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25.7. Reinstalling GRUB 2
Reinstalling GRUB 2 is a convenient way to fix certain problems usually caused by an incorrect installation of GRUB 2, missing files, or a broken system. Other reasons to reinstall GRUB 2 include the following:
- Upgrading from the previous version of GRUB.
- The user requires the GRUB 2 boot loader to control installed operating systems. However, some operating systems are installed with their own boot loaders. Reinstalling GRUB 2 returns control to the desired operating system.
- Adding the boot information to another drive.
25.7.1. Reinstalling GRUB 2 on BIOS-Based Machines
When using the
grub2-install command, the boot information is updated and missing files are restored. Note that the files are restored only if they are not corrupted.
Use the
grub2-install device command to reinstall GRUB 2 if the system is operating normally. For example, if sda is your device:
~]#grub2-install/dev/sda
25.7.2. Reinstalling GRUB 2 on UEFI-Based Machines
When using the
yum reinstall grub2-efi shim command, the boot information is updated and missing files are restored. Note that the files are restored only if they are not corrupted.
Use the
yum reinstall grub2-efi shim command to reinstall GRUB 2 if the system is operating normally. For example:
~]# yum reinstall grub2-efi shim25.7.3. Resetting and Reinstalling GRUB 2
This method completely removes all GRUB 2 configuration files and system settings. Apply this method to reset all configuration settings to their default values. Removing of the configuration files and subsequent reinstalling of GRUB 2 fixes failures caused by corrupted files and incorrect configuration. To do so, as
root, follow these steps:
- Run the
rm /etc/grub.d/*command; - Run the
rm /etc/sysconfig/grubcommand; - For EFI systems only, run the following command:
~]#
yum reinstall grub2-efi shim grub2-tools - For BIOS and EFI systems, run this command:
~]#
yum reinstall grub2-tools - Rebuild the
grub.cfgfile by running thegrub2-mkconfigcommand as follows:-o- On BIOS-based machines, issue the following command as
root:~]#
grub2-mkconfig -o /boot/grub2/grub.cfg - On UEFI-based machines, issue the following command as
root:~]#
grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
- Now follow the procedure in Section 25.7, “Reinstalling GRUB 2” to restore GRUB 2 on the
/boot/partition.
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