====== btrfs ======
Status: 
  * https://btrfs.readthedocs.io/en/stable/Status.html
  * https://silvenga.com/posts/btrfs-and-lessons-learned/

Paket: 
  * Debian: ''btrfs-progs btrfsmaintenance''

===== Dateisystem anlegen =====
ext? nach btrfs konvertieren:
  man btrfs-convert

oder besser:

Dateisystem anlegen und mounten:
  mkfs.btrfs /dev/sda2
  btrfs filesystem show
  mkdir /mnt/btrfs
  mount /dev/sda2 /mnt/btrfs
  cd /mnt/btrfs

Beispieldaten hinein kopieren:
  time cp -a /usr/share/ .

===== Daten komprimieren =====
Daten komprimieren: (( https://github.com/systemd/systemd/issues/9112 ))
  btrfs filesystem df -h .
-> ''Data, single: total=2.01GiB, used=1.53GiB''
  btrfs filesystem defragment -czstd -r share/
  btrfs filesystem df -h .
-> ''Data, single: total=3.01GiB, used=740.17MiB''
  btrfs filesystem usage .
===== Subvolumes =====
Informationen über das top-level Subvolume anzeigen:
  btrfs subvolume show .
-> ''Subvolume ID'': 5

  btrfs subvolume list .
-> noch keine Subvolumes

Subvolume anlegen und Daten hinein verschieben:
  btrfs subvolume create subvol1
  btrfs subvolume list .
  btrfs subvolume show subvol1
-> ''Subvolume ID'': 256
-> ''Parent ID'': 5
  time mv ./share/ ./subvol1/
  
Subvolume umbenennen:
  mv subvol1/ subvol2

Subvolume (erneut) mounten:
  mkdir /mnt/subvol2
  mount -o subvol=/subvol2 /dev/sda2 /mnt/subvol2  

===== Snapshots =====
Snapshot erstellen:
  time btrfs subvolume snapshot subvol2 snap1
  btrfs subvolume list .
  btrfs subvolume show snap1
-> Subvolume ID: 257
-> Parent ID: 5

Read-only Snapshot erstellen:
  btrfs subvolume snapshot -r subvol2 snap_ro1

  btrfs filesystem df -h .
  btrfs filesystem du -s --human-readable .
  du -sh .
  du -shx .
  btrfs filesystem du -s --human-readable subvol2
  du -sh subvol2
  btrfs filesystem du -s --human-readable snap1

===== Subvolume zum default-Volume machen =====
  cd /mnt/btrfs
Snapshot des root-Volumes erstellen:
  btrfs subvolume snapshot . 2025011300
Daten (nicht Subvolumes!) aus root-Volume löschen:
  ls 2025011300 | xargs echo rm -rf
-> prüfen, das da keine Verzeichnisse mit verschachtelten Subvolumes enthalten sind
  ls 2025011300 | xargs rm -rf
  btrfs subvolume show 2025011300
-> ''Subvolume ID'' kopieren, z.B. 258
  btrfs subvolume set-default 256 2025011300/

testen:
  ls
  cd ..
  umount btrfs
  mount btrfs
  ls btrfs

===== Top-Subvolume mounten =====
  mkdir /mnt/btrfs
  mount -o subvolid=5,subvol=/ /dev/sda2 /mnt/btrfs
<file txt /etc/fstab>
UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx /mnt/btrfs btrfs noauto,subvolid=5,subvol=/ 0 0
</file>

===== Datenträger tauschen =====
  btrfs device usage .
  btrfs device add /dev/sda6 .
  btrfs device usage .
  btrfs device del /dev/sda2 .
  btrfs device usage .

====== BTRFS bei SuSE ======
++++ SuSE default root layout |
SuSE default:

  mkfs.btrfs ${BOOT_DEVICE}2
  uuid=$(lsblk -n -o uuid ${BOOT_DEVICE}2)

  mkdir $target
  mount UUID="$uuid" $target || exit

  btrfs subvolume create ${target%/}/@
  btrfs subvolume create ${target%/}/@/.snapshots
  mkdir -p               ${target%/}/@/.snapshots/1
  btrfs subvolume create ${target%/}/@/.snapshots/1/snapshot
  mkdir -p               ${target%/}/@/boot/grub2
  btrfs subvolume create ${target%/}/@/boot/grub2/i386-pc
  btrfs subvolume create ${target%/}/@/boot/grub2/x86_64-efi
  btrfs subvolume create ${target%/}/@/opt
  btrfs subvolume create ${target%/}/@/srv
  btrfs subvolume create ${target%/}/@/tmp
  mkdir -p               ${target%/}/@/usr
  btrfs subvolume create ${target%/}/@/usr/local
  mkdir -p               ${target%/}/@/var
  btrfs subvolume create ${target%/}/@/var/crash
  mkdir -p               ${target%/}/@/var/lib/libvirt
  btrfs subvolume create ${target%/}/@/var/lib/libvirt/images
  btrfs subvolume create ${target%/}/@/var/lib/mailman
  btrfs subvolume create ${target%/}/@/var/lib/mariadb
  btrfs subvolume create ${target%/}/@/var/lib/mysql
  btrfs subvolume create ${target%/}/@/var/lib/named
  btrfs subvolume create ${target%/}/@/var/lib/pgsql
  btrfs subvolume create ${target%/}/@/var/log
  btrfs subvolume create ${target%/}/@/var/opt
  btrfs subvolume create ${target%/}/@/var/spool
  btrfs subvolume create ${target%/}/@/var/tmp

  subvolid=$(btrfs subvolume show $target/@/.snapshots/1/snapshot | sed -rn 's/.*Object ID:\s+//p')
  btrfs subvolume set-default "$subvolid" "$target"
++++