Btrfs: Difference between revisions
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== Usage == | == Usage == | ||
=== | === Subvolumes === | ||
Create a subvolume | Create a subvolume | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
Remove a subvolume | |||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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=== Snapshots === | === Snapshots === | ||
A snapshot in btrfs is simply a subvolume that shares its data (and metadata) with some other subvolume, using btrfs's | A snapshot in btrfs is simply a subvolume that shares its data (and metadata) with some other subvolume, using btrfs's CoW capabilities. Because of that, there is no special location for snapshots and you can decide where you want to store them. It can be a simple directory inside the root subvolume, or a directory inside a dedicated "snapshots" subvolume. | ||
For this example we are going to store snapshots in a directory <code>/snapshots</code>, that has to be created beforehand with <code>sudo mkdir /snapshots</code> | |||
To take a read-only (<code>-r</code>) snapshot called <code>home_snapshot_202302</code> of the subvolume mounted at <code>/home</code> | |||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
You can also snapshot the root subvolume. But keep in mind | You can also snapshot the root subvolume. But keep in mind that nested subvolumes are '''not''' part of a snapshot. So if you have subvolumes <code>/nix /home</code>, taking a snapshot of <code>/</code> will not include them. | ||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
Make snapshot read-write | Make snapshot read-write againː | ||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
However, changing read-only property of a snapshot in-place may [//lore.kernel.org/linux-btrfs/06e92a0b-e71b-eb21-edb5-9d2a5513b718@gmail.com/ causes issues] with any future incremental send/receive. | However, changing read-only property of a snapshot in-place may [//lore.kernel.org/linux-btrfs/06e92a0b-e71b-eb21-edb5-9d2a5513b718@gmail.com/ causes issues] with any future incremental send/receive. Instead, a read-only snapshot itself (being a simple subvolume) can be snapshotted again as a read-write snapshot like this:<syntaxhighlight lang="bash"> | ||
Instead, a read-only snapshot itself (being a simple subvolume) can be | |||
<syntaxhighlight lang="bash"> | |||
btrfs subvolume snapshot /snapshots/home_snapshot_202302 /snapshots/home_snapshot_202302_rw | btrfs subvolume snapshot /snapshots/home_snapshot_202302 /snapshots/home_snapshot_202302_rw | ||
</syntaxhighlight> | </syntaxhighlight> | ||
Or it can be restored directly to <code>/home</code> straight away like this: | Or it can be restored directly to <code>/home</code> straight away like this: | ||
{{warning|1=this will delete current <code>/home</code> and restore the snapshot! <code>/home</code> must be unmounted for this operation}} | {{warning|1=this will delete the current <code>/home</code> and restore the snapshot! <code>/home</code> must be unmounted for this operation}} | ||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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btrfs subvolume snapshot /snapshots/home_snapshot_202302 /home | btrfs subvolume snapshot /snapshots/home_snapshot_202302 /home | ||
</syntaxhighlight> | </syntaxhighlight> | ||
After this you can mount <code>/home</code> again. | After this you can mount <code>/home</code> again. | ||
=== Transfer snapshot === | === Transfer snapshot === | ||
Sending the snapshot <code>/snapshots/nixos_snapshot_202302</code> compressed to a remote host via ssh at <code>root@192.168.178.110</code> and saving it to a subvolume mounted | Sending the snapshot <code>/snapshots/nixos_snapshot_202302</code> compressed to a remote host via ssh at <code>root@192.168.178.110</code> and saving it to a subvolume mounted on a directory at <code>/mnt/nixos</code> | ||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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</syntaxhighlight> | </syntaxhighlight> | ||
You can use any device | You can use any device partition for your bootloader. Note that this bootloader is unencrypted by default: | ||
<code> | <code>mkfs.vfat -n BOOT "$DISK"p1</code> | ||
mkfs.vfat -n BOOT "$DISK"p1 | |||
</code> | |||
==== Creating | ==== Creating subvolumes ==== | ||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
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Unmount to mount on the subvolumes for the next steps: | Unmount to mount on the subvolumes for the next steps: | ||
<code> | <code>umount /mnt</code> | ||
umount /mnt | |||
</code> | Once the subvolumes have been created, mount them with the desired options. | ||
Example with [https://facebook.github.io/zstd/ Zstandard compression] and noatime: | |||
Example with [https://facebook.github.io/zstd/ | |||
<syntaxhighlight lang="bash"> | <syntaxhighlight lang="bash"> | ||
mount -o subvol=root,compress=zstd,noatime /dev/mapper/enc /mnt | mount -o subvol=root,compress=zstd,noatime /dev/mapper/enc /mnt | ||