RHCSA Rapid Track

Instructions

1. Use the ssh command to log in to the servera machine as the student user.

   [student@workstation ~]$ ssh student@servera
   ...output omitted...
   [student@servera ~]$

2. Determine the number of CPU cores on the servera machine, and then start two instances of the sha1sum /dev/zero & command for each core.

   1. Use the grep command to parse the number of existing virtual processors (CPU cores) from the /proc/cpuinfo file.

      [student@servera ~]$ grep -c '^processor' /proc/cpuinfo
      2

   2. Use a looping command to start multiple instances of the sha1sum /dev/zero & command. Start two instances for each virtual processor that was indicated in the previous step. In this example, a for loop creates four instances. The PID values in your output might vary from the example.

      [student@servera ~]$ for i in {1..4}; do sha1sum /dev/zero & done
      [1] 1132
      [2] 1133
      [3] 1134
      [4] 1135

3. Verify that the background jobs are running for each of the sha1sum processes.

   [student@servera ~]$ jobs
   [1]   Running                 sha1sum /dev/zero &
   [2]   Running                 sha1sum /dev/zero &
   [3]-  Running                 sha1sum /dev/zero &
   [4]+  Running                 sha1sum /dev/zero &

4. Use the ps and pgrep commands to display the percentage of CPU usage for each sha1sum process.

   [student@servera ~]$ ps u $(pgrep sha1sum)
   USER      PID %CPU %MEM    VSZ   RSS TTY     STAT START   TIME COMMAND
   student  1132 49.6  0.1 225336  2288 pts/0   R    11:40   2:40 sha1sum /dev/zero
   student  1133 49.6  0.1 225336  2296 pts/0   R    11:40   2:40 sha1sum /dev/zero
   student  1134 49.6  0.1 225336  2264 pts/0   R    11:40   2:40 sha1sum /dev/zero
   student  1135 49.6  0.1 225336  2280 pts/0   R    11:40   2:40 sha1sum /dev/zero

5. Terminate all sha1sum processes, and then verify that no jobs are running.

   1. Use the pkill command to terminate all running processes with the sha1sum name pattern.

      [student@servera ~]$ pkill sha1sum
      [2]   Terminated              sha1sum /dev/zero
      [4]+  Terminated              sha1sum /dev/zero
      [1]-  Terminated              sha1sum /dev/zero
      [3]+  Terminated              sha1sum /dev/zero

   2. Verify that no jobs are running.

      [student@servera ~]$ jobs
      [student@servera ~]$

6. Start multiple instances of the sha1sum /dev/zero & command, and then start one additional instance of the sha1sum /dev/zero & command with a nice level of 10. Start at least as many instances as the number of system virtual processors. In this example, three regular instances are started, plus another with a higher nice level.

   1. Use looping to start three instances of the sha1sum /dev/zero & command.

      [student@servera ~]$ for i in {1..3}; do sha1sum /dev/zero & done
      [1] 1207
      [2] 1208
      [3] 1209

   2. Use the nice command to start the fourth instance with a nice level of 10.

      [student@servera ~]$ nice -n 10 sha1sum /dev/zero &
      [4] 1210

7. Use the ps and pgrep commands to display the PID, percentage of CPU usage, nice value, and executable name for each process. The instance with the nice value of 10 displays a lower percentage of CPU usage than the other instances.

   [student@servera ~]$ ps -o pid,pcpu,nice,comm $(pgrep sha1sum)
     PID %CPU  NI COMMAND
    1207 64.2   0 sha1sum
    1208 65.0   0 sha1sum
    1209 63.9   0 sha1sum
    1210  8.2  10 sha1sum

8. Use the sudo renice command to lower the nice level of a process from the previous step. Use the PID value of the process instance with the nice level of 10 to lower its nice level to 5.

   [student@servera ~]$ sudo renice -n 5 1210
   [sudo] password for student: student
   1210 (process ID) old priority 10, new priority 5

9. Repeat the ps and pgrep commands to display the CPU percentage and nice level.

   [student@servera ~]$ ps -o pid,pcpu,nice,comm $(pgrep sha1sum)
     PID %CPU  NI COMMAND
    1207 62.9   0 sha1sum
    1208 63.2   0 sha1sum
    1209 63.2   0 sha1sum
    1210 10.9   5 sha1sum

10. Use the pkill command to terminate all running processes with the sha1sum name pattern.

    [student@servera ~]$ pkill sha1sum
    ...output omitted...

11. Return to the workstation machine as the student user.

    [student@servera ~]$ exit
    logout
    Connection to servera closed.
    [student@workstation ~]$

    Important

    Verify that you have terminated all exercise processes before leaving this exercise.