docker startup failure due to cgroups misconfiguration

Question

I am trying to start docker on a Centos-6-ish OS. It is failing for cgroups reasons. I believe the mount is correctly structured (docker recommends https://github.com/tianon/cgroupfs-mount/blob/master/cgroupfs-mount) so the final error message is unclear to me.

thrashin(bash):/base/data/tmp# ./cgroups-mount

thrashin(bash):/base/data/tmp# grep cgroup /proc/mounts
cgroup /sys/fs/cgroup tmpfs rw,relatime,mode=755 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,relatime,cpuset 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,relatime,blkio 0 0

thrashin(bash):/base/data/tmp# cat /proc/cgroups
#subsys_name    hierarchy       num_cgroups     enabled
cpuset  4       1       1
blkio   5       1       1

thrashin(bash):/base/data/tmp# dockerd &
[1] 7201
thrashin(bash):/base/data/tmp# WARN[0000] could not change group /var/run/docker.sock to docker: group docker not found
INFO[0000] libcontainerd: new containerd process, pid: 7214
WARN[0000] containerd: low RLIMIT_NOFILE changing to max  current=1024 max=4096
WARN[0001] unable to modify root key limit, number of containers could be limited by this quota: open /proc/sys/kernel/keys/root_maxkeys: no such file or directory
INFO[0001] [graphdriver] using prior storage driver: overlay2
INFO[0001] Graph migration to content-addressability took 0.00 seconds
WARN[0001] Your kernel does not support cgroup memory limit
WARN[0001] Unable to find cpu cgroup in mounts
WARN[0001] Your kernel does not support cgroup blkio throttle.read_bps_device
WARN[0001] Your kernel does not support cgroup blkio throttle.write_bps_device
WARN[0001] Your kernel does not support cgroup blkio throttle.read_iops_device
WARN[0001] Your kernel does not support cgroup blkio throttle.write_iops_device
WARN[0001] mountpoint for pids not found
Error starting daemon: Devices cgroup isn't mounted
^C
[1]+  Exit 1                  dockerd

cgroup device is mounted. Is the failure due to the warning that the cpu subsystem is not provided? If so, how do I provide this? Is this a kernel build option?

Answer 1

Solved this by rebuilding the kernel to provide the cpu cgroup subsystem.

It's not immediately clear that that should be the solution to solving

Error starting daemon: Devices cgroup isn't mounted

Given that there are other cgroup warnings, aside from the warning about the cpu subsystem.