linuxexpert-practice-labs/labs/ubuntu-server/4-1-processes-and-services/README.md

Ubuntu Server 4.1: Processes and services

A service's processes and who they run as, niceness, and signals.

Before you start

The lab doesn't install anything: installing nginx is part of task 1. Do task 2 as your own user, not root, and check before the sleep ends, about 16 minutes after you start it. Nothing here lasts over a reboot, so don't reboot before you check. Write answers to the files in /root/lab-answers/.

Tasks

1. Install nginx. Find its master process and its workers, the user each runs as, and the unit they belong to. Write the master's user to /root/lab-answers/1-master, the workers' user to /root/lab-answers/1-workers, and the unit to /root/lab-answers/1-unit.
2. As your own user, start sleep 1000 in the background with niceness 5, then change it to 12, then try to set it back to 5 without sudo (that fails with "Permission denied").
3. Make nginx reread its configuration with a signal rather than systemctl: the master keeps its PID and the workers get new ones. Then stop it so that it stays stopped.

Hints

• ps -C nginx -o pid,ppid,user,unit,cmd, pgrep -a nginx, systemctl status nginx.
• nice -n 5 sleep 1000 &, renice -n 12 -p PID, ps -o ni= -p PID.
• sudo kill -HUP of the master PID (systemctl show -p MainPID nginx), then pgrep -a nginx; sudo systemctl stop nginx, systemctl is-active nginx.