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Grub2 GRUB 2 is the default boot loader and manager for Ubuntu since version 9.10 (Karmic Koala). As the computer starts, GRUB 2 either presents a menu and awaits user input or automatically transfers control to an operating system kernel. GRUB 2 is a descendant of GRUB (GRand Unified Bootloader). It has been completely rewritten to provide the user significantly increased flexibility and performance. GRUB 2 is Free Software.
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In this guide, GRUB 2 is version 1.98 or later. GRUB legacy (version 0.97) will grub-install ll -v. be referred to as GRUB. To determine your version, use grub-insta Grub version 1.99 will be the default on Ubuntu 11.04 (Natty Narwhal) and introduces some major changes in the Grub file contents. The main user interface file, /etc/default/grub will appear relatively unchanged to the user, significantly more capabilities will be present in Grub 1.99. This guide primarily details Grub 1.98, the Grub release found in Ubuntu 10.04 LTS (Lucid Lynx). Content reflecti reflecting ng other versions versions of Grub 2 will be noted in the appropriate appropriate entry. Note: When working with multiple GNU/Linux distributions on the same system be aware aw are that other distributi distributions ons (notably OpenSuse and Fedora) have not necessaril necessarily y moved to Grub 2 yet which may complicate complicate Grub 2 configurati configuration. on.
Improvements GRUB 2's major improvements over the original GRUB include: Scripting support including conditional statements and functions Dynamic module loading Rescue mode Custom Menus Themes Graphical boot menu support and improved improved splash splash capability capability Boot LiveCD ISO images directly directly from hard drive New configuration file structure Non-x86 platform support support (such as PowerPC) Universal Universal support for UU IDs (not just Ubuntu)
GRUB vs GRUB 2 GRUB 2's default menu will look familiar to GRUB users but there are a great number of differences beneath the surface. On a new install of Ubuntu 9.10 or 10.04 with no other installed operating system, GRUB 2 will boot directly to the login prompt or Desktop. No menu will be displayed, even if multiple kernels are installed and later .
1. Improvements Improvements 2. GRUB GRUB vs GRUB GRUB 2 3. Installation Installation 1. Default Default Installation Installation 2. Upgrading Upgrading to GRUB 2 4. File Struc Structure ture 1. /boot/grub/grub.c /boot/grub/grub.cfg fg 2. /etc/default/ /etc/default/grub grub 3. /etc/grub.d/ /etc/grub.d/ (directory) (directory) 5. Configurin Configuring g GRUB GRUB 2 1. /etc/default/ /etc/default/grub grub (file) 6. Boot Display Display Behavior Behavior 1. Initial Default Default 2. Timed Display 3. Hidden Hidden 4. Saved Saved 5. Last Boot Failed Failed or Boot into Recovery Recovery Mode 7. Custom Menu Menu Entries Entries 1. Creating the Custom Custom Menu 8. Fallback Fallback mode 9. Command Line Line and Rescue Mode 1. Editing Menus During During Boot 2. Command Line Mode Mode 3. Using Using CLI to Boot Boot 4. Rescue Rescue Mode Mode 10. GRUB GRUB Errors 1. Resolving an "Unrecog "Unrecognized nized Device String" (Error 11) 2. File Not Not Found Found (Error 15) 3. update-grub update-grub complains complains about about missing devices 4. error: no such such partition partition 11. Splash Images Images and Theming Theming 1. GRUB GRUB 2 Splash Splash Images Images 2. Creating User User Splash Images Images 3. Themes Themes 12. Reinstalling Reinstalling GRUB GRUB 2 1. Reinstalling Reinstalling from LiveCD 2. Changing Changing or Moving Moving GRUB 2 13. Uninstalling Uninstalling GRUB 2 1. Reverting to GRUB GRUB Legacy 14. Selected Selected Problems Problems and Bugs 15. Miscellaneous Miscellaneous 1. Booting from a serial console console 16. Links Links 1. External Links
Hold down SHIFT to display the menu during boot (formerly ESC in GRUB legacy). No /boot/grub/menu.lst . It has been replaced by /boot/grub/grub.cfg . There is no "/find "/find boot/grub/st boot/grub/stage1" age1" at the grub prompt. prompt. Stage S tage 1.5 has been eliminat eliminated. ed. The main menu file, /boot/grub/grub.cfg , is not meant to be edited, even by 'root'. grub.cfg is overwritten overwritten anytime anytime there is an update, a kernel is added/removed, added/removed, or the user runs update-grub.
The list of accessible Linux kernels is automatically generated from the directory of files in /boot . It is not created by editing a list such as the one in the old menu.lst . Running update-grub updates the list. The user can use a custom file, /etc/grub.d/40_custom, in which the user can place his own entries. This file will not be overwritten. The primary configuration file for changing menu display settings is /etc/default/grub. There are multiple files for configuring the menu - /etc/default/grub mentioned above, and all the files in the /etc/grub.d/ directory.
Partition numbering has changed. The first partition is now 1 rather than 0. The first device is still hd0 by default (no change), although this can be changed in /boot/grub/devic /boot/grub/device.map. e.map. Automated Automated searches for other operating systems, systems, such as Windows, whenever update-grub is executed. No changes made in the configuration files will take effect until the update-grub command is also run.
Installation GRUB 2 is installed by default on new installations of Ubuntu 10.04 . Releases such as Ubuntu 9.04 Jaunty Jackalope which are upgraded to 9.10 will retain GRUB unless the user elects to upgrade to GRUB 2. Previous releases of Ubuntu can be upgraded to GRUB 2 if the user desires. You can check the current version installed on your system via Synaptic or from the command line. Open a Terminal and enter the following: grub-install grub-install -v
GRUB 2 should display a version number of 1.96 or later. Legacy GRUB is version 0.97.
Default Installation GRUB 2 will be the default bootloader on LiveCD installations of Ubuntu 9.10, Karmic Koala. The GRUB 2 package is grub-pc. The grub-common package will also be installed. grub2 is a dummy transitional package. It can safely be removed and will not be shown as installed in Synaptic.
Upgrading to GRUB 2 Upgrading to G RUB 2 from GRUB (legacy) (legacy) in Ubuntu 9.10 or earlier versions versions is relatively relatively easy. Importantly Importantly,, the upgrade offers a process to ensure GRUB 2 will work on your machine before the user commits to a full conversion. Note however that the developers made a decision to not use an automatic update to GRUB 2 as the default on upgrade installs. Users who upgrade to Ubuntu 9.10 may continue to use GRUB if desired. Before installing GRUB 2, refresh the repository indexes to ensure the system has the latest update list. This is normally sudo apt-ge apt-get t update update in a terminal or refreshing the lists in a GUI package manager such as accomplished via sudo Synaptic. Older GRUB packages may not contain updates which have fixed several bugs in the early versions of the installer. To upgrade to GRUB 2 install the grub-pc package. This package can be installed with Synaptic or running the command below. Once the installation begins, a simple script will guide the user through the rest of the installation: sudo sudo apt-ge apt-get t instal install l grub-p grub-pc c At this point the package manager may complain abo ut version conflicts and offer a solution to un-install grub. And this may cause you to worry that it might become impossible for you to use the "chain load to GRUB2 from legacy GRUB" option that is mentioned below. But never fear - for some reason reason - taking the un-install GRUB option here does not prevent prevent you booting with the legacy menu described in step 4 below.
1. At the first prompt, read the message, tab to select "OK", then press ENTER.
2. After selecting "OK" the next option allows the user to test GRUB 2 by adding an entry to their normal
GRUB menu. Select "Yes" to place a Chainload option on the GRUB menu. When GRUB boots the next time, the user can select a normal GRUB entry or transfer control to GRUB 2 via the Chainload entry. 3. The next step(s) will import sections from GRUB's menu.lst to the "Linux command line" (shown) and possibly the "Linux default command line". These entries allow the user to enter any special commands such as quiet, splash, noapic and others of that nature. GRUB 2 should automatically import these settings. Normally the user should accept any existing entries and TAB to "OK". If necessary, entries can be added later. Refer to the Configuring GRUB 2 section for more detail.
When installing on a fresh drive, you may need to mark the selected partition as bootable. 4. Once the system has installed GRUB 2, the user can reboot and will be greeted by an updated GRUB legacy menu. As shown, the user will see a "Chainload" option which will test the GRUB 2 installation. Selecting the Chainload option will transfer control to GRUB 2 and display a GRUB 2 menu.
4a. Jaunty users may experience an "Unrecognized device string" Error 11 when making a selection. If so, press "e" until you see the line beginning with "grub edit> root". Change "root" to "uuid", ENTER, then boot by pressing "b". More details on Error 11 are located in the Command Line and Rescue Mode section. 5. Test the new entries and note the Grub 1.9X version number (highlight added).
6. If the GRUB 2 menus function properly the user can upgrade to GRUB 2 at any time by running: sudo upgrade-from-grub-legacy
During installation the user will be prompted to provide the device(s) on which to install GRUB 2. Use the UP/DOWN keys to highlight a device (sda, sdb, etc), then the SPACE key to select the device. Once at least one device is selected, use the TAB key to highlight OK and press ENTER. Failure to select a drive will result in a GRUB Error 15 and failure of the installation. Upon successful installation of GRUB 2, a message w ill inform the user that some GRUB Legacy configuration files are still present and can be removed. The instructions provide the following command, which must be run as 'root': rm f /boot/grub/menu.lst* Use caution when running the rm command as "root". Incorrectly entering this command could result in permanently deleting necessary system files.
File Structure
GRUB 2 incorporates a totally revised directory and file hierarchy. The menu.lst of GRUB legacy is no longer used. To find out where GRUB 2 is installed, the user can run the following commands: sudo grub-probe t device /boot/grub for the device and sudo grub-probe -t fs_uuid /boot/grub for the UUID. The main directories and files used by GRUB 2 include:
/boot/grub/grub.cfg This is the file most closely resembling GRUB's /boot/grub/menu.lst . This file contains the GRUB 2 menu information but unlike GRUB's menu.lst the grub.cfg file is not meant to be edited. Each section is clearly delineated with "(### BEGIN)" and references the file in the /etc/grub.d directory from which the information was generated. grub.cfg is updated by running the update-grub command as root. The update-grub command is a stub for sudo grub-mkconfig -o /boot/grub/grub.cfg. For standardization, the command update-grub will be employed, run as "root" with sudo.
The file is automatically updated with kernel installations/removals or other updates which would affect its output. By default, and whenever the update-grub command is executed, this file is made "read-only". This is in keeping with the intent that the file should not be edited manually. The user will also see a multitude of *.mod files in the /boot/grub directory. These files reflect the modular nature of GRUB 2 and are loaded as necessary by the GRUB 2 bootloader.
/etc/default/grub This configuration file contains information formerly contained in the upper section of GRUB Legacy's menu.lst and items contained on the end of the kernel line. The entries in this file can be edited by a user with administrator (root) privileges and are incorporated into grub.cfg when it is updated. Specific configuration settings are detailed in the Configuring GRUB 2 section below.
/etc/grub.d/ (directory) The files in this directory are read during execution of the update-grub command and their instructions are incorporated into /boot/grub/grub.cfg . The placement of the menu items in the grub.cfg menu 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. 10_linux is run before 20_memtest , which would run before 40_custom . If files with alphabetic names exist, they are run after the numerically-named files. Custom entries can be added to the 40_custom file or in a newly created file. Based on its name, 40_custom entries by default appear at the bottom of the menu. A custom file beginning with 06_ would appear at the top of the menu since its alphanumeric sorting would place it ahead of 10_ through 40_ files. Only executable files generate output to grub.cfg during execution of update-grub. The default files in this directory are: 00_header Sets initial appearance items such as the graphics mode, default selection, timeout, etc. These settings are normally imported from information from /etc/default/grub. Users normally do not need to make changes to this file. 05_debian_theme The settings in this file set splash image, text colors, selection highlighting and themes. In the absence of a splash image, this file sets a monochromatic theme for the initial menu display. How to set font renderings and splash images are discussed in detail in the Splash Images and Themes section. 10_hurd Locates Hurd kernels. Not currently used. 10_linux Locates kernels on the root device for the operating system currently in use. It takes this information and establishes the names displayed on the menu for these kernels. Thanks to the code in this file, it is not necessary (or even possible) to explicitly construct the list of kernel names displayed on the menu. Note: If you don't want all your old kernels to appear in the menu list, remove their files from /boot . 20_memtest86+ Searches for /boot/memtest86+.bin and includes it as an option on the GRUB 2 boot menu. There is currently no line option to remove this entry from the menu. The display of memtest86+ can be inhibited by removing the executable bit from this file and running sudo update-grub. 30_os-prober This file uses os-prober , w hich searches for Linux and other operating systems. Results are placed in grub.cfg based on the scripts in this file. The file is divided into 4 sections, representing the types of operating systems handled by the scripts: Windows, Linux, O SX, and H urd. Variables in this file determine the format of the displayed names in /boot/grub/grub.cfg and on the GRUB 2 menu. Users familiar with basic scripting can alter these variables to change the format of the displayed menu entries. Alternatively, the user can insert an entry into /etc/default/grub which disables this script (see below). By default os-prober ignores any disks that possess dmraid signatures,
which can be listed via sudo dmraid -r -c. 40_custom A template for adding custom menu entries which will be inserted into grub.cfg upon execution of the update-grub command. The contents of this file, below the "exec tail -n +3 $0" line and the default comments, are imported directly into /boot/grub/grub.cfg without any changes.
Configuring GRUB 2 Important note: Configuration changes are normally made to /etc/default/grub and to the custom files located in /etc/grub.d . The /boot/grub/grub.cfg file should not be edited by the user; changes to this file are made by configuration scripts. After editing /etc/default/grub, you need to run sudo update-grub for your changes to take effect on the next boot.
Some of the most common changes, such as the default OS/kernel and menu timeout, can be changed from within a GUI app called StartUp-Manager. See the community doc StartUpManager for information about how to install and use this application.
/etc/default/grub (file) The main configuration file for changing default settings. Upon installation, the following lines are available for alteration by the user: GRUB_BACKGROUND - Sets the background image, enter the full path to the image here. See splash image configuration above for further details. GRUB_DEFAULT - Sets the default menu entry. Entries may be numeric, a complete menuentry quotation, or "saved"
Sets the default menu entry by menu position. As in GRUB, the first "menuentry" in grub.cfg is 0, the second is 1, etc. GRUB_DEFAULT=0
An exact menu entry, including the quotation symbols, may also be used. In this case, location in the menu will not matter. Example: GRUB_DEFAULT="Ubuntu, Linux 2.6.31-9-generic" GRUB_DEFAULT="xxxx"
GRUB_DEFAULT=saved
The information in this section applies to GRUB 1.98 and later. Enables the "grub-reboot" and "grub-set-default" commands to set the default OS. The default OS will not be set by an interactive selection of an OS from the menu. grub-set-default Sets the default boot entry until changed.
The format is sudo grub-set-default X , with X being the menu entry position (starting with 0 as the first entry) or the exact menu string. Examples: sudo grub-set-default 3 or sudo grub-set-default "Ubuntu, Linux 2.6.32-15-generic" To obtain the existing menu entry choice number (starting from 0) or the menu entry "string", run grep menuentry /boot/grub/grub.cfg grub-reboot This command sets the default boot entry for the next boot only. The format of the command is the same as for grub-set-default (see above). GRUB_SAVEDEFAULT= If set to true this setting will automatically set the last selected OS from the menu as the default OS on the next boot.
No commands need be run to set the default OS. Any time a menu entry is manually selected from the GRUB 2 menu, it becomes the default OS. This option currently does not work if your /boot directory resides on an LVM partition or RAID. GRUB_HIDDEN_TIMEOUT=0
This setting determines how long a screen without the GRUB 2 menu will be displayed. While the screen is blank, the user can press any key to display the menu. The default behavior is to hide the menu if only one operating system is present. If a user with only Ubuntu wishes to display the menu, place a # symbol at the start of this line to disable the hidden menu feature. For at least GRUB 1.97~beta - the version found in Karmic - whether or not the menu can include a timeout delay with a blank screen is dependent on whether GRUB 2 finds multiple operating systems. Note to multiple-OS users: If GRUB 2's os-prober identifies additional operating systems while running the /etc/grub.d/30_os-prober script the hidden menu timeout feature is disabled by conditional statements. This also disables the ability to use the SHIFT key to display the menu during boot. Users with multiple operating systems wishing to hide the menu can find script edits on various forums which will allow them to add a hidden timeout feature to the boot sequence (for example: ubuntuforums). GRUB_HIDDEN_TIMEOUT=0
on single operating system computers.
No menu is displayed. The system is immediately booted to the default OS. This is the default setting with only one identified operating system.
To display the menu under this condition, place a # symbol at the start of the line and ensure the GRUB_TIMEOUT setting is a positive integer. If the value is set to 0, a keystatus check is performed to determine if the SHIFT key is depressed. If GRUB 2 determines the SHIFT key is depressed during the boot process, the menu will be displayed. This gives the user a method of interrupting an automatic boot which would normally not display the menu. GRUB_HIDDEN_TIMEOUT=X
X is a positive integer (e.g. 1, 5, 10, etc)
The boot process will pause and display a blank screen or the designated splash image for X seconds. At the end of the time period, the system will boot. No menu will be displayed. While GRUB_HIDDEN_TIMEOUT is active, the menu can be displayed by pressing any key. GRUB_HIDDEN_TIMEOUT=
No value entered after the = sign The menu will be displayed for the number of seconds designated by GRUB_TIMEOUT. GRUB_HIDDEN_TIMEOUT_QUIET=true true
No countdown is displayed. The screen will be blank.
false A counter will display on a blank screen for the duration of the GRUB_HIDDEN_TIMEOUT value.
GRUB_TIMEOUT=10
This instruction defers to the GRUB_HIDDEN_TIMEOUT unless GRUB_HIDDEN_TIMEOUT is commented (#). If GRUB_HIDDEN_TIMEOUT is active, the GRUB_TIMEOUT only operates once, and if, the menu is displayed. Setting this value to -1 will cause the menu to display until the user makes a selection. The GRUB 2 menu is hidden by default unless another OS is detected by the system. If there is no other OS, this line may be commented out unless the user changes it. To display the menu on each boot, uncomment the line and use a value of 1 or higher. GRUB_DISTRIBUTOR=lsb_release -i -s 2> /dev/null || echo Debian
Retrieves the descriptive name in the menu entry. (Ubuntu, Xubuntu, Debian, etc.) GRUB_CMDLINE_LINUX
If it exists, this line imports any entries to the end of the 'linux' command line (GRUB legacy's "kernel" line) for both normal and recovery modes. This is similar to the "altoptions" line in menu.lst GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
This line imports any entries to the end of the 'linux' line (GRUB legacy's "kernel" line). The entries are appended to the end of the normal mode only. This is similar to the "defoptions" line in menu.lst. For a black screen with boot processes displayed in text, remove "quiet splash". To see the grub splash image plus a condensed text output, use "splash". The entry "acpi=off", if required, would also be an option entered on this line. #GRUB_TERMINAL=console
Uncomment to disable graphical terminal (grub-pc only) #GRUB_DISABLE_LINUX_UUID="true"
Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux A bug currently requires true be placed within quotation marks for this option, when uncommented, to take effect. Quotation marks currently are not the default and the user must add them. #GRUB_GFXMODE=640x480
You can remove the # symbol to make this line active. The entry sets the resolution of the graphical menu (the menu text size). It provides resolutions supported by the user's graphics card (e.g. 640x480 , 800x600, 1280x1024, etc). The setting applies only to the boot menu display, not the resolution of the operating system that boots. Tip: Setting the same resolution in GRUB 2 and the operating system will decrease boot times slightly. Although not required, the user can also specify the color bitdepth by appending it to the resolution setting. An example would be 1280x1024x24 or 640x480x32. The user can also add multiple resolutions. If GRUB 2 cannot use the first entry, it will try the next setting. Settings are separated by a comma. Example: 1280x1024x16,800x600x24,640x480. If using a splash image, make sure the resolution setting and the splash image size are compatible. If using an entry that produces a "not found" message when running update-grub, try adding or changing the color bitdepth. Resolutions available to GRUB 2 can be displayed by typing vbeinfo in the GRUB 2 command line. The command line is accessed by typing "c" when the main GRUB 2 menu screen is displayed. If this line is commented (#) or the resolution is unavailable GRUB 2 uses the default setting determined by /etc/grub.d/00_header .
For a guide to changing resolutions when using a splash image see the Splash Images and Theming section. GRUB_DISABLE_LINUX_RECOVERY=true
Add or uncomment this line to prevent "Recovery" mode kernel options from appearing in the menu. If you want a "Recovery" option for only one kernel, make a special entry in /etc/grub/40_custom. GRUB_INIT_TUNE="480 440 1"
When uncommented, plays a single beep just prior to the Grub 2 menu display. The format is tempo [pitch1 duration1] [pitch2 duration2] ... tempo is set once and applies to all duration settings. duration is the result of 60/tempo. A duration of 1 with a tempo of 60 would produce a 1 second beep. A duration of 1 with a tempo of 480 produces a .125 second beep.
Caution: The menu is displayed after the tune is complete. Creating a long tune will delay the appearance of the menu. Online documentation is available by typing info grub --index-search play in a terminal. It mentions the ability to play a tune with the command play file if the tune is composed with little-endian numbers. Additional instructions which may be included: GRUB_DISABLE_OS_PROBER=true
Enables/disables the os-prober check of other partitions for operating systems, including Windows, Linux, OSX and Hurd.
Boot Display Behavior GRUB 2 loads before any operating system. It's modular components are loaded on an as-needed basis. Menu display behavior is generally determined by settings in /etc/default/grub. Review the "Configuring GRUB 2" section for specific entry and formatting guidance.
Initial Default GRUB 2 will boot straight into the default operating system if no other operating system is detected. No menu will be displayed. If another operating system is detected, the GRUB 2 menu will display.
Timed Display The menu is displayed for a predetermined number of seconds. The default entry is highlighted and other selections may be made by the user until the timeout expires. The default timeout is now 3 seconds. The timer continues until any key is pressed or the highlighted entry is selected by pressing ENTER. If no user input is made GRUB 2 boots the default entry at the end of the timeout period. Once a key has been pressed the timeout is deactivated and the user must make a selection manually. The default entry is determined by the DEFAULT= setting in /etc/default/grub; the first "menuentry" has a value of "0".
Hidden No menu entries are displayed. The splash screen, if configured, w ill be displayed. The user can interrupt the boot process and display the menu by holding down the SHIFT key until the menu displays. GRUB 2 searches for a depressed SHIFT key signal during boot. If the key is pressed or GRUB 2 cannot determine the status of the key, the menu is displayed. The time the screen remains blank but available for display is determined by a setting in /etc/default/grub. GRUB 2 can display a countdown timer to provide visual feedback on the time remaining until the default selection is chosen. The timeout setting is enabled in /etc/default/grub At the end of the timeout, the default entry determined by settings in /etc/default/grub will be selected.
Saved Saving an OS can be achieved by running sudo grub-set-default if DEFAULT=saved is set in /etc/default/grub. It may also be saved if GRUB_SAVEDEFAULT=true is also set in /etc/default/grub. In this case, the default OS remains until a new OS is manually selected from the GRUB 2 menu or the grub-set-default command is executed.
Last Boot Failed or Boot into Recovery Mode If the last boot failed or after a boot into Recovery Mode the menu will be displayed until the user makes a selection. The timeout setting in /etc/default/grub do not apply in this case. To change this behaviour, /etc/grub.d/00_header must be modified (if
statement checking recordfail at the end of 00_header).
Custom Menu Entries GRUB 2 allows users to create customized menu selections which will be automatically added to the main menu when sudo update-grub is executed. An empty 40_custom file is available in /etc/grub.d/ for use or to serve as an example to create other custom menus. Here are some considerations for custom menus: The name of the file determines the order of the selections in the menu. Numeric filenames are run first, followed by alphabetic filenames. 10_linux entries will appear before 30_os-prober entries, which will be placed before 40_custom entries, which will preceed my.custom.entries inputs.
A user wishing for the custom menu entries to appear first on the main menu could name the directory 06_xxx so its listings are first in the menu. The file must be made executable: sudo chmod +x /etc/grub.d/filename. The contents of the file is added to grub.cfg without changes when the update-grub command is executed. Unlike grub.cfg , custom files can be edited at any time, are not read-only, and can be owned by the user if desired. Custom files are static. The contents will not be altered when new kernels are added or removed (unless the contents are affected by user-added scripts).
If the custom file places the menuentry listings at the top of grub.cfg , the user may wish to confirm the /etc/default/grub DEFAULT= setting after running update-grub. Make sure it still points to the desired menuentry listing. When counting, the first "menuentry" in /boot/grub/grub.cfg is 0.
Creating the Custom Menu The user can either edit the default /etc/grub.d/40_custom file or create a new one. The easiest way to create the content of a custom menu is to copy a working entry from /boot/grub/grub.cfg . Once copied, the contents of 40_custom can be tailored to the user's desires. According to the default sample custom file (/etc/grub.d/40_custom) the first two lines of any custom file in /etc/grub.d should be: #!/bin/sh exec tail -n +3 $0
The user can copy existing menuentries from the /boot/grub/grub.cfg file or from a GRUB legacy file. If the user wishes to copy from a GRUB legacy menu.lst file: A backup copy of this file may be in the /boot/grub directory if the user upgraded from GRUB to GRUB 2. The following entries from the GRUB menu listing must be changed for them to work: title is changed to menuentry. The line must end with { root is changed to set root= kernel must be changed to linux
Any partition designation (sda4, sdb6) must be changed, as GRUB and GRUB 2 count the partitions differently. The first partition for GRUB 2 is 1, not 0. Devices still start the count at 0. Look carefully at the format of any working GRUB 2 menulist entry to ensure the correct format is used. General menuentry Construction Rules: The first line must start with menuentry and end with { The area between the quotation symbols is what will appear on the GRUB 2 menu. Edit as desired. The last line of the menuentry must be } Do not leave empty spaces at the end of lines The set root= line should point to the GRUB 2 /boot location ( sdXY ) The root reference in in the linux line should point to the system partition. If GRUB 2 cannot find the referenced kernel, try replacing the UUID with the device name (example: /dev/sda6 ). A sample entry copied from the grub.cfg and altered by the user might look like this: menuentry "My Default Karmic" {
set root=(hd0,1) search --no-floppy --fs-uuid --set cb201140-52f8-4449-9a95-749b27b58ce8 linux /boot/vmlinuz-2.6.31-11-generic root=UUID=cb201140-52f8-4449-9a95-749b27b58 ce8 ro quiet splash
initrd /boot/initrd.img-2.6.31-11-generic }
A sample entry for a hard drive version of SystemRescueCD installed per the instructions on the web site (on sda8). menuentry "System Rescue CD" { set root=(hd0,8) linux /sysrcd/rescuecd subdir=sysrcd setkmap=us initrd /sysrcd/initram.igz }
A sample entry for chainloading to another GRUB bootloader. menuentry "Grub 1 Bootl oader" { set root=(hd0,8) chainloader+1 }
Fallback mode It is possible to configure Grub2 to fall back to a known good menu-entry if the default menu-entry for some reason fails to boot. An example script that can be used for this is available at this webpage (in German).
Command Line and Rescue Mode There are several ways for a user to attempt to resume a failed boot. If the menu is still available, menu settings can be viewed and altered by the user. Additionally, if GRUB 2 detects errors during boot and cannot pass control to the selected kernel because of a grub.cfg error or omission it will revert to the rescue mode. Both methods allow the user to recover to a usable system via a limited command line interface. If only the word "Grub" appears at the top of the screen without a prompt (access to the command line) or menu, refer to the Reinstalling from LiveCD section. TROUBLESHOOTING: If you are in this section, you are probably having problems booting to your OS. The following sections detail methods to use the edit and command-line capabilities of GRUB 2 to attempt to boot the system. One of the improvements of GRUB 2 is the ability to search the contents of partitions from the command line. If the instructions in the following sections do not work, especially if accompanied by "not found" or "the kernel must be loaded first" messages, use the following commands to explore the partitions. For Ubuntu, the /boot directory should normally contain at least one "vmlinuz" kernel and an "initrd" .img file. The /boot/grub directory should normally contain "grub.cfg" and various ".mod" files. X is the drive, starting with 0. Y is the partition number, starting with 1. For a pure Ubuntu install on a single drive, the main drive/partition is often hd0,1. For dual-boot with Windows on a single drive, the normal location is often hd0,5. Use the ls command by itself to see which drives/partitions are known to GRUB 2.
To explore the devices known to GRUB 2, press "c" from the GRUB 2 menu to enter the command line (if not already there): ls
Display the drives/partitions known to GRU B 2.
ls (hdX,Y)/
Display the contents of the / directory of the designated drive/partition.
ls (hdX,Y)/boot
Display the contents of the /boot directory. Example: ls (hd0,5)/boot
ls Display the contents of the /boot/grub directory. Example: ls (hd0,5)/boot/grub (hdX,Y)/boot/grub ls (vg-lv)/
Display the contents of the logical volume /dev/mapper/vg-lv or /dev/vg/lv (same thing). Example (ubuntu-root used as /): ls (ubuntu-root)/
Editing Menus During Boot If the menu is not normally displayed during boot, hold down the SHIFT key as the computer attempts to boot to display the GRUB 2 menu. With the menu displayed, press any key (except ENTER) to halt the countdown timer and select the desired entry with the up/down arrow keys. Press the 'e' key to reveal the selection's settings.
Use the keyboard to position the cursor. In this example, the cursor has been moved so the user can change or delete the numeral 9. Make a single or numerous changes to any or every line. Do not use ENTER to move between lines. Tab completion is available, which is especially useful in entering kernel and initrd entries. When complete, determine the next step: CTRL-x - boot with the changed settings (highlighted for emphasis). c - go to the command line to perform diagnostics, load modules, change settings, etc. ESC - Discard all changes and return to the main menu. The choices are listed at the bottom of the screen as a reminder.
Command Line Mode From the main GRUB 2 menu display the user can elect to drop to a command line by typing 'c'.
Here are some useful tips and features for use with the GRUB 2 command line: Turning off the splash image may make viewing the terminal easier. Press "c" to go to the command line and then type: set color_normal=white/blue or the color combination you wish to use. "black" as the second entry retains the menu's transparency and should be avoided as a selection if the user wants to work with a solid background color. To prevent scrolling past the top of the screen, first run set pager=1, which acts like the terminal's "| more" command. This will allow one full screen of data, with line advancement continued by pressing the ENTER key. Type help to view a list of all the commands. Type help x to view help commands beginning with the letter "x". Tab completion and using the up arrow to repeat commands work the same as in a normal terminal. The TAB completion feature is very handy. At any point, pressing the TAB key may complete an entry, if the element is unique, or display available options. Typing a few additional characters and pressing TAB again may allow tab completion to finish the entry. Some of the more useful commands include: Command
background_image
Result
Load an existing background image. Use tab completion to help complete filename entries! background_image=/usr/share/images/grub/then tab to display a list of all images. Useful command
when initially testing splash images. cat
Use to display the current file contents. cat /boot/grub/grub.cfg , cat /etc/fstab
help
View all available commands. Type help x to get a list of commands beginning with the letter x. help xxx for information about the xxx command. This command should b e preceded by running "set pager=1", which acts like the terminal's "| more" command, to prevent scrolling past the to p of the screen.
ls
Used alone, lists all devices known to GRUB 2, such as (hd0) (hd0,1), etc. View available partitions with ls. View /boot and /grub directory contents with `ls /boot, ls /boot/grub
initrd
Load an initrd .
linux
Load a linux kernel.
loopback
Mount a file as a device. `loopback loop (hd0,2)/iso/my.iso
lsmod
Display loaded modules
reboot
Reboot the machine
rescue
Enter the rescue mode
set
Show environmental variables in place. Combined with others, set variables such as
set gfxmode=640x480, set color_normal=cyan/black Use the latter command in command line mode
to test various menu font colors. Di spl ay avail abl e mo ni to r resol ut io ns.
vb ei nfo
Using CLI to Boot If the user has problems booting but the menu is available, the easiest method to boot the system is to edit the existing menu. Refer to Editing Menus During Boot . If GRUB 2 fails to find a usable grub.cfg file it should revert to the grub-rescue mode. The command line prompt will display grub-rescue> and no menu will be displayed. From this command line the user can attempt to manually enter the instructions to boot to a usable system. If the command line prompt is not already active press "c" to enter the Command Line mode. You will see the GRUB 2 prompt: grub> or grubrescue>
If you wish to cancel and start over at any time, ESC will remove changes and return the user to the previous menu. Use the following two commands to determine the device (drive) and partition of the system you wish to boot. set
When set is typed without additional entries the command displays the current GRUB 2 settings.
ls
Run ls to see the devices recognized by GRUB 2. Example: (hd0) (hd0,1) (hd1,5) In this example sda, sda1, sdb5 are recognized.
Express Boot to the Most Recent Kernel Command Summary *:
set root=(hdX,Y ) linux /vmlinuz root=/dev/sdXY ro initrd /initrd.img boot
Expanded Instructions *: Press ENTER after completing each line. Some entries will not provide feedback. This is normal. If a "file not found" or similar error message is displayed while running these commands, ensure you are using the correct X,Y values. The ls command can help determine the correct values. Once the X,Y values are confirmed run the following command: set prefix=(hdX,Y)/boot/grub
1*. set root=(hdX,Y )
Type with correct X,Y results from the ls command and press ENTER. Remember GRUB 2 counts the first drive as 0, the first partition as 1. Example: If the Ubuntu system is on sda5, enter: set root=(hd0,5)
2*. linux /vmlinuz root=/dev/sdXY ro
Example: linux /vmlinuz root=/dev/sda3 ro * Wubi users see note.
3. initrd /initrd.img
Selects the latest initrd image.
4. boot
Boot to the latest kernel on the selected partition.
* Wubi users only - substitute these commands in Steps 1 and 2: set root=(loop0) linux /vmlinuz root=/dev/sdXY loop=/ubuntu/disks/root.disk ro
These changes are not permanent. After successfully booting into the system the user should run sudo updategrub and inspect the GRUB 2 configuration file (/boot//grub/grub.cfg ). For problems with booting the main linux kernel, ensure the search, linux, and initrd lines in the [### BEGIN /etc/grub.d/10_linux ###] section of the file now correctly point to the correct locations. The user may need to reinstall GRUB 2 (sudo grubinstall /dev/sdX).
Boot a Specific Kernel Manually If a GRUB 2 menu is not available for editing during the boot process the command line may still allow booting a specific kernel. If GRUB 2 is looking in the correct location a user may be able to enter all the necessary information on the command line in a single entry. This section will provide a step-by-step guide on how to enter this information. The line will look similar to the
following when completed: Command Summary *:
set
linux /boot/vmlinuz- root=/dev/sdXY ro initrd /boot/initrd- boot
Expanded Instructions *: Press ENTER only after completing each step ("1", "2", "3" and "4"). Step 1*. Set the Root Partition set root=(hdX,Y )
Use the correct X,Y results from the ls command and ENTER. Remember GRUB 2 counts the first drive as 0, the first partition as 1. For example, if the Ubuntu system is on sda5, enter: set root=(hd0,5) * For a Wubi install inside Windows, substitute the following command: set root=(loop0) Step 2*. Enter the "linux" line information linux /boot/vmlinuz- root=/dev/sdXY ro
* For a Wubi install inside Windows, substitute the following command: root=/dev/sdXY loop=/ubuntu/disks/root.disk
Afer typing linux /boot/ , the user can TAB to display the available kernels. There is no space character after "/". If no kernels are visible, the address in the "Set Root" section may be incorrect. Enter the correct kernel by typing or using tab completion. For the root=/dev/ section use the correct device such as "/dev/sda1", "/dev/sdb5", etc Add any options, such as ro (read-only), at the end of the line (normally not required). Once all the information on the line is correct it should look similar to the sample below. linux /boot/vmlinuz-2.6.31-16-generic root=/dev/ sda1 ro
When correctly typed and ENTER, if the linux kernel is found, a line similar to the "Linux-bzImage" confirmation line highlighted below will appear.
If a "file not found" or similar error message occurs, either the device/partition/file does not exist or GRUB 2 is not looking at the correct drive, partition and/or directory. Determine the correct location using the ls command and then run the following command. Repeat Step 2. set prefix=(hdX,Y)/boot/grub Step 3. Enter the "initrd" line information initrd /boot/initrd.img-
Afer typing initrd /boot/ , the user can TAB to display the available initrd images. Do not leave a space after the "/". If no images are visible, the address in the "Set Root" section may be incorrect. Enter the correct image by typing or using tab completion. Once all the information on the line is correct it should look similar to the sample below. Press ENTER. Look for confirmation. initrd /boot/initrd-2.6.31-16-generic
When correctly typed and entered, if the initrd image is found, a line similar to the "Initrd"" confirmation line
highlighted in the graphic above should appear. Step 4. Boot boot
Type the command and press ENTER.
Rescue Mode The rescue mode is a major GRUB 2 enhancement. If GRUB 2 fails to find a useable grub.cfg and is unable to transfer control to a kernel it will drop to a grub-rescue> prompt. From this prompt the user can investigate problems, make changes, and retry the boot. The prefix setting must correctly point to the grub folder before the majority of the rescue commands can work. Until the prefix is correctly set and the linux module is loaded the kernel and initrd image cannot be loaded.
If the path to the grub folder (normally /boot/grub) is not correct, an unknown command or file not found message is likely. To help locate or verify the correct system partition is selected, use the ls command. First use the ls command to find the known partitions; then expand it's use to verify the location and contents of the grub folder. Examples: ls returns drives and partitions located by Grub 2: (hd0) (hd0,1) (hd0,5) (hd1) (hd1,1) ls (hd0,5)/boot returns the files and folders in sda5's /boot folder. If the path correctly points to Ubuntu's /boot folder the result should include the kernel and initrd images and the grub folder. If the command does not find the correc ls (hd0,5)/boot/grub returns the files and folders in the /boot/grub folder of sda5. If the path correctly points to Ubuntu's /boot/grub folder the result should include numerous *.mod files.
With the Ubuntu grub folder located, the prefix and root settings must be properly set. In the example above, the Ubuntu grub folder was located in sda5 (hd0,5). The command in this example would be: set prefix=(hd0,5)/boot/grub set root=(hd0,5)
The current prefix and root settings may be checked at any time with the set command. To remove a setting, use the unset command (example: unset prefix). Now the modules can be loaded. Modules must be loaded before they can be used. If a module has not been loaded a unknown command error is displayed. If an incorrect path is specified, a file not found error message may be displayed. The linux module must be loaded to be able to load both the kernel and the initrd image, others listed below such as the normal module may also be loaded. To load the linux module with the proper prefix set, run this command. insmod linux
or insmod /boot/grub/linux.mod
The rescue mode provides fewer commands than the normal GRUB prompt line, but also provides these additional commands: Command
Result
dump
Clears memory
exit
Exit GRUB 2
normal
Return to the standard "grub>" mode ifpossible.
Among the commands which can be used in the grub rescue mode if the normal module can be loaded: boot
cat
chain
help
insmod
linux
ls
multiboot
normal
search
set
unset
For a successful boot from the rescue prompt, the prefix path and root= setting must be correct, the linux module must be loaded, and the kernel (vmlinuz) and initrd image (initrd.img) must be accepted.
The user should attempt to load the normal module to regain more capabilities while in the Grub 2 terminal. Try loading the normal GRUB 2 module with insmod normal, followed by normal on a separate line to activate the module. If successfully loaded and activated, help and additional commands will be available. Command Summary *:
1. ls 2. set prefix=(hdX,Y)/boot/grub 3*. set root=(hdX,Y) 4. set 5. ls /boot 6. insmod /boot/grub/linux.mod 7*. linux /vmlinuz root=/dev/sdXY ro 8. initrd /initrd.img 9. boot * For Wubi installs (within Windows) only substitute these commands in Steps 3 and 7: set root=(loop0) linux /vmlinuz root=/dev/sdXY loop=/ubuntu/disks/root.disk ro
Expanded Instructions: 1. ls This will display the known devices and partitions. From this information, the user must determine the device and partition on which the system is installed. 2. set prefix=(hdX,Y)/boot/grub If incorrect, "no such disk" or "not found" errors will occur later. 3. set root=(hdX,Y) In this command, X is the device/drive, starting with 0. Y is the partition, starting with 1. Example: (hd0,1) is sda1. (hd2,5) is sdc5. 4. set Inspect the "prefix=" listing. It should match the root designation in Step 3, in the following format: prefix= (hdX,Y)/boot/grub. 5. ls /boot/ Inspect the contents. The user should see varioius kernels, initrd images and the grub directory. If not, use the ls command to inspect the device and attempt to find these files and directories. If necessary, set another device as root. 6. insmod /boot/grub/linux.mod Load (insert module) the linux module. Without this module loaded, the user will receive an "Unknown command linux" message when trying to load the kernel. 7. linux /vmlinuz root=/dev/sdXY ro Load the linux kernel, substituting the correct designations for "X" and "Y" (example: sda1). The user will see a message showing the kernel has been loaded. (See graphic in the previous section above) * Wubi users must use the alternate command presented earlier. 8. initrd /initrd.img Load the initrd image. When pressing ENTER the user may or may not see a message in the terminal. (See highlighted graphic above) 9. boot Attempt to boot using the information entered. These changes are not permanent. After successfully booting into the system the user should run sudo updategrub and inspect the GRUB 2 configuration file (/boot//grub/grub.cfg ). For problems with booting the main linux kernel, ensure the search, linux, and initrd lines in the [### BEGIN /etc/grub.d/10_linux ###] section of the file now point to the correct locations. The user may need to reinstall GRUB 2 using sudo grubinstall /dev/sdX.
GRUB Errors GRUB 2 does not report error numbers. If a number is associated with an error, it is a problem with the transition from GRUB legacy to GRUB 2.
Resolving an "Unrecognized Device String" (Error 11) This error message is usually the result of a bad or malformed line within the menuentry. The most common cause is a GRUB 2 upgrade from Jaunty when the user attempts to use the Chainload feature. 1. During a boot GRUB 2 displays the following message:
2. Remembering there was a problem with the Jaunty chainload entries, the user presses a key to return to the main menu, then "e" until seeing "grub edit>". Edit the highlighted "Chainload into GRUB 2" entry or whichever entry the user attempted to boot.
3. The user, who has a keen memory, remembers that "root" needs to be changed to "uuid". Using the arrow keys to position the cursor, the "root" entry is replaced with "uuid". When finished editing, the user presses ENTER, then "b" to boot the revised selection. Note these are different commands than used in GRUB 2.
If the user intends to keep the dual GRUB option, to correct the error open /boot/grub/menu.lst as root and change "root " to "uuid " in second line of the "Chainload into Grub 2" menu entry.
File Not Found (Error 15) This error is the result of a GRUB 2 installation to /boot but a Master Boot Record ( MBR ) which still contains Grub legacy. This can happen if you don't select your drive when running sudo upgrade-from-grub-legacy . Shortly after starting this command the user will be asked to select the device (sda, sdb, etc). Highlight the drive and press the space bar to select it when presented with this screen. Failure to select a drive will result in an Error 15. To recover from this error, GRUB 2 must be reinstalled. Go to Reinstalling from the LiveCD for instructions.
update-grub complains about missing devices update-grub will check every partition of every device in /boot/grub/device.map for bootable operating systems. If an entry in device.map is not present, update-grub w ill complain about this and stop working, which usually leads to a file not found error on boot the next time your kernel is updated. The solution is to edit or remove the customized device.map file, and sudo update-grub.
error: no such partition If you have an older computer it's possible the BIOS cannot see your GRUB 2 files if they reside past the BIOS limitations (generally 33 GB on very old computers and 137 GB on slightly newer computers). If this is the case the boot will fail and an error: no such partition message will be displayed. If at the grub prompt, type ls and ENTER. If the command does not display all the partitions, reboot and enter your computer's BIOS setup. Ensure the BIOS reports the full disk size. If it doesn't, check for LBA/partition settings or obtain a BIOS update from the manufacturer. If unable to eliminate the BIOS limitation, the user can create a separate /boot partition within the disk area seen by the BIOS. CreateBootPartitionAfterInstall
Splash Images and Theming GRUB 2 Splash Images GRUB 2's Splash Image capability is greatly enhanced over its predecessor. Configuring a boot splash image is a two step process: selecting the image to use and choosing the text colors to be displayed.
Install the default GRUB 2 splash image package, install the ''grub2-splashimages'' package
sudo apt-get install grub2splashimages Do not mistake this with the grub-splashimages package, which is not compatible with GRUB 2. The default location for these downloaded images is /usr/share/images/grub.
Users can create and use their own splash images.
Set the splash image The following guidance for setting the background image is for Grub 2 version 1.98 and later. This version is found on Lucid Lynx, Ubuntu 10.04 and later releases. Earlier versions of Grub 2 (1.97), found in Karmic Koala 9.10, use a less intuitive entry for setting the background. Refer to the Karmic Koala section for details. The GRUB 2 splash images are controlled by the GRUB_BACKGROUND variable in '/etc/default/grub'. Open this file for editing as root and find this line: GRUB_BACKGROUND=/usr/share/images/desktop-base/moreblue-orbit-grub.png
Change the line to reflect the correct path and filename for the image you wish to use as the Grub background image. Splash image selection: tga, png and jpeg (8-bit) images may be used. Use images with the RGB color mode. Indexed images will not display. Once you have entered the path and filename you can run sudo update-grub to add the information into grub.cfg . If adding the splash image was successful, the user will see "Found background image..." in the terminal as the command is executed. If this phrase is not seen, the image information was probably not incorporated into the grub.cfg file. Troubleshooting Images. If the image is not displayed, check: The path & filename in /etc/default/grub are correct. The image is of the proper size & format (tga, png, 8-bit jpg). The image was saved in the RGB mode, and is not indexed. The console mode is not enabled in /etc/default/grub. The update-grub command must be executed to place the background image information into the /boot/grub/grub.cfg file.
Grub 1.97 (Karmic Koala) Only:
Find the following line and edit the highlighted area, replacing it with the path and name of the GRUB 2 splash image you wish to use: for i in {/boot/grub,/usr/share/images/desktop-base}/moreblue-orbit-grub.{png,tga} ; do
There are several things to note about this entry: GRUB 2 by default will look for splash images in /boot/grub and /usr/share/images/desktop-base The grub2-splashimages package is not extracted to either of the above directories, but to /usr/share/images/grub The user must either: Change the directory location in the above line to point to the correct address, or Move the splash images to one of the directories referenced above. To add the grub directory, make the entry look like this, and change the filename to the desired splash image in /usr/share/images/grub directory. for i in {/boot/grub,/usr/share/images/desktop-base,/usr/share/images/gr ub}/moreblue-orbit-grub.{png,tga} ; do
The filename ends with a period (.) ( /moreblue-orbit-grub. ) Splash image selection:
If the same filename exists in more than one directory, the filename in the earliest-designated directory will be used. If the filename exists as more than one type (multiple extensions), the file with the earliest-designated extension will be selected. The user can make several changes to the above line to expand splash image flexibility: Add a user-owned directory in which GRUB 2 will search for available splash images. The following shows the addition of a user's own splash directory and added JPEG support: for i in {/boot/grub,/usr/share/images/grub,/home/drs/mysplash}/moreblue-orbit-grub.{png,tga,jpg,jpeg} ; do
Set menu font and highlight colors These lines are contained in /etc/grub.d/05_debian_theme . The lines to modify depend on whether or not a background image is selected. If a background image is in use: The color of selected menu entries is set by the color_highlight setting. Note in more recent versions of G rub2 the entry is uppercase. The color of non-selected menu entries is set by the color_normal setting if a background image is also in use. Note in more recent versions of Grub2 the entry is uppercase. If a background image is not in use, modify the lines in the set_mono_theme section: The color of selected menu entries is set by menu_color_highlight setting. The color of non-selected menu entries is set by menu_color_normal setting. The first color is the text color; the second is the background color. set color_normal=black /black
The code below sets the color of selected entries. The first color is the highlighted text color; the second is the background color of the selected line. If /black is the second entry, the highlighted line will be transparent and only the text will change color. set color_highlight=magenta/black
/black is the GRUB 2 default transparency color when listed second. Change only the first color (i.e. xxxxx/black) if using a splash image. If the second value in this line is changed to a color other than black the splash image will be hidden behind a solid color background.
In the following graphic, the color_normal setting is white/black . The color_highlight setting is cyan/blue
These colors are available in GRUB 2. "black" as a second entry is considered "transparent". black
blue
brown
cyan
dark-gray
green
light-cyan
light-blue
light-green
light-gray
lightmagenta
light-red
magenta
red
white
yellow
Save the file if any changes are made and then update GRUB 2: sudo update-grub
Testing Fonts and Splash Images
Rather than rebooting to test the color combinations, the user can see the changes by using GRUB 2's command line during the boot process. Select the splash image and initial font colors as described above, update GRUB 2's files with sudo update-grub, and reboot. When the GRUB 2 splash image/menu appears, press any key to stop the countdown timer. Press c to enter the GRUB 2 command line. Experiment with various color/highlight modes. Make changes by typing:
set color_normal=first-color/black and/or set color_highlight=firstcolor/second-color Text colors are viewable immediately after the command is entered. You can use the "up" arrow to recall the last
command and edit it to quicky test different color combinations. Once you are finished, press ESC to return to the menu. Repeat as desired. Remember the desired color combinations, boot normally and edit /etc/grub.d/05_debian_theme and make the changes permanent.
Save the file, then update GRUB 2: sudo update-grub
Changing Resolutions w/ Splash Images If the user wishes to change the resolution of the GRUB 2 screen while using a splash image follow these steps: 1. Set the desired resolution in /etc/default/grub Change the value of GRUB_GFXMODE= (Example: GRUB_GFXMODE=800x600) If unsure of what resolutions are available to GRUB 2 they can be displayed by typing vbeinfo in the GRUB 2 command line. The command line is accessed by typing "c" when the main GRUB 2 menu screen is displayed. 2. Select an image of the same proportions and make the change in /etc/grub.d/05_debian_theme The image name is located in the line beginning with " WALLPAPER=" (Grub 1.97-beta) The image name is located in the line beginning with " for i in {/boot " If an image of the correct size is not used, the menu will not be positioned correctly. Use the image editor of your choice to create/resize an image to the correct size. The user may be able to view the image size via Properties in a file browser (check the Properties Image tab in Nautilus). 3. Run update-grub as root to add the new settings to /boot/grub/grub.cfg
Creating User Splash Images GRUB 2's splash image management makes it easy to use a wide variety of splash images.
Resolution Settings The images in the grub2-splashimages package are primarily 640x480 images. GRUB 2 looks for a resolution setting in /etc/default/grub. If uncommented , the resolution is determined by this line: GRUB_GFXMODE=640x480
If no setting is found in /etc/default/grub, GRUB 2 uses the resolution established in /etc/grub.d/00_header , which is set at 640x480.
Image Creation and Setup
In Ubuntu, refer to the System, Preferences, Display menu for available monitor resolutions, or run vbeinfo in the GRUB 2 command line to display available resolutions. 1. Determine the resolution you will use for the GRUB 2 splash image. 2. Create or resize any image to to the appropriate size. GRUB 2 currently supports .png , .tga, and 8-bit .jpg/.jpeg images. If using GIMP, naming the file with the applicable extension will save the file in the given format. 3. Make the applicable changes in the GRUB 2 configuration files: /etc/default/grub: Uncomment the GRUB_GFXMODE=640x480 line and change the value if the resolution will be other than 640x480. /etc/grub.d/05_debian_theme : Enter the correct path and filename in the following line. Refer to the previous section for more information on how to edit this line. for i in {/boot/grub,/usr/share/images/desktop-base}/moreblue-orbit-grub.{png,tga} ; do
4. Run sudo update-grub to incorporate the changes into GRUB 2.
Themes GRUB 2 Theming is still under development, as is integration with gfxmenu. Theme elements will include colors, fonts, progress
indicators, menus, and labels. Both of these hold great promise but are not ready for release with Ubuntu 9.10. Check the Links section at the bottom of this page for references.
Reinstalling GRUB 2 There may be times when a user needs to either move or reinstall a GRUB 2 installation. GRUB 2 needs to be reinstalled when a user is presented with a blank screen with only the word "GRUB", no prompt, and no ability to enter commands. This often happens when the MBR of the booting device is altered and GRUB 2 is removed, such as when Windows is installed after Ubuntu. Additionally, if a user cannot boot into an operating system at all, even using the rescue mode mode, a complete reinstallation of GRUB 2 may be necessary.
Reinstalling from LiveCD If you cannot boot from GRUB 2 review the section Boot Problems and Rescue Mode. If a reinstall becomes necessary follow these instructions. Two methods are presented; both require booting from a LiveCD (Ubuntu 9.10, Karmic K oala or later version). If the first method does not work, follow the second method, which is more complex and contains more options and instructions.
SIMPLEST - Copy GRUB 2 Files from the LiveCD This is a quick and simple method of restoring a broken system's GRUB 2 files. The terminal is used for entering commands and the user must know the device name/partition of the installed system (sda1, sdb5, etc). The problem partition is located and mounted from the LiveCD. The files are then copied from the LiveCD libraries to the proper locations and MBR. It requires the least steps and fewer command line entries than the following methods. If for example Windows is on sda1 and Ubuntu is on sda5, and Windows has overwritten the MBR, then the target for grub installation will be /dev/sda5, and the MBR in the boot sector of sda will be re written for grub. 1. Boot to the LiveCD Desktop (Ubuntu 9.10 or later). 2. Open a terminal by selecting Applications, Accessories, Terminal from the menu bar. 3. Determine the partition with the Ubuntu installation. The fdisk option "-l" is a lowercase "L". a. sudo fdisk -l If the user isn't sure of the partition, look for one of the appropriate size or formatting. Running sudo blkid may provide more information to help locate the proper partition, especially if the partitions are labeled. The device/drive is designated by sdX , with X being the device designation. sda is the first device, sdb is the second, etc. For most users the MBR will be installed to sda, the first drive on their system. The partition is designated by the Y . The first partition is 1, the second is 2. Note the devices and partitions are counted differently. 4. Mount the partition containing the Ubuntu installation. sudo mount /dev/sdXY /mnt
Example: sudo mount /dev/sd a1 Note: If the user has a separate /boot partition, this must be mounted to /mnt/boot Note: If the user has a separate /home partition, this must be mounted to /mnt/home. Encrypted home partitions should work. 5. Run the grub-install command as described below. This will reinstall the GRUB 2 files on the mounted partition to the proper location and to the MBR of the designated device. sudo grub-install --root-directory=/mnt /dev/sdX
Example: sudo grub-install --root-directory=/mnt /dev/sd a 6. Reboot 7. Refresh the GRUB 2 menu with sudo update-grub
8. If the user wishes to explore why the system failed, refer to Post-Restoration Commands section below.
METHOD 2 - Copy GRUB 2 Files from the Installed Partition This is a quick and simple method of restoring a broken system's GRUB 2 files. The problem partition is located and mounted from the LiveCD. The files are then copied from the broken system's /boot/grub directory to the proper locations and MBR. It requires fewer steps and fewer command line entries than the following CHROOT method. For users with separate system partitions, such as a separate /boot partition, or other special circumstances, using the CHROOT method may provide better results. 1. Boot to the LiveCD Desktop (Ubuntu 9.10 or later). 2. Mount the partition with your Ubuntu installation. a. From the Places menu, select and click the partition containing your Ubuntu installation to mount it.
If the partition isn't recognized, look for one of the appropriate size or label. Once mounted, the user should see Ubuntu system directories such as /boot 3. Open a terminal by selecting Applications, Accessories, Terminal from the menu bar. 4. Run the grub-setup -d command as described below. T his will reinstall the GRUB 2 files on the mounted partition to the proper location and to the MBR of the designated device. a. Determine the mount point by referring to the location box in Places. Replace XXXX in the command with the UUID, or replace /media/XXXX with the correct location if the partition is not mounted in /media. The designation may be a UUID, or a label, if the user has created one (see note). b. If the location window is not in the format shown, click on the icon to the left to change the presentation.
c. When ready to copy the UUID/location, by highlighting it with the mouse. Paste it into the terminal by pressing the middle mouse button. If using the keyboard, use CTRL-SHIFT-arrow to select and CTRL-C to copy the location and CTRL-SHIFT-V to paste it into the terminal. d. The device/drive is designated by sdX , with X being the device designation. sda is the first device, sdb is the second, etc. For most users the MBR should be installed to sda, the first drive on their system. sudo grub-setup -d /media/XXXX/boot/grub /dev/sda
Example: sudo grub-setup -d / media/7848138a-41a0-4eba-8aed-d1b625ac8759/boot/grub /dev/sd a
e. If the user gets a " error: Cannot open /boot/grub/device.map" message, add the -m switch and path to the device.map to the command as follows: sudo grub-setup -d /media/XXXXX/boot/grub -m /media/XXXXX/boot/grub/device.map /dev/sda
Example: sudo grub-setup -d / media/7848138a-41a0-4eba-8aed-d1b625ac8759/boot/grub -m / media/7848138a-41a0-4eba8aed-d1b625ac8759/boot/grub/device.map /dev/sd a
f. Other switches are available for use with the grub-setup command. In a terminal, type grub-setup -help for a list of available options. g. You may find you get a repeated "error: Cannot open /boot/grub/device.map" message. If this happens try rebooting. The UUID method may actually work but throws an error message falsely. Using the label name does not seem to evoke the same repeated error message. 5. Reboot 6. Refresh the GRUB 2 menu with sudo update-grub 7. If the user wishes to explore why the system failed, refer to Post-Restoration Commands section below. Ubuntu 9.10 introduced a new application which can easily assign labels to existing partitions. Access Disk Utility from the System, Administration menu.
METHOD 3 - CHROOT This method of installation uses the chroot command to gain access to the broken system's files. Once the chroot command is issued, the LiveCD treats the broken system's / as its own. Commands run in a chroot environment will affect the broken systems filesystems and not those of the LiveCD. 1. Boot to the LiveCD Desktop (Ubuntu 9.10 or later). Please note that the Live CD must be the same as the system you are fixing - either 32-bit or 64-bit (if not then the chroot will fail). 2. Open a terminal - Applications, Accessories, Terminal . 3. Determine your normal system partition - (the switch is a lowercase "L") sudo fdisk -l
If you aren't sure, run df -Th. Look for the correct disk size and ext3 or ext4 format.
4. Mount your normal system partition: Substitute the correct partition: sda1, sdb5, etc. sudo mount /dev/sdXX /mnt # Example: sudo mount /dev/sda1 /mnt
5. Only if you have a separate boot partition: sdYY is the /boot partition designation (for example sdb3) sudo mount /dev/sdYY /mnt/boot
6. Mount the critical virtual filesystems: sudo sudo sudo sudo
mount mount mount mount
--bind --bind --bind --bind
/dev /mnt/dev /dev/pts /mnt/dev/pts /proc /mnt/proc /sys /mnt/sys
7. Chroot into your normal system device: sudo chroot /mnt
8. If there is no /boot/grub/grub.cfg or it's not correct, create one using update-grub
9. Reinstall GRUB 2: Substitute the correct device - sda, sdb, etc. Do not specify a partition number. grub-install /dev/sdX
10. Verify the install (use the correct device, for example sda. Do not specify a partition): sudo grub-install -recheck /dev/sdX 11. Exit chroot : CTRL-D on keyboard 12. Unmount virtual filesystems: sudo sudo sudo sudo
umount umount umount umount
/mnt/dev/pts /mnt/dev /mnt/proc /mnt/sys
If you mounted a separate /boot partition: sudo umount /mnt/boot
13. Unmount the LiveCD's /usr directory:
sudo umount /mnt/usr
14. Unmount last device: sudo umount /mnt
15. Reboot. sudo reboot
Post-Restoration Commands Once the user can boot to a working system, try to determine why the system failed to boot. The following commands may prove useful in locating and/or fixing the problem. To refresh the available devices and settings in /boot/grub/grub.cfg sudo update-grub
To look for the bootloader location. grub-probe -t device /boot/grub
To install GRUB 2 to the sdX partition's MBR (sda, sdb, etc.) sudo grub-install /dev/sdX
To recheck the installation. (sda, sdb, etc.) sudo grub-install --recheck /dev/sdX
Changing or Moving GRUB 2 The command to change the GRUB 2 installation device or boot files is grub-install run as root. This command allows the user to modify the installation by setting the ROOT directory, preload modules, run specific setup files and more. When executed, grub-install may run one or more other commands, such as grub-probe, grub-mkimage, and grub-setup. Here are some considerations when running grub-install: The grub-install command should be used rather than grub-setup under normal circumstances. grub-setup will be called by grub-install when needed. The command should specify a device and when executed will install the required GRUB files to the location called for in the options. (example: sudo grub-install /dev/sda ) If the user attempts to run the command with a specific partition (example: sudo grub-install /dev/sda6 ) a warning will be issued. Specifying a partition is not recommended due to the use of blocklists, w hich the developers consider unreliable. An option is provided on how to override this recommendation if the user still wishes to do so. The list of options available for grub-install can be displayed in a terminal with grub-install --help. The man page for grub-install currently does not display the all the available options.
Uninstalling GRUB 2 Reverting to GRUB Legacy If a user chooses to return to GRUB legacy (0.97), these steps will remove GRUB 2 and install GRUB. The command line produces a cleaner uninstall and reinstallation. While adding and removing the packages can be accomplished with Synaptic, certain steps must be accomplished in a terminal. 1. Open a terminal: Applications, Accessories, Terminal. 2. Optional: Make backup copies of the main GRU B 2 directories and files.
sudo cp /etc/default/grub /etc/default/grub.old sudo cp -R /etc/grub.d /etc/grub.d.old sudo cp -R /boot/grub /boot/grub.old 3. Remove GRUB 2
sudo apt-get purge grub2 grub-pc The system will be unbootable until another bootloader is installed. Once the packages are removed, many files will still remain in '/boot/grub' 4. Install GRUB 0.97
sudo apt-get install grub 5. With grub installed, the user must still create the menu.lst and stage1/stage2 files by running the following two commands. A. sudo update-grub
Generates menu.lst Tab to "Yes" when prompted. B. sudo grub-install /dev/sdX Choose the correct device (sda, sdb, etc), normally the one on which Ubuntu is installed. Creates the stage1 and stage2 files in /boot/grub and writes to the MBR. 6. Reboot
If the user receives an "Unrecognized device string Error 11" message on rebooting see the Resolving an "Unrecognized Device String" (Error 11) section for instructions on how to edit the menu and make the system bootable.
Selected Problems and Bugs External Drive Installs and ''grub-pc'' Updates Launchpad Bug 496435 Installs of Ubuntu on external drives can cause problems as grub-install uses device names (e.g. sda, sdb) rather than UUIDs in certain circumstances. If connected to another machine when an update of grub-pc is made, the upgrade may be written to the incorrect device and make the computer unbootable. A workaround is posted on the bug link above.
External Drive Installs and MBR Selection Launchpad Bug 414996 When installing Ubuntu to a USB drive, the potential exists for GRUB 2 to write to the hard drive's MBR or split the installation between the hard drive and the USB drive (rather than completely on the USB device). This can render the main drive unbootable. Workaround: During the final stages of the install there is an "Advanced" button which allows the user to select the install location. See the bug report for more details.
Boot Partition is in Logical Volume whose Volume Group contains a snapshot Launchpad Bug 563895 When your boot partition (the one providing /boot ) is a LV, make sure not to have any LVM snapshots inside the containing VG. At reboot this will render your system unbootable, dropping you in a " grub rescue>"-shell with the following message: " error: no such disk." The grub-rescue-shell provided does not help you, because all modules (esp. lvm) are unreachable. You'll have to boot from a install medium and remove all snapshots that are in the same VG as your boot partition by hand. This issue is extremely annoying if your server is in a remote datacenter since the origin of the problem cannot be spotted easily and repairing the system may be hard. While this will be fixed in the upcoming Maverick Meerkat 10.10 release, the current Lucid Lynx LTS 10.04 is affected. A workaround would be to install ubuntu using a separated non-LVM partition for /boot if you are using LVM snapshots regularly. There's some kind of irony that if you're careful and take a LVM snapshot before upgrading (and possibly rebooting) your system, this will trigger the bug.
Miscellaneous Booting from a serial console If you want GRUB to operate over a serial line, you will need to uncomment GRUB_TERMINAL in /etc/default/grub and set it to serial (instead of the console default). The default serial console settings are to operate on the first serial port (ttyS0) at a 9600 bit/s transfer rate with 8 data bits, 1 stop bit and no parity. If you w ant to use another serial port or if your console uses different settings, you must add a GRUB_SERIAL_COMMAND line to specify additional parameters to the serial command. The serial command in GRUB 2 uses the same syntax as its GRUB Legacy counterpart (documented here). For example, for a 4800 bit/s serial line with 7 data bits, 1 stop bit and even parity:
GRUB_SERIAL_COMMAND="serial --unit=0 --speed=4800 --word=7 --parity=even --stop=1"
Links GrubHowTo Grub 2 (Ubuntu Wiki)
External Links GNU GRUB GNU GRUB2 Manual Illustrated Dual Boot HomePage Mac OS X (XNU) Support Mac OS X Boot Snow Leopard GRUB Manual - Themes CategoryBootAndPartition CategoryRescueAndCloning Grub2 (last edited 2011-02-08 10:37:42 by duncan-lithgow)
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