you don't want to mount the btrfs root filesystem to
 `/mnt/btr_pool`, you might as well configure it like this:
    snapshot_dir /btrbk_snapshots
    subvolume    /home
 Start a dry run (-n, --dry-run):
    # btrbk run -n
 Create the first snapshot:
-    # btrbk run
+    sudo btrbk run
 Print schedule (-S, --print-schedule):
    # btrbk run -n -S
 If it works as expected, configure a cron job to run btrbk hourly:
@ -172,10 +138,13 @@ If it works as expected, configure a cron job to run btrbk hourly:
    #!/bin/sh
    exec /usr/bin/btrbk -q run
-Snapshots will now be created every hour. All snapshots are preserved for at
+Snapshots will now be created every hour, kept for 48h
-least 18 hours (`snapshot_preserve_min`), whether they are created by the cron
+(`snapshot_preserve`), then automatically removed.
-job or manually by calling `sudo btrbk run` on the command line. Additionally,
+
-48 hourly snapshots are preserved (`snapshot_preserve`).
+With this setup, the snapshots will be kept at least for 18 hours
 (`snapshot_preserve_min`). This can be useful to create manual
 snapshots by calling `sudo btrbk run` on the command line and keep
 them around for a while, in addition to the regular snapshots.
 Example: Backups to USB Disk
@ -208,9 +177,6 @@ Retention policy:
    snapshot_preserve_min   2d
    snapshot_preserve      14d
    # Create snapshots only if the backup disk is attached
    #snapshot_create ondemand
    target_preserve_min    no
    target_preserve        20d 10w *m
@ -236,11 +202,10 @@ Retention policy:
    * `/mnt/btr_backup/mylaptop/rootfs.YYYYMMDD`
    * `/mnt/btr_backup/mylaptop/home.YYYYMMDD`
-If you prefer triggering the backups manually, change the cron command
+If you want the snapshots to be created only if the backup disk is
-to run the `snapshot` action instead of `run`. Start the backups
+attached, simply add the following line to the config:
 manually by running:
-    # btrbk resume
+    snapshot_create ondemand
 For a quick additional snapshot of your home, run:
@ -250,8 +215,8 @@ For a quick additional snapshot of your home, run:
 Example: Host-initiated Backup on Fileserver
 --------------------------------------------
-Let's say you have a fileserver at "myserver.example.org" where you
+Let's say you have a fileserver at "myserver.mydomain.com" where you
-want to create backups of your laptop disk. The config could look like
+want to create backups of your laptop disk, the config would look like
 this:
    ssh_identity /etc/btrbk/ssh/id_rsa
@ -259,11 +224,11 @@ this:
    volume /mnt/btr_pool
      subvolume rootfs
        target /mnt/btr_backup/mylaptop
-        target ssh://myserver.example.org/mnt/btr_backup/mylaptop
+        target ssh://myserver.mydomain.com/mnt/btr_backup/mylaptop
 In addition to the backups on your local usb-disk mounted at
 `/mnt/btr_backup/mylaptop`, incremental backups would also be pushed
-to `myserver.example.org`.
+to `myserver.mydomain.com`.
 Example: Fileserver-initiated Backups from Several Hosts
@ -274,17 +239,17 @@ fileserver, the config would be something like:
    ssh_identity /etc/btrbk/ssh/id_rsa
-    volume ssh://alpha.example.org/mnt/btr_pool
+    volume ssh://alpha.mydomain.com/mnt/btr_pool
      target /mnt/btr_backup/alpha
      subvolume rootfs
      subvolume home
-    volume ssh://beta.example.org/mnt/btr_pool
+    volume ssh://beta.mydomain.com/mnt/btr_pool
      target /mnt/btr_backup/beta
      subvolume rootfs
      subvolume dbdata
-This will pull backups from alpha/beta.example.org and locally
+This will pull backups from alpha/beta.mydomain.com and locally
 create:
  * `/mnt/btr_backup/alpha/rootfs.YYYYMMDD`
@ -385,7 +350,7 @@ running btrbk. Something like:
    rsync -az --delete \
          --inplace --numeric-ids --acls --xattrs \
          -e 'ssh -i /etc/btrbk/ssh/id_rsa' \
-          myhost.example.org:/data/ \
+          myhost.mydomain.com:/data/ \
          /mnt/btr_backup/myhost_sync/
    exec /usr/bin/btrbk -q run
@ -412,7 +377,7 @@ compressed and piped through GnuPG.
    raw_target_compress   xz
    raw_target_encrypt    gpg
    gpg_keyring           /etc/btrbk/gpg/pubring.gpg
-    gpg_recipient         btrbk@example.org
+    gpg_recipient         btrbk@mydomain.com
    volume /mnt/btr_pool
      subvolume home
@ -428,7 +393,7 @@ host. For each backup, two files are created:
  * `/backup/home.YYYYMMDD.btrfs.xz.gpg.info`: sidecar file containing
    metadata used by btrbk.
-If you are using raw _incremental_ backups, please make sure you
+I you are using raw _incremental_ backups, please make sure you
 understand the implications (see [btrbk.conf(5)], TARGET TYPES).
@ -449,7 +414,7 @@ will need the `btrfs` executable from the [btrfs-progs] package.
 On the client side, create a ssh key dedicated to btrbk, without
 password protection:
-    # ssh-keygen -t rsa -b 4096 -f /etc/btrbk/ssh/id_rsa -C btrbk@example.org -N ""
+    ssh-keygen -t rsa -b 4096 -f /etc/btrbk/ssh/id_rsa -C btrbk@mydomain.com -N ""
 The content of the public key (/etc/btrbk/ssh/id_rsa.pub) is used for
 authentication in "authorized_keys" on the server side (see [sshd(8)]
@ -555,14 +520,14 @@ to run it whenever the key is used for authentication. Example
 "/root/.ssh/authorized_keys":
    # example backup source (also allowing deletion of old snapshots)
-    command="/backup/scripts/ssh_filter_btrbk.sh -l --source --delete",restrict <pubkey>...
+    command="/backup/scripts/ssh_filter_btrbk.sh -l --source --delete" <pubkey>...
    # example backup target (also allowing deletion of old snapshots)
-    command="/backup/scripts/ssh_filter_btrbk.sh -l --target --delete",restrict <pubkey>...
+    command="/backup/scripts/ssh_filter_btrbk.sh -l --target --delete" <pubkey>...
    # example fetch-only backup source (snapshot_preserve_min=all, snapshot_create=no),
    # restricted to subvolumes within /home or /data
-    command="/backup/scripts/ssh_filter_btrbk.sh -l --send -p /home -p /data",restrict <pubkey>...
+    command="/backup/scripts/ssh_filter_btrbk.sh -l --send -p /home -p /data" <pubkey>...
  [ssh_filter_btrbk(1)]: https://digint.ch/btrbk/doc/ssh_filter_btrbk.1.html
@ -680,8 +645,8 @@ Donate
 So btrbk saved your day?
-I will definitively continue to develop btrbk for free. If you want to
+I will definitively continue developing btrbk for free, but if you
-support my hard work with a donation, you are welcome to do so!
+want to support me you can do so:
 [![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=WFQSSCD9GNM4S)
@ -712,7 +677,7 @@ If you would like to contribute or have found bugs:
  * Visit the [btrbk project page on GitHub] and use the
    [issues tracker] there.
-  * Talk to us on [Libera.Chat] in `#btrbk`.
+  * Talk to us on Freenode in `#btrbk`.
  * Contact the author via email (the email address can be found in
    the sources).
@ -720,7 +685,6 @@ Any feedback is appreciated!
  [btrbk project page on GitHub]: https://github.com/digint/btrbk
  [issues tracker]: https://github.com/digint/btrbk/issues
  [Libera.Chat]: https://libera.chat
 License
--- a/2815
+++ b/2815
--- a/btrbk.conf.example
+++ b/btrbk.conf.example
@ -17,13 +17,6 @@
 # Enable transaction log
 transaction_log            /var/log/btrbk.log
 # Specify SSH private key for remote connections
 ssh_identity               /etc/btrbk/ssh/id_ed25519
 ssh_user                   root
 # Use sudo if btrbk or lsbtr is run by regular user
 backend_local_user         btrfs-progs-sudo
 # Enable stream buffer. Adding a buffer between the sending and
 # receiving side is generally a good idea.
 # NOTE: If enabled, make sure to install the "mbuffer" package!
@ -36,7 +29,7 @@ stream_buffer              256m
 # If you want to set a custom name for the snapshot (and backups),
 # use the "snapshot_name" option within the subvolume section.
 #
-# NOTE: btrbk does not automatically create this directory, and the
+# NOTE: btrbk does not autmatically create this directory, and the
 # snapshot creation will fail if it is not present.
 #
 snapshot_dir               _btrbk_snap
@ -74,6 +67,12 @@ snapshot_dir               _btrbk_snap
 #archive_preserve_min       no
 #archive_preserve           <NN>h <NN>d <NN>w <NN>m <NN>y
 # Specify SSH private key for "ssh://" volumes / targets:
 #ssh_identity               /etc/btrbk/ssh/id_ed25519
 #ssh_user                   root
 #ssh_compression            no
 #ssh_cipher_spec            default
 # Enable compression for remote btrfs send/receive operations:
 #stream_compress            no
 #stream_compress_level      default
@ -83,19 +82,19 @@ snapshot_dir               _btrbk_snap
 # can be run at a time.
 #lockfile                   /var/lock/btrbk.lock
-# Don't wait for transaction commit on deletion. Enable this to make
+# Don't wait for transaction commit on deletion. Set this to "after"
-# sure the deletion of subvolumes is committed to disk when btrbk
+# or "each" to make sure the deletion of subvolumes is committed to
-# terminates.
+# disk when btrbk terminates.
 #btrfs_commit_delete        no
 #
-# Volume section (optional): "volume <volume-directory>"
+# Volume section: "volume <volume-directory>"
 #
-#   <volume-directory>  Base path within a btrfs filesystem
+#   <volume-directory>  Directory of a btrfs volume (or subvolume)
-#                       containing the subvolumes to be backuped
+#                       containing the subvolume to be backuped
 #                       (usually the mount-point of a btrfs filesystem
-#                       mounted with subvolid=5 option).
+#                       mounted with subvolid=5 option)
 #
 # Subvolume section: "subvolume <subvolume-name>"
 #
@ -105,19 +104,19 @@ snapshot_dir               _btrbk_snap
 # Target section: "target <type> <volume-directory>"
 #
 #   <type>              (optional) type, defaults to "send-receive".
-#   <volume-directory>  Directory within a btrfs filesystem
+#   <volume-directory>  Directory of a btrfs volume (or subvolume)
 #                       receiving the backups.
 #
 # NOTE: The parser does not care about indentation, this is only for
-# human readability. All options apply to the last section
+# human readability. The options always apply to the last section
 # encountered, overriding the corresponding option of the upper
-# section. This means that the global options must be set on top,
+# section. This means that the global options must be set before any
-# before any "volume", "subvolume" or "target section.
+# "volume" section.
 #
 #
-# Example retention policy:
+# Example configuration:
 #
 snapshot_preserve_min   2d
 snapshot_preserve       14d
@ -125,49 +124,29 @@ snapshot_preserve       14d
 target_preserve_min     no
 target_preserve         20d 10w *m
 archive_preserve_min    latest
 archive_preserve        12m 10y
 #
 # Simple setup: Backup root and home to external disk
 #
 snapshot_dir /btrbk_snapshots
 target       /mnt/btr_backup
 subvolume    /
 subvolume    /home
 #
 # Complex setup
 #
 # In order to keep things organized, it is recommended to use "volume"
 # sections and mount the top-level subvolume (subvolid=5):
 #
 #  $ mount -o subvolid=5 /dev/sda1 /mnt/btr_pool
 #
 # Backup to external disk mounted on /mnt/btr_backup
 volume /mnt/btr_pool
-  # Create snapshots in /mnt/btr_pool/btrbk_snapshots
+  # no action if external disk is not attached
-  snapshot_dir btrbk_snapshots
+  snapshot_create  ondemand
-  # Target for all subvolume sections:
+  # propagates to all subvolume sections:
-  target /mnt/btr_backup
+  target /mnt/btr_backup/_btrbk
-  # Some default btrfs installations (e.g. Ubuntu) use "@" for rootfs
+  subvolume  root_gentoo
  # (mounted at "/") and "@home" (mounted at "/home"). Note that this
  # is only a naming convention.
  #subvolume @
  subvolume root
  subvolume home
  subvolume  kvm
-    # Use different retention policy for kvm backups:
+    # use different retention policy for kvm backups
    target_preserve     7d 4w
-# Backup data to external disk as well as remote host
+# Backup to external disk as well as some remote host
 volume /mnt/btr_data
-  subvolume  data
+  subvolume  home
-    # Always create snapshot, even if targets are unreachable
+    # always create snapshot, even if targets are unreachable
    snapshot_create  always
-    target /mnt/btr_backup
+    target /mnt/btr_backup/_btrbk
    target ssh://backup.my-remote-host.com/mnt/btr_backup
@ -176,22 +155,7 @@ volume ssh://my-remote-host.com/mnt/btr_pool
  subvolume data_0
    snapshot_dir   snapshots/btrbk
    snapshot_name  data_main
-    target /mnt/btr_backup/my-remote-host.com
+    target /mnt/btr_backup/_btrbk/my-remote-host.com
 # Backup on demand (noauto) to remote host running busybox, login as
 # regular user using ssh-agent with current user name (ssh_user no)
 # and default credentials (ssh_identity no).
 volume /home
  noauto  yes
  compat  busybox
  backend_remote  btrfs-progs-sudo
  ssh_user      no
  ssh_identity  no
  target ssh://my-user-host.com/mnt/btr_backup/home
  subvolume  alice
  subvolume  bob
 # Resume backups from remote host which runs its own btrbk instance
@ -201,4 +165,4 @@ volume ssh://my-remote-host.com/mnt/btr_pool
  snapshot_create        no
  snapshot_preserve_min  all
  subvolume home
-    target /mnt/btr_backup/my-remote-host.com
+    target /mnt/btr_backup/_btrbk/my-remote-host.com
--- a/contrib/bash/completion.bash
+++ b/contrib/bash/completion.bash
@ -4,7 +4,7 @@ _btrbk_init_cmds()
  #
  # for example, for this command:
  #
-  #     btrbk -v --override warn_unknown_targets=yes list config --long
+  #     btrbk -v list config --long
  #
  # then $cmds is:
  #
@ -14,11 +14,6 @@ _btrbk_init_cmds()
  local i
  for ((i = 1; i < cword; i++)); do
    case "${words[i-1]}" in
      '-c' | '--config' | '--exclude' | '-l' | '--loglevel' | '--format' | '--lockfile' | '--override')
        continue
        ;;
    esac
    [[ ${words[i]} != -* ]] && cmds+=(${words[i]})
  done
@ -34,28 +29,21 @@ _btrbk()
  case "$prev" in
    '-c' | '--config')
      _filedir
      return
      ;;
    '--exclude')
      return
      ;;
    '-l' | '--loglevel')
      COMPREPLY=($(compgen -W 'error warn info debug trace' -- "$cur"))
      return
      ;;
    '--format')
      COMPREPLY=($(compgen -W 'table long raw' -- "$cur"))
      return
      ;;
    '--lockfile')
      _filedir
      return
      ;;
    '--override')
      return
      ;;
  esac
  $split && return
  if [[ $cur == -* ]]; then
--- a/contrib/cron/btrbk-mail
+++ b/contrib/cron/btrbk-mail
@ -4,9 +4,6 @@
 now=$(date +%Y%m%d)
 declare -A rsync_src rsync_dst rsync_log rsync_rsh rsync_opt
 declare -A sync_fs_onchange
 #####  start config section  #####
 # Email recipients, separated by whitespace:
@ -33,9 +30,7 @@ rsync_opt[example_data]="-az --delete --inplace --numeric-ids --acls --xattrs"
 # If set, add "rsync_dst" to "sync_fs" (see below) if rsync reports files transferred
 #sync_fs_onchange[example_data]=yes
-# Enable all rsync declarations (all indices of rsync_src array)
+# Enabled rsync declarations (whitespace-separated list)
 #rsync_enable=${!rsync_src[@]}
 # Explicitly enable rsync declarations (whitespace-separated list)
 #rsync_enable="example_data"
 rsync_enable=
@ -60,8 +55,6 @@ btrbk_opts="-c /etc/btrbk/btrbk.conf"
 #mail_cmd_block_prefix='\\u200B' # zero-width whitespace
 #mail_cmd_block_prefix=". "
 # Newline character
 BR=$'\n'
 #####  end config section  #####
@ -90,47 +83,47 @@ send_mail()
        body+="$info"
    fi
    if [[ -n "$detail" ]] && [[ -n "$has_errors" ]] || [[ "${mail_detail:-no}" = "yes" ]]; then
-        [[ -n "$body" ]] && body+="${BR}${BR}DETAIL:${BR}"
+        [[ -n "$body" ]] && body+="\n\nDETAIL:\n"
        body+="$detail"
    fi
    # skip sending mail on empty body
    if [[ -z "$body" ]] && [[ -n "$has_errors" ]]; then
-        body+="FATAL: something went wrong (errors present but empty mail body)${BR}"
+        body+="FATAL: something went wrong (errors present but empty mail body)\n"
    fi
    [[ -z "$body" ]] && exit 0
    # send mail
-    echo "$body" | mail -s "$subject" $mailto
+    echo -e "$body" | mail -s "$subject" $mailto
    if [[ $? -ne 0 ]]; then
-        echo "$0: Failed to send btrbk mail to \"$mailto\", dumping mail:${BR}" 1>&2
+        echo -e "$0: Failed to send btrbk mail to \"$mailto\", dumping mail:\n" 1>&2
-        echo "<mail_subject>$subject</mail_subject>${BR}<mail_body>${BR}$body</mail_body>" 1>&2
+        echo -e "<mail_subject>$subject</mail_subject>\n<mail_body>\n$body</mail_body>" 1>&2
    fi
 }
 einfo()
 {
-    info+="$1${BR}"
+    info+="$1\n"
 }
 ebegin()
 {
    ebtext=$1
-    detail+="${BR}### $1${BR}"
+    detail+="\n### $1\n"
 }
 eend()
 {
    if [[ $1 -eq 0 ]]; then
        eetext=${3-success}
-        detail+="${BR}"
+        detail+="\n"
    else
        has_errors=1
        eetext="ERROR (code=$1)"
        [[ -n "$2" ]] && eetext+=": $2"
-        detail+="${BR}### $eetext${BR}"
+        detail+="\n### $eetext\n"
    fi
-    info+="$ebtext: $eetext${BR}"
+    info+="$ebtext: $eetext\n"
    return $1
 }
@ -146,10 +139,10 @@ run_cmd()
 {
    cmd_out=$("$@" 2>&1)
    local ret=$?
-    detail+="++ ${@@Q}${BR}"
+    detail+="++ ${@@Q}\n"
    if [[ -n "${mail_cmd_block_prefix:-}" ]] && [[ -n "$cmd_out" ]]; then
        detail+=$(echo -n "$cmd_out" | sed "s/^/${mail_cmd_block_prefix}/")
-        detail+="${BR}"
+        detail+="\n"
    else
        detail+=$cmd_out
    fi
@ -166,7 +159,7 @@ mount_all()
        if [[ $? -eq 0 ]]; then
            eend -1 "already mounted"
        else
-            detail+="${BR}"
+            detail+="\n"
            run_cmd mount --target $mountpoint
            eend $? && mounted+=" $mountpoint"
        fi
--- a/contrib/cron/btrbk-verify
+++ b/contrib/cron/btrbk-verify
@ -31,7 +31,7 @@
 #   NOTE: Depending on your setup (hardware, btrfs mount options),
 #   btrbk-verify may eat all your CPU power and use high bandwidth!
 #   Consider nice(1), ionice(1).
-#
+
 #   Incomplete resource eater list:
 #    - rsync: checksums, heavy disk I/O
 #    - btrfs: decompression, encryption
@ -77,7 +77,7 @@ set -u
 set -e
 set -o pipefail
-btrbk_version_min='0.32.0'
+btrbk_version_min='0.28.0'
 # defaults: ignore subvol dirs and root folder timestamp change
 ignore_nested_subvolume_dir=1
@ -107,8 +107,8 @@ options:
   --ignore-xattrs       ignore xattrs when verifying subvolumes
   --ssh-identity FILE   override ssh_identity from btrbk.conf(5) with FILE,
                         and clear all other ssh_* options (use with --ssh-user)
-   --ssh-user USER       override ssh_user from btrbk.conf(5) with USER, and
+   --ssh-user USER       override ssh_user from btrbk.conf(5) with USER
-                         clear all other ssh_* options(use with --ssh-identity)
+                         (only in conjunction with --ssh-identity)
   --ssh-agent           start ssh-agent(1) and add identity
 commands:
@ -157,6 +157,7 @@ while [[ "$#" -ge 1 ]]; do
          ;;
      --ssh-identity)
          # use different ssh identity (-i option) for rsync rsh.
          # if set, ssh_user defaults to root.
          # NOTE: this overrides all btrbk ssh_* options
          ssh_identity="$2"
          shift
@ -185,8 +186,6 @@ while [[ "$#" -ge 1 ]]; do
    shift
 done
 BR=$'\n'
 log_line()
 {
    echo "$@" 1>&2
@ -209,13 +208,13 @@ tlog()
    [[ -n "$dryrun" ]] && [[ "$status" == "starting" ]] && status="dryrun_starting"
    local line="$(date --iso-8601=seconds) verify-rsync ${status} ${target} ${source} - -"
    [[ -n "$comment" ]] && line="$line # $comment";
-    tlog_text+="$line${BR}"
+    tlog_text+="$line\n"
    log_debug "$line"
 }
 tlog_print()
 {
    # tlog goes to stdout
-    echo "${BR}TRANSACTION LOG${BR}---------------${BR}${tlog_text:-}"
+    echo -e "\nTRANSACTION LOG\n---------------\n${tlog_text:-}"
 }
 # parse "rsync -i,--itemize-changes" output.
@ -268,14 +267,11 @@ rsync_rsh()
    local rsh_match="(.*) ([a-z0-9_-]+)@([a-zA-Z0-9.-]+)$"
    if [[ -z "$rsh" ]]; then
-        return
+        echo
-    elif [[ -n "$ssh_user" ]] || [[ -n "$ssh_identity" ]]; then
+    elif [[ -n "$ssh_identity" ]]; then
        # override btrbk.conf from command line arguments
        log_debug "Overriding all ssh_* options from btrbk.conf"
-        local cmd="ssh -q"
+        echo "ssh -q -i $ssh_identity -l $ssh_user"
        [[ -n "$ssh_identity" ]] && cmd="$cmd -i '$ssh_identity'"
        [[ -n "$ssh_user" ]] && cmd="$cmd -l '$ssh_user'"
        echo "$cmd"
    elif [[ $rsh =~ $rsh_match ]]; then
        echo "${BASH_REMATCH[1]} -l ${BASH_REMATCH[2]}"
    else
@ -306,7 +302,7 @@ start_ssh_agent()
 eval_btrbk_resolved_line()
 {
-    local line=" $1"
+    local line=$1
    local prefix=$2
    local required_keys=$3
    # reset all variables first
@ -315,13 +311,25 @@ eval_btrbk_resolved_line()
    done
    for vv in $required_keys; do
        # basic input validation, set prefixed variable (eval)
-        local match=" ${vv}='([^']*('\\\\''[^']*)*)'"
+        local var_assignment=$(echo "$line" | grep -Eo "${vv}"'="[^"]*"')
-        if [[ $line =~ $match ]] ; then
+        if [[ $? -ne 0 ]] || [[ -z "$var_assignment" ]]; then
-            eval "${prefix}${vv}='${BASH_REMATCH[1]}'" || return 1
+            if [[ $vv == "target_type" ]]; then
-        else
+                # hack for btrbk <= 0.27.2 bug: missing "target_type" in $table_formats{resolved}
-            log_line "btrbk-verify: ERROR: Missing variable \"${vv}\""
+                # hardcode send-receive type, this results in rsync failing on raw targets with:
                # rsync: ERROR: cannot stat destination "xxx.btrfs.xz.gpg/": Not a directory (20)
                eval "${prefix}target_type=\"send-receive\"" || return 1
                continue
            fi
            if [[ $vv == "target_rsh" ]] && [[ -z "$R_target_host" ]]; then
                # hack for btrbk <= 0.27.2 bug: missing "target_rsh" in $table_formats{resolved}
                # note that target_rsh is not needed if target_host is not set.
                # variable has already been reset above, continue
                continue
            fi
            log_line "btrbk-verify: missing required variable \"${vv}\" in btrbk --format=raw line"
            return 1
        fi
        eval "${prefix}${var_assignment}" || return 1
    done
 }
@ -331,6 +339,10 @@ exit_trap_action()
    [[ $verbose -gt 0 ]] && tlog_print
 }
 # restrictions from rsync_rsh():
 [[ -z "$ssh_identity" ]] && [[ -n "$ssh_user" ]] && print_usage 2
 [[ -n "$ssh_identity" ]] && [[ -z "$ssh_user" ]] && print_usage 2
 # start ssh-agent(1)
 [[ -n "$ssh_start_agent" ]] && start_ssh_agent
@ -359,22 +371,20 @@ while read -r btrbk_list_line; do
    log_debug "Evaluating [btrbk list] line: $btrbk_list_line"
    [[ -z "$btrbk_list_line" ]] && continue
    if ! eval_btrbk_resolved_line "$btrbk_list_line" \
-         "R_" "snapshot_subvolume target_subvolume source_host target_host target_type source_rsh target_rsh"
+         "R_" "snapshot_path target_path source_host target_host target_type source_rsh target_rsh"
    then
-        log_line "btrbk-verify: ERROR: Parse error of command output: ${btrbk_cmd[@]}"
+        log_line "btrbk-verify: WARNING: Skipping task (parse error). Make sure to have >=btrbk-${btrbk_version_min} installed!"
-        log_line "Make sure to have >=btrbk-${btrbk_version_min} installed!"
+        continue
        exitstatus=1
        break
    fi
-    source="${R_snapshot_subvolume}/"
+    source="${R_snapshot_path}"
-    target="${R_target_subvolume}/"
+    target="${R_target_path}"
    [[ -n "$R_source_host" ]] && source="${R_source_host}:${source}"
    [[ -n "$R_target_host" ]] && target="${R_target_host}:${target}"
-    if [[ -z "$R_snapshot_subvolume" ]]; then
+    if [[ -z "$R_snapshot_path" ]]; then
        log_line "WARNING: Skipping task (missing snapshot): target=$target"
-    elif [[ -z "$R_target_subvolume" ]]; then
+    elif [[ -z "$R_target_path" ]]; then
        log_line "Skipping task (no target): source=$source"
    elif [[ "$R_target_type" != "send-receive" ]]; then
        log_line "Skipping task (target_type=$R_target_type): source=$source, target=$target"
@ -386,11 +396,10 @@ while read -r btrbk_list_line; do
        # rsync rsh is either source_rsh or target_rsh or empty
        eff_rsh="$R_source_rsh"
        [[ -z "$eff_rsh" ]] && eff_rsh="$R_target_rsh"
        eff_rsh=$(rsync_rsh "$eff_rsh")
        rsync_cmd=("rsync" "${rsync_args[@]}")
-        [[ -n "$eff_rsh" ]] && rsync_cmd+=("-e" "$eff_rsh")
+        [[ -n "$eff_rsh" ]] && rsync_cmd+=(-e "$(rsync_rsh "$eff_rsh")")
-        rsync_cmd+=("${source}" "${target}")
+        rsync_cmd+=("${source}/" "${target}/")
        log_cmd "${rsync_cmd[@]}"
        [[ -n "$dryrun" ]] && rsync_cmd=("cat" "/dev/null")
--- a/contrib/crypt/kdf_pbkdf2.py
+++ b/contrib/crypt/kdf_pbkdf2.py
@ -54,7 +54,7 @@ salt_hex = "".join(["{:02x}".format(x) for x in salt])
 dk_hex = "".join(["{:02x}".format(x) for x in dk])
 print("KEY=" + dk_hex);
-print("algorithm=pbkdf2_hmac");
+print("algoritm=pbkdf2_hmac");
 print("hash_name=" + hash_name);
 print("salt=" + salt_hex);
 print("iterations=" + str(iterations));
--- a/contrib/migration/raw_suffix2sidecar
+++ b/contrib/migration/raw_suffix2sidecar
@ -42,7 +42,7 @@ my $compress_format_alt = 'gz|bz2|xz|lzo|lz4';
 my $file_match = qr/[0-9a-zA-Z_@\+\-\.\/]+/;  # note: ubuntu uses '@' in the subvolume layout: <https://help.ubuntu.com/community/btrfs>
 my $uuid_match = qr/[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}/;
 my $timestamp_postfix_match = qr/\.(?<YYYY>[0-9]{4})(?<MM>[0-9]{2})(?<DD>[0-9]{2})(T(?<hh>[0-9]{2})(?<mm>[0-9]{2})((?<ss>[0-9]{2})(?<zz>(Z|[+-][0-9]{4})))?)?(_(?<NN>[0-9]+))?/;  # matches "YYYYMMDD[Thhmm[ss+0000]][_NN]"
-my $raw_postfix_match = qr/--(?<received_uuid>$uuid_match)(\@(?<parent_uuid>$uuid_match))?\.btrfs?(\.(?<compress>($compress_format_alt)))?(\.(?<encrypt>gpg))?(\.(?<split>split_aa))?(\.(?<incomplete>part))?/;  # matches ".btrfs_<received_uuid>[@<parent_uuid>][.gz|.bz2|.xz|...][.gpg][.split_aa][.part]"
+my $raw_postfix_match = qr/--(?<received_uuid>$uuid_match)(\@(?<parent_uuid>$uuid_match))?\.btrfs?(\.(?<compress>($compress_format_alt)))?(\.(?<encrypt>gpg))?(\.(?<split>split_aa))?(\.(?<incomplete>part))?/;  # matches ".btrfs_<received_uuid>[@<parent_uuid>][.gz|bz2|xz][.gpg][.split_aa][.part]"
 my $dryrun;
--- a/contrib/tools/btrbk_restore_raw.py
+++ b/contrib/tools/btrbk_restore_raw.py
@ -1,217 +0,0 @@
 #!/usr/bin/env python3
 import os
 import logging
 import subprocess
 import argparse
 logger = logging.getLogger(__name__)
 class TransformProcess:
    def run(self, bfile, options, **kw):
        return subprocess.Popen(self.get_cmd(bfile, options), **kw)
    def get_cmd(self, bfile, options):
        raise NotImplementedError()
    @classmethod
    def add_parser_options(cls, parser):
        pass
 class TransformOpensslDecrypt(TransformProcess):
    @staticmethod
    def get_cmd(bfile, options):
        return [
            'openssl', 'enc', '-d', '-' + bfile.info['cipher'], '-K',
            open(options.openssl_keyfile, 'r').read(), '-iv', bfile.info['iv']
        ]
    @staticmethod
    def add_parser_options(parser):
        parser.add_argument('--openssl-keyfile', help="path to private encryption key file")
 class TransformDecompress(TransformProcess):
    def __init__(self, program):
        self.p = program
    def get_cmd(self, bfile, options):
        return [self.p, '-d']
 class TransformBtrfsReceive(TransformProcess):
    @classmethod
    def run(cls, bfile, options, **kw):
        return subprocess.Popen(cls.get_cmd(bfile, options), **kw)
    @staticmethod
    def get_cmd(bfile, options):
        return ['btrfs', 'receive', options.restore_dir]
 TRANSFORMERS = (
    TransformOpensslDecrypt, TransformDecompress, TransformBtrfsReceive
 )
 class BtrfsPipeline:
    def __init__(self, bfile):
        self.bfile = bfile
        self.processors = []
    def append(self, transformer):
        self.processors.append(transformer)
    def run(self, options):
        processes = []
        with open(self.bfile.data_file, 'rb') as next_input:
            for transformer in self.processors:
                process = transformer.run(
                    self.bfile, options,
                    stdin=next_input, stdout=subprocess.PIPE,
                    stderr=subprocess.PIPE)
                next_input = process.stdout
                processes.append(process)
            btrfs_process = TransformBtrfsReceive.run(
                self.bfile, options, stdin=next_input,
                stderr=subprocess.PIPE, stdout=subprocess.DEVNULL)
            processes.append(btrfs_process)
            # warning: the code below is pretty ugly and hacky
            terminated = 0
            while terminated < len(processes):
                for p in processes:
                    if p.returncode is not None:
                        continue
                    msg = None
                    try:
                        p.wait(timeout=1)
                    except subprocess.TimeoutExpired as e:
                        pass
                    except Exception as e:
                        msg = e
                    else:
                        msg = p.stderr.read().decode('utf-8').strip()
                    finally:
                        if p.returncode is not None:
                            terminated += 1
                            if p.returncode != 0:
                                for p_other in processes:
                                    p_other.terminate()
                                    terminated += 1
                                if msg:
                                    logger.error(f"error running {p.args}: {msg}")
    def get_cmd(self, options):
        command_pipe = [['cat', self.bfile.data_file]]
        for transformer in self.processors:
            command_pipe.append(transformer.get_cmd(self.bfile, options))
        command_pipe.append(TransformBtrfsReceive.get_cmd(self.bfile, options))
        return ' | '.join(' '.join(x) for x in command_pipe)
 class BackupFile:
    def __init__(self, path):
        assert path.endswith('.info')
        self.info_file = path
        self.info = self._parse_info()
        self.uuid = self.info['RECEIVED_UUID']
        self.data_file = os.path.join(os.path.dirname(path), self.info['FILE'])
        self.parent = self.info.get('RECEIVED_PARENT_UUID')
        self.is_restored = False
    def _parse_info(self):
        config = {}
        with open(self.info_file, 'r') as fh:
            # skip command option line
            for line in fh.readlines():
                if '=' not in line:
                    continue
                key, val = line.strip().split('=', maxsplit=1)
                config[key] = val
        return config
    def get_transformers(self):
        if 'encrypt' in self.info:
            if self.info['encrypt'] == 'gpg':
                raise NotImplementedError('gpg encryption')
            elif self.info['encrypt'] == 'openssl_enc':
                yield TransformOpensslDecrypt()
            else:
                raise Exception(f'unknown encryption type: "{self.info["encrypt"]}"')
        if 'compress' in self.info:
            yield TransformDecompress(self.info['compress'])
    def restore_file(self, options):
        assert self.info.get('TYPE') == 'raw'
        assert not self.info.get('INCOMPLETE')
        pipeline = BtrfsPipeline(self)
        for transformer in self.get_transformers():
            pipeline.append(transformer)
        if options.dry_run:
            print(pipeline.get_cmd(options))
        else:
            logger.info(f"restoring backup {os.path.basename(self.data_file)}")
            pipeline.run(options)
        self.is_restored = True
 def restore_from_path(backup, options):
    path = os.path.dirname(backup)
    info_files = {}
    backup_file = BackupFile(backup + '.info')
    restored_files = set()
    for entry in os.scandir(path):
        if entry.is_file() and entry.name.endswith('.info'):
            info = BackupFile(entry.path)
            info_files[info.uuid] = info
    restored_files.update(restore_backup(backup_file, info_files, options))
    logger.info(f"finished; restored {len(restored_files)} backup files")
 def restore_backup(bfile, parents, options):
    if bfile.is_restored:
        return
    if bfile.parent:
        parent = parents.get(bfile.parent)
        if not parent:
            msg = (f"missing parent {bfile.parent} for"
                   f"'{os.path.basename(bfile.info_file)}'")
            if options.ignore_missing:
                logger.warning(msg)
            else:
                raise Exception(msg)
        else:
            yield from restore_backup(parent, parents, options)
    bfile.restore_file(options)
    yield bfile.uuid
 def main():
    parser = argparse.ArgumentParser(description="restore btrbk raw backup")
    parser.add_argument('backup', help="backup file to restore; for incremental"
                        " backups the parent files must be in the same directory")
    parser.add_argument('restore_dir', help="target directory for restored subvolumes"
                                            " (path argument for \"btrfs receive\")")
    parser.add_argument('-n', '--dry-run', action='store_true',
                        help="print commands that would be executed")
    parser.add_argument('--ignore-missing', action='store_true',
                        help="do not fail on missing parent snapshots")
    for transformer in TRANSFORMERS:
        transformer.add_parser_options(parser)
    args = parser.parse_args()
    if args.dry_run:
        logger.setLevel('ERROR')
    restore_from_path(args.backup, args)
 if __name__ == '__main__':
    logger.setLevel('INFO')
    logging.basicConfig(format='%(asctime)s %(levelname)s - %(message)s')
    main()
--- a/doc/FAQ.md
+++ b/doc/FAQ.md
@ -110,8 +110,8 @@ have to create a run-time (rw) snapshot before booting into it:
 How do I convert '/' (subvolid=5) into a subvolume?
 ---------------------------------------------------
-There's several ways to achieve this, the solution described below
+There's several ways to achieve this, the solution described below is
-guarantees not to create new files (extents) on disk.
+that it guarantees not to create new files (extents) on disk.
 ### Step 1: make a snapshot of your root filesystem
@ -191,7 +191,7 @@ What is the most efficient way to clone btrfs storage?
 ------------------------------------------------------
 It is very common (and avisable!) to keep backups on a separate
-location. In some situations, it is also required to transport the
+location. In some situations, is is also required to transport the
 data physically, either to the datacenter or to your safe in the
 basement.
--- a/doc/Makefile
+++ b/doc/Makefile
@ -1,4 +1,5 @@
-DOCS       = FAQ.md
+DOCS       = FAQ.md \
             upgrade_to_v0.23.0.md
 MAN_MAN1   = btrbk.1 \
             lsbtr.1 \
             ssh_filter_btrbk.1
@ -17,19 +18,8 @@ ifeq ($(COMPRESS), yes)
 endif
 # convert using "asciidoctor": <https://asciidoctor.org>
-# fallback to "a2x" from asciidoc package: <http://asciidoc.org>
+ASCIIDOCTOR_MANPAGE = asciidoctor -d manpage -b manpage
-ifneq (, $(shell command -v asciidoctor 2> /dev/null))
+ASCIIDOCTOR_HTML    = asciidoctor -b html5 -d article
  ASCIIDOC_MANPAGE = asciidoctor -d manpage -b manpage
  ASCIIDOC_HTML    = asciidoctor -b html5 -d article
 else ifneq (, $(shell command -v a2x 2> /dev/null))
  # NOTE: using -L (--no-xmllint), as xmllint is a separate package on many distros.
  ASCIIDOC_MANPAGE = a2x -L -d manpage -f manpage
  ASCIIDOC_HTML    = asciidoc -b html -d article
 else
  ASCIIDOC_ERR = $(error "please install either asciidoc or asciidoctor")
  ASCIIDOC_MANPAGE = $(ASCIIDOC_ERR)
  ASCIIDOC_HTML    = $(ASCIIDOC_ERR)
 endif
 # reproducible builds: reference date is ":date:" attribute from asciidoc source
 date_attr = $(shell sed -rn 's/:date:\s*//p' $(1))
@ -60,10 +50,10 @@ clean:
 	gzip -9 -n -c $< > $@
 %.1 : %.1.asciidoc
-	SOURCE_DATE_EPOCH=$(call source_date_epoch,$<) $(ASCIIDOC_MANPAGE) $<
+	SOURCE_DATE_EPOCH=$(call source_date_epoch,$<) $(ASCIIDOCTOR_MANPAGE) -o $@ $<
 %.5 : %.5.asciidoc
-	SOURCE_DATE_EPOCH=$(call source_date_epoch,$<) $(ASCIIDOC_MANPAGE) $<
+	SOURCE_DATE_EPOCH=$(call source_date_epoch,$<) $(ASCIIDOCTOR_MANPAGE) -o $@ $<
 %.html : %.asciidoc
-	SOURCE_DATE_EPOCH=$(call source_date_epoch,$<) $(ASCIIDOC_HTML) -o $@ $<
+	SOURCE_DATE_EPOCH=$(call source_date_epoch,$<) $(ASCIIDOCTOR_HTML) -o $@ $<
--- a/doc/btrbk.1.asciidoc
+++ b/doc/btrbk.1.asciidoc
@ -1,7 +1,7 @@
 btrbk(1)
 ========
-:date: 2023-03-25
+:date: 2021-03-21
-:release-version: 0.32.6
+:release-version: 0.31.2
 :man manual: Btrbk Manual
 :man source: Btrbk {release-version}
@ -20,12 +20,11 @@ btrbk [-h|--help] [--version]
      [-c|--config <file>] [-n|--dry-run] [--exclude <filter>]
      [-p|--preserve] [--preserve-snapshots] [--preserve-backups]
      [-v|--verbose] [-q|--quiet] [-l|--loglevel <level>]
-      [-t|--table] [-L|--long] [-1|--single-column]
+      [-t|--table] [-L|--long] [--format <output-format>] [--pretty]
      [--format <output-format>] [--pretty]
      [-S|--print-schedule] [--progress]
      [--lockfile <file>]
      [--override <config_option>=<value>]
-      <command> [[--] <filter>...]
+      <command> [<args>]
 DESCRIPTION
@ -45,27 +44,26 @@ btrbk.conf(5) for more details.
 === Snapshots and Backups
-Snapshots as well as backup subvolumes are created in the form:
+Snapshots as well as backup subvolumes are created in form:
    <snapshot-name>.<timestamp>[_N]
 Where '<snapshot-name>' is identical to the source subvolume name,
-unless the configuration option 'snapshot_name' is set. '<timestamp>'
+unless the configuration option 'snapshot_name' is set. The
-is a timestamp describing the creation time (local time of the host
+<timestamp> is either "YYYYMMDD" or "YYYYMMDDThhmm" (dependent of the
-running btrbk) of the snapshot/backup. The format can be configured
+'timestamp_format' configuration option), where "YYYY" is the year,
-using the 'timestamp_format' option, refer to btrbk.conf(5) for
+"MM" is the month, "DD" is the day, "hh" is the hour and "mm" is the
-details. If multiple snapshots/backups are created on the same
+minute of the creation time (local time of the host running btrbk). If
-date/time, 'N' will be incremented on each snapshot, starting at 1.
+multiple snapshots/backups are created on the same date/time, N will
 be incremented on each snapshot, starting at 1.
 If a snapshot or backup does not match the naming scheme above
-(e.g. if it has been renamed manually), btrbk will leave it untouched.
+(i.e. if it has been renamed manually), btrbk will leave it untouched.
-Note that in btrfs terminology, a 'snapshot' is a ``subvolume with
+Note that 'snapshot' is a btrfs terminology for a ``read-only
-a given initial content of the original subvolume'' (showing a
+subvolume'' (showing a parent-uuid, see btrfs-subvolume(8)); 'backup'
-parent-uuid, see btrfs-subvolume(8)), and they can be read-write
+is a btrbk terminology for a ``read-only subvolume created with
-(default) or read-only. In btrbk terminology, 'snapshot' means
+send/receive'' (showing a received-uuid).
 ``read-only btrfs snapshot'', and 'backup' means ``read-only subvolume
 created with send/receive'' (showing a received-uuid).
 OPTIONS
@ -88,15 +86,8 @@ OPTIONS
    commands that would be executed.
 --exclude <filter>::
-    Exclude configured sections matching '<filter>' (see
+    Exclude configured sections matching '<filter>'. See
-    <<_filter_statements,FILTER STATEMENTS>> below), or any specific
+    <<_filter_statements,FILTER STATEMENTS>> below.
    snapshot from being backuped or deleted, or any specific backup
    from being deleted.
 +
 Note that excluding specific snapshots from being backuped has impact
 on scheduling: e.g. if the "first snapshot of the day" is excluded,
 the "second snapshot of the day" shifts to "first", creating a backup
 as "first backup of the day".
 -p, --preserve::
    Preserve all snapshots and backups. Skips deletion of any
@ -112,7 +103,7 @@ as "first backup of the day".
    specified in the configuration file.
 --wipe::
-    Ignore configured snapshot retention policy, delete all but the latest
+    Ignore configured snapshot retention policy, delete all but latest
    snapshots instead. All snapshots needed for incremental backup
    (latest common) are also preserved. Useful if you are getting low
    on disk space (ENOSPC).
@ -135,15 +126,12 @@ as "first backup of the day".
 -L, --long::
    Print output in long table format (shortcut for "--format=long").
 -1, --single-column::
    Print output as single column (not available for all commands).
 --format table|long|raw|col:[h:]<columns>::
    Print output in specified format. If set to "raw", prints
-    space-separated, quoted key=value pairs (machine readable).
+    space-separated key="value" pairs (machine readable).
 +
 If set to "col:", prints only the <columns> specified (comma-separated
-list). Header lines are omitted if the "h:" modifier is present.
+list). Header lines are ommitted if the "h:" modifier is present.
 Columns prefixed with "-" are collapsed if empty. Columns postfixed
 with ":RALIGN" are right-aligned.
@ -161,9 +149,9 @@ with ":RALIGN" are right-aligned.
    command (version >= 20180505) installed on the host running btrbk.
 --lockfile <file>::
-    Place an exclusive lock on <file> during program execution, using
+    Create lockfile <file> on startup; checks lockfile before running
-    flock(2). If the lock is held by another process, exit before
+    any btrfs commands (using perl "flock"), and exits if the lock is
-    running any actions. Overrides configuration option
+    held by another btrbk instance. Overrides configuration option
    "lockfile". Ignored on dryrun ('-n', '--dry-run').
 --override <config_option>=<value>::
@ -222,9 +210,8 @@ configuring the retention policy.
    snapshots that are not preserved by their configured retention
    policy will be deleted. Note that the latest snapshot (the one
    created in step 1) as well as the latest snapshot/backup pair are
-    always preserved, regardless of the retention policy. If any
+    always preserved, regardless of the retention policy.
-    target is unreachable or has errors, all snapshots are preserved
+
    in order not to break the incremental chain.
 *dryrun* [filter...]::
    Don't run any btrfs commands that would alter the filesystem, just
@ -429,7 +416,8 @@ execution times and high ram usage. Consider setting 'cache_dir'.
    lsbtr(1).
 *config* print|print-all::
-    Prints the parsed configuration file.
+    Prints the parsed configuration file. Use the '--format' command
    line option to switch between different output formats.
 FILTER STATEMENTS
@ -480,9 +468,6 @@ Note that for *run* and *snapshot* commands, a filter matching a
 surrounding 'subvolume' section. If this is not desired, consider
 running *snapshot* and *resume* commands separately.
 Filter statements can match multiple times (e.g. on group as well as
 host name). In such a case, all matches are processed.
 FILES
 -----
--- a/doc/btrbk.conf.5.asciidoc
+++ b/doc/btrbk.conf.5.asciidoc
@ -1,7 +1,7 @@
 btrbk.conf(5)
 =============
-:date: 2023-03-25
+:date: 2021-03-21
-:release-version: 0.32.6
+:release-version: 0.31.2
 :man manual: Btrbk Manual
 :man source: Btrbk {release-version}
@ -36,21 +36,34 @@ global options must be set before any sections are defined.
 Blank lines are ignored. A hash character (#) starts a comment
 extending until end of line.
 Whitespace or unicode characters are not allowed for file
 names. Allowed characters are:
    [0-9] [a-z] [A-Z] and "._+-@"
 This is for sanity/safety/security reasons, we apologize for the
 inconvenience.
 SECTIONS
 --------
-*volume* <volume-directory>|<url> (optional)::
+*volume* <volume-directory>|<url>::
-    Absolute path pointing to a btrfs file system containing the
+    Directory of a btrfs volume containing the source subvolume(s) to
-    source subvolume(s) to be backed up. Usually the mount point of a
+    be backed up. '<volume-directory>' must be an absolute path and
-    btrfs filesystem mounted with the 'subvolid=5' option.
+    point to a btrfs volume (or subvolume). Usually the mount point of
    a btrfs filesystem mounted with the 'subvolid=5' option.
 *subvolume* <subvolume-name>::
-    Subvolume to be backed up, relative to the '<volume-directory>' of
+    Subvolume to be backed up, relative to the '<volume-directory>'
-    the 'volume' section, or absolute if the 'volume' section is
+    specified in the 'volume' section. Multiple 'subvolume' sections
-    omitted. Accepts wildcard character "*".
+    are allowed within 'volume' sections. Accepts wildcard character
    "*".
 +
 --
 If set to ".", the subvolume at '<volume-directory>' is used as backup
 source, and the snapshots will be created within the source subvolume
 itself (see 'snapshot_dir' option below), which is not recommended.
 Note that if this subvolume is btrfs root (id=5), it needs to have a
 valid UUID, which is not the case for file systems created with
 btrfs-progs < 4.16.
@ -96,7 +109,7 @@ otherwise.
 *timestamp_format* short|long|long-iso::
    Timestamp format used as postfix for new snapshot subvolume
-    names. Defaults to ``long''.
+    names. Defaults to ``short''.
 +
 --
 ifndef::backend-docbook,backend-manpage[]
@ -116,13 +129,12 @@ snapshots are created during a daylight saving time clock
 change).
 +
 Note that using ``long-iso'' has implications on the scheduling, see
-<<_reference_time,Reference Time>> below.
+<<_retention_policy,RETENTION POLICY>> (caveats) below.
 *snapshot_dir* <directory>::
    Directory in which the btrfs snapshots are created, relative to
-    '<volume-directory>' of the 'volume' section, or absolute if the
+    '<volume-directory>' of the 'volume' section. Note that btrbk does
-    'volume' section is omitted. Note that btrbk does not
+    not automatically create this directory, and the snapshot creation
    automatically create this directory, and the snapshot creation
    will fail if it is not present.
 *snapshot_name* <basename>::
@ -185,9 +197,10 @@ not be certain about this, such operations are disallowed in
    Defines after what time (in full hours since midnight) a
    snapshot/backup is considered to be a "daily" backup. Daily,
    weekly, monthly and yearly backups are preserved on this hour (see
-    <<_retention_policy,RETENTION POLICY>> below). Ignored on
+    <<_retention_policy,RETENTION POLICY>> below). If you set this
-    snapshots or backups without time information ('timestamp_format
+    option, make sure to also set 'timestamp_format' to ``long'' or
-    short'). Defaults to ``0''.
+    ``long-iso'' (backups and snapshots having no time information
    will ignore this option). Defaults to ``0''.
 *snapshot_preserve* no|<retention_policy>::
    Set retention policy for snapshots (see
@ -242,29 +255,32 @@ set to ``all'' (the default).
 === SSH Options
-*ssh_identity* <file>|no::
+*ssh_identity* <file>::
-    Absolute path to a ssh identity file (private key). If not set,
+    Absolute path to a ssh identity file (private key). Note that if
-    the ssh default is used (see ssh(1), "-i identity_file"). Note
+    the private key is password protected, btrbk will prompt for user
-    that if the identity key is password protected and no
+    input, which is usually not desired.
    authentication agent is used, btrbk will prompt for user input on
    every connection attempt.
-*ssh_user* <username>|no::
+*ssh_user* <username>::
    Remote username for ssh. Defaults to ``root''. Make sure the
    remote user is able to run "btrfs" with root privileges (see
-    option 'backend' for details). If set to ``no'', the ssh default
+    option 'backend' for details).
    is used.
 *ssh_compression* yes|no::
    Enables or disables the compression of ssh connections. Defaults
    to ``no''. Note that if *stream_compress* is enabled, ssh
    compression will always be disabled for send/receive operations.
-*ssh_cipher_spec* default|<cipher_spec>::
+*ssh_cipher_spec* <cipher_spec>::
    Selects the cipher specification for encrypting the session
    (comma-separated list of ciphers in order of preference). See the
    "-c cipher_spec" option in ssh(1) for more information. Defaults
-    to ``default'' (the ciphers specified in ssh_config(5)).
+    to ``default'' (the ciphers specified in 'ssh_config').
 Previous versions btrbk allowed you to set a *ssh_port* option, this
 has been dropped in favor of the `ssh://hostname:port` notation in the
 'volume' and 'target' <<_sections,sections>>. If you want to set a
 global port for all SSH connections to remote hosts, set the ``Port''
 option in ssh_config(5).
 === Data Stream Options
@ -274,7 +290,7 @@ set to ``all'' (the default).
    remote locations. Defaults to ``no''. If enabled, make sure that
    '<compress_command>' is available on the source and target
    hosts. Supported '<compress_command>': gzip, pigz, bzip2, pbzip2,
-    bzip3, xz, lzo, lz4, zstd.
+    xz, lzo, lz4, zstd.
 *stream_compress_level* default|<number>::
    Compression level for the specified '<compress_command>'. Refer to
@ -289,11 +305,7 @@ set to ``all'' (the default).
 *stream_compress_threads* default|<number>::
    Number of threads to use for <compress_command>. Only supported
-    for "pigz", "pbzip2", "bzip3", "zstd" and recent versions of "xz".
+    for "pigz", "pbzip2", "zstd" and recent versions of "xz".
 *stream_compress_adapt* yes|no::
    Enable adaptive compression for <compress_command>. Only supported
    for "zstd" (version >= 1.3.6). Defaults to ``no''.
 *stream_buffer* <size>|no::
    Add a buffer to the btrfs send stream (locally, on uncompressed
@ -359,14 +371,14 @@ constraints.
    daemon, auth, lpr, news, cron, authpriv, local0..local7.
 *lockfile* <file>|no::
-    Place an exclusive lock on <file> during program execution, using
+    Create lockfile <file> on startup; checks lockfile before running
-    flock(2). If the lock is held by another process, exit before
+    any btrfs commands (using perl "flock"), and exits if the lock is
-    running any actions. Ignored on dryrun ('-n', '--dry-run'). See
+    held by another btrbk instance. Ignored on dryrun ('-n',
-    also '--lockfile' command-line option.
+    '--dry-run'). See also '--lockfile' command-line option.
-*backend* <backend>::
+*backend* btrfs-progs|btrfs-progs-btrbk|btrfs-progs-sudo::
    Backend filesystem utilities to be used for btrfs specific
-    operations. Available backends:
+    operations. Defaults to ``btrfs-progs''.
 +
 --
 *btrfs-progs*::
@ -386,9 +398,6 @@ constraints.
    have appropriate (root) permissions for the "btrfs" command groups
    as well as the "readlink" and "test" commands in /etc/sudoers.
 *btrfs-progs-doas*::
    Similar to btrfs-progs-sudo, using prefix "doas -n".
 If you want to set this option for local or remote hosts only, set
 *backend_local* or *backend_remote* (e.g. "backend_remote
 btrfs-progs-btrbk").
@ -397,29 +406,12 @@ If you want to set this option for regular (non-root) user only, set
 *backend_local_user*.
 --
-*compat* <compat-option>...::
+*compat* busybox|no::
-    Enable compatibility options. Available 'compat-option':
+    If set to ``busybox'', use busybox compatible commands. Defaults
-+
+    to ``no''.
--
+    If you want to set this option for local or remote hosts only, you
-*busybox*::
+    can set *compat_local* or *compat_remote*
-    Use busybox compatible commands, at the expense of slight overhead
+    (e.g. "compat_remote busybox").
    while reading filesystem information.
 *ignore_receive_errors*  _*experimental*_::
    Tell btrfs-receive(8) to not terminate on errors by setting
    "--max-errors=0" option. Print warnings instead.
 +
 A known use case for this are target hosts lacking xattr support
 (e.g. some Synology NAS), while the send-stream contains "lsetxattr"
 commands. Another case is targets failing to set otime, complaining
 with "ERROR: attribute 12 requested but not present".
 +
 Note that there is *no guarantee that backups created with this
 option enabled can be restored at all*.
 If you want to set this option for local or remote hosts only, set
 *compat_local* or *compat_remote* (e.g. "compat_remote busybox").
 --
 *cache_dir* <directory>::
    If set, cache extent maps for the "btrbk extents" command.
@ -427,74 +419,28 @@ If you want to set this option for local or remote hosts only, set
 === Btrfs Specific Options
-*incremental_prefs* <list-spec>[:<amount>]...::
+*btrfs_commit_delete* after|each|no::
-    Specify the preferences to determine the best common (correlated)
+    If set, make sure the deletion of snapshot and backup subvolumes
-    parent and clone sources for incremental backups, by choosing from
+    are committed to disk when btrbk terminates. Defaults to ``no''.
    predefined candidate lists.
 +
 --
 The 'list-spec' defines from what candidate list the next
 parent/clone-src should be appended to a result list; 'amount' defines
 how many (e.g. "sro:1 sro:1" is identical to "sro:2"), or all if
 omitted. Any candidate which is already in the results is dropped.
-The resulting list of subvolumes is then used as parameters for the
+*incremental_clones* <number>::
-btrfs-send(8) command: the first for "-p <parent>", all others for
+    Maximum number of clone sources allowed for incremental send. If
-"-c <clone-src>".
+    set, btrbk adds "-c <clone-src>" to the btrfs-send(8) command for
-
+    all present snapshot/backup pairs (correlated subvolumes matching
-Available 'list-spec' (candidate lists = filtered subsets of
+    matching 'received_uuid', printed by "btrbk stats"). Set this to a
-correlated subvolumes):
+    high number if you want to make sure that no common data is missed
-
+    on incremental backups, in expense of btrfs-send
-*sro*,*srn*:: All from 'snapshot_dir' matching 'snapshot_name', with
+    performance. Defaults to 0.
 parent_uuid relationship, sorted by btrbk timestamp (o=older
 n=newer).
 *sao*,*san*:: All from 'snapshot_dir' matching 'snapshot_name', sorted
 by btrbk timestamp (o=older n=newer).
 *aro*,*arn*:: All from 'incremental_resolve', with parent_uuid
 relationship, sorted by cgen (o=older n=newer).
 Defaults to "sro:1 srn:1 sao:1 san:1 aro:1 arn:1". Note that for
 most operations the default resolves a single parent, as there usually
 are no newer snapshots, and all "sro:1 sao:1 aro:1" resolve to the
 same snapshot.
 Example: "defaults,sao,san,aro,arn" takes the defaults, and adds clone
 sources for all (!) known candidates on the filesystem.
 --
 *incremental_clones* yes|no::
    If enabled, btrbk adds "-c <clone-src>" to the btrfs-send(8)
    command for all correlated subvolumes resolved by
    'incremental_prefs'. If disabled, only "-p <parent>" is
    used. Defaults to ``yes''.
 *incremental_resolve* mountpoint|directory::
    Specifies where to search for the best common parent for
    incremental backups. If set to ``mountpoint'', use parents in the
-    filesystem tree below the mount point of the snapshot and target
+    filesystem tree below mount points of source
-    directory. If set to ``directory'', use parents strictly below
+    "<volume-directory>/<snapshot-dir>" and target
-    snapshot/target directories. Set this to ``directory'' if you get
+    "<target-directory>". If set to ``directory'', use parents
-    access problems (when not running btrbk as root). Defaults to
+    strictly below source/target directories. Set this to
-    ``mountpoint''.
+    ``directory'' if you get access problems (when not running btrbk
-
+    as root). Defaults to ``mountpoint''.
 *btrfs_commit_delete* yes|no::
    If set, wait for the transaction commit at the end of each
    snapshot or backup deletion (sets '--commit-each' option for
    "btrfs subvolume delete"). Defaults to ``no''.
 *send_protocol* <number>|no  _*experimental*_::
    Use btrfs send protocol version N. If enabled on 'target', btrbk
    adds "--proto <number>" to the btrfs-send(8) command. Defaults to
    ``no'' (btrfs default).
 *send_compressed_data* yes|no  _*experimental*_::
    Send data that is compressed on the filesystem directly without
    decompressing it. This requires protocol version 2 or higher
    (btrfs-progs >= 5.19), and implies "send_protocol 2". If enabled
    on 'target', btrbk adds "--compressed-data" to the btrfs-send(8)
    command. Defaults to ``no'' (btrfs default).
 *snapshot_qgroup_destroy* yes|no  _*experimental*_:: {blank}
 *target_qgroup_destroy* yes|no  _*experimental*_:: {blank}
@ -505,39 +451,30 @@ sources for all (!) known candidates on the filesystem.
    <https://bugzilla.kernel.org/show_bug.cgi?id=91751>
 === Informative Options
 *warn_unknown_targets* yes|no::
    If set, prints a warning if btrbk encounters a target subvolume at
    a unknown location (i.e. not following btrbk naming scheme, or
    outside the target directory). Defaults to ``no''.
 RETENTION POLICY
 ----------------
-Retention policies are defined individually for snapshots, backups and
+btrbk uses separate retention policies for snapshots and backups,
-archives (summarized as "backups" in the following text), using a
+which are defined by the 'snapshot_preserve_min', 'snapshot_preserve',
-combination of:
+'target_preserve_min', 'target_preserve', 'preserve_day_of_week' and
 'preserve_hour_of_day' configuration options.
-**_preserve_min* all|latest|no|<number>{h,d,w,m,y}::
+Within this section, any statement about "backups" is always valid for
-    Amount of time (duration) in which all backups are preserved.
+backups as well as snapshots, referring to 'target_preserve' or
-
+'snapshot_preserve' respectively.
 **_preserve* no|<retention_policy>::
    Schedule (single points in time) for which individual backups are
    preserved.
 Note that if "preserve_min" is set to ``all'' (the default), any
 setting of "preserve" obviously has no effect.
 The format for '<retention_policy>' is:
    [<hourly>h] [<daily>d] [<weekly>w] [<monthly>m] [<yearly>y]
 With the following semantics:
 *hourly*::
    Defines how many hours back hourly backups should be
    preserved. The first backup of an hour is considered an hourly
-    backup.
+    backup. Note that if you use <hourly> scheduling, make sure to
    also set 'timestamp_format' to ``long'' or ``long-iso'', or the
    scheduler will interpret the time as "00:00" (midnight).
 *daily*::
    Defines how many days back daily backups should be preserved. The
@ -564,31 +501,29 @@ Use an asterisk for ``all'' (e.g. "target_preserve 60d *m"
 states: "preserve daily backups for 60 days back, and all monthly
 backups").
 The reference time (which defines the beginning of a day, week, month
 or year) for all date/time calculations is the local time of the host
 running btrbk.
 Hint: Run btrbk with the '-S', '--print-schedule' option to get a
 comprehensive output of the scheduler results.
 Caveats:
-=== Reference Time
+* If you run a setup with several btrbk instances (e.g. one
  snapshot-only instance per remote client, and a separate fetch-only
  instance on the backup server), it makes perfectly sense to run
  btrbk with different local time on the clients, in order to make
  sure the backups from all the remote hosts are preserved for
  "midnight", and not at "00:00 UTC" (which would be "14:00" in
  Honolulu). If you want this behavior, do NOT use "timestamp_format
  long-iso".
-The local time on the host running btrbk defines the reference time
+* If "timestamp_format long-iso" is set, running btrbk from different
-for all date/time calculations, especially for "beginning of a day",
+  time zones leads to different interpretation of "first in day, week,
-and as a consequence for the first daily, weekly, monthly or yearly
+  month, or year". Make sure to run btrbk with the same time zone on
-backups. The local time on remote hosts (ssh source/target) is never
+  every host, e.g. by setting the TZ environment variable (see
-used.
+  tzset(3)).
 Unless "timestamp_format long-iso" is set, daily backups are preserved
 at "preserve_hour_of_day" (defaults to midnight) of the respective
 time zone (and not for "00:00 UTC", which would be "14:00" in
 Honolulu). This becomes relevant for setups with multiple btrbk
 instances, e.g. many snapshot-only instances (spread around the
 world), and a fetch-only instance on the backup server.
 Caveat:
 * If "timestamp_format long-iso" is set, each btrbk instance on has a
  different interpretation of "first in day". Make sure to run btrbk
  with the same time zone on every host, e.g. by setting the TZ
  environment variable (see tzset(3)).
 TARGET TYPES
@ -597,19 +532,24 @@ TARGET TYPES
 *send-receive*::
    Backup to a btrfs filesystem, using "btrfs send/receive". This is
    the recommended (standard) target type. The '<target-directory>'
-    must be an absolute path and point to a subvolume or directory
+    must be an absolute path and point to a btrfs volume (or
-    within a btrfs file system. See btrfs-send(8), btrfs-receive(8).
+    subvolume), or to a directory within a subvolume. See
    btrfs-send(8), btrfs-receive(8).
 *raw*  _*experimental*_::
    Backup to a raw (filesystem independent) file from the output of
    btrfs-send(8), with optional compression and encryption.
 +
 --
 Note that the target preserve mechanism is currently disabled for
 incremental raw backups (btrbk does not delete any incremental raw
 files)!
 Raw backups consist of two files: the main data file containing the
 btrfs send stream, and a sidecar file ".info" containing metadata:
-  <snapshot-name>.<timestamp>[_N].btrfs[.gz|.bz2|...][.gpg]
+  <snapshot-name>.<timestamp>[_N].btrfs[.gz|.bz2|.xz][.gpg]
-  <snapshot-name>.<timestamp>[_N].btrfs[.gz|.bz2|...][.gpg].info
+  <snapshot-name>.<timestamp>[_N].btrfs[.gz|.bz2|.xz][.gpg].info
 For 'incremental' backups ("incremental yes"), please note that:
@ -620,11 +560,6 @@ For 'incremental' backups ("incremental yes"), please note that:
  make sure that a non-incremental backup is triggered from time to
  time.
 * The scheduler will never delete dependent parents of backups
  preserved by the retention policy (run btrbk with the '-S',
  '--print-schedule' option to get a comprehensive output of the
  scheduler results).
 * There is currently no support for rotation of incremental backups:
  if 'incremental' is set, a full backup must be triggered manually
  from time to time in order to be able to delete old backups.
@ -634,8 +569,8 @@ Additional options for raw targets:
 *raw_target_compress* <compress_command>|no::
    Compression algorithm to use for raw backup target. Supported
-    '<compress_command>': gzip, pigz, bzip2, pbzip2, bzip3, xz, lzo,
+    '<compress_command>': gzip, pigz, bzip2, pbzip2, xz, lzo, lz4,
-    lz4, zstd.
+    zstd.
 *raw_target_compress_level* default|<number>::
    Compression level for the specified <compress_command>.
 *raw_target_compress_long* default|<number>::
@ -656,7 +591,7 @@ Additional options for "raw_target_encrypt gpg":
 *gpg_keyring* <file>::
    Keyring to use for gpg, e.g. "`/etc/btrbk/gpg/pubring.kbx`".
-*gpg_recipient* <name>...::
+*gpg_recipient* <name>::
    Encrypt for user id '<name>' (email address).
--- a/doc/install.md
+++ b/doc/install.md
@ -9,18 +9,16 @@ file, choose one of the following methods:
 ### Generic Linux System
 Install [asciidoctor] or [asciidoc] if you want to build the
 documentation.
 Download and unpack the latest [btrbk source tarball] and type:
    sudo make install
 #### Try latest master from Github:
-    wget https://raw.githubusercontent.com/digint/btrbk/master/btrbk
+### Gentoo Linux
-    chmod +x btrbk
+
-    sudo ./btrbk ls /
+btrbk is in portage:
    emerge app-backup/btrbk
 ### Debian Based Distros
@ -32,7 +30,7 @@ Packages are also available via NeuroDebian: http://neuro.debian.net/pkgs/btrbk.
 ### Fedora Linux
-btrbk is in the official Fedora repos: https://src.fedoraproject.org/rpms/btrbk
+btrbk is in the official Fedora repos: https://apps.fedoraproject.org/packages/btrbk
    sudo dnf install btrbk
@ -49,13 +47,6 @@ btrbk is in the community repository
    apk add btrbk
 ### Gentoo Linux
 btrbk is in portage:
    emerge app-backup/btrbk
 ### Void Linux
 btrbk is in Void's `current` repository
@ -64,5 +55,3 @@ btrbk is in Void's `current` repository
  [btrbk source tarball]: https://digint.ch/download/btrbk/releases/
  [asciidoctor]: https://asciidoctor.org
  [asciidoc]: https://asciidoc.org
--- a/doc/lsbtr.1.asciidoc
+++ b/doc/lsbtr.1.asciidoc
@ -1,7 +1,7 @@
 lsbtr(1)
 ========
-:date: 2023-03-25
+:date: 2021-03-21
-:release-version: 0.32.6
+:release-version: 0.31.2
 :man manual: Btrbk Manual
 :man source: Btrbk {release-version}
@ -17,12 +17,11 @@ SYNOPSIS
 [verse]
 lsbtr [-h|--help] [--version]
-      [-l|--long] [-u|--uuid] [-1|--single-column] [--raw]
+      [-l|--long] [-u|--uuid] [--raw]
      [--format <output-format>]
      [-v|--verbose]
      [-c|--config <file>]
      [--override <config_option>=<value>]
-      [[--] <path>|<url>...]
+      [<path>|<url>...]
 DESCRIPTION
@ -56,21 +55,9 @@ OPTIONS
 -u, --uuid::
    Print UUID table (parent/received relations).
 -1, --single-column::
    Print path column only (delimited by newline).
 --raw::
    Print space-separated key="value" pairs (machine readable).
 --format table|long|raw|col:[h:]<columns>::
    Print output in specified format. If set to "raw", prints
    space-separated key="value" pairs (machine readable).
 +
 If set to "col:", prints only the <columns> specified (comma-separated
 list). Header lines are omitted if the "h:" modifier is present.
 Columns prefixed with "-" are collapsed if empty. Columns postfixed
 with ":RALIGN" are right-aligned.
 -v, --verbose::
    Increase the level of verbosity.
--- a/doc/ssh_filter_btrbk.1.asciidoc
+++ b/doc/ssh_filter_btrbk.1.asciidoc
@ -1,7 +1,7 @@
 ssh_filter_btrbk(1)
 ===================
-:date: 2023-03-25
+:date: 2021-03-21
-:release-version: 0.32.6
+:release-version: 0.31.2
 :man manual: Btrbk Manual
 :man source: Btrbk {release-version}
@ -39,13 +39,13 @@ The following commands are always allowed:
 - "readlink"
 - "test -d" (only if "compat busybox" configuration option is set)
 - "cat /proc/self/mountinfo"
- - pipes through "gzip", "pigz", "bzip2", "pbzip2", "bzip3", "xz",
+ - pipes through "gzip", "pigz", "bzip2", "pbzip2", "xz", "lzop",
-   "lzop", "lz4", "zstd" (stream_compress)
+   "lz4", "zstd" (stream_compress)
 - pipes through "mbuffer" (stream_buffer, rate_limit)
 Example line in /root/.ssh/authorized_keys on a backup target host:
-    command="ssh_filter_btrbk.sh --target --delete --restrict-path /mnt/btr_backup",restrict ssh-rsa AAAAB3NzaC1...hwumXFRQBL btrbk@example.org
+    command="ssh_filter_btrbk.sh --target --delete --restrict-path /mnt/btr_backup" ssh-rsa AAAAB3NzaC1...hwumXFRQBL btrbk@mydomain.com
 OPTIONS
@ -82,11 +82,6 @@ OPTIONS
 -p, --restrict-path <path>::
    Restrict commands to <path>. Note that "btrfs subvolume show",
    "btrfs subvolume list" are NOT affected by this option.
 +
 It is not possible to restrict commands to exact subvolume names, as
 btrfs-receive(8) takes a <path> as argument (directory, not including
 the subvolume file name to be created, this is encoded in the
 send-stream).
 -l, --log::
    Log ACCEPT and REJECT messages to the system log.
--- a/doc/upgrade_to_v0.23.0.md
+++ b/doc/upgrade_to_v0.23.0.md
@ -0,0 +1,92 @@
 Upgrading to btrbk-v0.23.0
 ==========================
 In order to keep btrbk simple and intuitive while adding new features,
 it became inevitable to change the semantics of the "retention policy"
 related configuration options.
 What has changed?
 -----------------
 ### Preserve *first* instead of *last* snapshot/backup
 btrbk used to *always* transfer the latest snapshot to the target
 location, while considering the *last* snapshot/backup of a day as a
 daily backup (and also the last weekly as a monthly). This made it
 very cumbersome when running btrbk in a cron job as well as manually,
 because the last manually created snapshot was immediately transferred
 on every run, and used as the daily backup (instead of the one created
 periodically by the cron job).
 The new semantics are to consider the *first* (instead of *last*)
 snapshot of a hour/day/week/month as the one to be preserved, while
 only transferring the snapshots needed to satisfy the target retention
 policy.
 ### Preserve snapshots for a minimum amount of time
 In order to specify a minimum amount of time in which *all* snapshots
 should be preserved, the new "snapshot_preserve_min" and
 "target_preserve_min" configuration options were introduced. This was
 previously covered by "snapshot_preserve_daily", which caused a lot of
 confusion among users.
 Upgrading the configuration file: /etc/btrbk/btrbk.conf
 -------------------------------------------------------
 Please read the description of the "run" command in [btrbk(1)], as
 well as the "RETENTION POLICY" section in [btrbk.conf(5)] for a
 detailed description. Make sure to understand the new concept, and run
 `btrbk --print-schedule dryrun` after updating the configuration.
 ### Upgrade retention policy
 If you want the same behaviour as before:
    # replace this:
    snapshot_preserve_daily   <daily>
    snapshot_preserve_weekly  <weekly>
    snapshot_preserve_monthly <monthly>
    # with:
    snapshot_preserve_min  <daily>d
    snapshot_preserve      <weekly>w <monthly>m
    # ... do the same with "target_preserve_*" options
 But what you probably want is something like:
    snapshot_preserve_min  5d
    snapshot_preserve      <daily>d <weekly>w <monthly>m
    target_preserve_min    no
    target_preserve        <daily>d <weekly>w <monthly>m *y
 This states:
  * Keep all snapshots for five days (no matter how many there are)
  * Transfer only the first snapshot of a day to the target
  * Keep all "first snapshots of a day" for `<daily>` days, etc.
 ### Upgrade "resume_missing"
 If you have a line: "resume_missing yes" somwhere in your config,
 simply remove it. btrbk always resumes missing backups.
 If you have "resume_missing no", you can imitate this behaviour by
 setting:
    target_preserve_min  latest
    target_preserve      no
 This states: "always transfer the latest snapshot to the target".
  [btrbk(1)]: https://digint.ch/btrbk/doc/btrbk.1.html
  [btrbk.conf(5)]: https://digint.ch/btrbk/doc/btrbk.conf.5.html
--- a/ssh_filter_btrbk.sh
+++ b/ssh_filter_btrbk.sh
@ -1,11 +1,9 @@
-#!/bin/sh
+#!/bin/bash
-# initialise and sanitise the shell execution environment
+set -e
-unset -v IFS
+set -u
 export LC_ALL=C
 export PATH='/sbin:/bin:/usr/sbin:/usr/bin'
-set -e -u
+export PATH=/sbin:/bin:/usr/sbin:/usr/bin
 enable_log=
 restrict_path_list=
@ -14,70 +12,55 @@ allow_exact_list=
 allow_rate_limit=1
 allow_stream_buffer=1
 allow_compress=1
-compress_list='gzip|pigz|bzip2|pbzip2|bzip3|xz|lzop|lz4|zstd'
+compress_list="gzip|pigz|bzip2|pbzip2|xz|lzop|lz4|zstd"
 # note that the backslash is NOT a metacharacter in a POSIX bracket expression!
 option_match='-[a-zA-Z0-9=-]+'   # matches short as well as long options
-file_match_sane='/[0-9a-zA-Z_@+./-]*' # matches file path (equal to ${file_match} in btrbk < 0.32.0)
+file_match='[0-9a-zA-Z_@+./-]*'  # matches file path (equal to $file_match in btrbk)
 file_match="/[^']*" # btrbk >= 0.32.0 quotes file arguments: match all but single quote
 file_arg_match="('${file_match}'|${file_match_sane})" # support btrbk < 0.32.0
 log_cmd()
 {
-    local priority="$1"
+    if [[ -n "$enable_log" ]]; then
-    local authorisation_decision="$2"
+        logger -p $1 -t ssh_filter_btrbk.sh "$2 (Name: ${LOGNAME:-<unknown>}; Remote: ${SSH_CLIENT:-<unknown>})${3:+: $3}: $SSH_ORIGINAL_COMMAND"
    local reason="${3-}"
    if [ -n "${enable_log}" ]; then
        logger -p "${priority}" -t ssh_filter_btrbk.sh "${authorisation_decision} (Name: ${LOGNAME:-<unknown>}; Connection: ${SSH_CONNECTION:-<unknown>})${reason:+: ${reason}}: ${SSH_ORIGINAL_COMMAND}"
    fi
 }
 allow_cmd()
 {
-    local cmd="$1"
+    allow_list="${allow_list}|$1"
    allow_list="${allow_list}|${cmd}"
 }
 allow_exact_cmd()
 {
-    local cmd="$1"
+    allow_exact_list="${allow_exact_list}|$1"
    allow_exact_list="${allow_exact_list}|${cmd}"
 }
 reject_and_die()
 {
-    local reason="$1"
+    local reason=$1
-
+    log_cmd "auth.err" "btrbk REJECT" "$reason"
-    log_cmd 'auth.err' 'btrbk REJECT' "${reason}"
+    echo "ERROR: ssh_filter_btrbk.sh: ssh command rejected: $reason: $SSH_ORIGINAL_COMMAND" 1>&2
    printf 'ERROR: ssh_filter_btrbk.sh: ssh command rejected: %s: %s\n' "${reason}" "${SSH_ORIGINAL_COMMAND}" >&2
    exit 255
 }
 run_cmd()
 {
-    log_cmd 'auth.info' 'btrbk ACCEPT'
+    log_cmd "auth.info" "btrbk ACCEPT"
-    eval " ${SSH_ORIGINAL_COMMAND}"
+    eval " $SSH_ORIGINAL_COMMAND"
 }
 reject_filtered_cmd()
 {
-    if [ -n "${restrict_path_list}" ]; then
+    if [[ -n "$restrict_path_list" ]]; then
-	# match any of restrict_path_list,
+	# match any of restrict_path_list with or without trailing slash,
 	# or any file/directory (matching file_match) below restrict_path
-	path_match="'(${restrict_path_list})(${file_match})?'"
+	path_match="(${restrict_path_list})(/${file_match})?"
 	path_match_legacy="(${restrict_path_list})(${file_match_sane})?"
    else
 	# match any absolute file/directory (matching file_match)
-	path_match="'${file_match}'"
+	path_match="/${file_match}"
 	path_match_legacy="${file_match_sane}"
    fi
    # btrbk >= 0.32.0 quotes files, allow both (legacy)
    path_match="(${path_match}|${path_match_legacy})"
-    if [ -n "${allow_compress}" ]; then
+    if [[ -n "$allow_compress" ]]; then
        decompress_match="(${compress_list}) -d -c( -[pT][0-9]+)?"
        compress_match="(${compress_list}) -c( -[0-9])?( -[pT][0-9]+)?"
    else
@ -87,8 +70,8 @@ reject_filtered_cmd()
    # rate_limit_remote and stream_buffer_remote use combined
    # "mbuffer" as of btrbk-0.29.0
-    if [ -n "${allow_stream_buffer}" ] || [ -n "${allow_rate_limit}" ]; then
+    if [[ -n "$allow_stream_buffer" ]] || [[ -n "$allow_rate_limit" ]]; then
-        mbuffer_match='mbuffer -v 1 -q( -s [0-9]+[kmgKMG]?)?( -m [0-9]+[kmgKMG]?)?( -[rR] [0-9]+[kmgtKMGT]?)?'
+        mbuffer_match="mbuffer -v 1 -q( -s [0-9]+[kmgKMG]?)?( -m [0-9]+[kmgKMG]?)?( -[rR] [0-9]+[kmgtKMGT]?)?"
    else
        mbuffer_match=
    fi
@ -98,44 +81,35 @@ reject_filtered_cmd()
    stream_in_match="(${decompress_match} \| )?(${mbuffer_match} \| )?"
    stream_out_match="( \| ${mbuffer_match})?( \| ${compress_match}$)?"
    # `grep`’s `-q`-option is not used as it may cause an exit status of `0` even
    # when an error occurred.
    allow_stream_match="^${stream_in_match}${allow_cmd_match}${stream_out_match}"
-    if printf '%s' "${SSH_ORIGINAL_COMMAND}" | grep -E "${allow_stream_match}" >/dev/null 2>/dev/null; then
+    if [[ $SSH_ORIGINAL_COMMAND =~ $allow_stream_match ]] ; then
        return 0
    fi
    exact_cmd_match="^(${allow_exact_list})$";
-    if printf '%s' "${SSH_ORIGINAL_COMMAND}" | grep -E "${exact_cmd_match}" >/dev/null 2>/dev/null; then
+    if [[ $SSH_ORIGINAL_COMMAND =~ $exact_cmd_match ]] ; then
        return 0
    fi
-    local formatted_restrict_path_list="$(printf '%s' "${restrict_path_list}" | sed 's/|/", "/g')"
+    reject_and_die "disallowed command${restrict_path_list:+ (restrict-path: \"${restrict_path_list//|/\", \"}\")}"
    reject_and_die "disallowed command${restrict_path_list:+ (restrict-path: \"${formatted_restrict_path_list}\")}"
 }
 # check for "--sudo" option before processing other options
 sudo_prefix=
-for key in "$@"; do
+for key; do
-    if [ "${key}" = '--sudo' ]; then
+    [[ "$key" == "--sudo" ]] && sudo_prefix="sudo -n "
        sudo_prefix='sudo -n '
    fi
    if [ "${key}" = '--doas' ]; then
        sudo_prefix='doas -n '
    fi
 done
-while [ "$#" -ge 1 ]; do
+while [[ "$#" -ge 1 ]]; do
    key="$1"
-    case "${key}" in
+    case $key in
      -l|--log)
          enable_log=1
          ;;
-      --sudo|--doas)
+      --sudo)
          # already processed above
          ;;
@ -180,7 +154,7 @@ while [ "$#" -ge 1 ]; do
          ;;
      *)
-          printf 'ERROR: ssh_filter_btrbk.sh: failed to parse command line option: %s\n' "${key}" >&2
+          echo "ERROR: ssh_filter_btrbk.sh: failed to parse command line option: $key" 1>&2
          exit 255
          ;;
    esac
@ -189,21 +163,19 @@ done
 # NOTE: subvolume queries are NOT affected by "--restrict-path":
 # btrbk also calls show/list on the mount point of the subvolume
-allow_exact_cmd "${sudo_prefix}btrfs subvolume (show|list)( ${option_match})* ${file_arg_match}";
+allow_exact_cmd "${sudo_prefix}btrfs subvolume (show|list)( ${option_match})* ${file_match}";
 allow_cmd "${sudo_prefix}readlink"                    # resolve symlink
-allow_exact_cmd "${sudo_prefix}test -d ${file_arg_match}" # check directory (only for compat=busybox)
+allow_exact_cmd "${sudo_prefix}test -d ${file_match}" # check directory (only for compat=busybox)
-allow_exact_cmd 'cat /proc/self/mountinfo'            # resolve mountpoints
+allow_exact_cmd "cat /proc/self/mountinfo"            # resolve mountpoints
-allow_exact_cmd 'cat /proc/self/mounts'               # legacy, for btrbk < 0.27.0
+allow_exact_cmd "cat /proc/self/mounts"               # legacy, for btrbk < 0.27.0
 # remove leading "|" on alternation lists
-allow_list="${allow_list#\|}"
+allow_list=${allow_list#\|}
-allow_exact_list="${allow_exact_list#\|}"
+allow_exact_list=${allow_exact_list#\|}
-restrict_path_list="${restrict_path_list#\|}"
+restrict_path_list=${restrict_path_list#\|}
-case "${SSH_ORIGINAL_COMMAND}" in
+case "$SSH_ORIGINAL_COMMAND" in
    *\.\./*)  reject_and_die 'directory traversal'  ;;
    *'
 '*)           reject_and_die 'unsafe character LF'  ;;
    *\$*)     reject_and_die 'unsafe character "$"' ;;
    *\&*)     reject_and_die 'unsafe character "&"' ;;
    *\(*)     reject_and_die 'unsafe character "("' ;;
@ -212,7 +184,7 @@ case "${SSH_ORIGINAL_COMMAND}" in
    *\<*)     reject_and_die 'unsafe character "<"' ;;
    *\>*)     reject_and_die 'unsafe character ">"' ;;
    *\`*)     reject_and_die 'unsafe character "`"' ;;
-    *\|*)     [ -n "${allow_compress}" ] || [ -n "${allow_rate_limit}" ] || [ -n "${allow_stream_buffer}" ] || reject_and_die 'unsafe character "|"' ;;
+    *\|*)     [[ -n "$allow_compress" ]] || [[ -n "$allow_rate_limit" ]] || [[ -n "$allow_stream_buffer" ]] || reject_and_die 'unsafe character "|"' ;;
 esac
 reject_filtered_cmd
		`@ -1,3 +0,0 @@`
			`# These are supported funding model platforms`

			`custom: ['https://www.paypal.com/cgi-bin/webscr?cmd=_s-xclick&hosted_button_id=WFQSSCD9GNM4S', 'https://btc.com/19DYtoEepxBmn9ZPspJGZrhCtySKCxPcP1']`