= Using the GRUB2 boot prompt
[[using-the-grub-2-boot-prompt]]

If improperly configured, *GRUB2* may fail to load and subsequently drop
to a boot prompt. To boot into the system, proceed as follows:

. List the drives which *GRUB2* sees:
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grub2> ls
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. Examine the output to understand the partition table of the `/dev/sda` device. The following example shows a DOS partition table with three partitions:
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(hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1)
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A GPT partition table of the `/dev/sda` device with four partitions could look like this:
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(hd0) (hd0,gpt4) (hd0,gpt3)  (hd0,gpt2) (hd0,gpt1)
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. Probe each partition of the drive and locate your `vmlinuz` and `initramfs` files.
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ls (hd0,1)/ 
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The outcome of the previous command will list the files on `/dev/sda1`. The partition that contains the `/boot` directory is the correct one. There you will search for the full names of the `vmlinuz` and `initramfs` files.

. Pre-boot procedure for BTRFS filesystems.
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* On BIOS systems:
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Set *GRUB2* root to your boot partition. If your boot partition is `(hd0,msdos1)`, the command will be:
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set root=(hd0,msdos1)
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Next, select the desired kernel. Set the root partition (e.g. `/dev/sda2`):
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linux /vmlinuz-5.14.10-300.fc35.x86_64 root=/dev/sda2 ro rootflags=subvol=root
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* On UEFI systems:
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Set *GRUB2* root to your EFI system partition. If your EFI partition is `(hd0,gpt1)`, the command will be:
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set root=(hd0,gpt1)
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Next, select the desired kernel. Find the path to `vmlinuz` and set the root partition (e.g. `/dev/sda3`):
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linux (hd0,gpt2)/vmlinuz-5.14.10-300.fc35.x86_64 root=/dev/sda3 ro rootflags=subvol=root
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Select the RAM filesystem that will be loaded:
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initrd (hd0,gpt2)/initramfs-5.14.10-300.fc35.x86_64.img
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. Pre-boot procedure for LVM filesystems.
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Load the `xfs` and `lvm` modules if they are not already loaded (check this with `lsmod`):
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insmod xfs
insmod lvm
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* On BIOS systems:
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Set *GRUB2* root to your boot partition. If your boot partition is `(hd0,msdos1)`, the command will be:
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set root=(hd0,msdos1)
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Next, select the desired kernel. Set `root` to the `lvm` corresponding to the root directory:
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linux /vmlinuz-3.0.0-1.fc16.i686 root=/dev/mapper/fedora_localhost--live-root
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Select the RAM filesystem that will be loaded:
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initrd /initramfs-3.0.0-1.fc16.i686.img
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* On UEFI systems:
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Set *GRUB2* root to your EFI system partition. If your EFI partition is `(hd0,gpt1)`, the command will be:
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set root=(hd0,gpt1)
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Next, select the desired kernel. Find the path to `vmlinuz` and set `root` to the `lvm` corresponding to the root directory:
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linux (hd0,gpt2)/vmlinuz-3.0.0-1.fc16.i686 root=/dev/mapper/fedora_localhost--live-root
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Select the RAM filesystem that will be loaded:
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initrd (hd0,gpt2)/initramfs-3.0.0-1.fc16.i686.img
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. Boot with the selected settings.
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grub> boot
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. To restore the bootloader's functionality, 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].