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Added examples to btrfs' KB

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Michele Cereda
2022-05-17 16:33:10 +02:00
parent 2f0f329c46
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knowledge base/btrfs.md
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@@ -3,41 +3,111 @@
## TL;DR
```sh
# create a volume with single metadata and double data blocks (useless but good example)
sudo mkfs.btrfs --metadata single --data dup /dev/sdb
# Create a volume with single metadata and double data blocks
# Useless in practice but a good example.
mkfs.btrfs --metadata single --data dup /dev/sdb
# sparse a volume on multiple devices
sudo mkfs.btrfs --label data /dev/sd{a,c,d,e,f,g} --force
echo "LABEL=data /mnt/data btrfs compress=zstd 0 0" | sudo tee -a /etc/fstab
# Sparse a volume on multiple devices.
mkfs.btrfs --label data /dev/sd{a,c,d,e,f,g} --force \
&& echo "LABEL=data /mnt/data btrfs compress=zstd 0 0"
| tee -a /etc/fstab
# create a readonly snapshot of a subvolume
sudo btrfs subvolume snapshot -r /mnt/btrfs-volume/data /mnt/btrfs-volume/snapshot
# List all btrfs file systems.
btrfs filesystem show
# delete a subvolume
sudo btrfs subvolume delete --commit-each /mnt/btrfs-volume/data
# Show detailed `df` analogue for a filesystem.
btrfs filesystem df path/to/volume
# deduplicate a volume's blocks
sudo duperemove -Adrh --hashfile=/tmp/duperemove.hash /mnt/volume1 /mnt volume2
sudo jdupes --dedupe --recurse --softabort /mnt/btrfs-volume
# Resize online volumes.
# -2g decreases, +2g increases.
btrfs filesystem resize -2g path/to/volume
btrfs filesystem resize max path/to/volume
# send and receive snapshots
sudo btrfs send /source-dir/.snapshots/snapshot | sudo btrfs receive /dest-dir/.snapshots/
# Add new devices to a filesystem.
btrfs device add /dev/sdf /mnt
# get the properties of a subvolume/filesystem/inode/device
# Remove devices from a filesystem.
btrfs device delete missing /mnt
# List subvolumes.
btrfs subvolume list /mnt
# Create subvolumes.
btrfs subvolume create /mnt/subvolume
# Create a readonly snapshot of a subvolume.
sudo btrfs subvolume snapshot -r /mnt/volume/data /mnt/volume/snapshot
# Mount subvolumes without mounting their main filesystem.
mount -o subvol=sv1 /dev/sdb /mnt
# Delete a subvolume.
sudo btrfs subvolume delete --commit-each /mnt/volume/data
# Deduplicate a volume's blocks.
sudo duperemove -Adrh --hashfile=/tmp/dr.hash /mnt/volume1 /media volume2
sudo jdupes --dedupe -rZ /mnt/volume1 /media volume2
# Send and receive snapshots.
sudo btrfs send /source/.snapshots/snap \
| sudo btrfs receive /destination/.snapshots/
# Show the properties of a subvolume/filesystem/inode/device.
btrfs property get -ts /path/to/subvolume
btrfs property get -tf /path/to/filesystem
btrfs property get -ti /path/to/inode
btrfs property get -td /path/to/device
btrfs property get /path/to/autoselected/type/of/resource
# change a subvolume to ro on the fly
# Change a subvolume to RO on the fly.
btrfs property set -ts /path/to/subvolume ro true
# get info about a path
# Show a volume's information.
sudo btrfs subvolume show /path/to/subvolume
# check the compress ratio of a compressed path
sudo compsize /mnt/btrfs-volume
# Check the compress ratio of a compressed volume.
sudo compsize /mnt/volume
# Show the status of a running or paused balance operation.
sudo btrfs balance status path/to/filesystem
# Balance all block groups.
# Slow: rewrites all blocks in filesystem.
sudo btrfs balance start path/to/filesystem
sudo btrfs balance start path/to/filesystem --bg --enqueue
# Balance data block groups which are less than 15% utilized.
# Run the operation in the background
sudo btrfs balance start --bg -dusage=15 path/to/filesystem
# Balance a max of 10 metadata chunks with less than 20% utilization and at
# least 1 chunk on a given device 'devid'.
# Get the device's devid with `btrfs filesystem show`.
sudo btrfs balance start -musage=20,limit=10,devid=devid path/to/filesystem
# Convert data blocks to the raid6 profile, and metadata to raid1c3.
sudo btrfs balance start -dconvert=raid6 -mconvert=raid1c3 path/to/filesystem
# Convert data blocks to raid1 skipping already converted chunks.
# Useful after a previous cancelled conversion operation.
sudo btrfs balance start -dconvert=raid1,soft path/to/filesystem
# Cancel, pause or resume a running or paused balance operation.
sudo btrfs balance cancel path/to/filesystem
sudo btrfs balance pause path/to/filesystem
sudo btrfs balance resume path/to/filesystem
# Enable quota.
sudo btrfs quota enable path/to/subvolume
# Show quota.
sudo btrfs qgroup show path/to/subvolume
# Convert ext3/ext4 to btrfs.
btrfs-convert /dev/sdb1
# Convert btrfs to ext3/ext4.
btrfs-convert -r /dev/sdb1
```
## Check differences between 2 snapshots
@@ -56,13 +126,16 @@ sudo snapper -c config diff 445..446
- [Gentoo wiki]
- [Snapper]
[gentoo wiki]: https://wiki.gentoo.org/wiki/Btrfs
[snapper]: snapper.md
## Sources
- [cheat.sh]
- [does btrfs have an efficient way to compare snapshots?]
- [determine if a btrfs subvolume is read-only]
[snapper]: snapper.md
[cheat.sh]: https://cheat.sh/btrfs
[gentoo wiki]: https://wiki.gentoo.org/wiki/Btrfs
[determine if a btrfs subvolume is read-only]: https://unix.stackexchange.com/questions/375645/determine-if-btrfs-subvolume-is-read-only#375646
[does btrfs have an efficient way to compare snapshots?]: https://serverfault.com/questions/399894/does-btrfs-have-an-efficient-way-to-compare-snapshots#419444