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174 lines
3.8 KiB
Text
174 lines
3.8 KiB
Text
[[restoring-bootloader-using-live-disk]]
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= Restoring the bootloader using the Live disk.
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Sometimes, especially after a secondary operating systems has been installed,
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the master boot record gets damaged which then prevents the original Linux system
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from booting.
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If this happens, it is necessary to reinstall *GRUB2* to recreate the original
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settings. The process not only discovers all installed operating systems, but
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usually adds them to the *GRUB2* configuration files, so they will all become
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bootable by *GRUB2*.
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.Before you start
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* Get the Fedora Live ISO from link:https://download.fedoraproject.org/pub/fedora/linux/releases/[getfedora.org].
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* Prepare a bootable device using the downloaded ISO, either a CD or a USB.
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.Procedure
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. Boot the Fedora live system from the bootable device you have created.
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. Open the terminal.
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. Examine the partition layout and identify the `boot` and the `root` partition.
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----
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sudo fdisk -l
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----
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== For Default Installation in LVM.
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. Create the mount point for the root partition.
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+
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----
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mkdir -p /mnt/root
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----
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If you are using the default Fedora layout, there will be one `/dev/sda1`
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partition that holds the `/boot` directory and one `/dev/mapper/fedora-root`
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that holds the root file system.
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. Mount the root partition on the mount point.
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+
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----
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mount /dev/mapper/fedora-root /mnt/root
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----
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. Mount the boot partition in the `boot` directory of the filesystem that you have mounted in the previous step.
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+
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----
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mount /dev/sda1 /mnt/root/boot/
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----
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. Mount system processes and devices into the root filesystem in `/mnt/root`.
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+
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----
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mount -o bind /dev /mnt/root/dev
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mount -o bind /proc /mnt/root/proc
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mount -o bind /sys /mnt/root/sys
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mount -o bind /run /mnt/root/run
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----
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. If you use EFI boot, you may also want to bind the efivars and the EFI system partition:
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+
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----
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mount -o bind /sys/firmware/efi/efivars /mnt/root/sys/firmware/efi/efivars
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mount <efi system partition> /mnt/root/boot/efi
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----
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. Change your filesystem into the one mounted under `/mnt/root`.
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+
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----
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chroot /mnt/root
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----
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== For Default Installation in BTRFS
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. Create the mount point for the root partition.
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+
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----
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mkdir -p /mnt/
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----
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If you are using the default Fedora layout, there will be one `/dev/sda1`
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partition that holds the `/boot` directory and one `/dev/sda2` that holds the root file system.
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----
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mount /dev/sda2 /mnt
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mount /dev/sda1 /mnt/root/boot
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----
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. Change your filesystem into the one mounted under `/mnt/root`.
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+
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----
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chroot /mnt/root
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----
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IMPORTANT: Home Partition is mounted automatically under `/mnt/home`
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== For Default Installation in LUKS.
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. Make sure crypt module in use:
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+
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----
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sudo modprobe dm-crypt
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----
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. Find out which drive it was with the following command:
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+
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----
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sudo fdisk -l
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----
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You must mount `/dev/sda3 myvolume`
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. Use `cryptsetup`, device is accessible under `/dev/mapper/myvolume``
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+
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----
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sudo cryptsetup luksOpen /dev/sde3 myvolume
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----
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. Scan for LVM volumes and choose the right volume group name that you are looking for:
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+
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----
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sudo vgscan
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----
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. If it is eg. Fedora, activate it
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+
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----
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sudo vgchange -ay system
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----
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. Find out root volume
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----
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sudo lvs
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----
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. Mount it with the following command:
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----
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sudo mount /dev/system/root /mnt/
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----
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. To work in the volume use the following commands
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+
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----
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sudo mount --bind /dev /mnt/dev
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sudo mount --bind /dev/pts /mnt/dev/pts
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sudo mount --bind /proc /mnt/proc
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sudo mount --bind /sys /mnt/sys
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sudo chroot /mnt
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----
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IMPORTANT: consider mounting `/boot` also.
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== Continue with the follow Procedure.
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. Regenerate the *GRUB2* configuration file and reinstall the bootloader
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into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].
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. Exit this temporary root filesystem.
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+
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----
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exit
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----
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. Your bootloader should be now restored. Reboot your computer to boot into your normal system.
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----
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systemctl reboot
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----
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