Reinstalling GRUB Bootloader from the Rescue System
This document (000019909) is provided subject to the disclaimer at the end of this document.
SUSE Linux Enterprise Server 12
You are inside the chrooted root filesystem of the system in question. Ensure all needed filesystems are mounted, especially one holding /boot/grub2/<grub_cpu>-<grub_platform> (eg. /boot/grub2/x86_64-efi or /etc/grub2/i386-pc,...). If using an UEFI/EFI system, ensure /boot/efi filesystem is mounted. Inside chroot you can test with `mount -a -t nonfs,nonfs4,nocifs,noocfs2' for example (it mounts all but not NFS, CIFS, OCFS2 filesystems).
See How to Chroot in Rescue Mode for more details.
GRUB2 bootloader reinstallation
i386 / x86_64 UEFI/EFI systems
If you use an UEFI/EFI system, the bootloader is not installed into the beginning of a disk as in case of BIOS system (MBR, GPT), but into EFI system partition (with partition GUID 'C12A7328-F81F-11D2-BA4B-00A0C93EC93B'; visible for example with `sfdisk -d <disk>'). Thus, the specific command for that is:
Note that `shim-install' will call `grub2-install' command itself.
i386 BIOS systems
On i386 (here 'i386' does not refer to a specific processor but to the whole platform/architecture) the bootloader is installed into the beginning of a disk (MBR, GPT), thus disk device must be defined as paramenter.
From grub2-install(8) man page:
INSTALL_DEVICE must be system device filename. grub-install copies GRUB images into boot/grub2. On some platforms, it may also install GRUB into the boot sector.
The commands themselves:
grub2-install -v <root disk> grub2-mkconfig -o /boot/grub2/grub.cfg
Note: in case the root disk is part of LVM, then this is the physical volume (PV) holding root filesystem. E.g. /dev/sda.
On POWER systems, the destination of the bootloader is PReP partition, which must be the first one on the root disk. Note, if LVM is used for the root filesystem and the volume group (VG) consists of multiple physical volume (PV) located on multiple disks, all these disks must have PReP partition. Thus, always ensure the disk(s) holding root filesystem have PReP partition, otherwise the system may not boot. In contrast to BIOS systems, on a POWER system, the destination is the PReP partition.
grub2-install -v <PReP partition on root disk> grub2-mkconfig -o /boot/grub2/grub.cfg
Using YaST bootloader module
YaST bootloader module calls 'grub2-install' in the background, more precisely:
grub2-install --target=<grub_cpu>-<grub_platform> --force --skip-fs-probe <root_disk>
Using the `yast2 bootloader' module can help resolve grub issues by running the command list above and by allowing other selections.
If there was a bootloader update error during patching or otherwise, it should be logged in /var/log/pbl.log.
- (SLES 11 with legacy GRUB) : Reinstalling GRUB from the Rescue System
- How to Chroot in Rescue Mode
- grub2 on Power system can't find lvmid device when a 2nd disk is added to the root volume group
How to query root disk
`lsblk -s' could be used, search a line with '/' and up to first occurrence of 'disk'. An example:
# lsblk -s NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS ...snipped... system-root 254:2 0 50G 0 lvm /var │ /usr/local │ /tmp │ /srv │ /root │ /opt │ /boot/grub2/x86_64-efi │ /boot/grub2/i386-pc │ /.snapshots │ / └─cr_nvme-SAMSUNG_MZALQ512HALU-000L1_S4YCNF0NC31508-part2 254:0 0 476.4G 0 crypt └─nvme0n1p2 259:2 0 476.5G 0 part └─nvme0n1 259:0 0 476.9G 0 disk system-home 254:3 0 347.7G 0 lvm /home ...snipped... # lsblk -s | sed -nr '/[[:blank:]]+\/$/,/disk[[:blank:]]*$/p' │ / └─cr_nvme-SAMSUNG_MZALQ512HALU-000L1_S4YCNF0NC31508-part2 254:0 0 476.4G 0 crypt └─nvme0n1p2 259:2 0 476.5G 0 part └─nvme0n1 259:0 0 476.9G 0 disk
This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.
- Document ID:000019909
- Creation Date: 15-Dec-2022
- Modified Date:15-Dec-2022
- SUSE Linux Enterprise Server
For questions or concerns with the SUSE Knowledgebase please contact: tidfeedback[at]suse.com