Which of the following files holds the configuration information for GRUB?

This file contains the configuration of the GRUB 2 menu items. It replaces menu.lst used in GRUB Legacy. grub.cfg should not be edited—it is automatically generated by the command

### BEGIN /etc/grub.d/90_persistent ###

0.

### BEGIN /etc/grub.d/90_persistent ###

1

This optional file is directly sourced by grub.cfg at boot time and can be used to add custom items to the boot menu. Starting with openSUSE Leap Leap 42.2 these entries will also be parsed when using

### BEGIN /etc/grub.d/90_persistent ###

3.

### BEGIN /etc/grub.d/90_persistent ###

4

This file controls the user settings of GRUB 2 and usually includes additional environmental settings such as backgrounds and themes.

Scripts under

### BEGIN /etc/grub.d/90_persistent ###

5

The scripts in this directory are read during execution of the command

### BEGIN /etc/grub.d/90_persistent ###

0. Their instructions are integrated into the main configuration file

### BEGIN /etc/grub.d/90_persistent ###

7.

### BEGIN /etc/grub.d/90_persistent ###

8

This configuration file holds some basic settings like the boot loader type and whether to enable UEFI Secure Boot support.

### BEGIN /etc/grub.d/90_persistent ###

9,

These configuration files contain architecture-specific options.

GRUB 2 can be controlled in various ways. Boot entries from an existing configuration can be selected from the graphical menu [splash screen]. The configuration is loaded from the file /boot/grub2/grub.cfg which is compiled from other configuration files [see below]. All GRUB 2 configuration files are considered system files, and you need

### END /etc/grub.d/90_persistent ###

1 privileges to edit them.

Note: Activating Configuration Changes

After having manually edited GRUB 2 configuration files, you need to run

### BEGIN /etc/grub.d/90_persistent ###

0 to activate the changes. However, this is not necessary when changing the configuration with YaST, because YaST will automatically run this command.

The graphical splash screen with the boot menu is based on the GRUB 2 configuration file /boot/grub2/grub.cfg, which contains information about all partitions or operating systems that can be booted by the menu.

Every time the system is booted, GRUB 2 loads the menu file directly from the file system. For this reason, GRUB 2 does not need to be re-installed after changes to the configuration file. grub.cfg is automatically rebuilt with kernel installations or removals.

More general options of GRUB 2 belong here, such as the time the menu is displayed, or the default OS to boot. To list all available options, see the output of the following command:

tux > grep "export GRUB_DEFAULT" -A50 /usr/sbin/grub2-mkconfig | grep GRUB_

In addition to already defined variables, the user may introduce their own variables, and use them later in the scripts found in the

### END /etc/grub.d/90_persistent ###

5 directory.

After having edited

### BEGIN /etc/grub.d/90_persistent ###

4, update the main configuration file with

### BEGIN /etc/grub.d/90_persistent ###

0.

Note: Scope

All options set in this file are general options that affect all boot entries. Specific options for Xen kernels or the Xen hypervisor can be set via the GRUB_*_XEN_* configuration options. See below for details.

### END /etc/grub.d/90_persistent ###

8

Sets the boot menu entry that is booted by default. Its value can be a numeric value, the complete name of a menu entry, or “saved”.

### END /etc/grub.d/90_persistent ###

9 boots the third [counted from zero] boot menu entry.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

0 boots the first submenu entry of the third top-level menu entry.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

1 boots the menu entry with the title “Example boot menu entry”.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

2 boots the entry specified by the

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

3 or

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

4 commands. While

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

5 sets the default boot entry for the next reboot only,

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

4 sets the default boot entry until changed.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

7 lists the next boot entry.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

8

Waits the specified number of seconds for the user to press a key. During the period no menu is shown unless the user presses a key. If no key is pressed during the time specified, the control is passed to

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

9.

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

0 first checks whether Shift is pressed and shows the boot menu if yes, otherwise immediately boots the default menu entry. This is the default when only one bootable OS is identified by GRUB 2.

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

1

If

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

2 is specified, a countdown timer is displayed on a blank screen when the

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

8 feature is active.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

9

Time period in seconds the boot menu is displayed before automatically booting the default boot entry. If you press a key, the timeout is cancelled and GRUB 2 waits for you to make the selection manually.

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

5 will cause the menu to be displayed until you select the boot entry manually.

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6

Entries on this line are added at the end of the boot entries for normal and recovery mode. Use it to add kernel parameters to the boot entry.

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

7

Same as

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6 but the entries are appended in the normal mode only.

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

9

Same as

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6 but the entries are appended in the recovery mode only.

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

1

This entry will completely replace the

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6 parameters for all Xen boot entries.

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

3

Same as

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

1 but it will only replace parameters of

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

7.

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6

This entry specifies the kernel parameters for the Xen guest kernel only—the operation principle is the same as for

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6.

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

8

Same as

set superusers="root"
password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

6—the operation principle is the same as for

tux > sudo grub2-mkpasswd-pbkdf2
Password: ****
Reenter password: ****
PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

7.

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

1

Enables and specifies an input/output terminal device. Can be

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

2 [PC BIOS and EFI consoles],

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

3 [serial terminal],

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

4 [Open Firmware console], or the default

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

5 [graphics-mode output]. It is also possible to enable more than one device by quoting the required options, for example

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

6.

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

7

The resolution used for the

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

5 graphical terminal. Note that you can only use modes supported by your graphics card [VBE]. The default is ‘auto’, which tries to select a preferred resolution. You can display the screen resolutions available to GRUB 2 by typing

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

9 in the GRUB 2 command line. The command line is accessed by typing C when the GRUB 2 boot menu screen is displayed.

You can also specify a color depth by appending it to the resolution setting, for example /boot/grub2/grub.cfg0.

/boot/grub2/grub.cfg1

Set a background image for the

tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

5 graphical terminal. The image must be a file readable by GRUB 2 at boot time, and it must end with the /boot/grub2/grub.cfg3, /boot/grub2/grub.cfg4, /boot/grub2/grub.cfg5, or /boot/grub2/grub.cfg6 suffix. If necessary, the image will be scaled to fit the screen.

/boot/grub2/grub.cfg7

If this option is set to /boot/grub2/grub.cfg8, automatic searching for other operating systems is disabled. Only the kernel images in /boot/grub2/grub.cfg9 and the options from your own scripts in

### BEGIN /etc/grub.d/90_persistent ###

5 are detected.

menu.lst1

If this option is set to /boot/grub2/grub.cfg8, GRUB 2 can boot directly into Snapper snapshots. For more information, see Section 3.3, “System Rollback by Booting from Snapshots”.

For a complete list of options, see the GNU GRUB manual.

The scripts in this directory are read during execution of the command

### BEGIN /etc/grub.d/90_persistent ###

0. Their instructions are incorporated into /boot/grub2/grub.cfg. The order of menu items in grub.cfg is determined by the order in which the files in this directory are run. Files with a leading numeral are executed first, beginning with the lowest number. menu.lst6 is run before menu.lst7, which would run before menu.lst8. If files with alphabetic names are present, they are executed after the numerically-named files. Only executable files generate output to grub.cfg during execution of grub.cfg0. By default all files in the

### END /etc/grub.d/90_persistent ###

5 directory are executable.

Tip: Persistent Custom Content in grub.cfg

Because /boot/grub2/grub.cfg is recompiled each time grub.cfg0 is run, any custom content is lost. If you want to insert your lines directly into /boot/grub2/grub.cfg without losing them after grub.cfg0 is run, insert them between

### BEGIN /etc/grub.d/90_persistent ###

and

### END /etc/grub.d/90_persistent ###

The grub.cfg7 script ensures that such content will be preserved.

A list of the most important scripts follows:

menu.lst6

Sets environmental variables such as system file locations, display settings, themes, and previously saved entries. It also imports preferences stored in the

### BEGIN /etc/grub.d/90_persistent ###

4. Normally you do not need to make changes to this file.

menu.lst7

Identifies Linux kernels on the root device and creates relevant menu entries. This includes the associated recovery mode option if enabled. Only the latest kernel is displayed on the main menu page, with additional kernels included in a submenu.

### BEGIN /etc/grub.d/90_persistent ###

01

This script uses

### BEGIN /etc/grub.d/90_persistent ###

02 to search for Linux and other operating systems and places the results in the GRUB 2 menu. There are sections to identify specific other operating systems, such as Windows or macOS.

menu.lst8

This file provides a simple way to include custom boot entries into grub.cfg. Make sure that you do not change the

### BEGIN /etc/grub.d/90_persistent ###

05 part at the beginning.

The processing sequence is set by the preceding numbers with the lowest number being executed first. If scripts are preceded by the same number the alphabetical order of the complete name decides the order.

Tip:

### BEGIN /etc/grub.d/90_persistent ###

1

If you create

### BEGIN /etc/grub.d/90_persistent ###

1 and fill it with content, it will be automatically included into /boot/grub2/grub.cfg just after 40_custom at boot time.

12.2.4 Mapping between BIOS Drives and Linux Devices #Edit source

In GRUB Legacy, the

### BEGIN /etc/grub.d/90_persistent ###

09 configuration file was used to derive Linux device names from BIOS drive numbers. The mapping between BIOS drives and Linux devices cannot always be guessed correctly. For example, GRUB Legacy would get a wrong order if the boot sequence of IDE and SCSI drives is exchanged in the BIOS configuration.

GRUB 2 avoids this problem by using device ID strings [UUIDs] or file system labels when generating grub.cfg. GRUB 2 utilities create a temporary device map on the fly, which is usually sufficient, particularly in the case of single-disk systems.

However, if you need to override the GRUB 2's automatic device mapping mechanism, create your custom mapping file

### BEGIN /etc/grub.d/90_persistent ###

11. The following example changes the mapping to make

### BEGIN /etc/grub.d/90_persistent ###

12 the boot disk. Note that GRUB 2 partition numbers start with

### BEGIN /etc/grub.d/90_persistent ###

13 and not with

### BEGIN /etc/grub.d/90_persistent ###

14 as in GRUB Legacy.

[hd1]  /dev/disk-by-id/DISK3 ID
[hd2]  /dev/disk-by-id/DISK1 ID
[hd3]  /dev/disk-by-id/DISK2 ID

Even before the operating system is booted, GRUB 2 enables access to file systems. Users without root permissions can access files in your Linux system to which they have no access after the system is booted. To block this kind of access or to prevent users from booting certain menu entries, set a boot password.

Important: Booting Requires Password

If set, the boot password is required on every boot, which means the system does not boot automatically.

Proceed as follows to set a boot password. Alternatively use YaST [].

1. Encrypt the password using

   ### BEGIN /etc/grub.d/90_persistent ###

   15

   tux > sudo grub2-mkpasswd-pbkdf2
   Password: ****
   Reenter password: ****
   PBKDF2 hash of your password is grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

2. Paste the resulting string into the file

   ### BEGIN /etc/grub.d/90_persistent ###

   16 together with the

   ### BEGIN /etc/grub.d/90_persistent ###

   17 command.

   set superusers="root"
   password_pbkdf2 root grub.pbkdf2.sha512.10000.9CA4611006FE96BC77A...

3. To import the changes into the main configuration file, run:

   tux > sudo grub2-mkconfig -o /boot/grub2/grub.cfg

After you reboot, you will be prompted for a user name and a password when trying to boot a menu entry. Enter

### END /etc/grub.d/90_persistent ###

1 and the password you typed during the

### BEGIN /etc/grub.d/90_persistent ###

19 command. If the credentials are correct, the system will boot the selected boot entry.

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