Manuel Ganter
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
1.2 KiB
1.2 KiB
Identify Process Cgroup by PID
TL;DR
You can identify a process's cgroup by reading /proc/<PID>/cgroup.
Outcome
Multiple methods to find which cgroup a process belongs to using its PID.
Conversation
Question: Can I identify the process's cgroup by having its PID?
Answer: Yes, here are the main methods:
Method 1: Read /proc/<PID>/cgroup
cat /proc/<PID>/cgroup
This shows all cgroup controllers the process belongs to. For example:
12:blkio:/user.slice
11:memory:/user.slice/user-1000.slice
...
0::/user.slice/user-1000.slice/session-1.scope
Method 2: Using ps with format options
ps -o pid,cgroup -p <PID>
Method 3: Using systemd-cgls
If you're on a systemd system:
systemd-cgls --unit <unit-name>
# or to see the whole tree
systemd-cgls
Method 4: Check cgroup v2 unified hierarchy
On cgroup v2 systems, check:
cat /proc/<PID>/cgroup
# Output will look like: 0::/user.slice/user-1000.slice/session-1.scope
The path after :: is the cgroup path under /sys/fs/cgroup/.
Quick one-liner
cat /proc/self/cgroup # For current shell
cat /proc/$$/cgroup # Also current shell
cat /proc/1234/cgroup # For PID 1234