quick-docs/modules/ROOT/pages/_partials/proc_restoring-bootloader-using-live-disk.adoc

[[restoring-bootloader-using-live-disk]]
= Restoring the bootloader using the Live disk.

Sometimes, especially after a secondary operating systems has been installed, 
the master boot record gets damaged which then prevents the original Linux system
from booting.

If this happens, it is necessary to reinstall *GRUB2* to recreate the original 
settings. The process not only discovers all installed operating systems, but 
usually adds them to the *GRUB2* configuration files, so they will all become 
bootable by *GRUB2*.

.Before you start

* Get the Fedora Live ISO from link:https://download.fedoraproject.org/pub/fedora/linux/releases/[getfedora.org].

* Prepare a bootable device using the downloaded ISO, either a CD or a USB.

.Procedure

. Boot the Fedora live system from the bootable device you have created.

. Open the terminal.

. Examine the partition layout and identify the `boot` and the `root` partition.

----
sudo fdisk -l
----

== For Default Installation in LVM.

. Create the mount point for the root partition.
+
----
mkdir -p /mnt/root
----

If you are using the default Fedora layout, there will be one `/dev/sda1`
partition that holds the `/boot` directory and one `/dev/mapper/fedora-root`
that holds the root file system.

. Mount the root partition on the mount point.
+
----
mount /dev/mapper/fedora-root /mnt/root
----

. Mount the boot partition in the `boot` directory of the filesystem that you have mounted in the previous step.
+
----
mount /dev/sda1 /mnt/root/boot/
----

. Mount system processes and devices into the root filesystem in `/mnt/root`.
+
----
mount -o bind /dev /mnt/root/dev
mount -o bind /proc /mnt/root/proc
mount -o bind /sys /mnt/root/sys
mount -o bind /run /mnt/root/run
----

. If you use EFI boot, you may also want to bind the efivars and the EFI system partition:
+
----
mount -o bind /sys/firmware/efi/efivars /mnt/root/sys/firmware/efi/efivars
mount <efi system partition> /mnt/root/boot/efi
----

. Change your filesystem into the one mounted under `/mnt/root`.
+
----
chroot /mnt/root
----

== For Default Installation in BTRFS

. Create the mount point for the root partition.
+
----
mkdir -p /mnt/
----

If you are using the default Fedora layout, there will be one `/dev/sda1`
partition that holds the `/boot` directory and one `/dev/sda2` that holds the root file system.

----
mount /dev/sda2 /mnt
mount /dev/sda1 /mnt/root/boot
----

. Change your filesystem into the one mounted under `/mnt/root`.
+
----
chroot /mnt/root
----

IMPORTANT: Home Partition is mounted automatically under `/mnt/home`

== For Default Installation in LUKS.

. Make sure crypt module in use:
+
----
sudo modprobe dm-crypt
----

. Find out which drive it was with the following command:
+
----
sudo fdisk -l
----

You must mount `/dev/sda3 myvolume`

. Use `cryptsetup`, device is accessible under `/dev/mapper/myvolume``
+
----
sudo cryptsetup luksOpen /dev/sde3 myvolume
----

. Scan for LVM volumes and choose the right volume group name that you are looking for:
+
----
sudo vgscan
----

. If it is eg. Fedora, activate it
+
----
sudo vgchange -ay system
----

. Find out root volume
+
----
sudo lvs
----

. Mount it with the following command:
+
----
sudo mount /dev/system/root /mnt/
----

. To work in the volume use the following commands
+
----
sudo mount --bind /dev /mnt/dev 
sudo mount --bind /dev/pts /mnt/dev/pts
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt
----

IMPORTANT: consider mounting `/boot` also.

== Continue with the follow Procedure.

. Regenerate the *GRUB2* configuration file and reinstall the bootloader 
into the MBR, as described in xref:adding-other-operating-systems-grub2[Adding other operating systems to the *GRUB2* menu].

. Exit this temporary root filesystem.
+
----
exit
----

. Your bootloader should be now restored. Reboot your computer to boot into your normal system.

----
systemctl reboot
----