majiayu000 Process Cleanup
Detect and reap zombie processes using /bin/ps.
Background
A zombie (state Z) is a process that has exited but whose parent hasn't called wait() to collect its exit status. Zombies consume no CPU or memory, but they hold a PID slot and can accumulate. You can't kill a zombie — it's already dead. The only remedies are:
- Signal the parent with
SIGCHLDso it reaps the child - Kill the parent so
init/launchdadopts and reaps the orphan
Important: use ps for process state queries
Always use ps (BSD) for process state queries. If ps is aliased, use /bin/ps to bypass it.
# List zombies
/bin/ps ax -o pid,state,ppid,user,command | awk '$2 ~ /Z/'
# List all processes with state
/bin/ps ax -o pid,state,ppid,etime,args
Usage
Run the helper script to scan for zombies:
# Detect only (default) — list zombie processes
bash scripts/kill-zombies.sh
# Reap zombies — send SIGCHLD to parent processes
bash scripts/kill-zombies.sh --kill
Safety
- Default mode is detect-only — no processes are signaled
- With
--kill, the script sendsSIGCHLDto parent processes (non-destructive nudge to reap) - If a parent ignores
SIGCHLD, the script reports the parent PID — confirm with the user before killing it - Never kill PID 1 (
init/launchd)