Tuesday, March 27, 2007

Using GRUB to overcome boot problems

Troubleshooting boot problems can be a very frustrating and challenging process. Sometimes their repair requires the Linux rescue environment, but what can be done if rescue media is not handy? If the system gets past BIOS and loads the GRUB boot loader, often there is much that can be done to get it up and running again.

Basic GRUB usage

Each time a Linux system boots, GRUB flashes by on the screen while it performs a brief countdown. The default countdown on many systems is five seconds but the actual countdown period can be adjusted. GRUB loads the Linux kernel and initial RAM disk image into system memory then fires the system up. When everything goes well and GRUB is finished with its task, the system successfully boots into Linux.

Press any key to enter the menu

Booting Fedora Core (2.6.19-1.2911.fc6) in 5 seconds...
Typical GRUB countdown sequence

Occasionally, GRUB requires some simple intervention. Perhaps a new kernel isn’t working correctly with your system or maybe you want to bring the system into a different runlevel than the default. Hit the ESCAPE key to interrupt the GRUB countdown and bring up GRUB’s main menu.

Full Guide