GRUB
GRUB (GRand Unified Bootloader) is a boot loader. The current GRUB is also referred to as GRUB 2. The original GRUB, or GRUB Legacy, corresponds to versions 0.9x. This page exclusively describes GRUB 2.
esp denotes the mountpoint of the EFI system partition aka ESP.UEFI systems
Installation
- UEFI firmwares are not implemented consistently across manufacturers. The procedure described below is intended to work on a wide range of UEFI systems but those experiencing problems despite applying this method are encouraged to share detailed information, and if possible the workarounds found, for their hardware-specific case. A /EFI examples article has been provided for such cases.
- The section assumes you are installing GRUB for x86_64 systems. For IA32 (32-bit) UEFI systems (not to be confused with 32-bit CPUs), replace
x86_64-efiwithi386-efiwhere appropriate. - See Secure Boot for instructions on implementing it.
First, install the packages and : GRUB is the bootloader while efibootmgr is used by the GRUB installation script to write boot entries to NVRAM.
Then follow the below steps to install GRUB to your disk:
- Mount the EFI system partition and in the remainder of this section, substitute
espwith its mount point. - Choose a bootloader identifier, here named . A directory of that name will be created in to store the EFI binary and this is the name that will appear in the UEFI boot menu to identify the GRUB boot entry.
- Execute the following command to install the GRUB EFI application to and install its modules to .
After the above installation completed, the main GRUB directory is located at . Read /Tips and tricks#Alternative install method for how to specify an alternative location. Note that grub-install also tries to create an entry in the firmware boot manager, named in the above example – this will, however, fail if your boot entries are full; use efibootmgr to remove unnecessary entries.
Remember to #Generate the main configuration file after finalizing the configuration.
--removable then GRUB will be installed to esp/EFI/BOOT/BOOTX64.EFI (or esp/EFI/BOOT/BOOTIA32.EFI for the i386-efi target) and you will have the additional ability of being able to boot from the drive in case EFI variables are reset or you move the drive to another computer. Usually you can do this by selecting the drive itself similar to how you would using BIOS. If dual booting with Windows, be aware Windows usually places an EFI executable there, but its only purpose is to recreate the UEFI boot entry for Windows. If you are installing GRUB on a Mac, you will have to use this option.See UEFI troubleshooting in case of problems. Additionally see /Tips and tricks#UEFI further reading.
BIOS systems
GUID Partition Table (GPT) specific instructions
On a BIOS/GPT configuration, a BIOS boot partition is required. GRUB embeds its into this partition.
Create a mebibyte partition ( with fdisk or gdisk) on the disk with no file system and with partition type GUID .
- Select partition type for fdisk.
- Select partition type code for gdisk.
- For parted set/activate the flag on the partition.
This partition can be in any position order but has to be on the first 2 TiB of the disk. This partition needs to be created before GRUB installation. When the partition is ready, install the bootloader as per the instructions below.
The space before the first partition can also be used as the BIOS boot partition though it will be out of GPT alignment specification. Since the partition will not be regularly accessed performance issues can be disregarded, though some disk utilities will display a warning about it. In fdisk or gdisk create a new partition starting at sector 34 and spanning to 2047 and set the type. To have the viewable partitions begin at the base consider adding this partition last.
Master Boot Record (MBR) specific instructions
Usually the post-MBR gap (after the 512 byte MBR region and before the start of the first partition) in many MBR partitioned systems is 31 KiB when DOS compatibility cylinder alignment issues are satisfied in the partition table. However a post-MBR gap of about 1 to 2 MiB is recommended to provide sufficient room for embedding GRUB's (FS#24103). It is advisable to use a partitioning tool that supports 1 MiB partition alignment to obtain this space as well as to satisfy other non-512-byte-sector issues (which are unrelated to embedding of ).
Installation
Install the package. (It will replace if that is already installed.) Then do:
# grub-install --target=i386-pc /dev/sdX
where is deliberately used regardless of your actual architecture, and /dev/sdX is the disk (not a partition) where GRUB is to be installed. For example or , or . See Device file#Block device names for a description of the block device naming scheme.
Now you must generate the main configuration file.
If you use LVM for your , you can install GRUB on multiple physical disks.
See and GRUB Manual for more details on the grub-install command.
Configuration
On an installed system, GRUB loads the configuration file each boot. You can follow #Generated grub.cfg for using a tool, or #Custom grub.cfg for a manual creation.
Generated grub.cfg
This section only covers editing the /etc/default/grub configuration file. See /Tips and tricks for more information.
Generate the main configuration file
After the installation, the main configuration file needs to be generated. The generation process can be influenced by a variety of options in /etc/default/grub and scripts in .
If you have not done additional configuration, the automatic generation will determine the root filesystem of the system to boot for the configuration file. For that to succeed it is important that the system is either booted or chrooted into.
Use the grub-mkconfig tool to generate :
# grub-mkconfig -o /boot/grub/grub.cfg
By default the generation scripts automatically add menu entries for all installed Arch Linux kernels to the generated configuration.
To automatically add entries for other installed operating systems, see #Detecting other operating systems.
You can add additional custom menu entries by editing and re-generating . Or you can create /boot/grub/custom.cfg and add them there. Changes to /boot/grub/custom.cfg do not require re-running grub-mkconfig, since adds the necessary statement to the generated configuration file.
See #Boot menu entry examples for custom menu entry examples.
Detecting other operating systems
To have grub-mkconfig search for other installed systems and automatically add them to the menu, install the os-prober package and mount the partitions from which the other systems boot. Then re-run grub-mkconfig. If you get the following output: then edit /etc/default/grub and add/uncomment:
GRUB_DISABLE_OS_PROBER=false
Then try again.
Windows
For Windows installed in UEFI mode, make sure the EFI system partition containing the Windows Boot Manager () is mounted. Run as root to detect and generate an entry for it.
For Windows installed in BIOS mode, mount the Windows system partition (its file system label should be or SYSTEM). Run as root to detect and generate an entry for it.
Additional arguments
To pass custom additional arguments to the Linux image, you can set the + GRUB_CMDLINE_LINUX_DEFAULT variables in /etc/default/grub. The two are appended to each other and passed to kernel when generating regular boot entries. For the recovery boot entry, only is used in the generation.
It is not necessary to use both, but can be useful. For example, you could use where is the UUID of your swap partition to enable resume after hibernation. This would generate a recovery boot entry without the resume and without suppressing kernel messages during a boot from that menu entry. Though, the other (regular) menu entries would have them as options.
By default grub-mkconfig determines the UUID of the root filesystem for the configuration. To disable this, uncomment .
For generating the GRUB recovery entry you have to ensure that is not set to in /etc/default/grub.
See Kernel parameters for more info.
Setting the top-level menu entry
By default, grub-mkconfig sorts the included kernels using sort -V and uses the first kernel in that list as the top-level entry. This means that, for example, since is sorted before , if you have both and linux installed, the LTS kernel will be the top-level menu entry, which may not be desirable. This can be overridden by specifying in /etc/default/grub. For example, to make the regular kernel be the top-level menu entry, you can use .
LVM
If you use LVM for your or root partition, make sure that the lvm module is preloaded:
RAID
GRUB provides convenient handling of RAID volumes. You need to load GRUB modules or to allow you to address the volume natively:
For example, /dev/md0 becomes:
set root=(md/0)
whereas a partitioned RAID volume (e.g. ) becomes:
set root=(md/0,1)
To install grub when using RAID1 as the partition (or using housed on a RAID1 root partition), on BIOS systems, simply run grub-install on both of the drives, such as:
# grub-install --target=i386-pc --debug /dev/sda # grub-install --target=i386-pc --debug /dev/sdb
Where the RAID 1 array housing is housed on and .
Encrypted /boot
GRUB also has special support for booting with an encrypted . This is done by unlocking a LUKS blockdevice in order to read its configuration and load any initramfs and kernel from it. This option tries to solve the issue of having an unencrypted boot partition.
To enable this feature encrypt the partition with residing on it using LUKS as normal. Then add the following option to /etc/default/grub:
/etc/default/grub
GRUB_ENABLE_CRYPTODISK=y
This option is used by grub-install to generate the grub .
Make sure to install grub after modifying this option or encrypting the partition.
Without further changes you will be prompted twice for a passphrase: the first for GRUB to unlock the mount point in early boot, the second to unlock the root filesystem itself as implemented by the initramfs. You can use a keyfile to avoid this.
LUKS2
GRUB 2.06 has limited support for LUKS2. See GRUB bug #55093.
- Argon2id (cryptsetup default) and Argon2i PBKDFs are not supported (GRUB bug #59409), only PBKDF2 is.
grub-installdoes not support creating a core image that could be used for unlocking LUKS2. See the comments below or on for a workaround.
Use grub-install as described in the #Installation section. However, the generated EFI binary does not support LUKS2 and needs to be replaced.
Create . Replace with the output of lsblk -dno UUID /dev/nvme0n1p2 | tr -d -. Use instead of if your root drive is on an LVM logical volume inside the LUKS volume.
/boot/grub/grub-pre.cfg
set crypto_uuid=''UUID'' cryptomount -u $crypto_uuid set root=crypto0 set prefix=($root)/boot/grub insmod normal normal
Add lvm if you use LVM. Replace with or another filesystem module, if needed. Replace with or if need be:
$ grub-mkimage -p /boot/grub -O x86_64-efi -c grub-pre.cfg -o /tmp/grubx64.efi luks2 part_gpt cryptodisk gcry_rijndael pbkdf2 gcry_sha256 ext2
Copy to ESP:
# install -v /tmp/grubx64.efi esp/EFI/GRUB/grubx64.efi
If you enter an invalid passphrase during boot and end up at the GRUB rescue shell, try to mount all (hopefully only one) encrypted partitions or use cryptomount -u $crypto_uuid to mount a specific one. Then proceed with and as usual.
If you enter a correct passphrase, but an error is immediately returned, make sure that the right cryptographic modules are specified. Use and check whether the hash function (SHA-256, SHA-512) matches the modules (, ) installed and the PBKDF algorithm is pbkdf2. The hash and PBDKDF algorithms can be changed for existing keys by using cryptsetup luksConvertKey --hash sha256 --pbkdf pbkdf2 /dev/nvme0n1p2. Under normal circumstances it should take a few seconds before the passphrase is processed.
Custom grub.cfg
This section describes the manual creation of GRUB boot entries in instead of relying on grub-mkconfig.
A basic GRUB config file uses the following options:
- is the partition Y on disk X, partition numbers starting at 1, disk numbers starting at 0
- is the default boot entry that is chosen after timeout for user action
- is the time M to wait in seconds for a user selection before default is booted
menuentry "title" {entry options}is a boot entry titled- sets the boot partition, where the kernel and GRUB modules are stored (boot need not be a separate partition, and may simply be a directory under the "root" partition ()
Boot menu entry examples
For tips on managing multiple GRUB entries, for example when using both linux and kernels, see /Tips and tricks#Multiple entries.
For Archiso and Archboot boot menu entries see Multiboot USB drive#Boot entries.
"Restart" menu entry
menuentry "System restart" {
echo "System rebooting..."
reboot
}
EFI binaries
When launched in UEFI mode, GRUB can chainload other EFI binaries.
UEFI Shell
You can launch UEFI Shell by placing it in the root of the EFI system partition and adding this menu entry:
gdisk
Download the gdisk EFI application and copy to .
Chainloading a unified kernel image
If you have a unified kernel image generated from following Secure Boot or other means, you can add it to the boot menu. For example:
menuentry "Arch Linux" {
insmod fat
insmod chain
search --no-floppy --set=root --fs-uuid ''FILESYSTEM_UUID''
chainloader /EFI/Linux/Arch-linux.efi
}
GNU/Linux
Assuming that the other distribution is on partition :
Alternatively let GRUB search for the right partition by UUID or file system label:
If the other distribution has already a valid folder with installed GRUB, , kernel and initramfs, GRUB can be instructed to load these other files on-the-fly during boot. For example, for and the fourth GPT partition:
When choosing this entry, GRUB loads the file from the other volume and displays that menu. Any environment variable changes made by the commands in file will not be preserved after returns. Press Esc to return to the first GRUB menu.
Windows installed in UEFI/GPT mode
This mode determines where the Windows bootloader resides and chain-loads it after GRUB when the menu entry is selected. The main task here is finding the EFI system partition and running the bootloader from it.
where and $fs_uuid are obtained with the following two commands.
The $fs_uuid command determines the UUID of the EFI system partition:
Alternatively one can run and read the UUID of the EFI system partition from there.
The command will determine the location of the EFI system partition, in this case harddrive 0:
These two commands assume the ESP Windows uses is mounted at esp. There might be case differences in the path to Windows's EFI file, what with being Windows, and all.
Windows installed in BIOS/MBR mode
Throughout this section, it is assumed your Windows partition is . A different partition will change every instance of hd0,msdos1.
In both examples is the filesystem UUID which can be found with command .
For Windows Vista/7/8/8.1/10:
For Windows XP:
if [ "${grub_platform}" == "pc" ]; then
menuentry "Microsoft Windows XP" {
insmod part_msdos
insmod ntfs
insmod ntldr
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 ''XXXXXXXXXXXXXXXX''
ntldr /ntldr
}
fi
Using labels
It is possible to use file system labels, human-readable strings attached to file systems, by using the option to . First of all, make sure your file system has a label.
Then, add an entry using labels. An example of this:
menuentry "Arch Linux, session texte" {
search --label --set=root archroot
linux /boot/vmlinuz-linux root=/dev/disk/by-label/archroot ro
initrd /boot/initramfs-linux.img
}
Using the command shell
Since the MBR is too small to store all GRUB modules, only the menu and a few basic commands reside there. The majority of GRUB functionality remains in modules in , which are inserted as needed. In error conditions (e.g. if the partition layout changes) GRUB may fail to boot. When this happens, a command shell may appear.
GRUB offers multiple shells/prompts. If there is a problem reading the menu but the bootloader is able to find the disk, you will likely be dropped to the "normal" shell:
grub>
If there is a more serious problem (e.g. GRUB cannot find required files), you may instead be dropped to the "rescue" shell:
grub rescue>
The rescue shell is a restricted subset of the normal shell, offering much less functionality. If dumped to the rescue shell, first try inserting the "normal" module, then starting the "normal" shell:
grub rescue> set prefix=(hdX,Y)/boot/grub grub rescue> insmod (hdX,Y)/boot/grub/i386-pc/normal.mod rescue:grub> normal
Pager support
GRUB supports pager for reading commands that provide long output (like the command). This works only in normal shell mode and not in rescue mode. To enable pager, in GRUB command shell type:
sh:grub> set pager=1
Using the command shell environment to boot operating systems
grub>
The GRUB's command shell environment can be used to boot operating systems. A common scenario may be to boot Windows / Linux stored on a drive/partition via chainloading.
Chainloading means to load another boot-loader from the current one, ie, chain-loading.
The other bootloader may be embedded at the start of a partitioned disk (MBR), at the start of a partition or a partitionless disk (VBR), or as an EFI binary in the case of UEFI.
Chainloading a partition's VBR
set root=(hdX,Y) chainloader +1 boot
X=0,1,2... Y=1,2,3...
For example to chainload Windows stored in the first partition of the first hard disk,
set root=(hd0,1) chainloader +1 boot
Similarly GRUB installed to a partition can be chainloaded.
Chainloading a disk's MBR or a partitionless disk's VBR
set root=hdX chainloader +1 boot
Chainloading Windows/Linux installed in UEFI mode
insmod fat
set root=(hd0,gpt4)
chainloader (${root})/EFI/Microsoft/Boot/bootmgfw.efi
boot
insmod fat is used for loading the FAT file system module for accessing the Windows bootloader on the EFI system partition.
or is the EFI system partition in this example.
The entry in the line specifies the path of the .efi file to be chain-loaded.
Normal loading
See the examples in #Using the rescue console
Using the rescue console
See #Using the command shell first. If unable to activate the standard shell, one possible solution is to boot using a live CD or some other rescue disk to correct configuration errors and reinstall GRUB. However, such a boot disk is not always available (nor necessary); the rescue console is surprisingly robust.
The available commands in GRUB rescue include insmod, , , and . This example uses and insmod. modifies variables and insmod inserts new modules to add functionality.
Before starting, the user must know the location of their partition (be it a separate partition, or a subdirectory under their root):
grub rescue> set prefix=(hdX,Y)/boot/grub
where is the physical drive number and is the partition number.
/boot from the path (i.e. type set prefix=(hdX,Y)/grub).To expand console capabilities, insert the module:
grub rescue> insmod i386-pc/linux.mod
or simply
grub rescue> insmod linux
This introduces the and commands, which should be familiar.
An example, booting Arch Linux:
set root=(hd0,5) linux /boot/vmlinuz-linux root=/dev/sda5 initrd /boot/initramfs-linux.img boot
With a separate boot partition (e.g. when using UEFI), again change the lines accordingly:
set root=(hd0,5) linux (hdX,Y)/vmlinuz-linux root=/dev/sda6 initrd (hdX,Y)/initramfs-linux.img boot
After successfully booting the Arch Linux installation, users can correct as needed and then reinstall GRUB.
To reinstall GRUB and fix the problem completely, changing if needed. See #Installation for details.
GRUB removal
In general, in order to remove grub, one has to do the installation steps in reverse order. Perhaps cleaning any left over at the end. However, before doing anything, one has to decide if, and how, the machine will boot after the removal. Assuming one removes grub because they would like to use another boot loader, a safe, though a bit difficult, method is to make sure the other boot loader is working before removing grub.
In any case, even when removing grub before installing another boot loader, for the UEFI case, run:
$ efibootmgr
And verify the other boot loader is listed in the BootOrder line. If grub was not removed, the other boot loader should be listed before grub. If grub is already removed, grub should not be mentioned in that line. But note this is only a necessary, but not sufficient, condition for the machine to boot with the other boot loader. Neither it is a sufficient condition for the full removal of grub.
For both UEFI and non UEFI machines, grub-install was manually run as part of the installation of grub. One of its jobs for the UEFI case was to run the equivalent of . As part of grub removal, one has to remove the products of grub-install. The opposite of is , or an equivalent program. One way to obtain the number of the boot entry for the command is from the output of (with no arguments).
grub-install creates the directory that needs to be removed manually. Though some users will want to keep it, should they want to install grub again.
After migrating to GPT/UEFI one may want to remove the MBR boot code using dd:
# dd if=/dev/zero of=/dev/sdX bs=440 count=1
Troubleshooting
Unsupported file systems
In case that GRUB does not support the root file system, an alternative partition with a supported file system must be created. In some cases, the development version of GRUB may have native support for the file system.
If GRUB is used with an unsupported file system it is not able to extract the UUID of your drive so it uses classic non-persistent names instead. In this case you might have to manually edit and replace root=/dev/sdXx with . You can use the command to get the UUID of your device, see Persistent block device naming.
While GRUB supports F2FS since version 2.0.4, it cannot correctly read its boot files from an F2FS partition that was created with the flag enabled.
Enable debug messages
Add:
set pager=1 set debug=all
to .
msdos-style error message
grub-setup: warn: This msdos-style partition label has no post-MBR gap; embedding will not be possible!
grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists.
However, blocklists are UNRELIABLE and its use is discouraged.
grub-setup: error: If you really want blocklists, use --force.
This error may occur when you try installing GRUB in a VMware container. Read more about it here. It happens when the first partition starts just after the MBR (block 63), without the usual space of 1 MiB (2048 blocks) before the first partition. Read #Master Boot Record (MBR) specific instructions
Common installation errors
- If you have a problem when running grub-install with sysfs or procfs and it says you must run
modprobe efivarfs, try Unified Extensible Firmware Interface#Mount efivarfs. - Without or option, grub-install cannot determine for which firmware to install. In such cases
grub-installwill print . - If after running grub-install you are told your partition does not look like an EFI partition then the partition is most likely not .
Create a GRUB entry in the firmware boot manager
grub-install automatically tries to create a menu entry in the boot manager. If it does not, then see UEFI#efibootmgr for instructions to use to create a menu entry. However, the problem is likely to be that you have not booted your CD/USB in UEFI mode, as in UEFI#Create UEFI bootable USB from ISO.
As another example of creating a GRUB entry in the firmware boot manager, consider efibootmgr -c. This assumes that /dev/sda1 is the EFI System Partition, and is mounted at /boot/efi. Which are the default behavior of . It creates a new boot option, called "Linux", and puts it at the top of the boot order list. Options may be passed to modify the default behavior. The default OS Loader is \EFI\arch\grub.efi.
Drop to rescue shell
If GRUB loads but drops into the rescue shell with no errors, it can be due to one of these two reasons:
- It may be because of a missing or misplaced . This will happen if GRUB UEFI was installed with and is missing,
- It also happens if the boot partition, which is hardcoded into the file, has changed.
GRUB UEFI not loaded
An example of a working UEFI:
If the screen only goes black for a second and the next boot option is tried afterwards, according to this post, moving GRUB to the partition root can help. The boot option has to be deleted and recreated afterwards. The entry for GRUB should look like this then:
Boot0000* GRUB HD(1,800,32000,23532fbb-1bfa-4e46-851a-b494bfe9478c)File(\grubx64.efi)
Default/fallback boot path
Some UEFI firmwares require a bootable file at a known location before they will show UEFI NVRAM boot entries. If this is the case, grub-install will claim has added an entry to boot GRUB, however the entry will not show up in the VisualBIOS boot order selector. The solution is to install GRUB at the default/fallback boot path:
# grub-install --target=x86_64-efi --efi-directory=esp --removable
Alternatively you can move an already installed GRUB EFI executable to the default/fallback path:
# mv esp/EFI/grub esp/EFI/BOOT # mv esp/EFI/BOOT/grubx64.efi esp/EFI/BOOT/BOOTX64.EFI
Invalid signature
If trying to boot Windows results in an "invalid signature" error, e.g. after reconfiguring partitions or adding additional hard drives, (re)move GRUB's device configuration and let it reconfigure:
# mv /boot/grub/device.map /boot/grub/device.map-old # grub-mkconfig -o /boot/grub/grub.cfg
should now mention all found boot options, including Windows. If it works, remove .
Boot freezes
If booting gets stuck without any error message after GRUB loading the kernel and the initial ramdisk, try removing the add_efi_memmap kernel parameter.
Arch not found from other OS
Some have reported that other distributions may have trouble finding Arch Linux automatically with . If this problem arises, it has been reported that detection can be improved with the presence of . This file and updating tool is available with the package .
Warning when installing in chroot
When installing GRUB on a LVM system in a chroot environment (e.g. during system installation), you may receive warnings like
/run/lvm/lvmetad.socket: connect failed: No such file or directory
or
WARNING: failed to connect to lvmetad: No such file or directory. Falling back to internal scanning.
This is because is not available inside the chroot. These warnings will not prevent the system from booting, provided that everything has been done correctly, so you may continue with the installation.
GRUB loads slowly
GRUB can take a long time to load when disk space is low. Check if you have sufficient free disk space on your or partition when you are having problems.
error: unknown filesystem
GRUB may output and refuse to boot for a few reasons. If you are certain that all UUIDs are correct and all filesystems are valid and supported, it may be because your BIOS Boot Partition is located outside the first 2 TiB of the drive . Use a partitioning tool of your choice to ensure this partition is located fully within the first 2 TiB, then reinstall and reconfigure GRUB.
This error might also be caused by an ext4 filesystem having unsupported features set:
large_dir- unsupported.- - will be supported in GRUB 2.11 (commit).
grub-reboot not resetting
GRUB seems to be unable to write to root BTRFS partitions . If you use grub-reboot to boot into another entry it will therefore be unable to update its on-disk environment. Either run grub-reboot from the other entry (for example when switching between various distributions) or consider a different file system. You can reset a "sticky" entry by executing and setting in your /etc/default/grub (do not forget ).
Old BTRFS prevents installation
If a drive is formatted with BTRFS without creating a partition table (eg. /dev/sdx), then later has partition table written to, there are parts of the BTRFS format that persist. Most utilities and OS's do not see this, but GRUB will refuse to install, even with --force
# grub-install: warning: Attempting to install GRUB to a disk with multiple partition labels. This is not supported yet.. # grub-install: error: filesystem `btrfs' does not support blocklists.
You can zero the drive, but the easy solution that leaves your data alone is to erase the BTRFS superblock with wipefs -o 0x10040 /dev/sdx
Windows 8/10 not found
A setting in Windows 8/10 called "Hiberboot", "Hybrid Boot" or "Fast Boot" can prevent the Windows partition from being mounted, so will not find a Windows install. Disabling Hiberboot in Windows will allow it to be added to the GRUB menu.
VirtualBox EFI mode
For VirtualBox < 6.1, install GRUB to the default/fallback boot path.
See also VirtualBox#Installation in EFI mode on VirtualBox < 6.1.
GRUB rescue and encrypted /boot
When using an encrypted /boot, and you fail to input a correct password, you will be dropped in grub-rescue prompt.
This grub-rescue prompt has limited capabilities. Use the following commands to complete the boot:
See this blog post for a better description.
GRUB is installed but the menu is not shown at boot
Check /etc/default/grub if is set to , in which case set it to a positive number: it sets the number of seconds before the default GRUB entry is loaded. Also check if is set to hidden and set it to , so that the menu will be shown by default. Then regenerate the main configuration file and reboot to check if it worked.