Chapter 8: Processes

Exercise: Processes review

Run a small batch of work as a service user on servera: one process that survives a hangup, one that you reprioritise and pause, one that you end cleanly, and a tuned profile for the server.

Processes review

  • Start protected, reprioritised and paused processes as another user.
  • End a process with the right signal.
  • Install tuned and select a profile.

Before you start: reset the servers and complete this chapter's lessons. You work on servera as root (sudo -i); lab start and lab grade run on workstation. The grader looks at what is running at that moment, so leave the processes in place until you have graded.

  1. Create the user worker. As worker, start sleep 7000 in the background so that it survives a closed terminal, with niceness 5.
  2. As worker, start sleep 7001 in the background, change its niceness to 12 and pause it with a signal (it must be stopped, not ended).
  3. As worker, start sleep 7002, then end it with the default signal.
  4. Install tuned, enable and start it, and select the profile throughput-performance.
  5. On workstation, fill in the signal numbers in answers.txt.

Start the exercise

[student@workstation ~]$ lab start sa-proc-review
[student@workstation ~]$ cd ~/sa-proc-review
[student@workstation sa-proc-review]$ ssh student@servera
[student@servera ~]$ sudo -i
[root@servera ~]#

Create worker and start the three processes

[root@servera ~]# useradd -m worker
[root@servera ~]# su - worker -c 'nohup nice -n 5 sleep 7000 >/dev/null 2>&1 &'
[root@servera ~]# su - worker -c 'nohup sleep 7001 >/dev/null 2>&1 &'
[root@servera ~]# su - worker -c 'nohup sleep 7002 >/dev/null 2>&1 &'
[root@servera ~]# pgrep -u worker -a sleep
5101 sleep 7000
5102 sleep 7001
5103 sleep 7002

The nohup and & keep each process alive after su returns.

Reprioritise, pause and end

[root@servera ~]# renice -n 12 -p $(pgrep -f '^sleep 7001
Loading…

  #39;)
5102 (process ID) old priority 0, new priority 12
[root@servera ~]# kill -STOP $(pgrep -f '^sleep 7001
Loading…

  #39;)
[root@servera ~]# kill $(pgrep -f '^sleep 7002
Loading…

  #39;)
[root@servera ~]# ps -o pid,user,ni,stat,cmd -C sleep
    PID USER      NI STAT CMD
   5101 worker     5 SN   sleep 7000
   5102 worker    12 TN   sleep 7001

STAT T shows the paused process; 7002 is gone. Using pgrep -f '^sleep 7001

Loading…

#39; matches the whole command line exactly, so it cannot hit a different sleep.

Install tuned and choose the profile

[root@servera ~]# dnf install -y tuned
...output omitted...
[root@servera ~]# systemctl enable --now tuned
[root@servera ~]# tuned-adm profile throughput-performance
[root@servera ~]# tuned-adm active
Current active profile: throughput-performance

Record the signal numbers and grade

Leave servera, then on workstation edit answers.txt (use kill -l to look the numbers up) and grade:

Check your work with lab grade sa-proc-review, then put the exercise away with lab finish sa-proc-review.