Lab
A Cloud Guru

Maintaining Linux Systems

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.*

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Path Info

Level

Intermediate

Duration

30m

Published

Apr 05, 2019

Challenge

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/atd.pid to signal atd. No atd running?

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

systemctl start atd
Challenge

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 0.pool.ntp.org iburst

server 1.pool.ntp.org

server 2.pool.ntp.org

server 3.pool.ntp.org
Challenge

Modify GRUB to Boot a Different Kernel

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

Find the line that looks like

index=1

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.

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

What's a lab?

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.