Ошибка загрузки grub

This page provides the user with information on options available for repairing GRUB 2 boot issues and specific instructions on how to use the GRUB 2 terminal. The instructions are written for GRUB 1.99, which is the version of GRUB 2 which is included on Ubuntu 11.04, Natty Narwhal, and later. Differences for version 1.98 (Ubuntu 10.4, Lucid Lynx) are noted when the procedures differ.

GRUB 2’s ability to fix boot problems is greatly improved over the original GRUB bootloader. In addition to an automatic fallback mode if booting from a menuentry in a submenu, GRUB 2 allows the user to edit its menu before the operating system is loaded. The rescue mode GRUB 2 terminal can help boot an operating system so that permanent repairs to system files can be made.

The instructions on this page are written for a fully-installed Ubuntu operating system. WUBI boot problems are not covered in detail although they are addressed in several sections.

Overview

GRUB 2 boot problems can leave the system in several states. The user may see one of the following displays on the monitor when a boot fails. The display provides the first indication of what might be causing the failure to boot. Here are the failure prompts and displays, and the possible cause of each:

• grub> prompt: GRUB 2 loaded modules but was unable to find the grub.cfg file.

• grub rescue> prompt: GRUB 2 failed to find its grub folder, or failed to load the normal module.

• grub>: — The grub prompt on a blank screen.

  • GRUB 2 has found the boot information but has been either unable to locate or unable to use an existing GRUB 2 configuration file (usually grub.cfg).

• grub rescue>: — The rescue mode.

  • GRUB 2 is unable to find the grub folder or its contents are missing/corrupted. The grub folder contains the GRUB 2 menu, modules and stored environmental data.

• GRUB — a single word at the top left of the screen, with no prompt and no cursor.

  • GRUB has failed to find even the most basic information, usually contained in the MBR or boot sector.

• Busybox or Initramfs: GRUB 2 began the boot process but there was a problem passing control to the operating system. Possible causes include an incorrect UUID or root= designation in the ‘linux’ line or a corrupted kernel.

• Frozen splash screen, blinking cursor with no grub> or grub rescue prompt. Possible video issues with the kernel. While these failures are not of GRUB 2’s making, it may still be able to help. GRUB 2 allows pre-boot editing of its menu and the user may restore functionality by adding and/or removing kernel options in a menuentry before booting.

Each of the GRUB 2 failure modes can normally be corrected either from the GRUB 2 terminal or by using an Ubuntu LiveCD. Additionally, there are compatible 3rd party bootable «rescue» CD/USB options which may also work. If using an Ubuntu LiveCD, it is recommended, but not always necessary, to use the same version CD as the system you are trying to repair. This ensures compatability of any modules and configuration files that may be loaded while attempting to repair the system.

GRUB 2 Terminal Commands

Here are some useful tips and features for use with the GRUB 2 terminal:

• Turning off the splash image. This may make viewing the terminal easier. Press c at the GRUB 2 menu to get 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.

• TAB completion. This 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.

• set pager=1 To prevent text from scrolling off the screen, type set pager=1.

• Help. 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.

Normal

When GRUB 2 is fully functional, the GRUB 2 terminal is accessed by pressing c. If the menu is not displayed during boot, hold down the SHIFT key until it appears. If it still does not appear, try pressing the ESC key repeatedly.

From a GRUB 2 terminal with the grub> prompt, a wide variety of commands are available.

• A few of the more important commands:

  Command	Result / Example
  boot	Initiate the boot sequence, also F10 or CTRL-x
  cat	Display the contents of readable files; cat (hd0,1)/boot/grub/grub.cfg
  configfile	Load a GRUB 2 configuration file such as grub.cfg; configfile (hd0,5)/boot/grub/grub.cfg
  initrd	Loads the initrd.img, necessary for booting; initrd (hd0,5)/initrd.img
  insmod	Loads a module; insmod (hd0,5)/boot/grub/normal.mod, or insmod normal
  linux	Loads the kernel; insmod /vmlinuz root=(hd0,5) ro
  loop	Mount a file as a device; loopback loop (hd0,2)/iso/my.iso
  ls	Lists the contents of a partition/folder; ls, ls /boot/grub, ls (hd0,5)/, ls (hd0,5)/boot
  lsmod	List loaded modules
  normal	Activate the normal module, if loaded
  search	Search for a device. Type help search for the available options.
  set	Review current settings, or set XXX to set a variable such as colors, prefix, root
  vbeinfo	Display GRUB 2 available resolutions

  To view the complete command list, type help. For details on a particular command, type help [command]

grub>

When GRUB 2 is unable to boot or display the GRUB 2 menu the system will be left at a GRUB 2 terminal if possible. If the system boots to the grub> prompt, the usual modules and commands are normally available. The user may need to manually load modules using the insmod [module] command before some commands will work.

grub rescue>

In the grub rescue mode, only a limited set of commands are available. These commands are sufficient to investigate the contents of the drives, set prefix (path to the grub folder) and root (partition), load modules and boot.

The rescue mode provides fewer commands than the normal GRUB prompt line, but also provides these additional commands:

• Command	Result / Example
  dump	Clears memory
  exit	Exit GRUB 2
  normal	Return to the standard «grub>» mode if possible.

Among the commands which can be used in the grub rescue mode:

• boot	cat	chain	help	insmod	linux
  ls	multiboot	normal	search	set	unset

General Troubleshooting Preparation

Boot-Repair

The majority of this guide is devoted to working with the GRUB 2 terminal, which is used to enter commands to attempt to repair a broken bootloader. Boot-Repair is a GUI application which can automatically analyze boot problems and select the proper course of action to repair them. Its simple interface provides beginners as well as experienced Linux users an easy method of repairing the majority of GRUB 2 problems.

Additionally, Boot-Repair contains an automated method to run a boot info script which performs a series of tests and provides a file containing much valuable information regarding the status of the computer’s operating and boot systems. This file can be inspected by community helpers on forums or IRC channels to help diagnose boot problems.

Boot-Repair can be run from a LiveCD or an operating Linux system. To download the package run the following commands:

• sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
  sudo apt-get install -y boot-repair && boot-repair

Visit the Boot-Repair community document for more information.

Boot-Repair is available from the Launchpad repositories and can be run from a CD or a working Linux OS.

Search & Set

A great many boot problems are due to incorrect paths to required files. The GRUB 2 terminal, in either ‘failure’ mode, provides a robust ability to search hard drive(s) and partitions and to inspect their contents.

In order to boot successfully, the root, prefix, linux and initrd variables must be correct. The user must verify the paths and names of these items. If they are incorrect, use the commands below to find and fix them. GRUB 2 variable settings can be viewed with the set command.

In the following examples, X is a hard drive number; Y is a partition number. If a command example includes either of these replace them with the appropriate value.

How & Where to Search

In the graphic below, the text in red are commands to be entered by the user, and text in green is the output of the command on an operating system (i.e. what you would like to see if your Ubuntu installation is on sda1).

• The first hard drive is 0. The first partition is 1. Thus sda1 becomes (hd0,1), sdb5 is (hd1,5).

• Use the ls command in the follow manner

• «Tab completion» may work — enter part of the filename and press the TAB key.

* Note: Use the full kernel name, including -generic, when searching or setting a kernel variable. Using the «TAB completion» technique may eliminate some typing and be more accurate if available.

Use the following commands to set these parameters (if incorrect). Substitute the correct value for X and Y. (Example: set root=(hdX,Y) becomes set root=(hd0,5) )

Specific Troubleshooting

Use the section below based on the type of GRUB 2 terminal prompt displayed on the monitor.

The commands which follow assume you have determined the proper parameters for prefix, root, linux, and initrd. Review the Search & Set section of this page for guidance .

grub>

Terminal Display: The GRUB 2 header/version information and a grub> prompt.

If GRUB 2 leaves you at the grub> prompt, it has normally found the grub folder and loaded at least some basic modules. The configuration file (grub.cfg) may be missing, misnamed, or corrupted.

Quick Fix:

• Use the Search & Set section to confirm the correct paths are set. Inspect the contents of the /boot/grub folder. Look for the grub.cfg file. It could be misnamed or missing. If not located in /boot/grub, use the ls command look for another .cfg file or look in /boot or other locations. If you locate the correct .cfg file:

1. configfile /boot/grub/grub.cfg or configfile (hdX,Y)/boot/grub/grub.cfg

   If a .cfg with another name is located, substitute its path/filename in the command.

   If the configuration file is loaded and not corrupt, when the above command is executed the GRUB 2 menu should appear and the user can make a selection to boot. Once booted into the system, correct the filename or move the configuration file to its proper location. Run update-grub. If the configuration file is not found, a message will be generated and the user must enter the boot commands manually.

Extended Fix:

The following commands should set the root and prefix paths and load the kernel and initrd image. With this information, GRUB 2 does not need a configuration file and should be able to boot the system if the only problem was a corrupted or missing menu.

• 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 and the correct paths are set.

• Wubi users only — substitute these commands in Steps 1 and 2:

• 1.set root=(loop0)

  2. linux /vmlinuz root=/dev/sdXY loop=/ubuntu/disks/root.disk ro

If the system fails to boot:

1. Attempt to find the GRUB 2 configuration file. The normal name is grub.cfg file. If not found, look for a misnamed .cfg file or in alternate locations. The menu configuration file may contain settings required for a successful boot (such as non-standard kernel options) even if the paths/filenames are correct.

   1. Use the set command to confirm the correct root and prefix settngs. Also inspect the folders’ actual contents with the ls command. The grub prompt normally means the GRUB 2 folder is intact but doesn’t guarantee the integrity of other system files.

   2. root= should point to the drive and partition on which Ubuntu is installed. If you use the ls / command you should see the main Ubuntu system folders.

If the system boots, please refer to the [[#Post-Boot Follow Up|Post Boot Follow Up] section

If the system fails to boot, proceed to the [#grub rescue|grub rescue]] section for more detailed troubleshooting options.

grub rescue>

The GRUB 2 rescue mode is a major enhancement to the GRUB bootloader. The presence of the grub rescue> prompt signifies that GRUB 2 has failed to find the grub folder, the grub.cfg file, and/or the associated modules. The rescue prompt is presented so the user can provide the path to the grub folder, load the necessary modules, and provide the proper boot commands.

A common reason for the grub rescue> prompt is an incorrect path to the grub folder. Reasons for the prompt also include a failure to update GRUB 2 after certain system or partition operations, improper designation of the grub folder location, missing linux or initrd.img symlinks in /, or a failed installation.

To successfully boot from the grub rescue> prompt:

• The grub folder must exist and contain the necessary GRUB 2 files and modules.

• The proper paths must be set via the set prefix command.

  • Many GRUB 2 commands will not work until the correct path is set.

    If the path to the grub folder (normally /boot/grub) is not correct, an unknown command or file not found message is likely.

• The necessary modules must be loaded.
  • The kernel cannot be loaded until the ‘linux’ module is loaded.
• A Linux kernel and initrd.img must be located and loaded.

Use the General Troubleshooting Preparation section to locate the correct partitions and file locations. Once the user has confirmed the paths and existence of the proper folders using the Search & Set section, run the following commands:

• * Wubi users only — substitute these commands in Steps 2 and 7:

• 1.set root=(loop0)

  2. linux /vmlinuz root=/dev/sdXY loop=/ubuntu/disks/root.disk ro

Some additional considerations:

• 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

• 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 unless the normal module is loaded first.

• If the modules cannot be found in the /boot/grub folder, the user may be able to load them from the /usr/lib/grub/i386-pc folder. The address if Ubuntu was installed on sda1 would be (hd0,1)/usr/lib/grub/i386-pc and the command would be:

  • insmod (hd0,1)/usr/lib/grub/i386-pc/normal.mod

Refer to the Post Boot Follow Up section if the system successfully boots.

GRUB

Presence of the word GRUB at the top left of the monitor with no blinking cursor indicates that GRUB 2 can not even find the Master Boot Record (or equivalent) information. Thus, the core.img file, the /boot and /grub folder locations and contents are completely unknown to GRUB 2.

The seriousness of the problem cannot be assessed without the use of another operating system or an Ubuntu LiveCD or equivalent. The Ubuntu partition should be mounted for inspection and the user can then check to see if the system files are intact. If so, the user can use the »ChRoot» procedure from the LiveCD to reinstall GRUB 2 and rewrite the information to the MBR.

Details on this procedure are contained in the Grub2/Installing community documentation.

Following a failed boot, GRUB 2 is designed to display the GRUB 2 menu on the next boot and await user input. This will happen even if the user has set the system to boot without displaying the GRUB 2 menu. This provides the user the opportunity to select a different menu option or edit a menuentry to change boot parameters. While this can cause problems on a server, for most users it is a benefit which will prevent constant rebooting during unmonitored operations.

In addition to its troubleshooting benefits, pre-boot editing of the GRUB 2 menu also allows users to add or remove kernel options, change operating modes, and accomplish other tasks such as testing fonts and splash images. For users who like to experiment, the settings altered via the GRUB 2 terminal are non-persistent and won’t affect future boots.

• If the menu is displayed, the automatic countdown may be stopped by pressing any key other than the ENTER key.
• 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.
  • In certain circumstances, if holding the SHIFT key method does not display the menu pressing the ESC key repeatedly may display the menu.
• Press the ‘e’ key to reveal the selection’s settings.
• Use the UP/DN/Left/Right cursor keys to navigate to the desired point for editing.

• Make a single or numerous changes at any spot in the menu. Do not use ENTER to move between lines.

• TAB completion is available, which is useful in entering kernel and initrd entries.

  • After starting to type the kernel or initrd name, press TAB.
  • If additional characters are not added, look at the bottom of the menu as there may be multiple choices. Add characters until only one entry is visible at the bottom, then TAB again.
• When editing is complete:

  • CTRL-x or F10 — boot with the changed settings (highlighted for emphasis).

  • CTRL-c or F2 — jump to the command line to perform diagnostics, load modules, change settings, etc.

    • If an edit is incomplete and GRUB 2 detects an error in the kernel or initrd line it will return to the line when exiting this mode.

  • ESC — Discard all changes and return to the main menu.

  • The choices are listed at the bottom of the screen as a reminder.
• Edits made to the menu in this manner are non-persistent. They remain in effect only for the current boot.

  • Once successfully booted, the changes can be made permanent by editing the appropriate file, saving the file, and running update-grub as ‘root’.

• Change a kernel version if one is available but not listed on the GRUB 2 menu.

  • Use the TAB key after entering part of the kernel or initrd version to see which ones are available.

• Add or remove kernel options from the linux line.

  • Remove quiet to display system messages during boot.

  • Remove existing options and add nomodeset to avoid module loading, especially if having video issues.

• Boot to the recovery mode even if it is not listed on the menu.

  • Remove existing kernel options from the linux line and add single

• Remove references to UUIDs

  • Remove the entire search line

  • On the linux line, replace «root=UUID=<some alphanumeric>» with «root=/dev/sdXY»

Post Boot Follow Up

Any changes made from the GRUB 2 terminal are not permanent. After successfully booting into the system the user must take several steps to ensure the problem is permanently fixed.

1. Update the GRUB 2 configuration file

   • sudo update-grub

2. Reinstall GRUB 2 to the drive’s MBR or equivalent

   • Install to the drive, not to the partition. Example: sda, not sda1

     sudo grub-install /dev/sdX  

3. Inspect the GRUB 2 configuration file. The default is /boot/grub/grub.cfg

   • For problems with booting the main linux kernel, verify the search, linux, and initrd lines in the [### BEGIN /etc/grub.d/10_linux ###] section of the file.

     • Ensure the paths and kernel/initrd image versions are correct.
     • Confirm the UUID numbers.

     • UUIDs can be checked with the sudo blkid command.

4. Verify the existence and contents of the system boot folders.

   • / should contain the symlinks vmlinuz and initrd.img

   • /boot/ should contain the actual kernel (vmlinuz-X.X.X-XX…) and initrd image (initrd.img-X.X.X-XX…)

   • /boot/grub should contain grub.cfg and numerous module files (*.mod)

For a corrupted GRUB 2 installation, purging and reinstalling GRUB 2 is very easy if the user has a working Internet connection. Refer to Grub2/Installing#Purging & Reinstalling GRUB 2 for guidance.

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).

GRUB 2 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.

A GRUB 2 error will leave the user at the grub> or grub rescue> prompt, the word GRUB with no cursor, or a hung boot caused by improper system path designations or a corrupted operating system. These issues are addressed earlier on this page — go to the General Troubleshooting Preparation section to start the recovery process.

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.

insmod fails with «error: no such disk»

Several grub2 modules, such as the linux-module depends on other modules, which is attempted to be auto-loaded. For this to work, the variable $prefix, must be set to where the grub2 modules can be found. Usually, this is accomplished with the command «set prefix=/boot/grub«.

Links

Grub2

Grub2/Displays

Grub2/Installing

Grub2/Submenus

Grub2/Upgrading

Boot-Repair

CategoryBootAndPartition

Нередко возникает необходимость в установке двух принципиально разных операционных систем на один компьютер: Windows и Linux. Разумеется, подобное «соседство» будет связано с некоторыми неудобствами. Для установки, как правило, используют специальную программу GRUB. Но к сожалению, при её использовании можно столкнуться с рядом ошибок. В этой статье разберёмся с тем, как исправить ошибки загрузчика GRUB. Давайте же начнём. Поехали!

Для начала давайте определимся с тем, что из себя представляет эта программа. GRUB — представляет собой системный загрузчик, устанавливающийся непосредственно с Линукса и записывающий все данные на первый раздел диска (MBR).

Сам rescue mode является отличительной чертой GRUB 2 от его предыдущей версии. Этот режим запускается, если программе-загрузчику не удалось найти файл «grub.cfg» либо не удалось передать управление в kernel (ядро). В итоге не удаётся найти загрузочные файлы и запустить операционную систему. Именно тогда и возникает ошибка.

Способ 1

Что делать в случае ошибки unknown filesystem grub-rescue? Перед вами окно, в котором можно использовать только 4 команды, их вполне достаточно, чтобы исправить все проблемы и успешно загрузиться:

• ls — позволяет вывести всё содержимое;
• set — применяется для установки переменных;
• unset — очищает переменную;
• insmod — необходима для загрузки модулей.

Также можно сделать доступным ряд других команд. Сделать их доступными можно, загрузив модуль «normal». Для этого пропишите:

insmod normal

После этого станут доступны:

• dump — для очистки памяти;
• exit — команда выхода из загрузчика;
• chainloader — необходима, чтобы указать последующей команде boot передать управление цепочечному загрузчику;
• kfreebsd — несколько команд, позволяющих загрузить ядро FreeBSD, его модули;
• rmmod — позволяет выгрузить указанный модуль ядра;
• multiboot.

Первым делом нужно отыскать модули, чтобы загрузить их. Для этого введите:

ls

Результатом выполнения команды будет следующее:

(hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1) (hd1) (hd1,msdos2) (hd1,msdos1)

Из этого можно сделать вывод, что загрузчик не может определить файловые системы дисков, поэтому определяет их как msdos. Теперь необходимо угадать видимые диски. В конкретном примере перед вами два диска: hd0 (с тремя разделами) и hd1 (с двумя разделами). Допустим, вы знаете, что Linux инсталлирован на диск, который имеет три раздела. В таком случае вам нужен диск с индексом «0».

GRUB даёт названия разделам в обратном порядке. В связи с этим, неясно как трактовать запись: «(hd0,msdos3)». Ведь можно посчитать это как первым разделом, так и третьим. К счастью, из этой ситуации можно выйти при помощи такого синтаксиса команды: «(hd0,1)». Обратите внимание, что в программе-загрузчике GRUB отсчёт дисков идёт с 0, а разделов с 1.

Допустим, что Линукс хранится в первом разделе, тогда он будет обозначаться (hd0,1). В этом случае команда, которую необходимо прописать, будет иметь вид:

set prefix=(hd0,1)/boot/grub
set root=(hd0,1)

Теперь модули могут быть загружены. Использовать их можно только после загрузки.

После того как вы выбрали нужный диск, проверьте содержится ли там то, что нужно. Для этого пропишите:

ls /boot/grub

В результате выполнения на экране появится список md файлов.

Далее, пропишите:

insmod ext2
insmod normal
normal

После этого загрузчик будет переведён в режим полной функциональности. Затем автоматически будут найдены разделы с операционной системой, и откроется меню программы.

Теперь остаётся загрузить Linux. Делается это при помощи команды:

grub-install /dev/sda

Способ 2

Всё сильно упрощается, если использовать Live CD – загрузочный диск с системой Linux. Он может быть записан на флешке, на внешнем винчестере или на обычном диске – это неважно, главное, чтобы с него можно было загрузить компьютер.

После загрузки Linux стандартным способом устанавливается бесплатная утилита Boot Repair. Она предназначена именно для устранения ошибок загрузки с помощью загрузчика Grub и очень проста в использовании – достаточно кликнуть по кнопке.

Заметим, что иметь Live CD для линуксоида всегда полезно и даже необходимо. Это зачастую избавляет от множества проблем, так как позволяет загрузить полноценную систему с внешнего носителя и использовать весь её инструментарий. Скачать такой диск с любой версией Linux не представляет сложностей, в комплекте обычно идёт инструкция по записи его на флешку.

После выполнения всех этих действий ошибка будет устранена. Пишите в комментариях была ли полезна для вас эта статья и задавайте любые интересующие вопросы по рассмотренной теме.

The objective of this article is to list problems and errors that may occur in certain situations when using the GRUB Legacy bootloader. All these solutions have been acquired through the cooperation of users on the Gentoo Forums.

Starting notes

Acknowledgements

Many thanks to Earthwings, penetrode, loyaltonone, pilla, airhead, nephros, yamakawa and all the others for the suggestions on the original thread.

Disclaimer warning

The examples provided are just examples. Be sure to change partition numbers and the like according to the specific systems specs. Follow the solutions provided by this document at the readers own risk.

GRUB loading, please wait…

Situation

GRUB loading stage 1.5
GRUB loading, please wait...

After this message, the system stops. If attempting to boot the system using a GRUB floppy, the problem disappears.

Solution

According to The_Bell, changing the boot order in the BIOS can solve the problem.

Tell the BIOS to not boot from the floppy first.

[1] took hard disks off the system one-by-one until found out the problem was caused by the SiI3512A SATA RAID-controller.

penetrode wrote that this may also be due to bad CFLAGS settings. Although the current GRUB ebuild filters out-fstack-protector, it can’t hurt to recompile GRUB with clean CFLAGS if nothing else helps.

This problem appeared on a dell r320 server, caused by having serial and terminal options in grub.conf, problem disappeared after removing those options.

FILE grub.confoptions to remove

#serial --unit=1 --speed=19200  
#terminal --timeout=10 serial

GRUB Error 12

Situation

12 : Invalid device requested.

This error is returned if the device strings syntax is correct but other than that, an error occurred that isn’t defined by any other error.

Solution

When GRUB was installed in the boot record using the interactive commands, were the two lines below executed in the GRUB prompt?

(hd0,0) must be replaced with the boot partition and (hd0) with the HDD that was chosen. Remember that (hd0) will install the bootloader in the Master Boot Record of the first hard disk, the primary master.

GRUB error 15

Situation

This error can occur in two different stages of the GRUB configuration, either during the initial configuration (installing GRUB in the master boot record) or after booting the system and attempting to launch Linux (or any other entry).

Initial configuration:

 Filesystem type is xfs, partition type 0x83

 Checking if "/boot/grub/stage1" exists... no
 Checking if "/grub/stage1" exists... no

Error 15: File not found

Booting an entry:

Booting 'Gentoo Linux'
  
root (hd0,0)
Filesystem type is ext2fs, partition type 0x83
kernel (hd0,0)/boot/kernel-2.4.20 root=/dev/sda3 vga=792
  
Error 15: File not found
Press any key to continue...

Solution — Initial configuration

This error is returned if the specified file name cannot be found, but everything else (like the disk/partition info) is OK.

Frequently, the error notes a missing kernel image file. Make sure that the file it is referring to exists on the boot partition.

To find out the exact name of the kernel, boot from the installation cd, mount the root and (if applicable) boot partition. Next, chroot into the Gentoo system and do a listing of the available files to see what kernel images there are available:

This will list all the kernels that there are on the boot partition. If the kernel is missing make sure to have compiled a kernel (using genkernel or manually):

And that it has been copied to the boot partition:

Verify that the name of the kernel is exactly the same as the one mentioned in the grub.conf file. Also make sure that the kernel line in the grub.conf file is referring to that partition (either explicitly or implicitly).

Another reported mistake is to have the BIOS ignore the disk on which the kernel or GRUB stages reside. Also, the partition on which GRUB stores its stages should not use a software RAID-5 (or other striping technology) configuration.

Solution — Booting an entry

First, verify that the root and setup lines that were used are correct.

If it is certain they are valid, then there is the possibility of using a flawed GRUB version (0.93.20031222). Upgrade the Portage tree or mask this version of GRUB:

Another option is using the grub-install script as is recommended by the GRUB authors. The --root-directory option is needed if there is a separate boot partition, otherwise it should be left out.

When all this fails, the boot partition may be corrupt. Check the partition for errors:

GRUB error 17

Situation

root (hd0,0)
filesystem type unknown partition type 0x7
  
Error 17 : Cannot mount selected partition

Solution

This error is returned if the partition requested exists, but the filesystem type cannot be recognized by GRUB.

Be sure to check the root(x,y) settings in grub.conf.

Also, when trying to boot Windows, make sure that the grub.conf file has the root (hdX,Y) (or rootnoverify (hdX,Y) ) and chainloader (hdX,Y)+1 in it.

GRUB error 18

Situation

kernel (hd1,4)/bzImage root=/dev/sdb7
  
Error 18: Selected cylinder exceeds max supported by BIOS

Solution

This error is returned when a read is attempted at a linear block address beyond the end of the BIOS translated area. This generally happens if the disk is larger than the BIOS can handle (512 MB for (E)IDE disks on older machines or larger than 8 GB in general).

Try an update for the BIOS and/or move the boot partition to the front (or at least into the appropriate range).

GRUB GRUB GRUB GRUB GRUB …

Situation

GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB
  GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB GRUB
...

Solution

According to airhead this can be caused by having the BIOS detect the disks automatically. Try to set the BIOS entry to User Type HDD.

Another possibility is that Grub was installed on the MBR and then reinstalled (for instance due to hard disk changes) but using the wrong setup and root commands.

Probing devices to guess BIOS drives. This may take a long time

Situation

While trying to install GRUB, it hangs after displaying the following line:

Probing devices to guess BIOS drives. This may take a long time.

Solution

One reported cause was an exotic configuration of disk devices, like ultra/non-ultra DMA disks on one cable.

When installing GRUB, it just hangs

Situation

When installing GRUB, it hangs:

At this stage, the installation stops.

Solution

If there is no floppy drive, was the --no-floppy switch used?

Uncompressing Linux… Ok, booting the kernel

Situation

The system hangs after displaying the following line:

Uncompressing Linux... Ok, booting the kernel.

Solution

Strictly speaking, this is no GRUB error. One possible cause is that ACPI is not working correctly but is enabled in the kernel. Try to disable it in the BIOS or in the kernel. Another possible cause is that the kernel has been compressed to a format it does not support for decompression, such as LZO requiring LZO_DECOMPRESS.

GRUB just shows a GRUB prompt

Situation

When booting the system, a GRUB prompt appears instead of a list of entries that were defined in the grub.conf file.

Solution

Mount the boot partition and verify if the grub/grub.conf file exists.

Also make sure that the menu.lst symbolic link exists:

lrwxrwxrwx  1 root root 9 Mar  7 14:00 /mnt/gentoo/boot/grub/menu.lst -> grub.conf

If not, recreate the symbolic link:

If this is the case, reinstall GRUB:

Could not find device for /boot/boot: not found or not a block device

Situation

When running grub-install during the GRUB installation, the following error appears:

Could not find device for /boot/boot: not found or not a block device

Solution

Check that the following wasn’t forgotten:

Situation

After hitting the Enter (Return) key at the GRUB menu during the system boot, the system reboots.

Solution

Try disabling framebuffer support in the kernel. If this does not help, disable APM and ACPI.

Situation

After hitting Enter (Return) at the GRUB menu during system boot, the screen blanks out, but the system is responsive (for instance, the numlock LED is switchable).

Solution

Turn off framebuffer (typically remove vga=XYZ from grub.conf) and check the processor architecture in the kernel config.

Missing GRUB image

Situation

When booting the system, the spiffy Gentoo splash screen is not seen.

Solution

First of all check if the splash screen file that is being are referred to in grub.conf really exists. If that is the case, go and check the GRUB ebuild. Maybe the patch for the splash image is commented out in the version that is being used.

Failing To boot Windows from a second hard drive

Situation

After selecting the Windows entry, the system refuses to boot without any clear reason as to why.

Solution

cyrillic provides information that it is possible to «map» the disks in a different order by changing grub.conf‘s Windows entry like so:

FILE grub.confMapping disks

title Windows XP
  map (hd0) (hd1)
  map (hd1) (hd0)
  chainloader (hd1,0)+1

GRUB segfaults when trying to install

Situation

The situation described below is only relevant for grub-0.95.x at the moment of installing GRUB at the boot sector.

Segmentation fault

Solution

This is a known bug related to this problem and has been fixed in grub-0.96. It is also known that grub-0.94-r1 and grub-0.94-r2 should work correctly. If that fails too, try to emerge grub-static which is currently stable on amd64 and unstable on x86 and (~x86). Check out bug #79378 for additional information.

This page is based on a document formerly found on our main website gentoo.org.
The following people contributed to the original document: Hartwig Brandl, Ioannis Aslanidis
They are listed here because wiki history does not allow for any external attribution. If you edit the wiki article, please do not add yourself here; your contributions are recorded on each article’s associated history page.

Before reading: The answer below is meant for Ubuntu users who have just updated/recovered/reinstalled/installed OS X. It’s likely that the answer will work if this isn’t the case (for example, if there are any inconsistencies in your partition table), but I’m not sure.

For me, this happened after updating to OS X Mavericks (10.9). Basically what may have happened is that OS X created a recovery partition («Recovery HD») that the system only detects sometimes. For example, GParted in Ubuntu will see the recovery partition fine, but when listing the partitions in terminal (fdisk -l), you may not see the partitions.

Diagnosing the issue: Did the OS X update/format/recovery cause this problem?

In order to diagnose that this is indeed the case, first use GRUB rescue to boot into Ubuntu. In order to do this, follow this page or see if any of the other answers on this question can get you into Ubuntu. For me, running the below commands temporarily allowed me to boot the correct partition. Depending on how your hard drives and partitions are set up, it may vary:

grub rescue> set prefix=(hd0,6)/boot/grub
grub rescue> insmod normal
grub rescue> normal

Now, log in to Ubuntu and check GParted. If you see the recovery partition, open up a terminal and type fdisk -l to see if that detects the recovery partition. If it doesn’t list the same partitions, check the device/partition column and see if those also don’t match up (for example, in GParted your boot partition may be /dev/sda4, but it is /dev/sda3 when running fdisk). If this is the case, keep reading. If it’s not, it looks like your partitions are lined up correctly. You can either choose to keep reading and follow the instructions (which, if GRUB was working before the restore/reinstall/etc…, this should work properly), or just reinstall GRUB on the right partition.

Fixing it by removing/merging the recovery partition

To fix this issue, what we want to do is get rid of the recovery partition — it’s causing issues and inconsistencies, and removing it shouldn’t cause damage. Ideally you want to merge it with the normal HFS+ OS X partition, so follow this question and answer here. After merging, GRUB should be back to normal.