Process Management & System Services Flashcards

What is the primary purpose of the /proc virtual filesystem in Linux?

Answer: To provide a kernel interface exposing process and system information

/proc is a virtual filesystem that provides a dynamic kernel-to-userspace interface where files represent process and system state.

Which systemctl command lists all units that are currently loaded in memory, including active and failed units?

Answer: systemctl list-units

systemctl list-units displays all units that are loaded into memory; by default it filters to active units, but --all shows everything.

What happens when a process receives SIGTERM (signal 15)?

Answer: It receives a graceful termination request and can perform cleanup before exiting

SIGTERM requests graceful termination, allowing the process to save data, close files, and release resources before exiting.

Which journalctl command filters log output to show only entries from the systemd unit named 'nginx'?

Answer: journalctl -u nginx

journalctl -u filters the systemd journal to display only log entries associated with the specified unit.

Which command changes the scheduling priority of an already-running process with PID 1234 to a nice value of 5?

Answer: renice -n 5 -p 1234

renice adjusts the nice value of running processes specified by PID, user, or group without requiring a restart.

In the crontab entry '30 2 * * 1-5 /usr/local/bin/backup.sh', on which days will the script execute?

Answer: Weekdays only (Monday through Friday)

The day-of-week field '1-5' corresponds to Monday through Friday in cron notation, where 0 and 7 both represent Sunday.

What is a zombie process in Linux?

Answer: A process that has exited but remains in the process table because its parent has not read its exit status

A zombie process has completed execution but stays in the process table as a placeholder until its parent calls wait() to collect its exit status.