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BTRFS

Get profile info

To see how BTRFS partition is configured, use the following command:

btrfs fi usage /mnt/foo

Convert single setup to DUP

This is useful if you have only one physical disk and you still want data redundancy to some degree:

btrfs balance start -v -dconvert=dup,soft /path/to/mountpoint

To check and fix data on a disk with DUP profile, simply run btrfs scrub:

btrfs scrub start -B /path/to/mountpoint

Convert single setup to RAID1

Based on https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices#Conversion

Assuming your root btrfs subvolume on your primary disk (/dev/sda) is mounted on / and you want to add a btrfs partition (/dev/mapper/foo-root) as RAID1, which is on an LVM (named: foo) partition on a LUKS partition (/dev/sdb2).

FINISH THIS HOWTO'S TESTS

Setup to automount your LUKS partition first:

# mkdir /etc/luks-keys
# dd if=/dev/urandom of=/etc/luks-keys/sdb2.key bs=512 count=8
# chmod 600 /etc/luks-keys/*
# cryptsetup -v luksAddKey /dev/sdb2 /etc/luks-keys/sdb2.key 
Enter any existing passphrase: 
Key slot 0 unlocked.
Key slot 1 created.
Command successful.
# blkid | awk '$1 == "/dev/sdb2:" {print $2}'
# echo "foo_crypt UUID=the-above-uuid-of-sdb2 /etc/luks-keys/sdb2.key luks" >> /etc/crypttab
# update-initramfs -u  # TODO: TEST THIS!!!

Add the partition as RAID1:

cryptsetup open /dev/sdb2 foo_crypt
lvscan 
btrfs device add /dev/mapper/foo-root / ##### <- warning at the moment this will fail with READONLY filesystem
btrfs balance start -dconvert=raid1 -mconvert=raid1 /

Monitoring Disk Health

See https://github.com/ceremcem/monitor-btrfs-disk

Hotplugging SATA Disk

Enable "Hot Plug" option in BIOS for each SATA port. (https://unix.stackexchange.com/questions/368958/sata-hotplug-doesnt-work)

Restoring Files

btrfs restore -s /dev/mapper/foo-root --path-regex ^(|/rootfs.bak(|/var(|/lib(|/couchdb(|/shards(|/60000000-7fffffff(|/.*)))))))$ /mnt/backup-disk/hello/
  • -s: Enable subvolumes
  • rootfs.bak: The subvolume we want to search inside.