Maintaining Linux Systems

30 minutes
  • 3 Learning Objectives

About this Hands-on Lab

In this lab, we are going to practice scheduling updates, modifying NTP settings, and changing what kernel the server will reboot into.
Understanding how to do these tasks will prepare you for various administrative duties in the future.

*This course is not approved or sponsored by Red Hat.*

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Schedule a Job Using the `at` Utility

To schedule commands using the at command, you can run

at 12:00am

at> yum update -y

Pressing Ctrl+D will show a message, then send you back to the shell.

at> <EOT>

You can run atq to verify that the command is scheduled.

If you get an error similar to:
Can't open /var/run/ to signal atd. No atd running?

That means that the atd service isn’t running. You can resolve that by running

systemctl start atd

Modify the NTP Pools to Keep Clocks Synchronized

NTP configuration is set in /etc/chrony.conf.

The lines that need to be modified are at the top of the file. Edit them to look like:

server iburst




Modify GRUB to Boot a Different Kernel

List the currently installed kernels with grubby --info=ALL

Find the line that looks like


You’ll see information about that kernel following the index.

Run grubby --set-default-index=<index number>

Run grubby --default-index to verify it worked.

Additional Resources

We have a server that needs to be set up according to our policy.

First, we should make sure that it's completely updated before we move it to production. Schedule a job so that it updates at midnight tonight.

Second, we need to modify the NTP pools according to our standards. Use the following:

server iburst




Finally, the kernel we set as default needs to be kernel at index 1.

What are Hands-on Labs

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.

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