In the event of a permissions denied error, py-spy attempts to see if you are running in a docker container and if so displays an error message to make sure you've enabled SYS_PTRACE:
This works by checking the contents of /proc/self/cgroups - but only works with cgroups v1, and in cgroups v2 this fails since this file only contains 0::/ , and no message is displayed.
In the event of a permissions denied error, py-spy attempts to see if you are running in a docker container and if so displays an error message to make sure you've enabled SYS_PTRACE:
https://github.com/benfred/py-spy/blob/492b41c07c26c6edbe061da942c8dae41d86091e/src/main.rs#L474C1-L486
This works by checking the contents of /proc/self/cgroups - but only works with cgroups v1, and in cgroups v2 this fails since this file only contains
0::/, and no message is displayed.One idea is to directly test for the SYS_PTRACE capability https://github.com/benfred/py-spy/pull/459#discussion_r734874566
According to https://stackoverflow.com/questions/68816329/how-to-get-docker-container-id-from-within-the-container-with-cgroup-v2 , we can also probably inspect /proc/self/mountinfo to figure out if we're running in docker.
Another option is to look for the presence of a
/.dockerenvfile - though this isn't recommended https://github.com/moby/moby/issues/18355#issuecomment-220484748