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147 lines
4.4 KiB
Markdown
147 lines
4.4 KiB
Markdown
# BTRFS
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## TL;DR
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```sh
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# Create a volume with single metadata and double data blocks
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# Useless in practice but a good example.
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sudo mkfs.btrfs --metadata single --data dup /dev/sdb
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# Sparse a volume on multiple devices.
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sudo mkfs.btrfs --label data /dev/sd{a,c,d,e,f,g} --force \
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&& echo "LABEL=data /mnt/data btrfs compress=zstd 0 0"
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| tee -a /etc/fstab
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# List all btrfs file systems.
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sudo btrfs filesystem show
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# Show detailed `df` analogue for a filesystem.
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sudo btrfs filesystem df path/to/filesystem
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# Give more details about usage.
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sudo btrfs filesystem usage path/to/filesystem
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# Resize online volumes.
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# -2g decreases, +2g increases.
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sudo btrfs filesystem resize -2g path/to/volume
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sudo btrfs filesystem resize max path/to/volume
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# Add new devices to a filesystem.
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sudo btrfs device add /dev/sdf /mnt
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# Remove devices from a filesystem.
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sudo btrfs device delete missing /mnt
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# List subvolumes.
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sudo btrfs subvolume list /mnt
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# Create subvolumes.
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btrfs subvolume create ~/subvolume
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sudo btrfs subvolume create /mnt/subvolume
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# Create a readonly snapshot of a subvolume.
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btrfs subvolume snapshot ~/subvolume ~/snapshot
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sudo btrfs subvolume snapshot -r /mnt/volume/subvolume /mnt/volume/snapshot
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# Mount subvolumes without mounting their main filesystem.
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sudo mount -o subvol=sv1 /dev/sdb /mnt
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# Delete a subvolume.
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sudo btrfs subvolume delete --commit-each /mnt/volume/subvolume
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# Deduplicate a volume's blocks.
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sudo duperemove -Adrh --hashfile=/tmp/dr.hash /mnt/volume1 /media volume2
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sudo jdupes --dedupe -rZ /mnt/volume1 /media volume2
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# Send and receive snapshots.
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sudo btrfs send /source/.snapshots/snap \
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| sudo btrfs receive /destination/.snapshots/
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# Show the properties of a subvolume/filesystem/inode/device.
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btrfs property get -ts /path/to/subvolume
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btrfs property get -tf /path/to/filesystem
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btrfs property get -ti /path/to/inode
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btrfs property get -td /path/to/device
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btrfs property get /path/to/autoselected/type/of/resource
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# Change a subvolume to RO on the fly.
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btrfs property set -ts /path/to/subvolume ro true
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# Show a volume's information.
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sudo btrfs subvolume show /path/to/subvolume
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# Check the compress ratio of a compressed volume.
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sudo compsize /mnt/volume
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# Show the status of a running or paused balance operation.
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sudo btrfs balance status path/to/filesystem
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# Balance all block groups.
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# Slow: rewrites all blocks in filesystem.
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sudo btrfs balance start path/to/filesystem
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sudo btrfs balance start path/to/filesystem --bg --enqueue
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# Balance data block groups which are less than 15% utilized.
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# Run the operation in the background
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sudo btrfs balance start --bg -dusage=15 path/to/filesystem
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# Balance a max of 10 metadata chunks with less than 20% utilization and at
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# least 1 chunk on a given device 'devid'.
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# Get the device's devid with `btrfs filesystem show`.
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sudo btrfs balance start -musage=20,limit=10,devid=devid path/to/filesystem
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# Convert data blocks to the raid6 profile, and metadata to raid1c3.
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sudo btrfs balance start -dconvert=raid6 -mconvert=raid1c3 path/to/filesystem
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# Convert data blocks to raid1 skipping already converted chunks.
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# Useful after a previous cancelled conversion operation.
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sudo btrfs balance start -dconvert=raid1,soft path/to/filesystem
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# Cancel, pause or resume a running or paused balance operation.
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sudo btrfs balance cancel path/to/filesystem
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sudo btrfs balance pause path/to/filesystem
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sudo btrfs balance resume path/to/filesystem
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# Enable quota.
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sudo btrfs quota enable path/to/subvolume
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# Show quota.
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sudo btrfs qgroup show path/to/subvolume
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# Convert ext3/ext4 to btrfs.
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btrfs-convert /dev/sdb1
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# Convert btrfs to ext3/ext4.
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btrfs-convert -r /dev/sdb1
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```
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## Check differences between 2 snapshots
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See also [snapper].
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```sh
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sudo btrfs send --no-data -p /old/snapshot /new/snapshot | sudo btrfs receive --dump
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# requires you to be using snapper for your snapshots
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sudo snapper -c config diff 445..446
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```
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## Further readings
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- [Gentoo wiki]
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- [Snapper]
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## Sources
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- [cheat.sh]
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- [does btrfs have an efficient way to compare snapshots?]
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- [determine if a btrfs subvolume is read-only]
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[snapper]: snapper.md
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[cheat.sh]: https://cheat.sh/btrfs
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[gentoo wiki]: https://wiki.gentoo.org/wiki/Btrfs
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[determine if a btrfs subvolume is read-only]: https://unix.stackexchange.com/questions/375645/determine-if-btrfs-subvolume-is-read-only#375646
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[does btrfs have an efficient way to compare snapshots?]: https://serverfault.com/questions/399894/does-btrfs-have-an-efficient-way-to-compare-snapshots#419444
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