Lab 17.2: Change GRUB 2 boot options

Goal

Make the boot messages visible, change the menu timeout, and choose the default kernel.

Before you start

Work on server1 as root. Take a VM snapshot first: mistakes in GRUB can stop the boot.

Tasks

Show the kernel command line of the running kernel and the BLS entries in /boot.
Remove the options rhgb and quiet from all kernels, so you see the boot messages.
Set the GRUB menu timeout to 10 seconds.
Show the default kernel. If you have more than one kernel, make the older one the default, check it, and set the newest back.
Reboot. In the GRUB menu, press e and look at the linux line, then boot with Ctrl+X. Check the new command line.

Check your work

$cat /proc/cmdline
#grubby --info=DEFAULT | grep args
#grep GRUB_TIMEOUT /etc/default/grub
#grubby --default-kernel

/proc/cmdline has no rhgb and no quiet.
GRUB_TIMEOUT=10 and the menu waited 10 seconds.

Hints

Show the hints

grubby --update-kernel=ALL --remove-args="…".
Timeout: /etc/default/grub and grub2-mkconfig -o /boot/grub2/grub.cfg.
grubby --set-default.

Solution

Show the solution

Look at the current state.

$cat /proc/cmdline
#ls /boot/loader/entries/

Remove rhgb and quiet.

#grubby --update-kernel=ALL --remove-args="rhgb quiet"

Timeout of 10 seconds.

#sed -i 's/^GRUB_TIMEOUT=.*/GRUB_TIMEOUT=10/' /etc/default/grub
#grub2-mkconfig -o /boot/grub2/grub.cfg

Default kernel.

#grubby --default-kernel
#grubby --info=ALL | grep ^kernel
#grubby --set-default /boot/vmlinuz-OLDER-VERSION
#grubby --set-default /boot/vmlinuz-$(uname -r)

Reboot and check.
```
#systemctl reboot
$cat /proc/cmdline
```

Change GRUB 2 boot options

Goal

Before you start

Tasks

Check your work

Hints

Solution

My notes

Lessons for this lab

Commands in this lab