Chapter 18. Essential Troubleshooting Skills

Question 1

Which key do you need to press to enter the GRUB boot menu editor mode?

Answer 1

Press e to enter the GRUB boot menu editor mode.

Question 2

During startup, the boot procedure is not completed and the server asks for the root password instead. What is likely to be the reason of this?

Answer 2

An error in /etc/fstab prevents the fsck command on that file system from finishing successfully.

Question 3

You want to enter troubleshooting mode, but you do not know the root password. Which argument would you pass to the kernel to enter a mode that provides access to most of the machine’s functionality?

Answer 3

Pass systemd.unit=rescue.target to the kernel to enter a mode that provides access to most of the machine’s functionality.

Question 4

You start your server and nothing happens. You just see a blinking cursor and that’s all. What is the first step to troubleshoot this issue?

Answer 4

Start from a rescue system.

Question 5

You want to find out which units are available in a specific troubleshooting environment. Which command would you use?

Answer 5

systemctl list-units shows which units are available in a specific troubleshooting environment.

Question 6

You want to start troubleshooting a lost root password. Which argument would you pass to the GRUB 2 boot loader?

Answer 6

Pass rd.break to the GRUB 2 boot loader to start troubleshooting a lost root password

Question 7

From the shell that you have started to troubleshoot a lost password for user root, you want to load the SELinux policy. Which command enables you to do that?

Answer 7

load_policy -i loads the SELinux policy.

Question 8

While troubleshooting the root password, what do you need to do to make sure the SELinux labels are set correctly?

Answer 8

chcon -t shadow_t /etc/shadow ensures that the SELinux labels are set correctly.

Question 9

You have applied changes to the GRUB 2 boot loader and want to save them. How do you do that?

Answer 9

grub2-mkconfig -o /boot/grub2/grub.cfg saves changes applied to the GRUB 2 boot loader.

Question 10

You do know the root password on a machine where you want to enter the most minimal troubleshooting mode. Which GRUB 2 boot argument would you use?

Answer 10

systemd.unit=emergency.target enters the most minimal troubleshooting mode.