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