===== Ext2 Conversion =====
**btrfs-convert** is not well tested and recommended. Especially for Kernels > 4.0.
Personaly it generates errors on BTRFS which will appear after some time.
Better way is to use additional temporary disc to move data to newly created BTRFS.
<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>
mount /boot  # if on separate partition
update-grub
grub-install /dev/sda
umount /boot

exit  # from chrooted env

reboot
</code>

and remove Live CD / USB with Gparted

===== rollback to ext2 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>