Notes for advanced troubleshooting on RHEL

Issues , how to configure, and what to configure

POST -> Hardware configuration :

• best fix is to replace hardware

Selecting boot device :

• bios / uefi menu -> replace hardware or use rescue system

Loading the bootloader -> use grub2-install to configure and also edit the /etc/defaults/grub file to make changes.

To troubleshoot use the GRUB boot prompt and edi /etc/defaults/grub followed by grub2-mkconfig

Loading the Kernel :

same as the last phase, make edits to /etc/default/grub and then grub2-mkconfig

Starting /sbin/init :

• This is compiled into initramfs so this can’t be configured.
• To troubleshoot , use the “init=” kernel boot argument or the rd.break kernel argument

Processing initrd.target :

• This is also compiled into initramfs , so can’t be configured
• To resolve issues with this phase , use the dracut command

Switch to the root file :

• to configure this , edit the /etc/fstab file ( I have this issue alot sometimes )
• To resolve it , like before edit the /etc/fstab file.

Running the default target :

• to configure this you can set the default target for systemd to boot into. AKA use the systemctl set-default command to boot into another target that can be isolated. To find out which targets can be isolated , navigate to the /usr/lib/systemd/system and run

grep Isolate *.target

This shows you which targets can be used as default as they can be Isolated.