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btrbk
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Cerem Cem ASLAN 2017-04-29 16:47:40 +00:00 committed by GitHub
parent b4ec8d32a5 b35735ec84
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12
README.md
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@ -121,7 +121,7 @@ When playing around with config-files, it is highly recommended to
check the output using the `dryrun` command before executing the check the output using the `dryrun` command before executing the
backups: backups:
btrbk -c myconfig -v dryrun btrbk -c /path/to/myconfig -v dryrun
This will read all btrfs information on the source/target filesystems This will read all btrfs information on the source/target filesystems
and show what actions would be performed (without writing anything to and show what actions would be performed (without writing anything to
@ -135,11 +135,15 @@ Example: laptop with usb-disk for backups
In this example, we assume you have a laptop with: In this example, we assume you have a laptop with:
* a disk having a btrfs volume mounted as `/mnt/btr_pool`, * a disk having a btrfs root subvolume (subvolid=5) mounted on `/mnt/btr_pool`,
containing a subvolume `rootfs` for the root filesystem and a containing a subvolume `rootfs` for the root filesystem (i.e. mounted on `/`) and a
subvolume `home` for the user data. subvolume `home` for the user data.
* a backup disk having a btrfs volume mounted as `/mnt/btr_backup`, * a backup disk having a btrfs volume mounted as `/mnt/btr_backup`,
containing a subvolume `mylaptop` for the incremental backups. containing a subvolume or directory `mylaptop` for the incremental backups.
Make sure that you have `/mnt/btr_pool/btrbk_snapshots` subvolume or create it:
btrfs subvolume create btrbk_snapshots
Retention policy: Retention policy:

54
doc/FAQ.md
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@ -42,13 +42,13 @@ btrbk is designed to never alter your source subvolume. In the config
above, the btrbk snapshots would be created *inside* the source above, the btrbk snapshots would be created *inside* the source
subvolume, altering it. subvolume, altering it.
The same applies to **any "btrfs root" mount point** (subvolid=0). In The same applies to **any "btrfs root" mount point** (subvolid=5). In
the example below, you will **not be able to backup** `/mnt/data` the example below, you will **not be able to backup** `/mnt/data`
using btrbk: using btrbk:
/etc/fstab: /etc/fstab:
/dev/sda1 /mnt/data btrfs subvolid=0 [...] /dev/sda1 /mnt/data btrfs subvolid=5 [...]
btrbk is designed to operate on the subvolumes *within* `/mnt/data`. btrbk is designed to operate on the subvolumes *within* `/mnt/data`.
The recommended way is to split your data into subvolumes, e.g.: The recommended way is to split your data into subvolumes, e.g.:
@ -75,11 +75,11 @@ The btrbk configuration for this would be:
### Tech Answer ### Tech Answer
While *btrfs root* (subvolid=0) is a regular subvolume, it is still While *btrfs root* (subvolid=5) is a regular subvolume, it is still
special: being the root node, it does not have a "name" inside the special: being the root node, it does not have a "name" inside the
subvolume tree. subvolume tree.
Here, `/mnt/btr_pool` is mounted with `subvolid=0`: Here, `/mnt/btr_pool` is mounted with `subvolid=5`:
# btrfs sub show /mnt/btr_pool/ # btrfs sub show /mnt/btr_pool/
/mnt/btr_data is toplevel subvolume /mnt/btr_data is toplevel subvolume
@ -105,7 +105,7 @@ a good entry point.
If your linux root filesystem is btrfs, I recommend booting linux from If your linux root filesystem is btrfs, I recommend booting linux from
a btrfs subvolume, and use the btrfs root only as a container for a btrfs subvolume, and use the btrfs root only as a container for
subvolumes (i.e. NOT booting from "subvolid=0"). This has the big subvolumes (i.e. NOT booting from "subvolid=5"). This has the big
advantage that you can choose the subvolume in which to boot by simply advantage that you can choose the subvolume in which to boot by simply
switching the `rootflags=subvol=<subvolume>` kernel boot option. switching the `rootflags=subvol=<subvolume>` kernel boot option.
@ -124,7 +124,7 @@ have to create a run-time (rw) snapshot before booting into it:
# btrfs subvolume snapshot /mnt/btr_pool/backup/btrbk/rootfs-20150101 /mnt/btr_pool/rootfs_testing # btrfs subvolume snapshot /mnt/btr_pool/backup/btrbk/rootfs-20150101 /mnt/btr_pool/rootfs_testing
How do I convert '/' (subvolid=0) into a subvolume? How do I convert '/' (subvolid=5) into a subvolume?
--------------------------------------------------- ---------------------------------------------------
There's several ways to achieve this, the solution described below is There's several ways to achieve this, the solution described below is
@ -132,7 +132,7 @@ that it guarantees not to create new files (extents) on disk.
### Step 1: make a snapshot of your root filesystem ### Step 1: make a snapshot of your root filesystem
Assuming that '/' is mounted with `subvolid=0`: Assuming that '/' is mounted with `subvolid=5`:
# btrfs subvolume snapshot / /rootfs # btrfs subvolume snapshot / /rootfs
@ -140,26 +140,37 @@ Note that this command does NOT make any physical copy of the files of
your subvolumes within "/", it will only add some metadata. your subvolumes within "/", it will only add some metadata.
### Step 2: make sure that "/rootfs/etc/fstab" is ok. ### Step 2: (OPTIONAL) make sure that "/rootfs/etc/fstab" mounts your toplevel subvolume.
Add mount point for subvolid=0 to fstab, something like this: Add mount point for subvolid=5 to fstab, something like this:
/rootfs/etc/fstab: /rootfs/etc/fstab:
/dev/sda1 /mnt/btr_pool btrfs subvolid=0,noatime 0 0 /dev/sda1 /mnt/btr_pool btrfs subvolid=5,noatime 0 0
> This step is not critical for a proper root change, but will save your time by preventing
> further configurations/reboots and manually mounting the toplevel subvolume.
### Step 3: boot from the new subvolume "rootfs". ### Step 3: boot from the new subvolume "rootfs".
Either add `rootflags=subvol=rootfs` to grub.cfg, or set subvolume Either add `rootflags=subvol=rootfs` to grub.cfg , or set subvolume
"rootfs" as default: "rootfs" as default (**recommended**):
# btrfs subvolume set-default <subvolid> / # btrfs subvolume set-default <subvolid> /
> You can obtain `<subvolid>` via `btrfs subvolume show /rootfs | grep "Subvolume ID"`
> Editing grub.cfg manually may lead you some troubles if you perform some actions that will
> fire `grub-mkconfig`.
### Step 4: after reboot, check if everything went fine: ### Step 4: after reboot, check if everything went fine:
First check your **system log** for btrfs errors, then: First check your **system log** for btrfs errors:
cat /var/log/messages | grep btrfs | grep "error" | tail
then check if current `/` is our new subvolume:
# btrfs subvolume show / # btrfs subvolume show /
Name: rootfs Name: rootfs
@ -167,24 +178,19 @@ First check your **system log** for btrfs errors, then:
Great, this tells us that we just booted into our new snapshot! Great, this tells us that we just booted into our new snapshot!
# mount /mnt/btr_pool
# btrfs subvolume show /mnt/btr_pool # btrfs subvolume show /mnt/btr_pool
/mnt/btr_pool is btrfs root /mnt/btr_pool is toplevel subvolume
This means that the root volume (subvolid=0) is correctly mounted. This means that the root volume (subvolid=5) is correctly mounted.
### Step 5: delete old (duplicate) files ### Step 5: delete old (duplicate) files
Carefully delete all old files from `/mnt/btr_pool`, except "rootfs" Carefully delete all old files from `/mnt/btr_pool`, except "rootfs"
and all other subvolumes within "/". You can list all these by typing: and any other subvolumes within "/mnt/btr_pool".
# btrfs subvolume list -a /mnt/btr_pool In other words, delete any folders in `/mnt/btr_pool` that are
**NOT LISTED** by `btrfs subvolume list -a /mnt/btr_pool`:
Make sure you do NOT delete anything within the directories listed
here!
something like:
# cd /mnt/btr_pool # cd /mnt/btr_pool
# rm -rf bin sbin usr lib var ... # rm -rf bin sbin usr lib var ...