RHCSA Rapid Track

Instructions

1. On the workstation machine, open two terminal windows side by side. In this section, these terminals are referred to as left and right. In each terminal, use the ssh command to 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 the instance shell script in the new directory. Change the script permissions so that it is executable.

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

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

   2. Create the instance script file in the /home/student/bin directory. Press the i key to enter Vim interactive mode. The file must have the following content as shown. Use the :wq command to save the file.

      [student@servera ~]$ cd /home/student/bin
      [student@servera bin]$ vim /home/student/bin/instance
      #!/bin/bash
      while true; do
        echo -n "$@ " >> ~/instance_outfile
        sleep 5
      done

      Note

      The instance script runs until the process is terminated. It appends command-line arguments to the ~/instance_outfile file once every 5 seconds.

   3. Make the instance script file executable.

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

3. In the left terminal shell, change into the /home/student/bin/ directory. Start three processes with the instance script file, by passing the network, interface, and connection arguments. Start the processes in the background.

   [student@servera bin]$ instance network &
   [1] 3460
   [student@servera bin]$ instance interface &
   [2] 3482
   [student@servera bin]$ instance connection &
   [3] 3516

4. In the right terminal shell, verify that all three processes are appending content to the /home/student/instance_outfile file.

   [student@servera ~]$ tail -f ~/instance_outfile
   network interface network connection interface network connection interface network
   ...output omitted...

5. In the left terminal shell, list existing jobs.

   [student@servera bin]$ jobs
   [1]   Running                 instance network &
   [2]-  Running                 instance interface &
   [3]+  Running                 instance connection &

6. Use signals to suspend the instance network process. Verify that the instance network process is set to Stopped. Verify that the network process is no longer appending content to the ~/instance_output file.

   1. Stop the instance network process. Verify that the process is stopped.

      [student@servera bin]$ kill -SIGSTOP %1
      [1]+  Stopped                 instance network
      [student@servera bin]$ jobs
      [1]+  Stopped                 instance network
      [2]   Running                 instance interface &
      [3]-  Running                 instance connection &

   2. In the right terminal shell, view the tail command output. Verify that the word network is no longer appended to the ~/instance_outfile file.

      ...output omitted...
      interface connection interface connection interface connection interface

7. In the left terminal shell, terminate the instance interface process. Verify that the instance interface process disappeared. Verify that the instance interface process output is no longer appended to the ~/instance_outfile file.

   1. Terminate the instance interface process. Verify that the process is terminated.

      [student@servera bin]$ kill -SIGTERM %2
      [student@servera bin]$ jobs
      [1]+  Stopped                 instance network
      [2]   Terminated              instance interface
      [3]-  Running                 instance connection &

   2. In the right terminal shell, view the tail command output. Verify that the word interface is no longer appended to the ~/instance_outfile file.

      ...output omitted...
      connection connection connection connection connection connection connection connection

8. In the left terminal shell, resume the instance network process. Verify that the instance network process is set to Running. Verify that the instance network process output is appended to the ~/instance_outfile file.

   1. Resume the instance network process. Verify that the process is in the Running state.

      [student@servera bin]$ kill -SIGCONT %1
      [student@servera bin]$ jobs
      [1]+  Running                 instance network &
      [3]-  Running                 instance connection &

   2. In the right terminal shell, view the tail command output. Verify that the word network is appended to the ~/instance_outfile file.

      ...output omitted...
      network connection network connection network connection network connection network connection

9. In the left terminal shell, terminate the remaining two jobs. Verify that no jobs remain and that output is stopped.

   1. Terminate the instance network process. Next, terminate the instance connection process.

      [student@servera bin]$ kill -SIGTERM %1
      [student@servera bin]$ kill -SIGTERM %3
      [1]+ Terminated              instance network
      [student@servera bin]$ jobs
      [3]+ Terminated              instance connection

10. In the left terminal shell, list the current running processes in all open terminal shells. Terminate the tail processes. Verify that the processes are no longer running.

    1. List all current running processes. Refine the search to view only tail lines.

       [student@servera bin]$ ps -ef | grep tail
       student   4581 31358  0 10:02 pts/0    00:00:00 tail -f /home/student/instance_outfile
       student   4869  2252  0 10:33 pts/1    00:00:00 grep --color=auto tail

    2. Terminate the tail process. Verify that the process is no longer running.

       [student@servera bin]$ pkill -SIGTERM tail
       [student@servera bin]$ ps -ef | grep tail
       student   4874  2252  0 10:36 pts/1    00:00:00 grep --color=auto tail

    3. In the right terminal shell, verify that the tail command is no longer running.

       ...output omitted...
       network connection network connection network connection Terminated
       [student@servera ~]$

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

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