GNU GRUB manual

5.1.1 How to boot an OS directly with GRUB

Multiboot (see Motivation in The Multiboot Specification) is the native format supported by GRUB. For the sake of convenience, there is also support for Linux, FreeBSD, NetBSD and OpenBSD. If you want to boot other operating systems, you will have to chain-load them (see Chain-loading an OS).

FIXME: this section is incomplete.

1. Run the command boot (see boot).

However, DOS and Windows have some deficiencies, so you might have to use more complicated instructions. See DOS/Windows, for more information.

5.1.2 Kexec with grub2-emu

GRUB can be run in userspace by invoking the grub2-emu tool. It will read all configuration scripts as if booting directly (see See How to boot an OS directly with GRUB). With the --kexec flag, and kexec(8) support from the operating system, the linux command will directly boot the target image. For systems that lack working systemctl(1) support for kexec, passing the --kexec flag twice will fallback to invoking kexec(8) directly; note however that this fallback may be unsafe outside read-only environments, as it does not invoke shutdown machinery.

5.1.3 Chain-loading an OS

Operating systems that do not support Multiboot and do not have specific support in GRUB (specific support is available for Linux, FreeBSD, NetBSD and OpenBSD) must be chain-loaded, which involves loading another boot loader and jumping to it in real mode.

The chainloader command (see chainloader) is used to set this up. It is normally also necessary to load some GRUB modules and set the appropriate root device. Putting this together, we get something like this, for a Windows system on the first partition of the first hard disk:

menuentry "Windows" {
	insmod chain
	insmod ntfs
	set root=(hd0,1)
	chainloader +1
}

On systems with multiple hard disks, an additional workaround may be required. See DOS/Windows.

Chain-loading is only supported on PC BIOS and EFI platforms.

5.4.1 GNU/Hurd

Since GNU/Hurd is Multiboot-compliant, it is easy to boot it; there is nothing special about it. But do not forget that you have to specify a root partition to the kernel.

1. Set GRUB’s root device to the same drive as GNU/Hurd’s. The command search --set=root --file /boot/gnumach.gz or similar may help you (see search).
2. Load the kernel and the modules, like this:

   grub> multiboot /boot/gnumach.gz root=device:hd0s1
   grub> module  /hurd/ext2fs.static ext2fs --readonly \
                      --multiboot-command-line='${kernel-command-line}' \
                      --host-priv-port='${host-port}' \
                      --device-master-port='${device-port}' \
                      --exec-server-task='${exec-task}' -T typed '${root}' \
                      '$(task-create)' '$(task-resume)'
   grub> module /lib/ld.so.1 exec /hurd/exec '$(exec-task=task-create)'
   

3. Finally, run the command boot (see boot).

5.4.2 GNU/Linux

It is relatively easy to boot GNU/Linux from GRUB, because it somewhat resembles to boot a Multiboot-compliant OS.

1. Set GRUB’s root device to the same drive as GNU/Linux’s. The command search --set=root --file /vmlinuz or similar may help you (see search).
2. Load the kernel using the command linux (see linux):

   grub> linux /vmlinuz root=/dev/sda1
   

   If you need to specify some kernel parameters, just append them to the command. For example, to set acpi to ‘off’, do this:

   grub> linux /vmlinuz root=/dev/sda1 acpi=off
   

   See the documentation in the Linux source tree for complete information on the available options.

   With linux GRUB uses 32-bit protocol. Some BIOS services like APM or EDD aren’t available with this protocol. In this case you need to use linux16

   grub> linux16 /vmlinuz root=/dev/sda1 acpi=off
   

3. If you use an initrd, execute the command initrd (see initrd) after linux:

   grub> initrd /initrd
   

   If you used linux16 you need to use initrd16:

   grub> initrd16 /initrd
   

4. Finally, run the command boot (see boot).

5.4.3 NetBSD

Booting a NetBSD kernel from GRUB is also relatively easy: first set GRUB’s root device, then load the kernel and the modules, and finally run boot.

1. Set GRUB’s root device to the partition holding the NetBSD root file system. For a disk with a NetBSD disk label, this is usually the first partition (a:). In that case, and assuming that the partition is on the first hard disk, set GRUB’s root device as follows:

   grub> insmod part_bsd
   grub> set root=(hd0,netbsd1)
   

   For a disk with a GUID Partition Table (GPT), and assuming that the NetBSD root partition is the third GPT partition, do this:

   grub> insmod part_gpt
   grub> set root=(hd0,gpt3)
   

2. Load the kernel using the command knetbsd:

   grub> knetbsd /netbsd
   

   Various options may be given to knetbsd. These options are, for the most part, the same as in the NetBSD boot loader. For instance, to boot the system in single-user mode and with verbose messages, do this:

   grub> knetbsd /netbsd -s -v
   

3. If needed, load kernel modules with the command knetbsd_module_elf. A typical example is the module for the root file system:

   grub> knetbsd_module_elf /stand/amd64/6.0/modules/ffs/ffs.kmod
   

4. Finally, run the command boot (see boot).

5.4.4 DOS/Windows

GRUB cannot boot DOS or Windows directly, so you must chain-load them (see Chain-loading an OS). However, their boot loaders have some critical deficiencies, so it may not work to just chain-load them. To overcome the problems, GRUB provides you with two helper functions.

If you have installed DOS (or Windows) on a non-first hard disk, you have to use the disk swapping technique, because that OS cannot boot from any disks but the first one. The workaround used in GRUB is the command drivemap (see drivemap), like this:

drivemap -s (hd0) (hd1)

This performs a virtual swap between your first and second hard drive.

Caution: This is effective only if DOS (or Windows) uses BIOS to access the swapped disks. If that OS uses a special driver for the disks, this probably won’t work.

Another problem arises if you installed more than one set of DOS/Windows onto one disk, because they could be confused if there are more than one primary partitions for DOS/Windows. Certainly you should avoid doing this, but there is a solution if you do want to do so. Use the partition hiding/unhiding technique.

If GRUB hides a DOS (or Windows) partition (see parttool), DOS (or Windows) will ignore the partition. If GRUB unhides a DOS (or Windows) partition, DOS (or Windows) will detect the partition. Thus, if you have installed DOS (or Windows) on the first and the second partition of the first hard disk, and you want to boot the copy on the first partition, do the following:

parttool (hd0,1) hidden-
parttool (hd0,2) hidden+
set root=(hd0,1)
chainloader +1
parttool ${root} boot+
boot

7.2.1 Colors

Colors can be specified in several ways:

• HTML-style “#RRGGBB” or “#RGB” format, where *R*, *G*, and *B* are hexadecimal digits (e.g., “#8899FF”)
• as comma-separated decimal RGB values (e.g., “128, 128, 255”)
• with “SVG 1.0 color names” (e.g., “cornflowerblue”) which must be specified in lowercase.

7.2.2 Fonts

The fonts GRUB uses “PFF2 font format” bitmap fonts. Fonts are specified with full font names. Currently there is no provision for a preference list of fonts, or deriving one font from another. Fonts are loaded with the “loadfont” command in GRUB (loadfont). To see the list of loaded fonts, execute the “lsfonts” command (lsfonts). If there are too many fonts to fit on screen, do “set pager=1” before executing “lsfonts”.

7.2.3 Progress Bar

Progress bars are used to display the remaining time before GRUB boots the default menu entry. To create a progress bar that will display the remaining time before automatic boot, simply create a “progress_bar” component with the id “__timeout__”. This indicates to GRUB that the progress bar should be updated as time passes, and it should be made invisible if the countdown to automatic boot is interrupted by the user.

Progress bars may optionally have text displayed on them. This text is controlled by variable “text” which contains a printf template with the only argument %d is the number of seconds remaining. Additionally special values “@TIMEOUT_NOTIFICATION_SHORT@”, “@TIMEOUT_NOTIFICATION_MIDDLE@”, “@TIMEOUT_NOTIFICATION_LONG@” are replaced with standard and translated templates.

7.2.4 Circular Progress Indicator

The circular progress indicator functions similarly to the progress bar. When given an id of “__timeout__”, GRUB updates the circular progress indicator’s value to indicate the time remaining. For the circular progress indicator, there are two images used to render it: the *center* image, and the *tick* image. The center image is rendered in the center of the component, while the tick image is used to render each mark along the circumference of the indicator.

7.2.5 Labels

Text labels can be placed on the boot screen. The font, color, and horizontal alignment can be specified for labels. If a label is given the id “__timeout__”, then the “text” property for that label is also updated with a message informing the user of the number of seconds remaining until automatic boot. This is useful in case you want the text displayed somewhere else instead of directly on the progress bar.

7.2.6 Boot Menu

The boot menu where GRUB displays the menu entries from the “grub.cfg” file. It is a list of items, where each item has a title and an optional icon. The icon is selected based on the *classes* specified for the menu entry. If there is a PNG file named “myclass.png” in the “grub/themes/icons” directory, it will be displayed for items which have the class *myclass*. The boot menu can be customized in several ways, such as the font and color used for the menu entry title, and by specifying styled boxes for the menu itself and for the selected item highlight.

7.2.7 Styled Boxes

One of the most important features for customizing the layout is the use of *styled boxes*. A styled box is composed of 9 rectangular (and potentially empty) regions, which are used to seamlessly draw the styled box on screen:

To support any size of box on screen, the center slice and the slices for the top, bottom, and sides are all scaled to the correct size for the component on screen, using the following rules:

1. The edge slices (north, south, east, and west) are scaled in the direction of the edge they are adjacent to. For instance, the west slice is scaled vertically.
2. The corner slices (northwest, northeast, southeast, and southwest) are not scaled.
3. The center slice is scaled to fill the remaining space in the middle.

As an example of how an image might be sliced up, consider the styled box used for a terminal view.

7.2.8 Creating Styled Box Images

The Inkscape_ scalable vector graphics editor is a very useful tool for creating styled box images. One process that works well for slicing a drawing into the necessary image slices is:

1. Create or open the drawing you’d like use.
2. Create a new layer on the top of the layer stack. Make it visible. Select this layer as the current layer.
3. Draw 9 rectangles on your drawing where you’d like the slices to be. Clear the fill option, and set the stroke to 1 pixel wide solid stroke. The corners of the slices must meet precisely; if it is off by a single pixel, it will probably be evident when the styled box is rendered in the GRUB menu. You should probably go to File | Document Properties | Grids and enable a grid or create a guide (click on one of the rulers next to the drawing and drag over the drawing; release the mouse button to place the guide) to help place the rectangles precisely.
4. Right click on the center slice rectangle and choose Object Properties. Change the "Id" to “slice_c“ and click Set. Repeat this for the remaining 8 rectangles, giving them Id values of “slice_n“, “slice_ne“, “slice_e“, and so on according to the location.
5. Save the drawing.
6. Select all the slice rectangles. With the slice layer selected, you can simply press Ctrl+A to select all rectangles. The status bar should indicate that 9 rectangles are selected.
7. Click the layer hide icon for the slice layer in the layer palette. The rectangles will remain selected, even though they are hidden.
8. Choose File | Export Bitmap and check the *Batch export 9 selected objects* box. Make sure that *Hide all except selected* is unchecked. click *Export*. This will create PNG files in the same directory as the drawing, named after the slices. These can now be used for a styled box in a GRUB theme.

7.3.1 Global Properties

7.3.2 Format

Global properties are specified with the simple format:

• name1: value1
• name2: "value which may contain spaces"
• name3: #88F

In this example, name3 is assigned a color value.

7.3.3 Global Property List

7.3.4 Component Construction

Greater customizability comes is provided by components. A tree of components forms the user interface. *Containers* are components that can contain other components, and there is always a single root component which is an instance of a *canvas* container.

Components are created in the theme file by prefixing the type of component with a ’+’ sign:

+ label { text="GRUB" font="aqui 11" color="#8FF" }

properties of a component are specified as "name = value" (whitespace surrounding tokens is optional and is ignored) where *value* may be:

• a single word (e.g., “align = center“, “color = #FF8080“),
• a quoted string (e.g., “text = "Hello, World!"“), or
• a tuple (e.g., “preferred_size = (120, 80)“).

7.3.5 Component List

The following is a list of the components and the properties they support.

• label A label displays a line of text.

  Properties:

  id	Set to “__timeout__“ to display the time elapsed to an automatical boot of the default entry.
  text	The text to display. If “id“ is set to “__timeout__“ and no “text“ property is set then the amount of seconds will be shown. If set to “@KEYMAP_SHORT@“, “@KEYMAP_MIDDLE@“ or “@KEYMAP_LONG@“ then predefined hotkey information will be shown.
  font	The font to use for text display.
  color	The color of the text.
  align	The horizontal alignment of the text within the component. Options are “left“, “center“ and “right“.
  visible	Set to “false“ to hide the label.

• image A component that displays an image. The image is scaled to fit the component.

  Properties:

  file	The full path to the image file to load.

• progress_bar Displays a horizontally oriented progress bar. It can be rendered using simple solid filled rectangles, or using a pair of pixmap styled boxes.

  Properties:

  id	Set to “__timeout__“ to display the time elapsed to an automatical boot of the default entry.
  fg_color	The foreground color for plain solid color rendering.
  bg_color	The background color for plain solid color rendering.
  border_color	The border color for plain solid color rendering.
  text_color	The text color.
  bar_style	The styled box specification for the frame of the progress bar. Example: “progress_frame_*.png“ If the value is equal to “highlight_style“ then no styled boxes will be shown.
  highlight_style	The styled box specification for the highlighted region of the progress bar. This box will be used to paint just the highlighted region of the bar, and will be increased in size as the bar nears completion. Example: “progress_hl_*.png“. If the value is equal to “bar_style“ then no styled boxes will be shown.
  highlight_overlay	If this option is set to “true“ then the highlight box side slices (every slice except the center slice) will overlay the frame box side slices. And the center slice of the highlight box can move all the way (from top to bottom), being drawn on the center slice of the frame box. That way we can make a progress bar with round-shaped edges so there won’t be a free space from the highlight to the frame in top and bottom scrollbar positions. Default is “false“.
  font	The font to use for progress bar.
  text	The text to display on the progress bar. If the progress bar’s ID is set to “__timeout__“ and the value of this property is set to “@TIMEOUT_NOTIFICATION_SHORT@“, “@TIMEOUT_NOTIFICATION_MIDDLE@“ or “@TIMEOUT_NOTIFICATION_LONG@“, then GRUB will update this property with an informative message as the timeout approaches.

• circular_progress Displays a circular progress indicator. The appearance of this component is determined by two images: the *center* image and the *tick* image. The center image is generally larger and will be drawn in the center of the component. Around the circumference of a circle within the component, the tick image will be drawn a certain number of times, depending on the properties of the component.

  Properties:

  id	Set to “__timeout__“ to display the time elapsed to an automatical boot of the default entry.
  center_bitmap	The file name of the image to draw in the center of the component.
  tick_bitmap	The file name of the image to draw for the tick marks.
  num_ticks	The number of ticks that make up a full circle.
  ticks_disappear	Boolean value indicating whether tick marks should progressively appear, or progressively disappear as *value* approaches *end*. Specify “true“ or “false“. Default is “false“.
  start_angle	The position of the first tick mark to appear or disappear. Measured in "parrots", 1 "parrot" = 1 / 256 of the full circle. Use values “xxx deg“ or “xxx \xc2\xb0“ to set the angle in degrees.

• boot_menu Displays the GRUB boot menu. It allows selecting items and executing them.

  Properties:

  item_font	The font to use for the menu item titles.
  selected_item_font	The font to use for the selected menu item, or “inherit“ (the default) to use “item_font“ for the selected menu item as well.
  item_color	The color to use for the menu item titles.
  selected_item_color	The color to use for the selected menu item, or “inherit“ (the default) to use “item_color“ for the selected menu item as well.
  icon_width	The width of menu item icons. Icons are scaled to the specified size.
  icon_height	The height of menu item icons.
  item_height	The height of each menu item in pixels.
  item_padding	The amount of space in pixels to leave on each side of the menu item contents.
  item_icon_space	The space between an item’s icon and the title text, in pixels.
  item_spacing	The amount of space to leave between menu items, in pixels.
  menu_pixmap_style	The image file pattern for the menu frame styled box. Example: “menu_*.png“ (this will use images such as “menu_c.png“, “menu_w.png“, ‘menu_nw.png“, etc.)
  item_pixmap_style	The image file pattern for the item styled box.
  selected_item_pixmap_style	The image file pattern for the selected item highlight styled box.
  scrollbar	Boolean value indicating whether the scroll bar should be drawn if the frame and thumb styled boxes are configured.
  scrollbar_frame	The image file pattern for the entire scroll bar. Example: “scrollbar_*.png“
  scrollbar_thumb	The image file pattern for the scroll bar thumb (the part of the scroll bar that moves as scrolling occurs). Example: “scrollbar_thumb_*.png“
  scrollbar_thumb_overlay	If this option is set to “true“ then the scrollbar thumb side slices (every slice except the center slice) will overlay the scrollbar frame side slices. And the center slice of the scrollbar_thumb can move all the way (from top to bottom), being drawn on the center slice of the scrollbar frame. That way we can make a scrollbar with round-shaped edges so there won’t be a free space from the thumb to the frame in top and bottom scrollbar positions. Default is “false“.
  scrollbar_slice	The menu frame styled box’s slice in which the scrollbar will be drawn. Possible values are “west“, “center“, “east“ (default). “west“ - the scrollbar will be drawn in the west slice (right-aligned). “east“ - the scrollbar will be drawn in the east slice (left-aligned). “center“ - the scrollbar will be drawn in the center slice. Note: in case of “center“ slice: a) If the scrollbar should be drawn then boot menu entry’s width is decreased by the scrollbar’s width and the scrollbar is drawn at the right side of the center slice. b) If the scrollbar won’t be drawn then the boot menu entry’s width is the width of the center slice. c) We don’t necessary need the menu pixmap box to display the scrollbar.
  scrollbar_left_pad	The left scrollbar padding in pixels. Unused if “scrollbar_slice“ is “west“.
  scrollbar_right_pad	The right scrollbar padding in pixels. Unused if “scrollbar_slice“ is “east“.
  scrollbar_top_pad	The top scrollbar padding in pixels.
  scrollbar_bottom_pad	The bottom scrollbar padding in pixels.
  visible	Set to “false“ to hide the boot menu.

• canvas Canvas is a container that allows manual placement of components within it. It does not alter the positions of its child components. It assigns all child components their preferred sizes.
• hbox The *hbox* container lays out its children from left to right, giving each one its preferred width. The height of each child is set to the maximum of the preferred heights of all children.
• vbox The *vbox* container lays out its children from top to bottom, giving each one its preferred height. The width of each child is set to the maximum of the preferred widths of all children.

7.3.6 Common properties

The following properties are supported by all components:

‘left’

The distance from the left border of container to left border of the object in either of three formats:

x	Value in pixels
p%	Percentage
p%+x	mixture of both

‘top’

The distance from the left border of container to left border of the object in same format.

‘width’

The width of object in same format.

‘height’

The height of object in same format.

‘id’

The identifier for the component. This can be any arbitrary string. The ID can be used by scripts to refer to various components in the GUI component tree. Currently, there is one special ID value that GRUB recognizes:

“__timeout__“

Component with this ID will be updated by GRUB and will indicate time elapsed to an automatical boot of the default entry. Affected components: “label“, “circular_progress“, “progress_bar“.

15.1.1 biosnum

When chain-loading another boot loader (see Chain-loading an OS), GRUB may need to know what BIOS drive number corresponds to the root device (see root) so that it can set up registers properly. If the biosnum variable is set, it overrides GRUB’s own means of guessing this.

For an alternative approach which also changes BIOS drive mappings for the chain-loaded system, see drivemap.

15.1.2 check_appended_signatures

This variable controls whether GRUB enforces appended signature validation on certain loaded files. See Using appended signatures in GRUB.

15.1.3 check_signatures

This variable controls whether GRUB enforces GPG-style digital signature validation on loaded files. See Using GPG-style digital signatures in GRUB.

15.1.4 chosen

When executing a menu entry, GRUB sets the chosen variable to the title of the entry being executed.

If the menu entry is in one or more submenus, then chosen is set to the titles of each of the submenus starting from the top level followed by the title of the menu entry itself, separated by ‘>’.

15.1.5 cmdpath

The location from which core.img was loaded as an absolute directory name (see How to specify files). This is set by GRUB at startup based on information returned by platform firmware. Not every platform provides this information and some may return only device without path name.

15.1.6 color_highlight

This variable contains the “highlight” foreground and background terminal colors, separated by a slash (‘/’). Setting this variable changes those colors. For the available color names, see color_normal.

The default is ‘black/light-gray’.

15.1.7 color_normal

This variable contains the “normal” foreground and background terminal colors, separated by a slash (‘/’). Setting this variable changes those colors. Each color must be a name from the following list:

• black
• blue
• green
• cyan
• red
• magenta
• brown
• light-gray
• dark-gray
• light-blue
• light-green
• light-cyan
• light-red
• light-magenta
• yellow
• white

The default is ‘light-gray/black’.

The color support support varies from terminal to terminal.

‘morse’ has no color support at all.

‘mda_text’ color support is limited to highlighting by black/white reversal.

‘console’ on ARC, EMU and IEEE1275, ‘serial_*’ and ‘spkmodem’ are governed by terminfo and support only 8 colors if in modes ‘vt100-color’ (default for console on emu), ‘arc’ (default for console on ARC), ‘ieee1275’ (default for console on IEEE1275). When in mode ‘vt100’ then the color support is limited to highlighting by black/white reversal. When in mode ‘dumb’ there is no color support.

When console supports no colors this setting is ignored. When console supports 8 colors, then the colors from the second half of the previous list are mapped to the matching colors of first half.

‘console’ on EFI and BIOS and ‘vga_text’ support all 16 colors.

‘gfxterm’ supports all 16 colors and would be theoretically extendable to support whole rgb24 palette but currently there is no compelling reason to go beyond the current 16 colors.

15.1.8 config_directory

This variable is automatically set by GRUB to the directory part of current configuration file name (see config_file).

15.1.9 config_file

This variable is automatically set by GRUB to the name of configuration file that is being processed by commands configfile (see configfile) or normal (see normal). It is restored to the previous value when command completes.

15.1.10 debug

This variable may be set to enable debugging output from various components of GRUB. The value is a list of debug facility names separated by whitespace or ‘,’, or ‘all’ to enable all available debugging output. The facility names are the first argument to grub_dprintf. Consult source for more details.

15.1.11 default

If this variable is set, it identifies a menu entry that should be selected by default, possibly after a timeout (see timeout). The entry may be identified by number (starting from 0 at each level of the hierarchy), by title, or by id.

For example, if you have:

menuentry 'Example GNU/Linux distribution' --class gnu-linux --id example-gnu-linux {
	...
}

then you can make this the default using:

default=example-gnu-linux

If the entry is in a submenu, then it must be identified using the number, title, or id of each of the submenus starting from the top level, followed by the number, title, or id of the menu entry itself, with each element separated by ‘>’. For example, take the following menu structure:

GNU/Hurd --id gnu-hurd
  Standard Boot --id=gnu-hurd-std
  Rescue shell --id=gnu-hurd-rescue
Other platforms --id=other
  Minix --id=minix
    Version 3.4.0 --id=minix-3.4.0
    Version 3.3.0 --id=minix-3.3.0
  GRUB Invaders --id=grub-invaders

The more recent release of Minix would then be identified as ‘Other platforms>Minix>Version 3.4.0’, or as ‘1>0>0’, or as ‘other>minix>minix-3.4.0’.

This variable is often set by ‘GRUB_DEFAULT’ (see Simple configuration handling), grub2-set-default, or grub2-reboot.

15.1.12 fallback

If this variable is set, it identifies a menu entry that should be selected if the default menu entry fails to boot. Entries are identified in the same way as for ‘default’ (see default).

15.1.13 gfxmode

If this variable is set, it sets the resolution used on the ‘gfxterm’ graphical terminal. Note that you can only use modes which your graphics card supports via VESA BIOS Extensions (VBE), so for example native LCD panel resolutions may not be available. The default is ‘auto’, which selects a platform-specific default that should look reasonable. Supported modes can be listed by ‘videoinfo’ command in GRUB.

The resolution may be specified as a sequence of one or more modes, separated by commas (‘,’) or semicolons (‘;’); each will be tried in turn until one is found. Each mode should be either ‘auto’, ‘widthxheight’, or ‘widthxheightxdepth’.

15.1.14 gfxpayload

If this variable is set, it controls the video mode in which the Linux kernel starts up, replacing the ‘vga=’ boot option (see linux). It may be set to ‘text’ to force the Linux kernel to boot in normal text mode, ‘keep’ to preserve the graphics mode set using ‘gfxmode’, or any of the permitted values for ‘gfxmode’ to set a particular graphics mode (see gfxmode).

Depending on your kernel, your distribution, your graphics card, and the phase of the moon, note that using this option may cause GNU/Linux to suffer from various display problems, particularly during the early part of the boot sequence. If you have problems, set this variable to ‘text’ and GRUB will tell Linux to boot in normal text mode.

The default is platform-specific. On platforms with a native text mode (such as PC BIOS platforms), the default is ‘text’. Otherwise the default may be ‘auto’ or a specific video mode.

This variable is often set by ‘GRUB_GFXPAYLOAD_LINUX’ (see Simple configuration handling).

15.1.15 gfxterm_font

If this variable is set, it names a font to use for text on the ‘gfxterm’ graphical terminal. Otherwise, ‘gfxterm’ may use any available font.

15.1.16 grub_cpu

In normal mode (see normal), GRUB sets the ‘grub_cpu’ variable to the CPU type for which GRUB was built (e.g. ‘i386’ or ‘powerpc’).

15.1.17 grub_platform

In normal mode (see normal), GRUB sets the ‘grub_platform’ variable to the platform for which GRUB was built (e.g. ‘pc’ or ‘efi’).

15.1.18 icondir

If this variable is set, it names a directory in which the GRUB graphical menu should look for icons after looking in the theme’s ‘icons’ directory. See Theme file format.

15.1.19 lang

If this variable is set, it names the language code that the gettext command (see gettext) uses to translate strings. For example, French would be named as ‘fr’, and Simplified Chinese as ‘zh_CN’.

grub2-mkconfig (see Simple configuration handling) will try to set a reasonable default for this variable based on the system locale.

15.1.20 locale_dir

If this variable is set, it names the directory where translation files may be found (see gettext), usually /boot/grub2/locale. Otherwise, internationalization is disabled.

grub2-mkconfig (see Simple configuration handling) will set a reasonable default for this variable if internationalization is needed and any translation files are available.

15.1.21 menu_color_highlight

This variable contains the foreground and background colors to be used for the highlighted menu entry, separated by a slash (‘/’). Setting this variable changes those colors. For the available color names, see color_normal.

The default is the value of ‘color_highlight’ (see color_highlight).

15.1.22 menu_color_normal

This variable contains the foreground and background colors to be used for non-highlighted menu entries, separated by a slash (‘/’). Setting this variable changes those colors. For the available color names, see color_normal.

The default is the value of ‘color_normal’ (see color_normal).

15.1.23 net_<interface>_boot_file

See Booting GRUB from the network.

15.1.24 net_<interface>_dhcp_server_name

See Booting GRUB from the network.

15.1.25 net_<interface>_domain

See Booting GRUB from the network.

15.1.26 net_<interface>_extensionspath

See Booting GRUB from the network.

15.1.27 net_<interface>_hostname

See Booting GRUB from the network.

15.1.28 net_<interface>_ip

See Booting GRUB from the network.

15.1.29 net_<interface>_mac

See Booting GRUB from the network.

15.1.30 net_<interface>_next_server

See Booting GRUB from the network.

15.1.31 net_<interface>_rootpath

See Booting GRUB from the network.

15.1.32 net_default_interface

See Booting GRUB from the network.

15.1.33 net_default_ip

See Booting GRUB from the network.

15.1.34 net_default_mac

See Booting GRUB from the network.

15.1.35 net_default_server

See Booting GRUB from the network.

15.1.36 pager

If set to ‘1’, pause output after each screenful and wait for keyboard input. The default is not to pause output.

15.1.37 prefix

The location of the ‘/boot/grub’ directory as an absolute file name (see How to specify files). This is normally set by GRUB at startup based on information provided by grub2-install. GRUB modules are dynamically loaded from this directory, so it must be set correctly in order for many parts of GRUB to work.

15.1.38 pxe_blksize

See Booting GRUB from the network.

15.1.39 pxe_default_gateway

See Booting GRUB from the network.

15.1.40 pxe_default_server

See Booting GRUB from the network.

15.1.41 root

The root device name (see How to specify devices). Any file names that do not specify an explicit device name are read from this device. The default is normally set by GRUB at startup based on the value of ‘prefix’ (see prefix).

For example, if GRUB was installed to the first partition of the first hard disk, then ‘prefix’ might be set to ‘(hd0,msdos1)/boot/grub’ and ‘root’ to ‘hd0,msdos1’.

15.1.42 superusers

This variable may be set to a list of superuser names to enable authentication support. See Security.

15.1.43 theme

This variable may be set to a directory containing a GRUB graphical menu theme. See Theme file format.

This variable is often set by ‘GRUB_THEME’ (see Simple configuration handling).

15.1.44 timeout

If this variable is set, it specifies the time in seconds to wait for keyboard input before booting the default menu entry. A timeout of ‘0’ means to boot the default entry immediately without displaying the menu; a timeout of ‘-1’ (or unset) means to wait indefinitely.

If ‘timeout_style’ (see timeout_style) is set to ‘countdown’ or ‘hidden’, the timeout is instead counted before the menu is displayed.

This variable is often set by ‘GRUB_TIMEOUT’ (see Simple configuration handling).

15.1.45 timeout_style

This variable may be set to ‘menu’, ‘countdown’, or ‘hidden’ to control the way in which the timeout (see timeout) interacts with displaying the menu. See the documentation of ‘GRUB_TIMEOUT_STYLE’ (see Simple configuration handling) for details.

16.1.1 menuentry

Command: menuentry title [--class=class …] [--users=users] [--unrestricted] [--hotkey=key] [--id=id] [arg …] { command; … } ¶

This defines a GRUB menu entry named title. When this entry is selected from the menu, GRUB will set the chosen environment variable to value of --id if --id is given, execute the list of commands given within braces, and if the last command in the list returned successfully and a kernel was loaded it will execute the boot command.

The --class option may be used any number of times to group menu entries into classes. Menu themes may display different classes using different styles.

The --users option grants specific users access to specific menu entries. See Security.

The --unrestricted option grants all users access to specific menu entries. See Security.

The --hotkey option associates a hotkey with a menu entry. key may be a single letter, or one of the aliases ‘backspace’, ‘tab’, or ‘delete’.

The --id may be used to associate unique identifier with a menu entry. id is string of ASCII aphanumeric characters, underscore and hyphen and should not start with a digit.

All other arguments including title are passed as positional parameters when list of commands is executed with title always assigned to $1.

16.1.2 submenu

Command: submenu title [--class=class …] [--users=users] [--unrestricted] [--hotkey=key] [--id=id] { menu entries … } ¶

This defines a submenu. An entry called title will be added to the menu; when that entry is selected, a new menu will be displayed showing all the entries within this submenu.

All options are the same as in the menuentry command (see menuentry).

16.2.1 serial

Command: serial [--unit=unit] [--port=port] [--speed=speed] [--word=word] [--parity=parity] [--stop=stop] ¶

Initialize a serial device. unit is a number in the range 0-3 specifying which serial port to use; default is 0, which corresponds to the port often called COM1. port is the I/O port where the UART is to be found; if specified it takes precedence over unit. speed is the transmission speed; default is 9600. word and stop are the number of data bits and stop bits. Data bits must be in the range 5-8 and stop bits must be 1 or 2. Default is 8 data bits and one stop bit. parity is one of ‘no’, ‘odd’, ‘even’ and defaults to ‘no’.

The serial port is not used as a communication channel unless the terminal_input or terminal_output command is used (see terminal_input, see terminal_output).

See also Using GRUB via a serial line.

16.2.2 terminal_input

Command: terminal_input [--append|--remove] [terminal1] [terminal2] … ¶

List or select an input terminal.

With no arguments, list the active and available input terminals.

With --append, add the named terminals to the list of active input terminals; any of these may be used to provide input to GRUB.

With --remove, remove the named terminals from the active list.

With no options but a list of terminal names, make only the listed terminal names active.

16.2.3 terminal_output

Command: terminal_output [--append|--remove] [terminal1] [terminal2] … ¶

List or select an output terminal.

With no arguments, list the active and available output terminals.

With --append, add the named terminals to the list of active output terminals; all of these will receive output from GRUB.

With --remove, remove the named terminals from the active list.

With no options but a list of terminal names, make only the listed terminal names active.

16.2.4 terminfo

Command: terminfo [-a|-u|-v] [-g WxH] [term] [type] ¶

Define the capabilities of your terminal by giving the name of an entry in the terminfo database, which should correspond roughly to a ‘TERM’ environment variable in Unix.

The currently available terminal types are ‘vt100’, ‘vt100-color’, ‘ieee1275’, and ‘dumb’. If you need other terminal types, please contact us to discuss the best way to include support for these in GRUB.

The -a (--ascii), -u (--utf8), and -v (--visual-utf8) options control how non-ASCII text is displayed. -a specifies an ASCII-only terminal; -u specifies logically-ordered UTF-8; and -v specifies "visually-ordered UTF-8" (in other words, arranged such that a terminal emulator without bidirectional text support will display right-to-left text in the proper order; this is not really proper UTF-8, but a workaround).

The -g (--geometry) can be used to specify terminal geometry.

If no option or terminal type is specified, the current terminal type is printed.

16.3.1 [

Command: [ expression ] ¶

Alias for test expression (see test).

16.3.2 acpi

Command: acpi [-1|-2] [--exclude=table1,…|--load-only=table1,…] [--oemid=id] [--oemtable=table] [--oemtablerev=rev] [--oemtablecreator=creator] [--oemtablecreatorrev=rev] [--no-ebda] filename … ¶

Modern BIOS systems normally implement the Advanced Configuration and Power Interface (ACPI), and define various tables that describe the interface between an ACPI-compliant operating system and the firmware. In some cases, the tables provided by default only work well with certain operating systems, and it may be necessary to replace some of them.

Normally, this command will replace the Root System Description Pointer (RSDP) in the Extended BIOS Data Area to point to the new tables. If the --no-ebda option is used, the new tables will be known only to GRUB, but may be used by GRUB’s EFI emulation.

Note: The command is not allowed when lockdown is enforced (see Lockdown when booting on a secure setup). Otherwise an attacker can instruct the GRUB to load an SSDT table to overwrite the kernel lockdown configuration and later load and execute unsigned code.

16.3.3 authenticate

Command: authenticate [userlist] ¶

Check whether user is in userlist or listed in the value of variable ‘superusers’. See see superusers for valid user list format. If ‘superusers’ is empty, this command returns true. See Security.

16.3.4 background_color

Command: background_color color ¶

Set background color for active terminal. For valid color specifications see see Colors. Background color can be changed only when using ‘gfxterm’ for terminal output.

This command sets color of empty areas without text. Text background color is controlled by environment variables color_normal, color_highlight, menu_color_normal, menu_color_highlight. See Special environment variables.

16.3.5 background_image

Command: background_image [[--mode ‘stretch’|‘normal’] file] ¶

Load background image for active terminal from file. Image is stretched to fill up entire screen unless option --mode ‘normal’ is given. Without arguments remove currently loaded background image. Background image can be changed only when using ‘gfxterm’ for terminal output.

16.3.6 badram

Command: badram addr,mask[,addr,mask...] ¶

Filter out bad RAM.

This command notifies the memory manager that specified regions of RAM ought to be filtered out (usually, because they’re damaged). This remains in effect after a payload kernel has been loaded by GRUB, as long as the loaded kernel obtains its memory map from GRUB. Kernels that support this include Linux, GNU Mach, the kernel of FreeBSD and Multiboot kernels in general.

Syntax is the same as provided by the Memtest86+ utility: a list of address/mask pairs. Given a page-aligned address and a base address / mask pair, if all the bits of the page-aligned address that are enabled by the mask match with the base address, it means this page is to be filtered. This syntax makes it easy to represent patterns that are often result of memory damage, due to physical distribution of memory cells.

The command is similar to cutmem command.

Note: The command is not allowed when lockdown is enforced (see Lockdown when booting on a secure setup). This prevents removing EFI memory regions to potentially subvert the security mechanisms provided by the UEFI secure boot.

16.3.7 blocklist

Command: blocklist file ¶

Print a block list (see How to specify block lists) for file.

16.3.8 boot

Command: boot ¶

Boot the OS or chain-loader which has been loaded. Only necessary if running the fully interactive command-line (it is implicit at the end of a menu entry).

16.3.9 cat

Command: cat [--dos] file ¶

Display the contents of the file file. This command may be useful to remind you of your OS’s root partition:

grub> cat /etc/fstab

If the --dos option is used, then carriage return / new line pairs will be displayed as a simple new line. Otherwise, the carriage return will be displayed as a control character (‘<d>’) to make it easier to see when boot problems are caused by a file formatted using DOS-style line endings.

16.3.10 chainloader

Command: chainloader [--force] file ¶

Load file as a chain-loader. Like any other file loaded by the filesystem code, it can use the blocklist notation (see How to specify block lists) to grab the first sector of the current partition with ‘+1’. If you specify the option --force, then load file forcibly, whether it has a correct signature or not. This is required when you want to load a defective boot loader, such as SCO UnixWare 7.1.

16.3.11 clear

Command: clear ¶

Clear the screen.

16.3.12 cmosclean

Command: cmosclean byte:bit ¶

Clear value of bit in CMOS at location byte:bit. This command is available only on platforms that support CMOS.

16.3.13 cmosdump

Dump: CMOS contents ¶

Dump full CMOS contents as hexadecimal values. This command is available only on platforms that support CMOS.

16.3.14 cmostest

Command: cmostest byte:bit ¶

Test value of bit in CMOS at location byte:bit. Exit status is zero if bit is set, non zero otherwise. This command is available only on platforms that support CMOS.

16.3.15 cmp

Command: cmp file1 file2 ¶

Compare the file file1 with the file file2. If they differ in size, print the sizes like this:

Differ in size: 0x1234 [foo], 0x4321 [bar]

If the sizes are equal but the bytes at an offset differ, then print the bytes like this:

Differ at the offset 777: 0xbe [foo], 0xef [bar]

If they are completely identical, nothing will be printed.

16.3.16 configfile

Command: configfile file ¶

Load file as a configuration file. If file defines any menu entries, then show a menu containing them immediately. Any environment variable changes made by the commands in file will not be preserved after configfile returns.

16.3.17 cpuid

Command: cpuid [-l] [-p] ¶

Check for CPU features. This command is only available on x86 systems.

With the -l option, return true if the CPU supports long mode (64-bit).

With the -p option, return true if the CPU supports Physical Address Extension (PAE).

If invoked without options, this command currently behaves as if it had been invoked with -l. This may change in the future.

16.3.18 crc

Command: crc arg … ¶

Alias for hashsum --hash crc32 arg …. See command hashsum (see hashsum) for full description.

16.3.19 cryptomount

Command: cryptomount device|-u uuid|-a|-b ¶

Setup access to encrypted device. If necessary, passphrase is requested interactively. Option device configures specific grub device (see Naming convention); option -u uuid configures device with specified uuid; option -a configures all detected encrypted devices; option -b configures all geli containers that have boot flag set.

GRUB suports devices encrypted using LUKS, LUKS2 and geli. Note that necessary modules (luks, luks2 and geli) have to be loaded manually before this command can be used. For LUKS2 only the PBKDF2 key derivation function is supported, as Argon2 is not yet supported.

Also, note that, unlike filesystem UUIDs, UUIDs for encrypted devices must be specified without dash separators.

16.3.20 cutmem

Command: cutmem from[K|M|G] to[K|M|G] ¶

Remove any memory regions in specified range.

This command notifies the memory manager that specified regions of RAM ought to be filtered out. This remains in effect after a payload kernel has been loaded by GRUB, as long as the loaded kernel obtains its memory map from GRUB. Kernels that support this include Linux, GNU Mach, the kernel of FreeBSD and Multiboot kernels in general.

The command is similar to badram command.

Note: The command is not allowed when lockdown is enforced (see Lockdown when booting on a secure setup). This prevents removing EFI memory regions to potentially subvert the security mechanisms provided by the UEFI secure boot.

16.3.21 date

Command: date [[year-]month-day] [hour:minute[:second]] ¶

With no arguments, print the current date and time.

Otherwise, take the current date and time, change any elements specified as arguments, and set the result as the new date and time. For example, ‘date 01-01’ will set the current month and day to January 1, but leave the year, hour, minute, and second unchanged.

16.3.22 devicetree

Command: devicetree file ¶

Load a device tree blob (.dtb) from a filesystem, for later use by a Linux kernel. Does not perform merging with any device tree supplied by firmware, but rather replaces it completely.

Note: The command is not allowed when lockdown is enforced (see Lockdown when booting on a secure setup). This is done to prevent subverting various security mechanisms.

16.3.23 distrust

Command: distrust pubkey_id ¶

Remove public key pubkey_id from GRUB’s keyring of trusted keys. pubkey_id is the last four bytes (eight hexadecimal digits) of the GPG v4 key id, which is also the output of list_trusted (see list_trusted). Outside of GRUB, the key id can be obtained using gpg --fingerprint). These keys are used to validate signatures when environment variable check_signatures is set to enforce (see check_signatures), and by some invocations of verify_detached (see verify_detached). See Using GPG-style digital signatures in GRUB, for more information.

16.3.24 distrust_certificate

Command: distrust_certificate cert_number ¶

Remove the x509 certificate numbered cert_number from GRUB’s keyring of trusted x509 certificates for verifying appended signatures.

cert_number is the certificate number as listed by list_certificates (see list_certificates).

These certificates are used to validate appended signatures when environment variable check_appended_signatures is set to enforce or forced (see check_appended_signatures), and by verify_appended (see verify_appended). See See Using appended signatures in GRUB for more information.

16.3.25 drivemap

Command: drivemap -l|-r|[-s] from_drive to_drive ¶

Without options, map the drive from_drive to the drive to_drive. This is necessary when you chain-load some operating systems, such as DOS, if such an OS resides at a non-first drive. For convenience, any partition suffix on the drive is ignored, so you can safely use ${root} as a drive specification.

With the -s option, perform the reverse mapping as well, swapping the two drives.

With the -l option, list the current mappings.

With the -r option, reset all mappings to the default values.

For example:

drivemap -s (hd0) (hd1)

16.3.26 echo

Command: echo [-n] [-e] string … ¶

Display the requested text and, unless the -n option is used, a trailing new line. If there is more than one string, they are separated by spaces in the output. As usual in GRUB commands, variables may be substituted using ‘${var}’.

The -e option enables interpretation of backslash escapes. The following sequences are recognised:

\\

backslash

\a

alert (BEL)

\c

suppress trailing new line

\f

form feed

\n

new line

\r

carriage return

\t

horizontal tab

\v

vertical tab

When interpreting backslash escapes, backslash followed by any other character will print that character.

16.3.27 eval

Command: eval string ... ¶

Concatenate arguments together using single space as separator and evaluate result as sequence of GRUB commands.

16.3.28 export

Command: export envvar ¶

Export the environment variable envvar. Exported variables are visible to subsidiary configuration files loaded using configfile.

16.3.29 false

Command: false ¶

Do nothing, unsuccessfully. This is mainly useful in control constructs such as if and while (see Writing full configuration files directly).

16.3.30 gettext

Command: gettext string ¶

Translate string into the current language.

The current language code is stored in the ‘lang’ variable in GRUB’s environment (see lang). Translation files in MO format are read from ‘locale_dir’ (see locale_dir), usually /boot/grub2/locale.

16.3.31 gptsync

Command: gptsync device [partition[+/-[type]]] … ¶

Disks using the GUID Partition Table (GPT) also have a legacy Master Boot Record (MBR) partition table for compatibility with the BIOS and with older operating systems. The legacy MBR can only represent a limited subset of GPT partition entries.

This command populates the legacy MBR with the specified partition entries on device. Up to three partitions may be used.

type is an MBR partition type code; prefix with ‘0x’ if you want to enter this in hexadecimal. The separator between partition and type may be ‘+’ to make the partition active, or ‘-’ to make it inactive; only one partition may be active. If both the separator and type are omitted, then the partition will be inactive.

16.3.32 halt

Command: halt --no-apm ¶

The command halts the computer. If the --no-apm option is specified, no APM BIOS call is performed. Otherwise, the computer is shut down using APM.

16.3.33 hashsum

Command: hashsum --hash hash --keep-going --uncompress --check file [--prefix dir]|file … ¶

Compute or verify file hashes. Hash type is selected with option --hash. Supported hashes are: ‘adler32’, ‘crc64’, ‘crc32’, ‘crc32rfc1510’, ‘crc24rfc2440’, ‘md4’, ‘md5’, ‘ripemd160’, ‘sha1’, ‘sha224’, ‘sha256’, ‘sha512’, ‘sha384’, ‘tiger192’, ‘tiger’, ‘tiger2’, ‘whirlpool’. Option --uncompress uncompresses files before computing hash.

When list of files is given, hash of each file is computed and printed, followed by file name, each file on a new line.

When option --check is given, it points to a file that contains list of hash name pairs in the same format as used by UNIX md5sum command. Option --prefix may be used to give directory where files are located. Hash verification stops after the first mismatch was found unless option --keep-going was given. The exit code $? is set to 0 if hash verification is successful. If it fails, $? is set to a nonzero value.

16.3.34 help

Command: help [pattern …] ¶

Display helpful information about builtin commands. If you do not specify pattern, this command shows short descriptions of all available commands.

If you specify any patterns, it displays longer information about each of the commands whose names begin with those patterns.

16.3.35 initrd

Command: initrd file [file …] ¶

Load, in order, all initial ramdisks for a Linux kernel image, and set the appropriate parameters in the Linux setup area in memory. This may only be used after the linux command (see linux) has been run. See also GNU/Linux.

16.3.36 initrd16

Command: initrd16 file [file …] ¶

Load, in order, all initial ramdisks for a Linux kernel image to be booted in 16-bit mode, and set the appropriate parameters in the Linux setup area in memory. This may only be used after the linux16 command (see linux16) has been run. See also GNU/Linux.

This command is only available on x86 systems.

16.3.37 insmod

Command: insmod module ¶

Insert the dynamic GRUB module called module.

16.3.38 keystatus

Command: keystatus [--shift] [--ctrl] [--alt] ¶

Return true if the Shift, Control, or Alt modifier keys are held down, as requested by options. This is useful in scripting, to allow some user control over behaviour without having to wait for a keypress.

Checking key modifier status is only supported on some platforms. If invoked without any options, the keystatus command returns true if and only if checking key modifier status is supported.

16.3.39 linux

Command: linux file … ¶

Load a Linux kernel image from file. The rest of the line is passed verbatim as the kernel command-line. Any initrd must be reloaded after using this command (see initrd).

On x86 systems, the kernel will be booted using the 32-bit boot protocol. Note that this means that the ‘vga=’ boot option will not work; if you want to set a special video mode, you will need to use GRUB commands such as ‘set gfxpayload=1024x768’ or ‘set gfxpayload=keep’ (to keep the same mode as used in GRUB) instead. GRUB can automatically detect some uses of ‘vga=’ and translate them to appropriate settings of ‘gfxpayload’. The linux16 command (see linux16) avoids this restriction.

16.3.40 linux16

Command: linux16 file … ¶

Load a Linux kernel image from file in 16-bit mode. The rest of the line is passed verbatim as the kernel command-line. Any initrd must be reloaded after using this command (see initrd16).

The kernel will be booted using the traditional 16-bit boot protocol. As well as bypassing problems with ‘vga=’ described in linux, this permits booting some other programs that implement the Linux boot protocol for the sake of convenience.

This command is only available on x86 systems.

16.3.41 list_certificates

Command: list_certificates ¶

List all x509 certificates trusted by GRUB for validating appended signatures. The output is a numbered list of certificates, showing the certificate’s serial number and Common Name.

The certificate number can be used as an argument to distrust_certificate (see distrust_certificate).

See See Using appended signatures in GRUB for more information.

16.3.42 list_env

Command: list_env [--file file] ¶

List all variables in the environment block file. See The GRUB environment block.

The --file option overrides the default location of the environment block.

16.3.43 list_trusted

Command: list_trusted ¶

List all public keys trusted by GRUB for validating signatures. The output is in GPG’s v4 key fingerprint format (i.e., the output of gpg --fingerprint). The least significant four bytes (last eight hexadecimal digits) can be used as an argument to distrust (see distrust). See Using GPG-style digital signatures in GRUB, for more information about uses for these keys.

16.3.44 load_env

Command: load_env [--file file] [--skip-sig] [whitelisted_variable_name] … ¶

Load all variables from the environment block file into the environment. See The GRUB environment block.

The --file option overrides the default location of the environment block.

The --skip-sig option skips signature checking even when the value of environment variable check_signatures is set to enforce (see check_signatures).

If one or more variable names are provided as arguments, they are interpreted as a whitelist of variables to load from the environment block file. Variables set in the file but not present in the whitelist are ignored.

The --skip-sig option should be used with care, and should always be used in concert with a whitelist of acceptable variables whose values should be set. Failure to employ a carefully constructed whitelist could result in reading a malicious value into critical environment variables from the file, such as setting check_signatures=no, modifying prefix to boot from an unexpected location or not at all, etc.

When used with care, --skip-sig and the whitelist enable an administrator to configure a system to boot only signed configurations, but to allow the user to select from among multiple configurations, and to enable “one-shot” boot attempts and “savedefault” behavior. See Using GPG-style digital signatures in GRUB, for more information.

Extra care should be taken when combining this command with appended signatures (see Using appended signatures in GRUB), as this file is not validated by an appended signature and could set check_appended_signatures=no if GRUB is not in see Lockdown when booting on a secure setup mode.

16.3.45 loadfont

Command: loadfont file … ¶

Load specified font files. Unless absolute pathname is given, file is assumed to be in directory ‘$prefix/fonts’ with suffix ‘.pf2’ appended. See Fonts.

16.3.46 loopback

Command: loopback [-d] device file ¶

Make the device named device correspond to the contents of the filesystem image in file. For example:

loopback loop0 /path/to/image
ls (loop0)/

With the -d option, delete a device previously created using this command.

16.3.47 ls

Command: ls [arg …] ¶

List devices or files.

With no arguments, print all devices known to GRUB.

If the argument is a device name enclosed in parentheses (see How to specify devices), then print the name of the filesystem of that device.

If the argument is a directory given as an absolute file name (see How to specify files), then list the contents of that directory.

16.3.48 lsfonts

Command: lsfonts ¶

List loaded fonts.

16.3.49 lsmod

Command: lsmod ¶

Show list of loaded modules.

16.3.50 md5sum

Command: md5sum arg … ¶

Alias for hashsum --hash md5 arg …. See command hashsum (see hashsum) for full description.

16.3.51 module

Command: module [–nounzip] file [arguments] ¶

Load a module for multiboot kernel image. The rest of the line is passed verbatim as the module command line.

16.3.52 multiboot

Command: multiboot [–quirk-bad-kludge] [–quirk-modules-after-kernel] file … ¶

Load a multiboot kernel image from file. The rest of the line is passed verbatim as the kernel command-line. Any module must be reloaded after using this command (see module).

Some kernels have known problems. You need to specify –quirk-* for those. –quirk-bad-kludge is a problem seen in several products that they include loading kludge information with invalid data in ELF file. GRUB prior to 0.97 and some custom builds preferred ELF information while 0.97 and GRUB 2 use kludge. Use this option to ignore kludge. Known affected systems: old Solaris, SkyOS.

–quirk-modules-after-kernel is needed for kernels which load at relatively high address e.g. 16MiB mark and can’t cope with modules stuffed between 1MiB mark and beginning of the kernel. Known afftected systems: VMWare.

16.3.53 nativedisk

Command: nativedisk ¶

Switch from firmware disk drivers to native ones. Really useful only on platforms where both firmware and native disk drives are available. Currently i386-pc, i386-efi, i386-ieee1275 and x86_64-efi.

16.3.54 normal

Command: normal [file] ¶

Enter normal mode and display the GRUB menu.

In normal mode, commands, filesystem modules, and cryptography modules are automatically loaded, and the full GRUB script parser is available. Other modules may be explicitly loaded using insmod (see insmod).

If a file is given, then commands will be read from that file. Otherwise, they will be read from $prefix/grub.cfg if it exists.

normal may be called from within normal mode, creating a nested environment. It is more usual to use configfile (see configfile) for this.

16.3.55 normal_exit

Command: normal_exit ¶

Exit normal mode (see normal). If this instance of normal mode was not nested within another one, then return to rescue mode.

16.3.56 parttool

Command: parttool partition commands ¶

Make various modifications to partition table entries.

Each command is either a boolean option, in which case it must be followed with ‘+’ or ‘-’ (with no intervening space) to enable or disable that option, or else it takes a value in the form ‘command=value’.

Currently, parttool is only useful on DOS partition tables (also known as Master Boot Record, or MBR). On these partition tables, the following commands are available:

‘boot’ (boolean)

When enabled, this makes the selected partition be the active (bootable) partition on its disk, clearing the active flag on all other partitions. This command is limited to primary partitions.

‘type’ (value)

Change the type of an existing partition. The value must be a number in the range 0-0xFF (prefix with ‘0x’ to enter it in hexadecimal).

‘hidden’ (boolean)

When enabled, this hides the selected partition by setting the hidden bit in its partition type code; when disabled, unhides the selected partition by clearing this bit. This is useful only when booting DOS or Windows and multiple primary FAT partitions exist in one disk. See also DOS/Windows.

16.3.57 password

Command: password user clear-password ¶

Define a user named user with password clear-password. See Security.

16.3.58 password_pbkdf2

Command: password_pbkdf2 user hashed-password ¶

Define a user named user with password hash hashed-password. Use grub2-mkpasswd-pbkdf2 (see Invoking grub2-mkpasswd-pbkdf2) to generate password hashes. See Security.

16.3.59 play

Command: play file | tempo [pitch1 duration1] [pitch2 duration2] … ¶

Plays a tune

If the argument is a file name (see How to specify files), play the tune recorded in it. The file format is first the tempo as an unsigned 32bit little-endian number, then pairs of unsigned 16bit little-endian numbers for pitch and duration pairs.

If the arguments are a series of numbers, play the inline tune.

The tempo is the base for all note durations. 60 gives a 1-second base, 120 gives a half-second base, etc. Pitches are Hz. Set pitch to 0 to produce a rest.

16.3.60 probe

Command: probe [--set var] --driver|--partmap|--fs|--fs-uuid|--label|--part-uuid device ¶

Retrieve device information. If option --set is given, assign result to variable var, otherwise print information on the screen.

The option --part-uuid is currently only implemented for MSDOS and GPT formatted disks.

16.3.61 rdmsr

Command:: rdmsr 0xADDR [-v VARNAME] ¶

Read a model-specific register at address 0xADDR. If the parameter -v is used and an environment variable VARNAME is given, set that environment variable to the value that was read.

Please note that on SMP systems, reading from a MSR that has a scope per hardware thread, implies that the value that is returned only applies to the particular cpu/core/thread that runs the command.

Also, if you specify a reserved or unimplemented MSR address, it will cause a general protection exception (which is not currently being handled) and the system will reboot.

16.3.62 read

Command: read [var] ¶

Read a line of input from the user. If an environment variable var is given, set that environment variable to the line of input that was read, with no terminating newline.

16.3.63 reboot

Command: reboot ¶

Reboot the computer.

16.3.64 regexp

Command: regexp [--set [number:]var] regexp string ¶

Test if regular expression regexp matches string. Supported regular expressions are POSIX.2 Extended Regular Expressions. If option --set is given, store numberth matched subexpression in variable var. Subexpressions are numbered in order of their opening parentheses starting from ‘1’. number defaults to ‘1’.

16.3.65 rmmod

Command: rmmod module ¶

Remove a loaded module.

16.3.66 save_env

Command: save_env [--file file] var … ¶

Save the named variables from the environment to the environment block file. See The GRUB environment block.

The --file option overrides the default location of the environment block.

This command will operate successfully even when environment variable check_signatures is set to enforce (see check_signatures), since it writes to disk and does not alter the behavior of GRUB based on any contents of disk that have been read. It is possible to modify a digitally signed environment block file from within GRUB using this command, such that its signature will no longer be valid on subsequent boots. Care should be taken in such advanced configurations to avoid rendering the system unbootable. See Using GPG-style digital signatures in GRUB, for more information.

16.3.67 search

Command: search [--file|--label|--fs-uuid] [--set [var]] [--no-floppy] name ¶

Search devices by file (-f, --file), filesystem label (-l, --label), or filesystem UUID (-u, --fs-uuid).

If the --set option is used, the first device found is set as the value of environment variable var. The default variable is ‘root’.

The --no-floppy option prevents searching floppy devices, which can be slow.

The ‘search.file’, ‘search.fs_label’, and ‘search.fs_uuid’ commands are aliases for ‘search --file’, ‘search --label’, and ‘search --fs-uuid’ respectively.

16.3.68 sendkey

Command: sendkey [--num|--caps|--scroll|--insert|--pause|--left-shift|--right-shift|--sysrq|--numkey|--capskey|--scrollkey|--insertkey|--left-alt|--right-alt|--left-ctrl|--right-ctrl ‘on’|‘off’]… [no-led] keystroke ¶

Insert keystrokes into the keyboard buffer when booting. Sometimes an operating system or chainloaded boot loader requires particular keys to be pressed: for example, one might need to press a particular key to enter "safe mode", or when chainloading another boot loader one might send keystrokes to it to navigate its menu.

You may provide up to 16 keystrokes (the length of the BIOS keyboard buffer). Keystroke names may be upper-case or lower-case letters, digits, or taken from the following table:

Name	Key
escape	Escape
exclam	!
at	@
numbersign	#
dollar	$
percent	%
caret	^
ampersand	&
asterisk	*
parenleft	(
parenright	)
minus	-
underscore	_
equal	=
plus	+
backspace	Backspace
tab	Tab
bracketleft	[
braceleft	{
bracketright	]
braceright	}
enter	Enter
control	press and release Control
semicolon	;
colon	:
quote	’
doublequote	"
backquote	‘
tilde	~
shift	press and release left Shift
backslash	\
bar	|
comma	,
less	<
period	.
greater	>
slash	/
question	?
rshift	press and release right Shift
alt	press and release Alt
space	space bar
capslock	Caps Lock
F1	F1
F2	F2
F3	F3
F4	F4
F5	F5
F6	F6
F7	F7
F8	F8
F9	F9
F10	F10
F11	F11
F12	F12
num1	1 (numeric keypad)
num2	2 (numeric keypad)
num3	3 (numeric keypad)
num4	4 (numeric keypad)
num5	5 (numeric keypad)
num6	6 (numeric keypad)
num7	7 (numeric keypad)
num8	8 (numeric keypad)
num9	9 (numeric keypad)
num0	0 (numeric keypad)
numperiod	. (numeric keypad)
numend	End (numeric keypad)
numdown	Down (numeric keypad)
numpgdown	Page Down (numeric keypad)
numleft	Left (numeric keypad)
numcenter	5 with Num Lock inactive (numeric keypad)
numright	Right (numeric keypad)
numhome	Home (numeric keypad)
numup	Up (numeric keypad)
numpgup	Page Up (numeric keypad)
numinsert	Insert (numeric keypad)
numdelete	Delete (numeric keypad)
numasterisk	* (numeric keypad)
numminus	- (numeric keypad)
numplus	+ (numeric keypad)
numslash	/ (numeric keypad)
numenter	Enter (numeric keypad)
delete	Delete
insert	Insert
home	Home
end	End
pgdown	Page Down
pgup	Page Up
down	Down
up	Up
left	Left
right	Right

As well as keystrokes, the sendkey command takes various options that affect the BIOS keyboard status flags. These options take an ‘on’ or ‘off’ parameter, specifying that the corresponding status flag be set or unset; omitting the option for a given status flag will leave that flag at its initial state at boot. The --num, --caps, --scroll, and --insert options emulate setting the corresponding mode, while the --numkey, --capskey, --scrollkey, and --insertkey options emulate pressing and holding the corresponding key. The other status flag options are self-explanatory.

If the --no-led option is given, the status flag options will have no effect on keyboard LEDs.

If the sendkey command is given multiple times, then only the last invocation has any effect.

Since sendkey manipulates the BIOS keyboard buffer, it may cause hangs, reboots, or other misbehaviour on some systems. If the operating system or boot loader that runs after GRUB uses its own keyboard driver rather than the BIOS keyboard functions, then sendkey will have no effect.

This command is only available on PC BIOS systems.

16.3.69 set

Command: set [envvar=value] ¶

Set the environment variable envvar to value. If invoked with no arguments, print all environment variables with their values.

16.3.70 sha1sum

Command: sha1sum arg … ¶

Alias for hashsum --hash sha1 arg …. See command hashsum (see hashsum) for full description.

16.3.71 sha256sum

Command: sha256sum arg … ¶

Alias for hashsum --hash sha256 arg …. See command hashsum (see hashsum) for full description.

16.3.72 sha512sum

Command: sha512sum arg … ¶

Alias for hashsum --hash sha512 arg …. See command hashsum (see hashsum) for full description.

16.3.73 sleep

Command: sleep [--verbose] [--interruptible] count ¶

Sleep for count seconds. If option --interruptible is given, allow pressing ESC, F4 or holding down SHIFT to interrupt sleep. With --verbose show countdown of remaining seconds. Exit code is set to 0 if timeout expired and to 1 if timeout was interrupted using any of the mentioned keys.

16.3.74 smbios

Command: smbios [--type type] [--handle handle] [--match match] (--get-byte | --get-word | --get-dword | --get-qword | --get-string | --get-uuid) offset [--set variable] ¶

Retrieve SMBIOS information.

The smbios command returns the value of a field in an SMBIOS structure. The following options determine which structure to select.

• Specifying --type will select structures with a matching type. The type can be any integer from 0 to 255.
• Specifying --handle will select structures with a matching handle. The handle can be any integer from 0 to 65535.
• Specifying --match will select structure number match in the filtered list of structures; e.g. smbios --type 4 --match 2 will select the second Process Information (Type 4) structure. The list is always ordered the same as the hardware’s SMBIOS table. The match number must be a positive integer. If unspecified, the first matching structure will be selected.

The remaining options determine which field in the selected SMBIOS structure to return. Only one of these options may be specified at a time.

• When given --get-byte, return the value of the byte at offset bytes into the selected SMBIOS structure. It will be formatted as an unsigned decimal integer.
• When given --get-word, return the value of the word (two bytes) at offset bytes into the selected SMBIOS structure. It will be formatted as an unsigned decimal integer.
• When given --get-dword, return the value of the dword (four bytes) at offset bytes into the selected SMBIOS structure. It will be formatted as an unsigned decimal integer.
• When given --get-qword, return the value of the qword (eight bytes) at offset bytes into the selected SMBIOS structure. It will be formatted as an unsigned decimal integer.
• When given --get-string, return the string with its index found at offset bytes into the selected SMBIOS structure.
• When given --get-uuid, return the value of the UUID (sixteen bytes) at offset bytes into the selected SMBIOS structure. It will be formatted as lower-case hyphenated hexadecimal digits, with the first three fields as little-endian, and the rest printed byte-by-byte.

The default action is to print the value of the requested field to the console, but a variable name can be specified with --set to store the value instead of printing it.

For example, this will store and then display the system manufacturer’s name.

smbios --type 1 --get-string 4 --set system_manufacturer
echo $system_manufacturer

16.3.75 source

Command: source file ¶

Read file as a configuration file, as if its contents had been incorporated directly into the sourcing file. Unlike configfile (see configfile), this executes the contents of file without changing context: any environment variable changes made by the commands in file will be preserved after source returns, and the menu will not be shown immediately.

16.3.76 test

Command: test expression ¶

Evaluate expression and return zero exit status if result is true, non zero status otherwise.

expression is one of:

string1 == string2

the strings are equal

string1 != string2

the strings are not equal

string1 < string2

string1 is lexicographically less than string2

string1 <= string2

string1 is lexicographically less or equal than string2

string1 > string2

string1 is lexicographically greater than string2

string1 >= string2

string1 is lexicographically greater or equal than string2

integer1 -eq integer2

integer1 is equal to integer2

integer1 -ge integer2

integer1 is greater than or equal to integer2

integer1 -gt integer2

integer1 is greater than integer2

integer1 -le integer2

integer1 is less than or equal to integer2

integer1 -lt integer2

integer1 is less than integer2

integer1 -ne integer2

integer1 is not equal to integer2

prefixinteger1 -pgt prefixinteger2

integer1 is greater than integer2 after stripping off common non-numeric prefix.

prefixinteger1 -plt prefixinteger2

integer1 is less than integer2 after stripping off common non-numeric prefix.

file1 -nt file2

file1 is newer than file2 (modification time). Optionally numeric bias may be directly appended to -nt in which case it is added to the first file modification time.

file1 -ot file2

file1 is older than file2 (modification time). Optionally numeric bias may be directly appended to -ot in which case it is added to the first file modification time.

-d file

file exists and is a directory

-e file

file exists

-f file

file exists and is not a directory

-s file

file exists and has a size greater than zero

-n string

the length of string is nonzero

string

string is equivalent to -n string

-z string

the length of string is zero

( expression )

expression is true

! expression

expression is false

expression1 -a expression2

both expression1 and expression2 are true

expression1 expression2

both expression1 and expression2 are true. This syntax is not POSIX-compliant and is not recommended.

expression1 -o expression2

either expression1 or expression2 is true

16.3.77 true

Command: true ¶

Do nothing, successfully. This is mainly useful in control constructs such as if and while (see Writing full configuration files directly).

16.3.78 trust

Command: trust [--skip-sig] pubkey_file ¶

Read public key from pubkey_file and add it to GRUB’s internal list of trusted public keys. These keys are used to validate digital signatures when environment variable check_signatures is set to enforce. Note that if check_signatures is set to enforce when trust executes, then pubkey_file must itself be properly signed. The --skip-sig option can be used to disable signature-checking when reading pubkey_file itself. It is expected that --skip-sig is useful for testing and manual booting. See Using GPG-style digital signatures in GRUB, for more information.

16.3.79 trust_certificate

Command: trust_certificate x509_certificate ¶

Read an DER-formatted x509 certificate from the file x509_certificate and add it to GRUB’s internal list of trusted x509 certificates. These certificates are used to validate appended signatures when the environment variable check_appended_signatures is set to enforce or forced.

Note that if check_appended_signatures is set to enforce or forced when trust_certificate is executed, then x509_certificate must itself bear an appended signature. (It is not sufficient that x509_certificate be signed by a trusted certificate according to the x509 rules: grub does not include support for validating signatures within x509 certificates themselves.)

See See Using appended signatures in GRUB for more information.

16.3.80 unset

Command: unset envvar ¶

Unset the environment variable envvar.

16.3.81 verify_appended

Command: verify_appended file ¶

Verifies an appended signature on file against the trusted certificates known to GRUB (See see list_certificates, see trust_certificate, and see distrust_certificate).

Exit code $? is set to 0 if the signature validates successfully. If validation fails, it is set to a non-zero value. See See Using appended signatures in GRUB, for more information.

16.3.82 verify_detached

Command: verify_detached [--skip-sig] file signature_file [pubkey_file] ¶

Verifies a GPG-style detached signature, where the signed file is file, and the signature itself is in file signature_file. Optionally, a specific public key to use can be specified using pubkey_file. When environment variable check_signatures is set to enforce, then pubkey_file must itself be properly signed by an already-trusted key. An unsigned pubkey_file can be loaded by specifying --skip-sig. If pubkey_file is omitted, then public keys from GRUB’s trusted keys (see list_trusted, see trust, and see distrust) are tried.

Exit code $? is set to 0 if the signature validates successfully. If validation fails, it is set to a non-zero value. See Using GPG-style digital signatures in GRUB, for more information.

16.3.83 videoinfo

Command: videoinfo [[WxH]xD] ¶

List available video modes. If resolution is given, show only matching modes.

16.3.84 wrmsr

Command:: wrmsr 0xADDR 0xVALUE ¶

Write a 0xVALUE to a model-specific register at address 0xADDR.

Please note that on SMP systems, writing to a MSR that has a scope per hardware thread, implies that the value that is written only applies to the particular cpu/core/thread that runs the command.

Also, if you specify a reserved or unimplemented MSR address, it will cause a general protection exception (which is not currently being handled) and the system will reboot.

Note: The command is not allowed when lockdown is enforced (see Lockdown when booting on a secure setup). This is done to prevent subverting various security mechanisms.

16.3.85 xen_hypervisor

Command: xen_hypervisor file [arguments] … ¶

Load a Xen hypervisor binary from file. The rest of the line is passed verbatim as the kernel command-line. Any other binaries must be reloaded after using this command. This command is only available on AArch64 systems.

16.3.86 xen_module

Command: xen_module [–nounzip] file [arguments] ¶

Load a module for xen hypervisor at the booting process of xen. The rest of the line is passed verbatim as the module command line. Modules should be loaded in the following order: - dom0 kernel image - dom0 ramdisk if present - XSM policy if present This command is only available on AArch64 systems.

16.4.1 net_add_addr

Command: net_add_addr interface card address ¶

Configure additional network interface with address on a network card. address can be either IP in dotted decimal notation, or symbolic name which is resolved using DNS lookup. If successful, this command also adds local link routing entry to the default subnet of address with name interface‘:local’ via interface.

16.4.2 net_add_dns

Command: net_add_dns server ¶

Resolve server IP address and add to the list of DNS servers used during name lookup.

16.4.3 net_add_route

Command: net_add_route shortname ip[/prefix] [interface | ‘gw’ gateway] ¶

Add route to network with address ip as modified by prefix via either local interface or gateway. prefix is optional and defaults to 32 for IPv4 address and 128 for IPv6 address. Route is identified by shortname which can be used to remove it (see net_del_route).

16.4.4 net_bootp

Command: net_bootp [card] ¶

Alias for net_dhcp, for compatibility with older Grub versions. Will perform the same DHCP handshake with potential fallback to BOOTP as the net_dhcp command (see net_dhcp).

16.4.5 net_del_addr

Command: net_del_addr interface ¶

Remove configured interface with associated address.

16.4.6 net_del_dns

Command: net_del_dns address ¶

Remove address from list of servers used during name lookup.

16.4.7 net_del_route

Command: net_del_route shortname ¶

Remove route entry identified by shortname.

16.4.8 net_dhcp

Command: net_dhcp [card] ¶

Perform configuration of card using DHCP protocol. If no card name is specified, try to configure all existing cards. Falls back to the BOOTP protocol, if needed. If configuration was successful, interface with name card‘:dhcp’ and configured address is added to card. Additionally the following DHCP options are recognized and processed:

‘1 (Subnet Mask)’

Used to calculate network local routing entry for interface card‘:dhcp’.

‘3 (Router)’

Adds default route entry with the name card‘:dhcp:default’ via gateway from DHCP option. Note that only option with single route is accepted.

‘6 (Domain Name Server)’

Adds all servers from option value to the list of servers used during name resolution.

‘12 (Host Name)’

Sets environment variable ‘net_’<card>‘_dhcp_hostname’ (see net_<interface>_hostname) to the value of option.

‘15 (Domain Name)’

Sets environment variable ‘net_’<card>‘_dhcp_domain’ (see net_<interface>_domain) to the value of option.

‘17 (Root Path)’

Sets environment variable ‘net_’<card>‘_dhcp_rootpath’ (see net_<interface>_rootpath) to the value of option.

‘18 (Extensions Path)’

Sets environment variable ‘net_’<card>‘_dhcp_extensionspath’ (see net_<interface>_extensionspath) to the value of option.

‘66 (TFTP Server Name)’

Sets environment variable ‘net_’<card>‘_dhcp_server_name’ (see net_<interface>_dhcp_server_name) to the value of option.

‘67 (Filename)’

Sets environment variable ‘net_’<card>‘_boot_file’ (see net_<interface>_boot_file) to the value of option.

16.4.9 net_bootp6

Command: net_bootp6 [card] ¶

Perform configuration of card using DHCPv6 protocol. If no card name is specified, try to configure all existing cards. If configuration was successful, interface with name card‘:dhcp6’ and configured address is added to card.

‘1 (Domain Name Server)’

Adds all servers from option value to the list of servers used during name resolution.

16.4.10 net_get_dhcp_option

Command: net_get_dhcp_option var interface number type ¶

Request DHCP option number of type via interface. type can be one of ‘string’, ‘number’ or ‘hex’. If option is found, assign its value to variable var. Values of types ‘number’ and ‘hex’ are converted to string representation.

16.4.11 net_ipv6_autoconf

Command: net_ipv6_autoconf [card] ¶

Perform IPv6 autoconfiguration by adding to the card interface with name card‘:link’ and link local MAC-based address. If no card is specified, perform autoconfiguration for all existing cards.

16.4.12 net_ls_addr

Command: net_ls_addr ¶

List all configured interfaces with their MAC and IP addresses.

16.4.13 net_ls_cards

Command: net_ls_cards ¶

List all detected network cards with their MAC address.

16.4.14 net_ls_dns

Command: net_ls_dns ¶

List addresses of DNS servers used during name lookup.

16.4.15 net_ls_routes

Command: net_ls_routes ¶

List routing entries.

16.4.16 net_nslookup

Command: net_nslookup name [server] ¶

Resolve address of name using DNS server server. If no server is given, use default list of servers.