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linux:fs:btrfs_as_root [2016/04/20 11:06] – niziaklinux:fs:btrfs_as_root [2017/01/18 21:41] (current) – niziak
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   - btrfs utils version 3.17   - btrfs utils version 3.17
  
- 
-===== Conversion ===== 
-<code bash> 
-fsck -f /dev/sda1 
-fsck -f /dev/sda6 
- 
-btrfs-convert /dev/sda1 
-</code> 
- 
-  Disk usage before conversion: used 1.56GB, free 2.53GB 
-  after conversion: used 1.65GB, free 2.43GB 
- 
-<code bash>btrfs check /dev/sda1</code> 
- 
-===== Update system ===== 
-Mount new root filesystem: 
- 
-<code bash> 
-mount /dev/sda1 /mnt 
-for i in dev dev/pts proc sys ; do mount --bind /$i /mnt/$i ; done 
-chroot /mnt 
-</code> 
- 
-get new UUID of /dev/sda1 using "blkid" 
-mount /dev/sda1 somewhere, go to etc/fstab and update to new UUID: 
- 
-  UUID=a74f5787-aee1-4981-b7e6-fbd3cb6ac919 /               btrfs    defaults 0       1 
- 
-<code bash> 
-update-grub 
-grub-install /dev/sda 
- 
-exit 
- 
-reboot 
-</code> 
- 
-and remove Live CD with Gparted 
- 
-===== rollback to ext FS ===== 
-Rollback to ext2 is possible. There is subvolume ext2_saved on filesystem. 
-<code bash>btrfs subvolume list /</code> 
-To delete backup 
-<code bash>btrfs subvolume delete /ext2_saved</code> 
  
 ===== Update to kernel 4 ===== ===== Update to kernel 4 =====
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 +===== Converting dirs into subvolumes  =====
 +To make backups, snapshots, moving much easier and faster, every directory you want to backup by snapshot should be a subvolume. Also root filesystem should be created in separate subvolume not in btrfs root.
 +
 +To distinguish volumes from directories we will use @ character at beginning of subvolume name. This is Ubuntu naming convention for subvolumes.
 +
 +Proposed subvolumes structure (where / is BTRFS root)
 +  * /@
 +  * /@home
 +  * /@var
 +
 +Mount BTRFS filesystem (BTRFS root) to /mnt/btrfs.
 +
 +==== root ====
 +  * take a snapshot of root volume. Name of snapshot is '@'
 +    * ''btrfs subvolume snapshot /mnt/btrfs @''
 +  * delete files on BTRFS root (/mnt/btrfs)
 +  * make @ subvolume a default root
 +      * update fstab:<file | /etc/fstab>UUID=739e6086-d925-4bdb-94f5-26d8c10dc171 / btrfs defaults,subvol=@</file>
 +    * OR 
 +      * get @ subvolume id ''btrfs subvolume list /mnt/btrfs''
 +      * set default subvolume to use when system is mounted ''btrfs subvolume set-default 256 /mnt/btrfs''
 +
 +
 +==== subdirectories ====
 +  * On BTRFS root create a new subvolume
 +    * ''btrfs subvolume create /mnt/btrfs/@home''
 +  * move files into the new subvolume as if it were a directory
 +    * ''mv /mnt/btrs/@/home/* /mnt/btrfs/@home/''
 +    * ''cp --reflink'' is much faster on BTRFS
 +  * remove old directory
 +    * ''rmdir /mnt/btrfs/@/home''
 +  * update /etc/fstab to mount @home as /home
 +
 +===== fstab ====
 +Do not use ''errors=remount-ro'' option which is not valid for BTRFS.
 +Example working fstab file:
 +<file | /etc/fstab>
 +UUID=ed730508-753e-4a7f-ac1e-bf8646f7bd63 / btrfs defaults,subvol=@,compress=no 0 0
 +UUID=ed730508-753e-4a7f-ac1e-bf8646f7bd63 /var btrfs defaults,subvol=@var,compress=no 0 0
 +UUID=ed730508-753e-4a7f-ac1e-bf8646f7bd63 /var/log btrfs defaults,subvol=@varlog,compress=no 0 0
 +UUID=ed730508-753e-4a7f-ac1e-bf8646f7bd63 /home btrfs defaults,subvol=@home,compress=no 0 0
 +UUID=ed730508-753e-4a7f-ac1e-bf8646f7bd63 /mnt/btrfs btrfs noauto,defaults,subvolid=5,compress=no 0 0
 +</file>
  
 +To prevent systemd to halt system during startup if device is not found (nofail and x-systemd.device-timeout):
 +<file | /etc/fstab>
 +UUID=<the_device_uuid> /mount/point btrfs nofail,x-systemd.device-timeout=10,noatime,compress=lzo,autodefrag 0 0
 +</file>
 +NOTE: do not use autodefrag - it consumes lots of cpu