LXC, Cgroups and weird numbers
Running docker inside of an LXC container is not as trivial as I
expected. Here I would like to clarify one of the many things that
puzzled me along the way. The enigmatic configuration lines in the lxc
configuration file (
lxc.cgroup.devices.allow = b 7:* rwm
With some effort I figured out the
b is a block device.
character device (no idea what those are at the moment) and
‘all’ or both.
m are relatively easy too; read, write and
mknod (make node I guess).
What remained unclear were the digits. In the man page they are refert to as \‘major/minor’.
After some digging I found
which lists the devices. There I couldn’t find the devices Docker was
complaining missing. The command
lxc-cgroup eventually cleared
everything up. This command can be used to add devices to a running
container. Where I should have been looking was
/dev. The numbers
there can be used in the container configuration file.
Helpful where the posts of Stéphane Graber on LXC.
Hope this helps someone.