btrbk(1)
========
:date:        2018-03-05
:revision:    0.26.1
:man manual:  Btrbk Manual
:man source:  Btrbk


NAME
----

btrbk - backup tool for btrfs subvolumes


SYNOPSIS
--------

[verse]
btrbk [-h|--help] [--version]
      [-c|--config <file>] [-n|--dry-run]
      [-p|--preserve] [--preserve-snapshots] [--preserve-backups]
      [-v|--verbose] [-q|--quiet] [-l|--loglevel <level>]
      [-t|--table] [--format <output-format>]
      [--progress] [--print-schedule]
      [--override <config_option>=<value>]
      [--lockfile <file>]
      <command> [<args>]


DESCRIPTION
-----------

*btrbk* is a backup tool for btrfs subvolumes, taking advantage of
btrfs specific capabilities to create atomic snapshots and transfer
them incrementally to a target btrfs filesystem. It is able to perform
backups from one source to multiple destinations.

Snapshots as well as backup subvolume names 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. The
<timestamp> is either "YYYYMMDD" or "YYYYMMDDThhmm" (dependent of the
'timestamp_format' configuration option), where "YYYY" is the year,
"MM" is the month, "DD" is the day, "hh" is the hour and "mm" is the
minute of the creation time (local time of the host running btrbk). If
multiple snapshots/backups are created on the same date/time, N will
be incremented on each snapshot, starting at 1.


OPTIONS
-------

-h, --help::
    Prints the synopsis and a list of the commands.

--version::
    Prints the btrbk version.

-n, --dry-run::
    Don't run anything that would alter the filesystem, just show the
    snapshots and backup subvolumes that would be created/deleted by
    the *run*, *snapshot*, *resume*, *prune*, *archive* and *clean*
    commands. Use in conjunction with '-l debug' to see the btrfs
    commands that would be executed.

-c, --config <file>::
    Read the configuration from <file>.

-p, --preserve::
    Preserve all snapshots and backups. Skips deletion of any
    snapshots and backups, even if specified in the configuration file
    (shortcut for "--preserve-snapshots --preserve-backups").

--preserve-snapshots::
    Preserve all snapshots. Skips deletion of any snapshots, even if
    specified in the configuration file.

--preserve-backups::
    Preserve all backups. Skips deletion of any backups, even if
    specified in the configuration file.

--wipe::
    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).

-v, --verbose::
    Verbose output (shortcut for "--loglevel=info").

-q, --quiet::
    Quiet operation. If set, btrbk does not print the summary after
    executing the *run*, *snapshot*, *resume*, *prune*, or *archive*
    commands.

-l, --loglevel <level>::
    Set the level of verbosity. Accepted levels are warn, info, debug,
    and trace.

-t, --table::
    Print output in table format (shortcut for "--format=table").

--format table|long|raw::
    Print output in specified format. If set to "raw", prints
    space-separated key="value" pairs (machine readable). Affects
    output format for *run*, *snapshot*, *resume*, *prune*, *archive*
    and *list* commands. Useful for further exporting/scripting.

--progress::
    Show progress bar on send-receive operation.

--print-schedule::
    Print detailed scheduler information on *run*, *snapshot*,
    *resume*, *prune* and *archive* commands. Use the '--format'
    command line option to switch between different output formats.

--lockfile <file>::
    Create lockfile <file> on startup; checks lockfile before running
    any btrfs commands (using perl "flock"), and exits if the lock is
    held by another btrbk instance. Overrides configuration option
    "lockfile". Ignored on dryrun ('-n', '--dry-run').

--override <config_option>=<value>::
    Override a configuration option <config_option> with
    <value>. Globally, for ALL contexts. Use with care!


COMMANDS
--------

=== Actions

The following commands are used to create snapshots and/or
backups. All actions can operate in dry-run mode ('-n', '--dry-run').
Use the '--format' command line option to switch between different
output formats.

See section RETENTION POLICY in *btrbk.conf*(5) for information on
configuring the retention policy.

*run* [filter...]::
    Perform snapshot and backup operations as specified in the
    configuration file. If the optional [filter...] arguments are
    present, snapshots and backups are only performed for the
    subvolumes/targets matching a filter statement (see
    <<_filter_statements,FILTER STATEMENTS>> below).
+
*Step 0: Read Data*;;
    Read information from the source and target btrfs filesystems in
    order to perform sanity checks and identify parent/child and
    received-from relationships.
+
*Step 1: Create Snapshots*;;
    If the checks succeed, btrbk creates snapshots for the source
    subvolumes specified in the configuration file, according to the
    'snapshot_create' option.
+
*Step 2: Create Backups*;;
    For each specified target, btrbk creates the backups as follows:
    After comparing the backups to the source snapshots, btrbk
    transfers all missing snapshots needed to satisfy the configured
    target retention policy, incrementally from the latest common
    parent subvolume found. If no common parent subvolume is found (or
    if the 'incremental' option is set to ``no''), a full
    (non-incremental) backup is created.
+
*Step 3: Delete Backups*;;
    Unless the -p, --preserve or --preserve-backups option is set,
    backup subvolumes that are not preserved by their configured
    retention policy will be deleted. Note that the latest
    snapshot/backup pair are always preserved, regardless of the
    retention policy.
+
*Step 4: Delete Snapshots*;;
    Unless the -p, --preserve or --preserve-snapshots option is set,
    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.


*dryrun* [filter...]::
    Don't run any btrfs commands that would alter the filesystem, just
    show the snapshots and backup subvolumes that would be
    created/deleted by the *run* command. Use in conjunction with '-l
    debug' to see the btrfs commands that would be executed.

*snapshot* [filter...]::
    Snapshot only: skips backup creation and deletion (steps 2 and
    3). Use in conjunction with -p, --preserve (or
    --preserve-snapshots) if you also want to skip snapshot deletion
    (step 4). Note that snapshot deletion is skipped if the target is
    not accessible, as it is still required in order to determine the
    latest snapshot/backup pair.

*resume* [filter...]::
    Resume backups: skips snapshot creation (step 1), transfers and
    deletes snapshots/backups in order to satisfy their configured
    retention policy. Use in conjunction with -p, --preserve,
    --preserve-backups, --preserve-snapshots if you want to skip
    backup and/or snapshot deletion (steps 3, 4).

*prune* [filter...]::
    Prune snapshots and backups: skips snapshot and backup creation
    (steps 1, 2), only deletes snapshots and backups in order to
    satisfy their configured retention policy. Useful for cleaning the
    disk after changing the retention policy. Use in conjunction with
    --preserve-backups, --preserve-snapshots if you want to skip
    backup or snapshot deletion (steps 3, 4).

*archive* <source> <target> _*experimental*_::
    Recursively copy all subvolumes created by btrbk from <source> to
    <target> directory, optionally rescheduled using
    'archive_preserve_*' configuration options. Also creates directory
    tree on <target> (see bugs below). Useful for creating extra
    archive copies (clones) from your backup disks. Note that you can
    continue using btrbk after swapping your backup disk with the
    archive disk.
+
Note that this feature needs a *linux kernel >=4.4* to work correctly!
Kernels >=4.1 and <4.4 have a bug when re-sending subvolumes (the
archived subvolumes will have incorrect received_uuid, see
<http://thread.gmane.org/gmane.comp.file-systems.btrfs/48798>), so
make sure you run a recent kernel.
+
Known bugs: If you want to use nested subvolumes on the target
filesystem, you need to create them by hand (e.g. by running "btrfs
subvolume create <target>/dir"). Check the output of --dry-run if
unsure.

*clean* [filter...]::
    Delete incomplete (garbled) backups. Incomplete backups can be
    left behind on network errors or kill signals while a send/receive
    operation is ongoing, and are identified by the "received_uuid"
    flag not being set on a target (backup) subvolume.

The following table gives a quick overview of the action commands and
resulting snapshot creation (S+), backup creation (B+), snapshot
deletion (S-), and backup deletion (B-):

ifdef::backend-docbook,backend-manpage[]
....
Command   Option                 S+ B+ S- B-
--------------------------------------------
run                              x  x  x  x
run       --preserve             x  x
run       --preserve-snapshots   x  x     x
run       --preserve-backups     x  x  x
snapshot                         x     x
snapshot  --preserve             x
resume                              x  x  x
resume    --preserve                x
resume    --preserve-snapshots      x     x
resume    --preserve-backups        x  x
prune                                  x  x
prune     --preserve-snapshots            x
prune     --preserve-backups           x
....
endif::backend-docbook,backend-manpage[]
ifndef::backend-docbook,backend-manpage[]
[cols="2*<m,4*^", options="header,autowidth,compact", style="monospaced"]
|=======
|Command  |Option                |S+ |B+ |S- |B-
|run      |                      | x | x | x | x
|run      |--preserve            | x | x |   |
|run      |--preserve-snapshots  | x | x |   | x
|run      |--preserve-backups    | x | x | x |
|snapshot |                      | x |   | x |
|snapshot |--preserve            | x |   |   |
|resume   |                      |   | x | x | x
|resume   |--preserve            |   | x |   |
|resume   |--preserve-snapshots  |   | x |   | x
|resume   |--preserve-backups    |   | x | x |
|prune    |                      |   |   | x | x
|prune    |--preserve-snapshots  |   |   |   | x
|prune    |--preserve-backups    |   |   | x |
|=======
endif::backend-docbook,backend-manpage[]


=== Informative Commands

The following commands are informative only, and will not alter the
file system.

*stats* [filter...]::
    Print statistics of snapshot and backup subvolumes. Optionally
    filtered by [filter...] arguments (see <<_filter_statements,FILTER
    STATEMENTS>> below).

*list* <subcommand> [filter...]::
    Print information defined by <subcommand> in a tabular
    form. Optionally filtered by [filter...] arguments (see
    <<_filter_statements,FILTER STATEMENTS>> below).
+
Available subcommands:
+
--
ifndef::backend-docbook,backend-manpage[]
[horizontal]
endif::backend-docbook,backend-manpage[]

*snapshots*;; List all snapshots (and corresponding backups). Note
              that all snapshots related to configured subvolumes are
              listed, not only the ones created by btrbk.
*backups*;;   List all backups (and corresponding snapshots).
*latest*;;    List most recent common snapshot/backup pair, or most
              recent snapshot if no common found.
*config*;;    List configured source/snapshot/target relations.
*source*;;    List configured source/snapshot relations.
*volume*;;    List configured volume sections.
*target*;;    List configured targets.
--
+
Use the '--format' command line option to switch between
different output formats.


*usage* [filter...]::
    Print filesystem usage information for all source/target volumes,
    optionally filtered by [filter...] arguments (see
    <<_filter_statements,FILTER STATEMENTS>> below). Note that the
    "free" value is an estimate of the amount of data that can still
    be written to the file system.

*origin* <subvolume>::
    Print the subvolume origin tree: Shows the parent-child
    relationships as well as the received-from information. Use the
    '--format' command line option to switch between different output
    formats.

*diff* <from> <to>::
    Print new files since subvolume <from> for subvolume <to>.

*config* print|print-all::
    Prints the parsed configuration file. Use the '--format' command
    line option to switch between different output formats.


FILTER STATEMENTS
-----------------

Filter arguments are accepted in form:

<group-name>::
Matches the 'group' configuration option of a 'volume',
'subvolume' or 'target' section.

[hostname:]<volume-directory>::
    Matches all subvolumes and targets of a 'volume' configuration
    section.

[hostname:]<volume-directory>/<subvolume-name>::
    Matches the specified subvolume and all targets of a 'subvolume'
    configuration section.

[hostname:]<target-directory>::
    Matches all targets of a 'target' configuration section.

[hostname:]<target-directory>/<snapshot-name>::
    Matches a single target of a 'target' section within a 'subvolume'
    section with given <snapshot-name>.

For convenience, [hostname:] can be specified as either "hostname:" or
"ssh://hostname/".


FILES
-----

+/etc/btrbk.conf+::
+/etc/btrbk/btrbk.conf+::
    Default configuration file. The file format and configuration
    options are described in *btrbk.conf*(5).


EXIT STATUS
-----------

*btrbk* returns the following error codes:

ifndef::backend-docbook,backend-manpage[]
[horizontal]
endif::backend-docbook,backend-manpage[]
0::   No problems occurred.
1::   Generic error code.
2::   Parse error: when parsing command-line options or configuration
      file.
3::   Lockfile error: if lockfile is present on startup.
10::  Backup abort: At least one backup task aborted.
255:: Script error.


AVAILABILITY
------------

Please refer to the btrbk project page *<https://digint.ch/btrbk/>*
for further details.


SEE ALSO
--------

*btrbk.conf*(5),
*btrfs*(8)

For more information about btrfs and incremental backups, see the web
site at https://btrfs.wiki.kernel.org/index.php/Incremental_Backup


AUTHOR
------

Axel Burri <axel@tty0.ch>
