I have a btrfs partition (mounted on /srv) on my host system with a subvolume (old). I would like to manage it from a docker container (I have launched it with -v /srv:/srv).

While I'm perfectly able to create a snapshot of it, I can not list other subvolume and/or delete them:

user@host:~$ docker exec -ti jenkins-slave bash
root@a5496f6bd14b:~# btrfs subvolume snapshot /srv/old /srv/new
Create a snapshot of '/srv/old' in '/srv/new'
root@a5496f6bd14b:~# ls /srv
new old
root@a5496f6bd14b:~# btrfs subvolume delete /srv/new
Delete subvolume (no-commit): '/srv/new'
ERROR: cannot delete '/srv/new': Operation not permitted
root@a5496f6bd14b:~# btrfs subvolume list /srv/new
ERROR: can't perform the search - Operation not permitted
root@a5496f6bd14b:~# ls /srv
new old

While I'm still able to do it from the host system.


It appears this behavior is due to a Docker configuration setting.

I was able to get this to work by adding the "Linux Capability" CAP_SYS_ADMIN at Docker runtime.

docker run -d -t --cap-add SYS_ADMIN -v /mnt.btrfs:/mnt.btrfs debbtrfs

Perform a range of system administration operations including: quotactl(2), mount(2), umount(2), swapon(2), swapoff(2), sethostname(2), and setdomainname(2)

There are a whole series of other "Linux Capabilities", including a verbose description of CAP_SYS_ADMIN which can be found in the man pages:

$ man 7 capabilities

Which of these capabilities are Docker defaults, and which can be added/dropped can be found here, under "Runtime privilege and Linux capabilities":

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.