Red Hat System Administration I

Instructions

1. On the workstation machine, open two terminal windows side by side. In this section, these two terminals are referred to as left and right. In each terminal, log in to the servera machine as the student user.

   [student@workstation ~]$ ssh student@servera
   [student@servera ~]$

2. In the left terminal shell, create the /home/student/bin directory. Create a shell script called control in the /home/student/bin directory. Change the script permissions to make it executable.

   1. Create the /home/student/bin directory.

      [student@servera ~]$ mkdir /home/student/bin

   2. Create a script called control in the /home/student/bin directory. To enter Vim interactive mode, press the i key. Use the :wq command to save the file and quit.

      [student@servera ~]$ vim /home/student/bin/control
      #!/bin/bash
      while true; do
        echo -n "$@ " >> ~/control_outfile
        sleep 1
      done

      Note

      The control script runs until the process is terminated. The script appends command-line arguments to the ~/control_outfile file once per second.

   3. Make the control file executable.

      [student@servera ~]$ chmod +x /home/student/bin/control

3. Execute the control script. The script continuously appends the word "technical" and a space to the ~/control_outfile file at one-second intervals.

   [student@servera ~]$ control technical

4. In the right terminal shell, verify that the new process is writing to the /home/student/control_outfile file.

   [student@servera ~]$ tail -f ~/control_outfile
   technical technical technical technical
   ...output omitted...

5. In the left terminal shell, press Ctrl+z to suspend the running process. The shell returns the job ID in square brackets. In the right terminal shell, confirm that the process output is stopped.

   ^Z
   [1]+  Stopped                 control technical
   [student@servera ~]$

   technical technical technical technical
   ...no further output...

6. In the left terminal shell, view the jobs command output. Remember that the + sign indicates the default job. Restart the job in the background. In the right terminal shell, verify that the process output is again active.

   1. View the list of jobs.

      [student@servera ~]$ jobs
      [1]+  Stopped                 control technical

   2. Restart the control job in the background.

      [student@servera ~]$ bg
      [1]+ control technical &

   3. Verify that the control job is running again.

      [student@servera ~]$ jobs
      [1]+  Running                 control technical &

   4. In the right terminal shell, confirm that the tail command is producing output.

      ...output omitted...
      technical technical technical technical technical technical technical technical

7. In the left terminal shell, start two more control processes to append to the ~/output file. Use the ampersand (&) special command to start the processes in the background. Replace technical with documents and then with database. Replacing the arguments helps to differentiate between the three processes.

   [student@servera ~]$ control documents &
   [2] 6579
   [student@servera ~]$ control database &
   [3] 6654

8. In the left terminal shell, use the jobs command to view the three running processes. In the right terminal shell, verify that all three processes are appending to the file.

   [student@servera ~]$ jobs
   [1]   Running                 control technical &
   [2]-  Running                 control documents &
   [3]+  Running                 control database &

   ...output omitted...
   technical documents database technical documents database technical documents database technical documents database
   ...output omitted...

9. Suspend the control technical process. Confirm that it is suspended. Terminate the control documents process and verify that it is terminated.

   1. In the left terminal shell, foreground the control technical process. Press Ctrl+z to suspend the process. Verify that the process is suspended.

      [student@servera ~]$ fg %1
      control technical
      ^Z
      [1]+  Stopped                 control technical
      [student@servera ~]$ jobs
      [1]+  Stopped                 control technical
      [2]   Running                 control documents &
      [3]-  Running                 control database &

   2. In the right terminal shell, verify that the control technical process is no longer sending output.

      database documents  database documents  database
      ...no further output...

   3. In the left terminal shell, run the control documents process in the foreground. Press Ctrl+c to terminate the process. Verify that the process is terminated.

      [student@servera ~]$ fg %2
      control documents
      ​^C
      [student@servera ~]$ jobs
      [1]+  Stopped                 control technical
      [3]-  Running                 control database &

   4. In the right terminal shell, verify that the control documents process is no longer sending output.

      ...output omitted...
      database database database database database database database database
      ...no further output...

10. In the left terminal shell, view the remaining jobs. The suspended jobs have a state of T. The other background jobs are sleeping and have a state of S.

    [student@servera ~]$ ps jT
     PPID   PID  PGID   SID TTY      TPGID STAT   UID   TIME COMMAND
     27277 27278 27278 27278 pts/1    28702 Ss    1000   0:00 -bash
     27278 28234 28234 27278 pts/1    28702 T     1000   0:00 /bin/bash /home/student/bin/control technical
     27278 28251 28251 27278 pts/1    28702 S     1000   0:00 /bin/bash /home/student/bin/control database
     28234 28316 28234 27278 pts/1    28702 T     1000   0:00 sleep 1
     28251 28701 28251 27278 pts/1    28702 S     1000   0:00 sleep 1
     27278 28702 28702 27278 pts/1    28702 R+    1000   0:00 ps jT

11. In the left terminal shell, view the current jobs. Terminate the control database process and verify that it is terminated.

    [student@servera ~]$ jobs
    [1]+  Stopped                 control technical
    [3]-  Running                 control database &

    Use the fg command with the job ID to run the control database process in the foreground. Press Ctrl+c to terminate the process. Verify that the process is terminated.

    [student@servera ~]$ fg %3
    control database
    ​^C
    [student@servera ~]$ jobs
    [1]+  Stopped                 control technical

12. In the right terminal shell, use the Ctrl+c command to stop the tail command. Delete the ~/control_outfile file.

    ...output omitted...
    ​^C
    [student@servera ~]$ rm ~/control_outfile

13. Close the extra terminal. Return to the workstation system as the student user.

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