Comment 2 for bug 1333773

after executing

$sudo apt-get remove btrfs-tools

Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  btrfs-tools
0 upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
After this operation, 2,508 kB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 247597 files and directories currently installed.)
Removing btrfs-tools (3.12-1) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for man-db (2.6.7.1-1) ...
Processing triggers for initramfs-tools (0.103ubuntu4.2) ...
update-initramfs: Generating /boot/initrd.img-3.13.0-32-generic
W: TMPDIR is mounted noexec, will not cache run scripts.
Processing triggers for libc-bin (2.19-0ubuntu6) ...

in the last third line it updates initramfs

Any way I used $ update-initramfs -u, it had no effect.