CompTIA Linux+ (XK0-006)TroubleshootingMedium
An administrator investigates a server with poor responsiveness and runs `top`, noticing several processes in state `Z` that persist over many refresh cycles. What is the correct explanation and remedy for these processes?
- AThey are actively consuming CPU cycles; killing them with kill -9 immediately frees resources
- BThey have already terminated but their exit status hasn't been reaped by the parent process; killing or restarting the parent clears them
- CThey indicate a kernel panic is imminent and the server must be rebooted immediately
- DThey are waiting on disk I/O; increasing swap space will clear them
Show answer & explanationAnswer & explanation
Correct answer: B. They have already terminated but their exit status hasn't been reaped by the parent process; killing or restarting the parent clears them
A zombie (Z state) process has finished execution but still holds an entry in the process table until its parent calls wait() to read its exit status. Zombies consume no CPU or memory beyond the table entry; the fix is to have the parent reap them, often by restarting or killing the parent process, since the zombie itself cannot be killed directly.
Why the other options are wrong
- A. Zombies use no CPU cycles, and kill -9 has no effect on an already-dead process.
- C. A few zombie processes are common and do not indicate an impending kernel panic.
- D. Zombies are not waiting on I/O; swap space is unrelated to process reaping.
Zombie (Defunct) Processes
A zombie is a terminated process whose exit status has not yet been collected by its parent via wait(), leaving a process table entry until reaped.
- Shown as state Z in top/ps
- Cannot be killed directly since it's already dead
- Remedy: fix or restart the parent process so it reaps children
Memory trick: A zombie is dead but its paperwork isn't filed until the parent signs off.