How to access the container's name inside the container?

[Zhenshan-Jin]

I am wondering if it is possible to access the container's name inside the container?

For example, I create a container with

sudo runc run MY_CONTAINER

is it possible to access MY_CONTAINER inside the container?

The use case is that in each of the created container, I will create a unix socket so that the server in the container coud be called by the outside.

Any help is appreciated : )

[cyphar]

There is no guaranteed way of getting that information, since the container name is just used by runc for managing its containers.

However (unless the container is configured with custom cgroup configuration) you can find the name of the container as the final component of the cgroup pathnames in /proc/self/cgroup inside the container:

% runc run -b bundle ctr
# cat /proc/self/cgroup
0::/user.slice/user-1000.slice/ctr

(On cgroupv1 systems there will be more cgroup entries.) Please note this is not guaranteed -- it is possible to specify a custom cgroup path which will hide this information.

[Zhenshan-Jin]

Thank you @cyphar. I tried the steps but when I do cat /proc/self/cgroup, I only see 0:: without other information. Maybe I missed some steps ?

[cyphar]

If you're using cgroup namespaces then you won't be able to see anything.

[Zhenshan-Jin]

Thank you! @cyphar

[lifubang]

How about passing it through an env variable in “config.json”?

[cyphar]

config.json doesn't have any variable substitution or any other similar feature you'd need to do that. runc is intended to be used as part of a container manager -- if you need this feature, the simplest solution would be to write a script to be written which fills in the relevant environment variable using jq before spawning the container.