CODEWITHSUNDEEP
cgroups
doraemon
doraemon

Reputation: 2512

move a process to a new cgroup in cgroup v2

I am using cgroup v2, and I want to create a new cgroup and let an existing process use that cgroup. I did the following but not successful. What is wrong here?

    $ cd /sys/fs/cgroup
    $ sudo mkdir g1
    $ sudo chown -R name.name g1  # name is the user name
    $ echo 4000 | tee g1/cgroup.procs
    tee: cgroup.procs: Permission denied

    $ echo 4000 | sudo tee g1/cgroup.procs
    # this works

Why can't I write to cgroup.procs even I am the owner of all the controller interface?

Upvotes: 2

Views: 2033

Answers (1)

jdi
jdi

Reputation: 92627

This caught me out as well. A rule of cgroup v2 is that in order to move a pid from a source to a target group, the current user must have write permissions to the common ancestor of source and target. Your echo command is likely running in a user.slice, which you can verify if you check the cgroup of your current shell:

cat /proc/self/cgroup
# 0::/user.slice/user-1234.slice/session-5124.scope

That means the common ancestor group is "/". The reason the sudo works is because it is running as root to write the pid, which has permissions to /sys/fs/cgroup/cgroup.procs

And therefore, in order for your current user to have the same capability, you would need write permissions opened up to /sys/fs/cgroup/cgroup.procs, which I know, kind of sucks.

Upvotes: 1

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