Process Management & System Services Flashcards

Which command displays all running processes in a hierarchical tree format showing parent-child relationships?

Answer: pstree

pstree displays processes in a tree structure that clearly shows parent-child relationships between processes.

What signal number is used to forcefully terminate a process, bypassing any cleanup handlers?

Answer: 9 (SIGKILL)

SIGKILL (signal 9) immediately terminates a process at the kernel level without allowing the process to perform any cleanup.

Which systemctl command enables a service to start automatically at system boot?

Answer: systemctl enable

systemctl enable creates the necessary symlinks so the service is started during the appropriate boot target automatically.

What is the effect of running a process with a higher nice value such as 'nice +19'?

Answer: The process receives lower CPU scheduling priority

Higher nice values (up to +19) indicate lower scheduling priority, meaning the process yields CPU time to other processes.

Which file is the system-wide crontab that includes a username field for specifying which user runs each job?

Answer: /etc/crontab

/etc/crontab is the system-wide crontab file with an extra username field, distinguishing it from per-user crontabs.

Which command shows the current runtime status, recent log entries, and PID of a systemd-managed service?

Answer: systemctl status

systemctl status displays the service state, active PID, recent journal entries, and other runtime details in a concise summary.

Which command sends a signal to all processes matching a given name without requiring the PID?

Answer: pkill

pkill sends signals to processes based on their name or other attributes, eliminating the need to look up PIDs first.