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Arnold Nikiforov
Arnold Nikiforov

Install Grub On Usb Mac

Assuming all went well, you now have Linux running on your Mac and you can test it out or install it outright if you're tired of macOS. You still have an Apple recovery partition which is accessible by holding Cmd + R while your machine boots. This can help you reinstall macOS (or apply other fixes) if you decide to go back.

Install Grub On Usb Mac

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For more, check out how to install macOS from a USB flash drive. And if you'd prefer to install Linux on your internal drive, our guide on how to dual-boot Linux on your Mac is your essential next read.

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 boot loader as per the instructions below.

where i386-pc 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 /dev/sda or /dev/nvme0n1, or /dev/mmcblk0. See Device file#Block device names for a description of the block device naming scheme.

After the installation, the main configuration file /boot/grub/grub.cfg needs to be generated. The generation process can be influenced by a variety of options in /etc/default/grub and scripts in /etc/grub.d/.

You can add additional custom menu entries by editing /etc/grub.d/40_custom and re-generating /boot/grub/grub.cfg. 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 /etc/grub.d/41_custom adds the necessary source statement to the generated configuration file.

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: Warning: os-prober will not be executed to detect other bootable partitions then edit /etc/default/grub and add/uncomment:

For Windows installed in BIOS mode, mount the Windows system partition (its file system label should be System Reserved or SYSTEM). Run os-prober as root to detect and generate an entry for it.

To pass custom additional arguments to the Linux image, you can set the GRUB_CMDLINE_LINUX + 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 GRUB_CMDLINE_LINUX is used in the generation.

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 /boot/vmlinuz-linux-lts is sorted before /boot/vmlinuz-linux, if you have both linux-lts and linux installed, the LTS kernel will be the top-level menu entry, which may not be desirable. This can be overridden by specifying GRUB_TOP_LEVEL=path_to_kernel" in /etc/default/grub. For example, to make the regular kernel be the top-level menu entry, you can use GRUB_TOP_LEVEL="/boot/vmlinuz-linux".

If you enter a correct passphrase, but an Invalid passphrase error is immediately returned, make sure that the right cryptographic modules are specified. Use cryptsetup luksDump /dev/nvme0n1p2 and check whether the hash function (SHA-256, SHA-512) matches the modules (gcry_sha256, gcry_sha512) 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.

If the other distribution has already a valid /boot folder with installed GRUB, grub.cfg, kernel and initramfs, GRUB can be instructed to load these other grub.cfg files on-the-fly during boot. For example, for hd0 and the fourth GPT partition:

When choosing this entry, GRUB loads the grub.cfg file from the other volume and displays that menu. Any environment variable changes made by the commands in file will not be preserved after configfile returns. Press Esc to return to the first GRUB menu.

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 /boot/grub/, 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.

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.

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.

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 efibootmgr --create. As part of grub removal, one has to remove the products of grub-install. The opposite of efibootmgr --create is efibootmgr --delete-bootnum, or an equivalent program. One way to obtain the number of the boot entry for the efibootmgr --delete-bootnum command is from the output of efibootmgr (with no arguments).

In case that GRUB does not support the root file system, an alternative /boot partition with a supported file system must be created. In some cases, the development version of GRUB grub-gitAUR 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 /dev/sdXx names instead. In this case you might have to manually edit /boot/grub/grub.cfg and replace root=/dev/sdXx with root=UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX. You can use the blkid command to get the UUID of your device, see Persistent block device naming.

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

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 efibootmgr 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 efibootmgr. 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.

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 efibootmgr 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:

This is because /run 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 may output error: unknown filesystem 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 [1]. Use a partitioning tool of your choice to ensure this partition is located fully within the first 2 TiB, then reinstall and reconfigure GRUB.

GRUB seems to be unable to write to root Btrfs partitions [2]. 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 grub-editenv create and setting GRUB_DEFAULT=0 in your /etc/default/grub (do not forget grub-mkconfig -o /boot/grub/grub.cfg).

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

A setting in Windows 8/10 called "Hiberboot", "Hybrid Boot" or "Fast Boot" can prevent the Windows partition from being mounted, so grub-mkconfig will not find a Windows install. Disabling Hiberboot in Windows will allow it to be added to the GRUB menu.

Check /etc/default/grub if GRUB_TIMEOUT is set to 0, 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 GRUB_TIMEOUT_STYLE is set to hidden and set it to menu, so that the menu will be shown by default. Then regenerate the main configuration file and reboot to check if it worked.


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