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linux:sysadmin:bootloaders

Boot loaders

In computing, booting (booting up) is a bootstrapping process that starts operating systems when the user turns on a computer system. A boot sequence is the initial set of operations that the computer performs when it is switched on. The bootloader typically loads the main operating system for the computer.

Grub

Edit the grub configuration:

vim /boot/grub/grub.conf

Boot options

  1. When entering the splash screen on boot push any button to see the different grub entries
  2. Select the kernel you want to boot
  3. enter a to append boot options (see below)

available boot options

mode description
single single user mode
fastboot skip file system check (fsck)

LILO

Edit the lilo configuartion:

vim /etc/lilo.conf

Run the lilo command to notify the system about the changes:

lilo
Added 2.4.21-58.ELsmp *
Added 2.4.21-58.EL
Added 2.4.21-57.ELsmp
Added 2.4.21-57.EL

Kernel Upgrades

Procedure to install/boot a new kernel:

  1. install a new kernel using the package manager of you choice
  2. edit your boot loader configuration, i.e. grub.conf (the yum/up2date update process will do this for you)
  3. reboot the server with the new kernel
After upgrading or changing the Kernel, you must reboot your computer for the changes to take effect.

Default Kernel

Configure your default Kernel within /etc/sysconfig/kernel. Yum and up2date use this file to configure the boot loader. If you want to use kernel-PAE as default edit the “DEFAULTKERNEL” setting in the file as below:

# UPDATEDEFAULT specifies if new-kernel-pkg should make
# new kernels the default
UPDATEDEFAULT=yes
 
# DEFAULTKERNEL specifies the default kernel package type
DEFAULTKERNEL=kernel-PAE

Special Kernels

Red Hat 4

kernel-smp:

  • multiple processors support

kernel-hugemem:

  • multiple processors
  • support more than 4GB MEM (up to 64GB for x86)

Red Hat 5

kernel-PAE

  • physical address extension for x86 machines with more then 4 GB of memory

kernel-xen

  • Xen enabled RedHat Kernel to run the hypervisor
/srv/wiki.niwos.com/data/pages/linux/sysadmin/bootloaders.txt · Last modified: 2010/07/07 14:40 (external edit)