GRUB 2 - A Guide for Users
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GRUB 2 A Guide for Users
Updated: 9/11/09, 9/12/09, 9/20/09, 9/22/09, 9/23/09, 10/04/09, 10/6/09, 10/7/09, 10/9/09, 10/12/09 (Dual
booting, drivemap in Reply #1), 12/4/09 (edited References)
Bugs and Questions: See REFERENCES at the end.
In Progress -- pending the completion of the GRUB 2 Manual: http://grub.enbug.org/Manual.
GRUB 2 Practical Reminders (a cheat sheet for those who know what they are doing)See end of SECTION 4 Special Topics.
Installing Kubuntu--GRUB 2 placement
Telling the Live CD installer where to put GRUB 2
-> See the Appendix
New:
Booting Windows XP on a non-first hard drive
See Reply #1
NEW Notes about some of the new GRUB 2 commands: See Reply #1
NEW comment (10-0-09)
update-grub vs grub-mkconfig
It appears that update-grub has been replaced by grub-mkconfig.
HOWEVER, it appears that update-grub works fine, at least in 9.10 Karmic.
update-grub is usually easier to use.
(To Do: Track the status of this)
I have made the switch throughout the how-to (in the first post of this thread).
Note: update-grub
The command update-grub generates a new grub.cfg file and replaces the existing grub.cfg with the newly
generated grub.cfg (by default).
But, as explained next, you must specify the output file when using grub-mkconfig:Note that
sudo grub-mkconfig
prints its output to the screen (default = stdout).
To print to the grub.cfg, use
sudo grub-mkconfig -o /boot/grub/grub.cfg
or
sudo grub-mkconfig --output=/boot/grub/grub.cfg
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TABLE of CONTENTS
SECTION 1
Introduction
History: GRUB Legacy, GRUB 2
Differences between GRUB Legacy and GRUB 2
GRUB 2 commands
Notes about some of the new GRUB 2 commands: See Reply #1
SECTION 2
Key Facts About the Boot menu, grub.cfg
Quick version -- Overview -- Details
/etc/grub/default --> /etc/grub.d --> /boot/grub/menu.lst
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Rules for editing grub.cfg, /etc/default/grub, and the script files in /etc/grub.d
GRUB 2 device numbering is different: Partitions start at 1
Details
SECTION 3 Fixing Things
A checklist of things to try to fix a broken system
A Troubleshooting Outline
Ctrl+Alt+Del will reboot your PC
Super Grub Disk: Very Important
Key commands: grub-mkconfig and sudo grub-installTimeout & Default OS, changing
Kernel options, changing
To see or to hide the boot menu
Missing OS entry in the boot menu
Editing the boot menu during booting: "e" key
The GRUB prompt grub> -- What to do with it
=> Getting information and booting an OS
Re-installing GRUB 2 using Live CD: Key Rescue Method
Using a Live CD to edit files in your OS
SECTION 4
Special TopicsInstalling GRUB 2 to your PC
grub-install The most useful command
The various types of command modes.
"c," grub>, Konsole BASH, edit "e", emu
TAB Completion
How to get information about your drives and devices
At Konsole : sudo fdisk -lu
At the GRUB 2 prompt: grub> ls
Boot menu: Adding or removing an OS entry
Boot menu: Create a custom boot entry
Boot menu: Making your own custom grub.cfg
Boot menu: Changing resolution, text colors, setting background image4 ways to boot an OS: configfile, symlinks, direct booting, chainloader
Boot menu: Background image editing tip for those with widescreen monitors
Dedicated GRUB 2 partition: How to build it
GRUB 2 Flashdrive: How to build it
Use of the term "root"
GRUB's Root Device, the Linux statement: root=UUID=,
--root-directory=DIR INSTALL_DEVICE
Dual booting: See Reply #1
Booting XP on a non-first hard drive (drivemap): See Reply #1
Cheat sheet: GRUB 2 Practical Reminders
Appendix: Techniques
--- Installing Kubuntu--GRUB 2 placement
--- Working as root, editing a file
--- Permissions: read, write, execute; change the execute bit
--- Chroot -- how to
References and Tutorials
See also REPLY #1 below this post for more GRUB 2 topics:
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Notes about some of the new GRUB 2 commands
Included: chainloader, ls, grub-emu, grub-mkconfig (many tips!), root, rootnoverify (is gone), grub-setup
grub-install: See SECTION 4 above.
drivemap: See Reply #17 below; See Reply #1
loopback: See Boot From ISO (below)
Dual booting: How to set it up
Installing two or more Linux operating systems
RECOMMENDED METHOD
PROBLEMSMessing up the booting -- fixing GRUB without re-installing Kubuntu
Windows topics
Installing XP (or 7? or Vista?) & Kubuntu:
How to set up dual booting (recommended outline)
Re-installed XP and now can't boot Kubuntu
XP on a non-first hard drive: (hdx,y), x > 1
Booting XP on a non-first hard drive
The drivemap command in GRUB 2
Boot From ISO -- use of GRUB 2 loopback
Boot your Kubuntu Live CD ISO from your flashdrive
GPT: GUID Partition Table
... for Kubuntu 9.10 and GRUB 2
=> Overcoming the "2 TB disk size limit"associated with the conventional MBR
=> Testing GRUB 2 on your GPT-partitioned flash drive
= = = = = = = = = = = = = = = = = = = =
SECTION 1
Introduction
History: GRUB Legacy, GRUB 2Differences between GRUB Legacy and GRUB 2
GRUB 2 commands
Notes about some of the new GRUB 2 commands: See Reply #1
History: GRUB Legacy, GRUB 2
"Briefly, boot loaderis the first software program that runs when a computer starts. It is responsible for loading and
transferring control to the operating system kernel software (such as the Hurd or the Linux). The kernel, in turn,
initializes the rest of the operating system (e.g. GNU)." (gnu.org)
The original GRUB (GRand Unified Bootloader) was developed by Erich Stefan Boleyn, from which came the GRUB
most of us know, GRUB version 0.9x, and that is now referred to as GRUB Legacy (or even GRUB 1 by some writers).GRUB 2 replaces GRUB Legacy. (GRUB 2 is actually the end result of versions GRUB 1.xx; e.g., 1,96, 1.97, ...)
For the history of GRUB and some interesting links, see
http://www.gnu.org/software/grub/
GRUB 2 is cleaner, more efficient, powerful, and more elegant, in many ways it is simpler to use than GRUB Legacy.
GRUB 2: http://www.gnu.org/software/grub/grub-2.en.html
Its mailing list for development,
GRUB-devel: http://lists.gnu.org/mailman/listinfo/grub-devel
And the Wiki: http://grub.enbug.org/
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GRUB 2 is the default bootloader in 9.10
https://lists.ubuntu.com/archives/ubuntu-devel-announce/2009-June/000573.html
Differences between GRUB Legacy and GRUB 2
From the user's view, the biggest difference between the two versions of GRUB concerns the boot menu
configuration file.
GRUB 2: /boot/grub/grub.cfg
GRUB Legacy: /boot/grub/menu.lstThe configuration file is used to generate the boot menu you see at boot time.
In GRUB Legacy, you can edit menu.lst directly and in any way you wish.
In GRUB 2, you should not edit grub.cfg directly. Instead, you edit the file /etc/default/grub (which contains some
default settings); this file feeds data to scripts in the folder /etc/grub.d. And you may edit the scripts (text files) in
the folder /etc/grub.d; these scripts are used to generate the configuration file /boot/grub/grub.cfg. When you
need a new grub.cfg, simply do sudo grub-mkconfig -o /boot/grub/grub.cfg.
It is conceptually simple in GRUB 2:
You can edit the file /etc/default/grub and you can edit the scripts in /etc/grub.d, then run the command sudo grub-
mkconfig -o /boot/grub/grub.cfg, and the file grub.cfg is automatically generated.
The configuration file in GRUB 2 grub.cfg looks different than the GRUB Legacy menu.lst. For example, in GRUBlegacy, you use
default 0
timeout 5
In GRUB 2, default and timeout are variables, and it is
set default=0
set timeout=5
A boot entry in GRUB Legacy menu.lst might look like this:
title Ubuntu 8.04.3 LTS, kernel 2.6.24-24-generic
root (hd1,2)
kernel /boot/vmlinuz-2.6.24-24-generic root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
In GRUB 2 grub.cfg, it would look like this:
### BEGIN /etc/grub.d/10_Linux ###
menuentry "Ubuntu 8.04.3 LTS, kernel 2.6.24-24-generic" {
set root=(hd1,2)
linux /boot/vmlinuz-2.6.24-24-generic root=UUID=0df17bc5-0056-4ef7-bfca-251194b6eb44 ro quiet splash
initrd /boot/initrd.img-2.6.24-24-generic
}
### END /etc/grub.d/10_Linux ###
Note how the title line is changed in GRUB 2: Use menuentry instead, put the text in quotes, and start the bootentry with a left brace {, ending it with a right brace }. Instead of kernel, the word linux is used; initrd is the same.
Instead of root=, in GRUB 2 it is set root= (in GRUB 2, root is a variable).
sudo grub does not get you a GRUB 2 shell at Konsole
In GRUB Legacy, the user may open a GRUB shell by typing sudo grub, and then use it to install/re-install GRUB (root-
setup-quit) to a Master Boot Record or to a partition boot sector. In GRUB 2, there is no such option. Instead, the
key command is the Konsole (BASH) command grub-install. At Konsole, as root, you will use sudo grub-install to
install/re-install GRUB 2 to a Master Boot Record or to a partition boot sector.
Device names have changed. In GRUB Legacy, the numbering of both hard drives and partitions start at zero.
(hd0,0) is the first hard drive (hd0), the first partition (partition zero). In GRUB 2, the numbering of hard drives also
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starts at zero: hd0 is the first hard drive. But partition numbering starts at 1: (hd0,1) is the first hard drive, the first
partition (partition one).
In GRUB Legacy, we use the find command; e.g., grub>find /boot/grub/menu.lst. In GRUB 2, the search command
replaces the find command: grub>search /boot/grub/grub.cfg.
In GRUB Legacy, the geometry command (at the grub> prompt) is very useful for listing devices as GRUB sees them
on your PC. It is not used in GRUB 2. Instead the list command ls (at the grub> prompt) replaces the geometry
command.
GRUB Legacy uses stages: stage_1, stage_1.5, and stage_2. Those are replaced in GRUB 2 by boot.img (a 512-byte
file that corresponds to stage_1 and is installed to a MBR); there is no stage_1.5 in GRUB 2; and core.img in GRUB 2
takes the place of stage_2 (or, perhaps, of both stage 1.5 and stage_2). Details: See Section 4 the subsection "grub-
install: A key command."
GRUB 2 Commands -- compared to GRUB Legacy
Comparison chart:
http://grub.enbug.org/CommandList
Key useful items to note:
GRUB Legacy GRUB 2
find is replaced with search
geometry is gone and replaced by ls
kernel (in menu.lst) is replaced by linux (and other terms for different OSs)
title (in menu.lst) is replaced by menuentry (in grub.cfg)
root is still used but is now a variable
setup is gone; the work is done by grub-install
map is replaced by drivemap
device is replaced by loopback (makes a drive out of a file)
set is a GRUB 2 term used to set a variable
Notes about some of the new GRUB 2 commands: See Reply #1
= = = = = = = = = = = = = = = = = = = =
= = = = = = = = = = = = = = = = = = = =
SECTION 2 Key Facts About the Boot menu, grub.cfg
Quick version -- Overview -- Details
/etc/grub/default --> /etc/grub.d --> /boot/grub/menu.lst
Rules for editing grub.cfg, /etc/default/grub, and the script files in /etc/grub.d
GRUB 2 device numbering is different: Partitions start at 1
Details
Quick version:/etc/grub/default --> /etc/grub.d --> /boot/grub/menu.lst
Rules:
-- The file /boot/grub/grub/cfg generates the boot menu.
-- Do not directly edit /boot/grub/grub/cfg.
-- You may edit (as root) /etc/default/grub.
(timeout, default OS, kernel options, resolution of the boot menu)
-- You may edit (as root) the scripts in /etc/grub.d.
-- Together, /etc/default/grub and the scripts in /etc/grub.d generate /boot/grub/grub.cfg.
-- To create a script, start with a text file as root: kdesudo kate
-- To makefilename executable: sudo chmod 744 /etc/grub.d/filename
or, sudo chmod +x /etc/grub.d/filename
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-- To remove execute permission fromfilename: sudo chmod -x /etc/grub.d/filename
-- To open Konqueror (Dolphin) as root: kdesudo konqueror
-- Generate a new configuration file /boot/grub/grub.cfg after editing /etc/default/grub and after editing, creating,
or deleting scripts in /etc/grub.d, as follows:
sudo grub-mkconfig -o /boot/grub/grub.cfg
Examples of grub.cfg
http://svn.savannah.gnu.org/viewvc/trunk/grub2/docs/grub.cfg?root=grub&view=markup
Or: /usr/share/doc/grub-pc/examples/grub.cfg.
Also: http://grub.enbug.org/grub.cfgAlso: GRUB 2 Basics http://ubuntuforums.org/showthread.php?t=1195275
GRUB 2 device numbering is new: Partitions y start at 1
In GRUB 2 (as in GRUB Legacy), hard drives start at zero: hd0 is the first hard drive. In GRUB 2 (unlike GRUB Legacy),
partition numbering starts at 1: (hd0,1) is the first partition in the first hard drive; (hd0,2) is the second partition in
the first hard drive; (hd1,2) is the second partition in the second hard drive.
Linux device notation is the same as in GRUB Legacy
sda is the first hard drive; sdb is the second hard drive; sdc is the third; etc.
sda1 is the first partition of the first hard drive; sda2 is the second partition of the first hard drive; etc.
Details
The configuration file is called /boot/grub/grub.cfg, and it generates the boot menu you see on your screen when
you boot your PC (and so, /boot/grub/grub.cfg can be called the boot menu configuration file). You are NOT
supposed to edit it (it is read-only). It is generated from a folder of scripts called /etc/grub.d. Another key file is
/etc/grub/default and it feeds default data to the scripts in /etc/grub.d. You may edit /etc/grub/default (as root).
You may also edit the scripts in /etc/grub.d (as root). If you create a new file in /etc/grub.d, you must make it
executable if you want the entry included in the configuration file grub.cfg. If you do not want a script to execute
(and so remove that entry from grub.cfg), you must remove the execute bit (i.e., remove the execute permission).
>>> Key reminder:
Generate a new grub.cfg after changing anything in /etc/default/grub or /etc/grub.d by:grub-mkconfig -o /boot/grub/grub.cfg
Experts: Editing grub.cfg
The file is read-only, so change permission to include Write:
sudo chmod +w /boot/grub/grub.cfg
Then do the edits as root and Save. When grub-mkconfig is run, the file returns to read-only (chmod 444 or 400),
AND your edits may be overwritten (and therefore gone).
Optional: After editing, restore permissions to disallow writing:
sudo chmod -w /boot/grub/grub.cfg or
sudo chmod 444 /boot/grub/grub.cfg
The default settings file /etc/grub/default
This file feeds data to the scripts in /etc/grub.d. It contains the Default operating system, the Timeout, kernel
options, resolution of the graphical boot menu, and other default settings. You may edit this file with root privileges.
The folder of scripts /etc/grub.d
These scripts generate /boot/grub/grub.cfg when the grub-mkconfig command is run (as root). The order of the
entries in grub.cfg corresponds to the order of the files in /etc/grub.d, starting with 00_header, then 01_scriptname,
etc., through all files starting with NN_ where NN is a 2-digit number and _ is the underscore (Shift+(minus sign));
then comes scripts whose names start with a letter (e.g., a_anotherscript).
You may edit the script files (as root) or create new ones. To create a new entry in grub.cfg, you simply create a new
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script file: a text file that you make executable (like a program). To remove an entry from grub.cfg, remove the
execute permission from the corresponding script file in /etc/grub.d. (If the entry corresponds to a custom script
you wrote, you may also delete that script file from /etc/grub.d).
See SECTION 4 Special Topics -- Create a custom boot entry.
Editing the script files in /etc/grub.d:
Do your work as root.
To make the file /etc/grub.d/filename executable:
sudo chmod 744 /etc/grub.d/filename
To remove the execute bit from the filefilename:sudo chmod -x /etc/grub.d/filename
When done, run
sudo grub-mkconfig -o /boot/grub/grub.cfg
to generate a new boot menu configuration file /boot/grub/grub.cfg.
GUI: How to set permissions
Open Konqueror or Dolphin as root (e.g., kdesudo konqueror).
Open the file.
Right-click > Properties > Permissions, Advanced Permissions
Tip: To open a file in /etc/grub.d (as root)
The files in /etc/grub.d are scripts. So, as root, if you click on one, it will want to execute or run like a program.
Instead, to open a script for editing/viewing, right-click on the script file, Open With Kate or Kwrite. That opens thefile as a text file. Now you can read it or edit it.
Details:
GUI, working as root: Open Konqueror (Dolphin) as root and work from there:
kdesudo konqueror
CLI, working as root: kdesudo kate /etc/grub.d/script_name
Quick reference
The (standard) files in /etc/grub.d (each is a script) are:
00_header
05_debian_theme: Set background, text colors, themes
10_hurd Locates Hurd kernels10_linux Locates Linux kernels based on results of the lsb_release command.
The target are kernels located on the same partition as the root partition
of the current OS you are in (where this grub.cfg is located).
In contrast to: 30_os-prober (see below)
20_memtest86+: If the file /boot/memtest86+.bin exists, it is included in the boot menu.
30_os-prober: Searches for Linux and otherOS's on allpartitions; includes them in the boot menu.
40_custom: A template for adding custom boot menu entries.
See Appendix: permissions, working as root, making a file executable, Konsole, and other topics.
= = = = = = = = = = = = = = = = = = = == = = = = = = = = = = = = = = = = = = =
SECTION 3 Fixing Things
A checklist of things to try to fix a broken system
A Troubleshooting Outline
Ctrl+Alt+Del will reboot your PC
Super Grub Disk: Very Important
Key commands: grub-mkconfig and sudo grub-install
Timeout & Default OS, changing
Kernel options, changing
To see or to hide the boot menu
Missing OS entry in the boot menu
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Editing the boot menu during booting: "e" key
The GRUB prompt grub> -- What to do with it
=> Getting information and booting an OS
Re-installing GRUB 2 using Live CD: A Key rescure method
Using a Live CD to edit files in your OS
Troubleshooting Outline
When you can't boot into your OS, there are two possible causes:the boot menu is flawed, and/or
the GRUB 2 installation is flawed.
To fix it, you have two choices:
boot into the OS somehow and fix it;
or
fix it from outside the OS (e.g., live CD, another OS, or live flash drive).
Before looking at these two choices, note two important things:
> To fix the boot menu means to fix its configuration file /boot/grub/grub.cfg. You can sometimes do that
temporarily using the edit-on-the-fly "e" key (see subsection below). To fix it permanently, you do NOT edit grub.cfg
directly; but rather you edit the file /etc/default/grub and/or you edit the script(s) in /etc/grub.d, and then you usethe command grub-mkconfig to generate a new grub.cfg.
> To fix the GRUB 2 installation, that usually means re-installing GRUB 2 using, at Konsole, the command grub-
install. You can do this from inside the OS (if you can boot into it somehow), or from a Live Kubuntu CD or from
another Linux OS on your hard drive. You cannot do it from the GRUB 2 prompt (grub>) when booting the PC. (In
GRUB Legacy, you could do it by getting the grub> prompt and using the root and setup commands.)
Now let's look at each of your two choices for fixing the problem.
--> How to boot into your OS when you can't seem to boot into your OS:
(1) SGD, or (2) use the grub>, or (3) use the "e" key.
Some tips and details:
> Use Super Grub Disk to boot into it. You may have SGD fix the boot (under GNU/Linux options), or simply use SGD
to boot the OS so you can get into it. If you use SGD to fix the boot, it will re-install GRUB to your drive, so make sure
that's what you want; also, it may do so using either GRUB Legacy or GRUB 2, depending on the SGD CD version you
are using. Of course, if you can get booted into the OS, then you can fix anything and everything, so maybe you
won't be feeling too picky at this point.
Note: Along these lines, you can also use your own GRUB 2 disk/flashdrive to boot your OS, if you built one.
> Boot into your OS yourself, manually, using the GRUB 2 prompt, grub>, ASSUMING you can get the prompt!
(Sometimes, you can't.) See the Subsection below titled "The GRUB prompt grub> -- What to do with it."
> Boot into your OS yourself by fixing the boot menu (editing it "on-the-fly" using the "e" key when you see it on the
screen). But sometimes, you don't see the boot menu. See the Subsection below titled "Editing the boot menuduring booting: 'e' key" If you are successful, since these "e" edits are only temporary, after booting into the OS, you
must make the changes permanent (by editing /etc/default/grub or the script(s) in /etc/grub.d and then generate a
new grub.cfg using grub-mkconfig -o /boot/grub/grub.cfg.
--> How to fix the problem from outside the OS:
(1) Use a Live CD, or (2) Fix it from another OS.
Some details:
> Use a Live CD.
From a Live Kubuntu CD (or most any live Linux CD), you can re-install GRUB and/or perform edits on files
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(/etc/default/grub or the script(s) in /etc/grub.d). See the subsections below: "Re-installing GRUB 2 using Live CD:
Key Rescue Method" and "Using a Live CD to edit files in your OS."
> Fix the problem from another Linux OS, ASSUMING you are able to boot into one!
From there, you can edit files in your broken OS and/or re-install GRUB 2 using grub-install.
(NOTE: From the second OS, or even from a Live CD, you'd have to mount the broken OS partition; or perhaps
looking in your file manager you'd see it is automatically mounted for you.)
[End of Troubleshooting Outline]
Ctrl+Alt+Del will reboot your PC
If your PC freezes up during the experiments/testing/troubleshooting of your bootloader, use Ctrl+Alt+Del to re-
boot the PC. Be prepared to do something, though!
Examples of what to do:
-- Before using Ctrl+Alt+Del, put the Super Grub Disk CD in the CD tray so you can re-boot to it and rescue your OS.
-- Be prepared to press the key required to enter your BIOS setup. That will buy you some time, or give you a
chance to change hard drive booting order, or put a live CD or SGD in the CD tray, or get your notes ready, etc.
-- If you have been getting a boot menu, let the PC reboot into it, then enter Edit mode (pressing the "e" key) or
enter the GRUB 2 CLI (pressing the key "c"), then try to fix things from there.
Super Grub Disk: Very Important
Whether you think you need it or not, get it now, free, as a bootable CD which will get you booted into your
operating system in case you can't. SGD can be downloaded here: http://www.supergrubdisk.org/ . Look for a CD
ROM iso version, download it, burn it as an iso image to a CD (using K3b), test it briefly (by running it and stepping
through a few menus but not choosing anything; then Quit; or, use it to boot into your OS).
Tip (using SGD to boot into your broken OS)
Choose GNU/Linux > Fix Boot, then select the broken partition.
Should you decide to simply Quit the SGD (without doing anything), do so, select reboot, enter your BIOS setup,
remove the SGD CD, exit BIOS, and continue rebooting.
Key commands: sudo grub-mkconfig and sudo grub-install
Use these two commands to "freshen up" your GRUB 2 installation.
grub-mkconfig: builds a new boot menu configuration file boot/grub/grub.cfg.
grub-install: builds a complete, fresh GRUB 2 installation, including /boot/grub/grub.cfg.
grub-mkconfig
will generate a new boot menu /boot/grub/grub.cfg. To do so, it uses /etc/default/grub and the scripts in
/etc/grub.d. You should run this command after editing the default file or the scripts:
sudo grub-mkconfig -o /boot/grub/grub.cfg
or
sudo grub-mkconfig --output= /boot/grub/grub.cfgSee Reply #1 (to this post): Notes about some of the new GRUB 2 commands
sudo grub-install [INSTALL_ DEVICE]
installs or re-installs GRUB 2 to INSTALL_DEVICE.
See SECTION 4: grub-install: A key command
For now, here's some highlights.
sudo grub-install /dev/sda
installs GRUB 2 to the Master Boot Record of drive sda. And
sudo grub-install /dev/sda1
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installs GRUB 2 to the boot sector of the partition sda1.
In doing so, grub-install does a complete job of setting up everything.
Here's what it does: It builds the directory /boot/grub (if it doesn't already exit), copies GRUB 2 files to it from the
"master" image directory /usr/lib/grub/i386-pc, probes your drives and devices and partition table, makes a new
device.map, builds and installs boot.img (to MBR) and core.img, and builds /boot/grub/grub.cfg.
> Man page: (8)GRUB-INSTALL - Install GRUB on your drive.
http://grub.enbug.org/FranklinPiat/grub-install.manpage
Troubleshooting-- After running grub-mkconfig, make sure that the line set default=(hdx,y) is correct (i.e., that the order of the
menuentries did not change the default OS position).
-- sudo grub-install --recheck [INSTALL_DEVICE]
=> If you get an error running sudo grub-install, try it again with sudo grub-install --recheck [INSTALL_DEVICE].
Timeout and Default OS, changing
The timeout is the length of time in seconds before the (highlighted) default OS is automatically booted (if you do
not intervene by touching a key). To change these values, open the file /etc/default/grub as root, make the changes,
Save, exit, then generate a new /boot/grub/grub.cfg by running sudo grub-mkconfig -o /boot/grub/grub.cfg.
Opening /etc/default/grub as rootIf your file manager supports it, open the file manager, navigate to /etc/default/grub, right-click on the file, Actions,
Edit as Root. Otherwise:
Open the file manager as root and work from there:
kdesudo konqueror
kdesudo dolphin
Or, open the file as root using Kate or Kwrite:
kdesudo kate /etc/default/grub
Example
GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DEFAULT=0 selects boot entry #0 (i.e., the first entry) as the default OS to be booted automatically. Boot
entries can be seen in your /boot/grub/grub.cfg file; they start with a line
menuentry "some descriptive text" {
and end with
}
Boot entries are counted from zero; so the first menuentry is boot entry #0, the second menuentry is boot entry #1,
etc.
Troubleshooting Tip: Check default OS setting after grub-mkconfig
If you recently added/removed a boot entry (by editing a /etc/grub.d script) and ran grub-mkconfig to generate a
new boot menu, you might have to check and edit the line "GRUB_DEFAULT= " (in /etc/default/grub) if the defaultsequence number changed.
(TO DO: Check also: sudo grub-set-default N.)
Kernel options, changing
To change these values, open the file /etc/default/grub as root, make the changes, Save, exit. (See Timeout and
Default OS above for editing tips.) The line in /etc/default/grub looks like this (or similar):
GRUB_CMDLINE_LINUX="quiet splash"
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To see or to hide the boot menu
Look for this line in the file /etc/default/grub:
# GRUB_HIDDEN_TIMEOUT=0
With the # sign present, you will see the boot menu upon booting your PC.
With the # removed, you will not see the boot menu.
For a detailed explanation of the other ways this works, see
GRUB 2 Basics drs305
http://ubuntuforums.org/showthread.php?t=1195275
Missing OS entry in the boot menu
If you run grub-mkconfig, and there is a missing entry in your boot menu, you can add that entry as a custom entry.
See SECTION 4 below, Special Topics Boot menu: Create a custom boot entry.
Editing the boot menu during booting using the "e" key
When you boot/re-boot your PC, the boot menu appears. If you select an entry (an OS to boot into) and get an
error, and if you are able to return to the boot menu (or re-boot again to get it), you may be able to fix things or to
experiment with your boot menu to see if something will work. See the help tips at the bottom of the boot menu.
At the boot menu, highlight an entry, press the "e" key, and you'll see the menuentry statements for that OS. Seethe help tips at the bottom of that menu. If you highlight a line, press the "e" key, that line will be displayed so you
can edit it (using arrow keys, delete, etc.). Pressing ESC returns you to the previous screen.
The edits you make to the boot menu are "on-the-fly" edits and are not permanent. To make them permanent,
you'll have to edit /etc/default/grub and/or the script files in /etc/grub.d, perhaps even making a custom boot entry
if necessary (SECTION 4 Special Topics Boot menu: Create a custom boot entry), then generate a new
/boot/grub/grub.cfg file using grub-mkconfig.
The GRUB prompt grub> -- What to do with it
=> Getting information and booting an OS
You may get the GRUB prompt grub> in three ways:
> "c" key: You re-boot and upon seeing the boot menu, press the "c" key to get the grub>. (Or Control+c at the
Edit mode menu.) (By pressing the ESC key, you get back to the boot menu.)
Or:
> No boot menu! Perhaps, you re-booted your PC and didn't see any boot menu but instead got dropped to the
GRUB 2 prompt: grub>.
Or:
> You get a grub> when re-booting using your own GRUB 2 flash drive (which is what is usually supposed to
happen!).
From the grub> prompt, you may be able to issue commands tohelp you gather information about your drives
or
boot your computer.
Use these resources:
SECTION 4 Special Topics, the subsection
"4 ways to boot an OS" -- direct booting configfile, symlinks, chainloader
SECTION 4 Special Topics, the subsection
"How to get information about your drives and devices"
=> In particular, take special note of the ls command and the use of TAB completion.
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Re-installing GRUB 2 using Live CD: Key Rescue Method
There are two main ways of doing this: By chrooting into the broken partition and by not chrooting. For the
chrooting way, see GRUB 2 Live CD Install Guide: http://grub.enbug.org/Grub2LiveCdInstallGuide For details about
chrooting, see the Appendix in the first post (above).
For "my" way, I'll call "Method 1," of re-installing GRUB2 from a live CD, read on.
Method 1: Installing or re-installing GRUB 2 using a Live CD
Your Kubuntu Live CD contains GRUB 2 files; specifically, in a live session, you will find the master GRUB 2 "image"
files in /usr/lib/grub/i386-pc. Thus, they can be used to install or re-install GRUB 2. Here's how ...
Start your Kubuntu Live CD.
Choose the option to try Kubuntu without installing.
Open Konsole (Terminal): K-Menu > System > Konsole
Explore your partitions using
sudo fdisk -lu
Determine your root partition. In this example, ours is sda2.
Make a mount point (directory) for partition sda2:
sudo mkdir /media/sda2Mount sda2 on the mount point:
sudo mount /dev/sda2 /media/sda2
Make a mount point (directory) for /dev:
sudo mkdir /media/dev
Mount the devices in your Live CD session:
sudo mount --bind /dev /media/dev
Install (or re-install) GRUB 2 (into the MBR of drive sda) using the GRUB 2 files in sda2:
sudo grub-install --root-directory=/media/sda2 /dev/sda
You may get this error:
grub-probe: error: Cannot find a GRUB drive for /dev/sda2. Check your device.map.
Auto-detection of a filesystem module failed.Please specify the module with the option `--modules' explicitly.
If so, try this:
sudo grub-install --recheck --root-directory=/media/sda2 /dev/sda
Maybe you'll get lucky and see this:
Installation finished. No error reported.
This is the contents of the device map /media/sda2/boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
fix it and re-run the script `grub-install'.
(hd0) /dev/sda
(=> and so this was successful)
Then, unmount both filesystems:
sudo umount /dev/sda2 /media/sda2
sudo umount /dev /media/dev
Leave Konsole:
exit
Test it:
Exit out of the Live CD, reboot, see if you fixed your booting problem (by booting into the broken partition).
[End of Method 1]
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Using a Live CD to edit files in your OS
This is done as you would normally do it. Of course, if you wish, you may use Super Grub Disk to boot into your OS
and do the editing from there. Here is an outline of a standard way to use your Kubuntu Live CD.
Boot the Live Kubuntu CD, open Konsole, then as root make a directory, mount the filesystem containing the file you
need to edit, open that file (possibly as root), edit it, save, quit, unmount the filesystem, exit.
Example
If the file you need to edit is called file_name and is on sdb3 (=(hd1,3)), start a Live CD Kubuntu session, openKonsole:
sudo fdisk -lu # to see/check your partitions, if necessary
Make a directory called /media/sdb3:
sudo mkdir /media/sdb3
Mount device sdb3 on directory /media/sdb3:
sudo mount /dev/sdb3 /media/sdb3
Change to that directory:
cd /media/sdb3
Then you may proceed in various ways:
Open Konqueror/Dolphin as root, then open the file_name:
in 8.10 or later: kdesudo konqueror (or dolphin)
in 8.04: kdesu konqueror (dolphin)Make your edits, then File > Save, File > Quit.
Or, open file_name as root using Kate, then do the edits:
in 8.10 or later: kdesudo kate /path_to file_name
in 8.04: kdesu kate /path_to file_name
Make your edits, then File > Save, File > Quit
Unmount the directory; note the spelling of umount:
sudo umount /media/sdb3
= = = = = = = = = = = = = = = = = = = =
= = = = = = = = = = = = = = = = = = = =
SECTION 4Special Topics
Installing GRUB 2 to your PC
grub-install The most useful command
The various types of command modes.
"c," grub>, Konsole BASH, edit "e", emu
TAB Completion
How to get information about your drives and devices
At Konsole : sudo fdisk -lu
At the GRUB 2 prompt: grub> ls
Boot menu: Adding or removing an OS entry
Boot menu: Create a custom boot entry
Boot menu: Making your own custom grub.cfgBoot menu: Changing resolution, text colors, setting background image
4 ways to boot an OS: configfile, symlinks, direct booting, chainloader
Dedicated GRUB 2 partition: How to build it
GRUB 2 Flashdrive: How to build it
Use of the term "root"
GRUB's Root Device, the Linux statement: root=UUID=,
--root-directory=DIR INSTALL_DEVICE
Dual booting: How to set it up
Booting XP on a non-first hard drive: The drivemap command in GRUB 2
Cheat sheet: GRUB 2 Practical Reminders
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Installing GRUB 2 To Your PC
To install GRUB 2 to your PC so it boots your PC into your OSs, two steps are required.
1 You need to get the GRUB 2 files installed to your PC, somewhere in the Kubuntu filesystem.
2 Then use those GRUB 2 files to install GRUB 2 to your PC's drives or devices so it can serve as a bootloader to boot
your PC into your Kubuntu and your other OSs.
Step 1: Get the GRUB 2 files
Install the GRUB 2 package in your Kubuntu OS using your package manager. Or, at Konsole, issue the following
command:
sudo apt-get install grub-pc
Check it: Open your file manager (Konqueror or Dolphin or other), and see the GRUB 2 files under
/usr/lib/grub/i386-pc (called the GRUB 2 image directory, and contains a set of "master" GRUB files).
Step 2: Install the GRUB 2 files so they serve as a bootloader
Suppose your first BIOS boot drive is sda (as seen in Kubuntu using at Konsole the command sudo fdisk -lu). Then,
install GRUB 2 to the Master Boot Record of sda:
sudo grub-install /dev/sda
This also copies the GRUB 2 files into /boot/grub.
Then to generate a fresh boot menu configuration file (/boot/grub/grub.cfg), run
sudo grub-mkconfig -o /boot/grub/grub.cfg.
More Details About This
CAUTION, fair warning:
Have a bootable Super Grub Disk CD handy in case this messes up booting your PC.
To install GRUB 2 files to your PC, open Konsole and run the commands
sudo apt-get updatesudo apt-cache search grub-pc
(returns: grub-pc - GRand Unified Bootloader, version 2 (PC/BIOS version))
sudo apt-get install grub-pc
Then, install GRUB 2 to the Master Boot Record of your first BIOS boot drive. For example, if that MBR is sda, the
command would be
sudo grub-install /dev/sda
And then update grub.cfg:
sudo grub-mkconfig -o /boot/grub/grub.cfg
Reboot to see what happens.
The old GRUB may also still be there (in which case you saw an entry on the boot menu to chainload into GRUB 2), in
which case you may run
sudo update-from-grub-legacyto replace GRUB Legacy with GRUB 2 IF YOU WISH TO DO SO.
Troubleshooting
Installing GRUB 2 to the MBR: using --recheck
Example
sudo grub-install /dev/sda
grub-probe: error: cannot find a GRUB drive for /dev/sda.
Auto-detection of a filesystem module failed.
Please specify the module with the option `--modules' explicitly.
So, try this:
sudo grub-install --recheck /dev/sda
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-- Konsole (BASH), in Kubuntu, at your regular prompt (as root), ~#:
-- GRUB 2 emu (from Konsole, issue sudo grub-emu [OPTION]; this gives you a grub> prompt)
=>TODO: More on this later.
-- GRUB 2 command line interface (CLI), grub>.
When you re-boot your PC, get the boot menu, and press the "c" key, you get a GRUB 2 prompt, grub>. That is the
GRUB 2 CLI. You will also get "grub>" upon re-booting if you don't have a boot menu, grub.cfg, or if your boot menu
is broken. (See SECTION 3, the subsection titled "The GRUB prompt grub> -- What to do with it")
-- Edit mode. Editing on the fly: when you re-boot and see your GRUB 2 boot menu, you can use the "e" key to edit
your boot menu on a temporary basis (the edits are not permanent unless you later make them so). (See SECTION 3
-- Editing the boot menu during booting: "e" key.)
=> In all cases, help is nearby, and the commands are generally the same (or nearly so) in all modes, with a few
differences.
Help
Konsole BASH CLI:
Appending --help to a command in CLI; for example: grub-mkconfig --help.
GRUB CLI (grub>):
At the GRUB 2 prompt simply type help and press Enter.
To get help with a command, type help .
Example: grub>help ls tells you about the command ls.
Edit mode:The key tips are at the bottom of the screen after your press "e"
to enter the edit mode from your on-screen boot menu.
Also, at that point, you can press Control+c to get a grub>,
then type help and/or use TAB completion.
TAB completion (grub>)
While typing after the grub>, try pressing the TAB key and see what happens: in many cases, GRUB will try to help
you complete the line with something meaningful or with choices. So type as much as you can recall or type a guess,
then press TAB, then you may have to type another guess and press TAB again, and so on until you complete the line
the way you want it.
GRUB 2 device numbering is different(hdx,y): hard drive x, partition y
Hard drives start at zero (x=0), same as for GRUB Legacy.
Partitions start at 1 (y=1); in GRUB Legacy, partitions start at zero.
- - - - -
How to get information about your drives, devices, and files
Key: at Konsole sudo fdisk -lu; and grub> ls
We'll look at two cases: At the command line in Kubuntu (Konsole); and at the grub> prompt.
Konsole (BASH) command line
Exploring your hard drive(s): sudo fdisk -lu
=> sudo fdisk -lu is very useful, very important.
GRUB version number: grub-install -v
Drive space: df -h -T
UUIDs (see NOTE below):
blkid (or try sudo blkid); also:
ls /dev/disk/by-uuid/ -alh
grub.cfg, to see it: cat /boot/grub/grub.cfg
fstab (filesystem table), to see it: cat /etc/fstab
Mounting, how filesystems are mounted: cat /etc/mtab or: mount
Boot directory /boot, to find it: df /boot
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Kernel version and gcc version (gcc=the GNU compiler used to build the kernel):
cat /proc/version
Kernel version: uname -r
Linux version/name: lsb_release -a
(hold the Shift key and the minus sign key to get _ . LSB = Linux Standard Base)
KDE version (KDE=K Desktop Environment)
for KDE 3.5: kde-config version and for KDE 4: kde4-config --version
NOTE: UUID = Universally Unique Identifier
Starting with Kubuntu version 8.10, UUIDs are used to identify partitions. A UUID is a 16-byte number (= 128 bits).In canonical form, a UUID consists of 32 hexidecimal digits, displayed in 5 groups separated by hyphens.
At a GRUB prompt, grub>
Exploring your hard drive(s): grub> ls
=> Very useful, very important.
(in GRUB Legacy, the geometry command is used instead of ls)
The ls command is very useful
grub>ls
gives you a list of your hard drives and partitions as GRUB sees them, in (hdx,y) GRUB 2 device notation.
grub>ls /shows you the files under the current GRUB 2 root device. You can set that device using set root=. For example:
grub>set root=(hd0,8)
grub>ls /
shows you all files under root. Or: grub>ls (hd0,8)/ .
grub>ls /boot
shows you all files--including kernels--under /boot.
UUIDs and filesystem type
grub>ls (hd0,8)
shows you information about the partition (hd0,8) including its filesystem type and its UUID.
The contents of a directory: grub>ls -l /directoryExample
grub>ls -l /boot
shows you the kernel and initrd files.
(The option -l indicates "long form" and gives more information. To see all files, including hidden files, use the
option -a: grub>ls -a -l /boot; or grub>ls -al /boot)
GRUB 2 emulation sudo grub-emu
At Konsole, to get a grub> prompt, type sudo grub-emu.
To exit emu and return to Konsole, type exit.
>>> IMPORTANT sudo grub-emu and then grub>ls
While you are working at Konsole in Kubuntu, you may need to know how GRUB sees your drives and partitions, the
(hdx,y)'s. You can switch into emulation made (sudo grub-emu)) and issue the list (ls) command at the GRUB prompt(grub>ls) to see your drives and GRUB devices. Type exit to return to BASH mode in Konsole.
Using search and cat
GRUB files, what partitions they are in: grub>search /boot/grub/boot.img
Boot menu, what partition(s) it is in: grub>search /boot/grub/grub.cfg
Kernel, where it is: grub>search /vmlinuz
Boot menu, to see it: grub>cat (hdx,y)/boot/grub/grub.cfg
fstab, to see it: grub>cat (hdx,y)/etc/fstab
Device.map, to see it: grub>cat (hdx,y)/boot/grub/device.map
(NOTE: In GRUB Legacy, the find command is used instead of search.)
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Restart (reboot), or shutdown (halt) your PC at a command line
At Konsole:
sudo shutdown -r now (re-boots the PC)
sudo shutdown -h now (shuts down the PC)
In GRUB:
grub>reboot (re-boots the PC)
grub>halt (shuts down the PC)
- - - - -
Boot menu: Adding or removing an OS entry to grub.cfg
Rule: You do NOT edit grub.cfg directly. Instead, you work with script files in the folder /etc/grub.d or with settings
in /etc/default/grub.
-- Linux operating systems, added automatically
Look at your grub.cfg. The section
### BEGIN /etc/grub.d/10_linux ###
### END /etc/grub.d/10_linux ###
contains Linux operating systems that were automatically detected by GRUB 2 using the script file
/etc/grub.d/10_linux. Most of your Linux OSs should be detected this way and included in the boot menu grub.cfg.
If not, you can create a custom boot entry (see below, "Boot menu: Create a custom boot entry").
-- Windows and other OSs added automatically
This is done by the script /etc/grub.d/30_os-prober.
-- Adding or removing OSs from your PC. After doing so,
generate a new grub.cfg: sudo grub-mkconfig -o /boot/grub/grub.cfg.
-- Add a boot menu entry by making your own custom boot entry, then run:
sudo grub-mkconfig -o /boot/grub/grub.cfg
to generate a new grub.cfg.
(See subsection below: "Boot menu: Create a custom boot entry")
-- Removing a boot entry from grub.cfg:
Two choices.
(1) Simply remove the execute bit from the script file in /etc/grub.d that corresponds to (i.e., generates) the boot
entry.
Example: If that file is named 43_MyOS-1, then run the Konsole commands
sudo chmod -x /etc/grub.d/43_MyOS-1
sudo grub-mkconfig -o /boot/grub/grub.cfg
(2) Or, remove the script file (for the boot entry) from the folder /etc/grub.d. Then run
sudo grub-mkconfig -o /boot/grub/grub.cfg to generate the new grub.cfg file.
NOTE: If a custom file contains more than one boot entry, you may remove any number of them, leaving the rest.
Then use grub-mkconfig to generate your new boot menu, grub.cfg.
Boot menu: Custom boot entry
This is easy, usually.
-- There are 4 ways to make a boot entry (see "4 Ways To Boot an OS").
-- There is a custom template at /etc/grub.d/40_custom.
-- After you write the script file for your custom boot entry, make it executable.
-- Then generate a new grub.cfg by running sudo grub-mkconfig -o /boot/grub/grub.cfg.
Troubleshooting: Sometimes when you run grub-install or grub-mkconfig, it will fail to detect one of your OSs and
excludes it from the boot menu grub.cfg. In that case, you could make a custom entry for it (as a script file in
/etc/grub.d).
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Direct booting To get a model for some of the entries, you have two choices: (1) Get it from your old boot menu
(/boot/grub/menu.lst) from GRUB Legacy (if that is available on your PC). Or, it may also be here, made by GRUB 2:
menu.lst_backup_by_grub2_postinst. (2) Go into the operating system itself (the one you wish to include), or
perhaps access its filesystem using a live CD, and get the information from its own boot menu.
Example
Making a custom entry for sidux. Method: Direct booting.
It helps if you have a model for some of the entries. In the old boot menu (/boot/grub/menu.lst) from my GRUB
Legacy, I had this boot entry for sidux:
title Debian GNU/Linux, sidux kernel 2.6.28-5.slh.3-sidux-686
root (hd0,2)
kernel /boot/vmlinuz-2.6.28-5.slh.3-sidux-686 root=UUID=306d94a5-107b-4c9e-ae03-a159e18dc1c7 ro quiet
vga=791
initrd /boot/initrd.img-2.6.28-5.slh.3-sidux-686
Using a template (e.g., /etc/grub.d/40_custom), create an executable file for the sidux boot entry:
Open an empty text document (as root)
kdesudo kate
Save the new file as, say, /etc/grub.d/41_sidux_sda3
Copy the kernel & initrd lines from menu.lst, change kernel to linux, adjust the sidux partition number toconform to GRUB 2 convention:
Legacy GRUB: (hd0,2)
GRUB 2: (hd0,3)
Also, double check the UUID for sda3 by running sudo blkid.
Result:
The file /etc/grub.d/41_sidux_sda3 looks like this:
#!/bin/sh
echo "Adding sidux" >&2
cat
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set root=(hd1,2)
configfile /boot/grub/grub.cfg
An equivalent way of doing it is this:
configfile (hd1,2)/boot/grub/grub.cfg
That tells your GRUB 2 to access partition (hd1,2), find the file /boot/grub/grub.cfg, show you that file so you can
make a choice of which OS to boot, then boot the OS you choose. The GRUB doing the work is your native GRUB,
the one you are using, not the GRUB in (hd1,2). Your native GRUB must be able to interpret the commands it finds in
the grub.cfg of the OS you wish to boot.
When to avoid configfile
When there is a mixture of GRUB versions on your PC, it is best to avoid using configfile.
Instead, use chainloader or symlinks.
Example (Taken from a grub.cfg. The # sign indicates a comment.)
# Kubuntu 8.04.3 on sdb2, by configfile
menuentry Kubuntu 8.04.3 on sdb2, by configfile {
set root=(hd1,2)
configfile /boot/grub/grub.cfg
}
>>> Symlinks used in a boot entry
Symlinks are like shortcuts, and they direct control from the link to the file they point at. Symlinks for the kernel and
initrd files are already set up for you. Look for yourself. List all files (-a) in long or detailed form (-l) under your root
partition (/) by issuing the following command at Konsole:
ls -a -l /
lrwxrwxrwx 1 root root 33 2009-08-02 11:01 initrd.img -> boot/initrd.img-2.6.24-24-generic
lrwxrwxrwx 1 root root 33 2009-04-19 17:14 initrd.img.old -> boot/initrd.img-2.6.24-23-generic
lrwxrwxrwx 1 root root 30 2009-08-02 11:01 vmlinuz -> boot/vmlinuz-2.6.24-2 4-generic
lrwxrwxrwx 1 root root 30 2009-04-19 17:14 vmlinuz.old -> boot/vmlinuz-2.6.24-23-generic
The symlink for the kernel is vmlinuz, and vmlinuz points at the NEWEST kernel.
The symlink for the initrd is initrd.img, and initrd.img points at the NEWEST initrd.
NOTE: The "l" at the left indicates "link." Note how the links point at their target files following the symbol ->. Note
that the symlinks are stored in your OS at the root level.
NOTE: If you wish to make a boot entry for the older kernel and initrd, you must use the symlinks for them,
vmlinuz.old and initrd.img.old.
If you use direct booting, you have to write out the exact kernel and initrd names:
linux /boot/vmlinuz-2.6.24-24-generic root=UUID= vb687f89-ggjd-6ach-7755-77241i4b4fk3 ro quiet splashinitrd /boot/initrd.img-2.6.24-24-generic
With symlinks, vmlinuz starts at root and points at vmlinuz-2.6.24-24-generic and initrd.img starts at root and
points at initrd.img-2.6.24-24-generic, so you can write more simply,
linux /vmlinuz root=UUID= vb687f89-ggjd-6ach-7755-77241i4b4fk3 ro quiet splash
initrd /initrd.img
However, to simplify this when you are in an emergency trying to boot at the GRUB prompt (grub>), do it this way:
Suppose this OS is Kubuntu 9.10 in (hd0,8) = sda8. Then you'd have
menuentry Kubuntu 9.10 on sda8, by symlinks {
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set root=(hd0,8)
linux /vmlinuz root=/dev/sda8 ro quiet splash
initrd /initrd.img
}
or even simpler, when you can't remember the kernel options "ro quiet splash":
menuentry Kubuntu 9.10 on sda8, by symlinks {
set root=(hd0,8)
linux /vmlinuz root=/dev/sda8initrd /initrd.img
}
(ro = Read-Only and is the default. Thanks to dibl for this information.)
NOTE about the paths
Notice the paths to the symlinks start at root / (since the symlinks are stored under root /); whereas the paths to the
actual kernel & initrd files start at /boot (since the kernel and initrd are stored under /boot)
Another Example
# Kubuntu 9.10 on sdb7 symlinks, normal modemenuentry Kubuntu 9.10 on sdb7, by symlinks {
set root=(hd1,7)
linux /vmlinuz root=/dev/sdb7 ro quiet splash
initrd /initrd.img
}
This is normal mode. If you want recovery mode (single user),
replace the kernel options ro quiet splash with ro single (without quotes)
>>> Direct booting
In direct booting, you use the actual kernel and initrd file names in the boot menuentry.NOTE
If you use direct booting at the GRUB CLI, ie., at grub> prompt, you may use TAB completion to make your job easier.
For example,
grub>linux /boot/
and you will get some choices, such as vmlinuz-2.6.24-24-generic
Example
# Kubuntu 8.04 on sdb3, direct booting
menuentry "Kubuntu 8.04 on sdb3, direct booting" {
set root=(hd1,3)
linux /boot/vmlinuz-2.6.24-24-generic root=UUID=db287e84-cbdd-4ca1-8745-85241a3b3fe2 ro quiet splashinitrd /boot/initrd.img-2.6.24-24-generic
}
>>> Chainloader booting
When you boot an OS by chainloading, you use the chainloader command to pass control of the booting from your
native GRUB to some other bootloader located in the MBR of a disk somewhere or in the
boot sector of a partition.
NOTE: For this to work, a bootloader must first be installed to the target MBR or a partition boot sector.
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A Linux example
menuentry Kubuntu 9.10 on sdb7, by chainloader {
set root=(hd1,7)
chainloader +1
}
"chainloader +1" says to go to sector 1 (of (hd1,7)) and turn control over to the bootloader found there.
For this example to work, a bootloader (e.g., GRUB 2) must be installed to the partition (hd1,7).To install GRUB 2 to the boot sector of partition sdb7 (=(hd1,7)):
sudo grub-install /dev/sdb7
This is another way to write the same boot entry:
menuentry Kubuntu 9.10 on sdb7, by chainloader {
chainloader (hd1,7)+1
}
Another Linux example
menuentry Drive sdc = hd2 by chainloader {
chainloader (hd2)+1}
If a bootloader (e.g., GRUB 2) has been installed to the Master Boot Record of drive sdc (= hd2), the menuentry will
boot that hard drive by turning control over to the bootloader in its MBR.
For this example to work, a bootloader (e.g., GRUB 2) must be installed to the Master Boot Record of drive sdc (=
hd2). To install GRUB 2 to the Master Boot Record of drive sdc:
sudo grub-install /dev/sdc
Example
Windows XP on sda1menuentry Windows XP on sda1, by chainloader {
set root=(hd0,1)
chainloader +1
}
Dedicated GRUB 2 Partition: How To Build It
Again, this is straightforward, much easier than in GRUB Legacy.
1 Create the GRUB 2 partition.
Create a partition to be used as your dedicated GRUB 2 partition and format it. I use GParted Live CD to do this. Atthat time, you may if you wish, again using GParted, set a Label on your partition; e.g., GRUB2 (without the
quotation marks) (in GParted, use Partition > Labels).
(Check the size of the /boot/grub folder to determine how big to make the partition. GRUB 2 files use just 572 KB
(96 files, including 12 old ones) on my installation.)
2 Create grub.cfg.
In your home directory, create a text file called grub.cfg and build your custom boot menu for the dedicated GRUB 2
partition. (For a sample, see below.)
(To create the text file, two ways: (1) Right-click on your Desktop, Create New > Text File; or (2) open text editor
Kate to an empty document by typing at Konsole kate and save it under the name grub.cfg in your home directory
only! To do this as root, use kdesudo kate, but that is not necessary at this point.)
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Caution: You may want to completely build your boot menu now and have it ready to go. To make your boot entries
in your grub.cfg, see the subsection above "4 Ways To Boot an OS."
3 Install GRUB 2 to the MBR.
From your Kubuntu OS, install GRUB 2 to the Master Boot Record (of your first BIOS boot drive) using GRUB 2 files
set up in your dedicated GRUB 2 partition.
Example
Suppose sdb1 is your dedicated GRUB 2 partition, and assume it is mounted as /media/sdb1 (or, if you set the label
GRUB2 on sdb1, this might be /media/GRUB2). And suppose you wish to install GRUB 2 to the MBR of sda which is
set in BIOS to be your first boot drive.Do it this way:
sudo grub-install root-directory=/media/sdb1 /dev/sda
See: http://grub.enbug.org/FranklinPiat/grub-install.manpage
(That will also build the directory /boot/grub for you in your GRUB 2 partition.)
4 As root, copy your grub.cfg from your home directory to the GRUB 2 partition under the folder /boot/grub. (To
do this in GUI, open your file manager as root and work from there; e.g., kdesudo konqueror or kdesudo dolphin.)
5 Set the boot flag on your dedicated GRUB 2 partition and re-boot to test it.
Set the boot flag on the dedicated GRUB 2 partition:
Do that using GParted either from your OS (K > System > Partition editor) or from the GParted Live CD. If you do itusing the GParted Live CD, you might go this way now:
After completing Step 4 (copying the grub.cfg file into the partition), put the GParted Live CD in the CD tray, let it be
recognized, re-boot into GParted Live, set the boot flag on your dedicated GRUB 2 partition (Partition > Manage
Flags), GParted > Quit, then double click GParted (large menu at top) to quit and re-boot, when prompted remove
the GParted Live CD, and let the PC re-boot (and it will now be using your dedicated GRUB 2 partition), and see if it
works.
CAUTION: Remember to keep Super Grub Disk live CD handy.
IMPORTANT NOTE ABOUT KERNEL UPDATES:
Using this method of building a dedicated GRUB 2 partition, YOU are in charge of the boot configuration file
/boot/grub/grub.cfg that is located in the GRUB 2 partition. The stuff we talked about above--/etc/default/grub andthe scripts /etc/grub.d and grub-mkconfig--does not apply. You must keep these two "shows" separate. Edit the
dedicated GRUB 2 file grub.cfg manually. If there ever is a problem, you may have to manually re-install GRUB 2 to
the MBR (of the first BIOS boot drive) from the dedicated GRUB 2 partition.
Example Here's my dedicated GRUB 2 /boot/grub/grub.cfg:
# grub.cfg
# This is my custom boot menu, called /boot/grub/grub.cfg, located in my dedicated Grub 2 partition sda1.
# Set the timeout
set timeout=10
# Set the default boot entry.
set default=0
# Kubuntu 9.10 on sda8 by chainload
menuentry "Kubuntu 9.10 on sda8, by chainload" {
chainloader (hd0,8)+1
}
# Kubuntu 9.10 on sda8 by configfile
menuentry "Kubuntu 9.10 on sda8, by configfile" {
configfile (hd0,8)/boot/grub/cfg
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}
# Kubuntu 9.10 on sda8 by symlink
menuentry "Kubuntu 9.10 on sda8, by symlink" {
set root=(hd0,8)
linux /vmlinuz root=/dev/sda8 ro quiet splash
initrd /initrd.img
}
# Kubuntu 8.04.3 on sda2, by configfilemenuentry "Kubuntu 8.04.3 on sda2, by configfile" {
configfile (hd0,2)/boot/grub.cfg
}
# sidux on sda3, by direct booting
menuentry "sidux on sda3" {
set root=(hd0,3)
linux /boot/vmlinuz-2.6.28-5.slh.3-sidux-686 root=UUID=306d94a5-107b-4c9e-ae03-a159e18dc1c7 ro quiet
vga=791
initrd /boot/initrd.img-2.6.28-5.slh.3-sidux-686
}
GRUB 2 Flashdrive (USB flash drive)
For the principles of installing GRUB 2, see the discussion under "Installing GRUB 2" and "The grub-install
Command."
Example
I used a 1 GB Kingston; the GRUB 2 files used just 51 MB.
Partition and format the flash drive as ext2 (using GParted Partition Editor). (You could also use FAT32 or ext3 or
some other filesystem.)Set the boot flag on the newly created partition (use GParted to do that: Partition > Manage Flags).
Exit GParted. Unplug the flashdrive, then plug it in.
In Kubuntu, to see how it is named, at Konsole run
sudo fdisk -lu
Output:
Disk /dev/sdb: 1031 MB, 1031798784 bytes
255 heads, 63 sectors/track, 125 cylinders, total 2015232 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0x000f0fe1
Device Boot Start End Blocks Id System
/dev/sdb1 63 2008124 1004031 83 Linux
Konqueror (or Dolphin) indicated it is mounted as /media/disk.
=> So it is seen as sdb with the partition sdb1 mounted as /media/disk.
Install GRUB 2 to the flash drive. At Konsole:
sudo grub-install --root-directory=/media/disk /dev/sdb
Output:
Installation finished. No error reported.
This is the contents of the device map /media/disk/boot/grub/device.map.
Check if this is correct or not. If any of the lines is incorrect,
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fix it and re-run the script `grub-install'.
(hd0) /dev/sda
(hd1) /dev/sdb
(This is the device.map on the flash drive, /boot/grub/device.map. I will ignore this! Doesn't matter too much. You
could edit it as root to read
(hd0) /dev/sda
as seen from the point of view of the flash drive when it is used as a boot drive.)
Let's move on, now ...
Check to see that /boot/grub is created and filled with GRUB 2 files.
Reboot, setting BIOS to boot from the flash drive (USB booting).
The next thing I saw on the screen was:
grub>
I used the GRUB 2 command ls to see my drives and partitions (on the PC):
grub>ls
Since the PC booted from the flash drive, it was seen as hd0 with partition (hd0,1). (The drive that the PC actually
boots from is always seen during its booting session as hd0--this is a general fact.)
My regular HDD, normally seen as hd0 was now seen as hd1 and my Kubuntu 9.10 was in (hd1,8).So, to boot into Kubuntu, I did
grub>chainloader (hd1,8)+1
grub>boot
NOTE:
Previously I had already installed GRUB 2 to the partition boot sector of Kubuntu in case I ever needed to chainload
into it. (I used at Konsole in Kubuntu, sudo grub-install /dev/sda8, where sda8 is my Kubuntu partition when there is
no other drive attached to the PC.) Had I not already done this, I could could NOT chainload into Kubuntu and would
have to boot into Kubuntu in some other way, for example using symlinks:
grub>ls
would show me that Kubuntu is on (hd1,8) when booting from my GRUB 2 flash drive, and so to boot it, I'd do:
grub>set root=(hd1,8)
grub>linux /vmlinuz root=/dev/sda8grub>initrd /initrd.img
grub>boot
Or, you could do this (if you remembered how!):
grub>set root=(hd1,8)
grub>linux /vmlinuz root=/dev/sda8 ro quite splash
grub>initrd /initrd.img
grub>boot
Thus, I booted into Kubuntu using the GRUB 2 flash drive.
Building a boot menu for the flash drive:
You can create a text file /boot/grub/grub.cfg for the flash drive exactly as demonstrated under building a DedicatedGRUB 2 Partition.
Technical Note: To do so, you will probably have to work as root, say by opening Konqueror or Dolphin as root
(kdesudo konqueror), or by opening Kate as root (kdesudo kate). However, you do not necessarily need a grub.cfg
on the flash drive. You can simply use it as I did to explore your drives and then boot into an OS. If you do build a
grub.cfg for it, you might include the OS(s) on your hard drive(s), and use the GRUB 2 flash drive to boot in
emergencies, as you would use Super Grub Disk. Just remember that from the point of view of the grub.cfg on your
flash drive, the other drives in your PC are shifted by 1 since upon booting the flash drive, it will be seen as hd0. If
adrian15 builds Super Grub Disk for GRUB 2 and includes his usbshift function, then the story changes--for the
principle of "USB drive shifting," see my how on building a GRUB flash drive:
-- How To Make GRUB Thumb Drive
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/etc/grub.d Folder of boot menu scripts:
00_header; 05_debian_theme: Background, text colors, themes
10_hurd Locates Hurd kernels; 10_linux Locates Linux kernels; 20_memtest86+
30_os-prober: Searches for Linux and other OS's on all partitions
40_custom: Template for custom boot menu entries
More: /boot/grub/device.map, boot.img (MBR), core.img
Fixing Things, Rescue
Ctrl+Alt+Del reboot PC; Super Grub Disk
New grub.cfg: sudo grub-mkconfig -o /boot/grub/grub.cfgInstall, re-install GRUB 2: sudo grub-install [INSTALL_DEVICE]
to MBR: sudo grub-install /dev/sdx; partition: sudo grub-install /dev/sdxn
If error: grub-install --recheck /dev/sdx; sudo grub-install --recheck /dev/sdxn
Install GRUB 2 to MBR of sda using GRUB 2 in /dev/sdb1/boot/grub:
sudo grub-install root-directory=/media/sdb1 /dev/sda
Install GRUB 2 to PC (/usr/lib/grub/i386-pc/): sudo apt-get install grub-pc
Live CD rescue: Re-install GRUB 2
sudo mkdir /media/sda2 /media/dev
sudo mount /dev/sda2 /media/sda2
sudo mount --bind /dev /media/dev
Install GRUB 2 to MBR of sdb [or to partition sda2] using GRUB 2 files in sda2:sudo grub-install --root-directory=/media/sda2 /dev/sdb [or /dev/sda2]
umount /media/sda2 /media/dev
Drives, partitions, information sudo fdisk -lu & grub>ls
Naming: (hdx,y) or sdzy: drive x starts at 0; partitions y start at 1
Konsole: sudo fdisk -lu; df -hT; mounting: cat /etc/mtab; or: mount
UUIDs: sudo blkid; ls /dev/disk/by-uuid/ -alh
Kernel ver: uname -r; cat /proc/version; Linux ver: lsb_release -a
sudo grub-emu and then grub>ls
GRUB devices/drives: grub>ls; grub>ls -al directory
UUID of (hdx,y): grub>ls (hdx,y)
Finding: grub>search /boot/grub/grub.cfg; grub>search /boot/grub/boot.img
Syntax, booting choices
configfile: set root=(hdx,y) and configfile /boot/grub/grub.cfg; or:
configfile (hdx,y)/boot/grub/grub.cfg
symlinks: linux /vmlinuz root=UUID= xxx ro quiet splash; initrd /initrd.img
symlinks: linux /vmlinuz root=/dev/sdxn ro quiet splash
chainload: set root=(hdx,y) and chainloader +1; chainloader (hdx,y)+1
chainload a MBR: chainloader (hdx)+1
Permissions
Executable: sudo chmod 744 /etc/grub.d/file; Remove: sudo chmod -x /etc/grub.d/file
Read only, everyone: sudo chmod 444 /etc/grub.d/fileGUI: kdesudo konqueror (dolphin), rt-click onfile, Properties, Permissions
grub.cfg: sudo chmod +w /boot/grub/grub.cfg; sudo chmod -w /boot/grub/grub.cfg
Create a script called /etc/grub.d/NN_myscript
Empty text doc: kdesudo kate; File > Save As /etc/grub.d/NN_myscript
Type it (see template below).
Make executable: sudo chmod 744 /etc/grub.d/NN_myscript
or, sudo chmod +x /etc/grub.d/NN_myscript
GUI: kdesudo konqueror (dolphin), rt-click, Properties, Permissions
Make new grub.cfg: sudo grub-mkconfig -o /boot/grub/grub.cfg
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> Template, custom boot entry for file /etc/grub.d/NN_name
#!/bin/sh
echo "Adding name" >&2
cat Save, Exit. New grub.cfg: sudo up-date grub; sudo grub-mkconfig
Flash drive /dev/sdc, sdc1 mounted at /media/disk; set boot flag; install GRUB 2:
sudo grub-install --root-directory=/media/disk /dev/sdc
Separate GRUB 2 partition: mounted at /media/sdb1; sda=MBR of 1st BIOS drive
sudo grub-install root-directory=/media/sdb1 /dev/sda
Working as root (8.10+: kdesudo; 8.04: kdesu)
kdesudo kate /path-to-file; kdesudo konqueror (or dolphin)
Terminal as root: sudo i; sudo su
GUI file manager, navigate to file, right-click on file, Actions, Edit as Root.
sudo [COMMAND]; sudo grub-install [INSTALL_DEVICE];
sudo grub-mkconfig -o /boot/grub/grub.cfg
[End of GRUB 2 Practical Reminders]
= = = = = = = = = = = = = = = = = = = =
= = = = = = = = = = = = = = = = = = = =
Appendix: Techniques
--- Installing Kubuntu--GRUB 2 placement
--- Working as root
--- Permissions: read, write, execute; change the execute bit
--- Chroot -- how to
See Part 3 of Commands at Konsole: Beginners: 3 parts
http://kubuntuforums.net/forums/index.php?topic=3091607.0
= = = = = = = = = = = = = = = = = = = =
Installing Kubuntu--GRUB 2 placement
Live CD method
The Live CD method of installing Kubuntu is easy, fast, and convenient because afterwards, you then have a Live CD
to use for rescue and repair of your system.
Installing GRUB 2 files
GRUB 2 is standard on Kubuntu starting with 9.10. During its installation from the Live CD, you can specify if you
want GRUB 2installed, and if so, where to put it. Here's how:
Start the Live CD installer.
Step: Disk Setup
"Specify Partitions Manually"
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Step: Summary
Advanced button at lower right
Check or un-check to install GRUB 2 bootloader
Choose from the drop-down list where to install GRUB 2
sda = the MBR of drive sda
sda1 = the first partition of drive sda
sdb = the MBR of drive sdb
etc.
Caution:
> If you install GRUB to a MBR (sda, sdb, sdc, etc.), it will overwrite any other bootloader already installed to that
MBR, and the GRUB 2 from the OS you are currently installing will then control the boot menu you see when you
boot up your PC. That is OK, just so you know.
> If you install GRUB 2 to the partition boot sector where you are currently installing the OS (e.g., sdan, for some
n=1,2,3,4...), when you re-boot your PC, you will have to manually boot into your new OS you just installed. Do so
using chainloader, as follows:
-- Re-boot
-- If you get some boot menu (from a prior Linux OS installation), press the "c" key to get a GRUB prompt, grub>. If
you don't get a boot menu but only the GRUB prompt grub>, then that's OK, too.
-- Let's say your new Kubuntu OS was installed to sda9. That is the same as (hd0,9). Thengrub>chainloader (hd0,9)+1
grub>boot
and you will boot into your new OS.
Building new boot menus
> In your new OS, you can build a full boot menu simply by doing sudo grub-mkconfig -o /boot/grub/grub.cfg.
> In your existing OSs, you can re-build boot menus to include the new OS the same way:
Konsole
sudo grub-mkconfig -o /boot/grub/grub.cfg
> Worst case, if for some reason that doesn't work, you can make a custom boot entry to include your new OS. See
SECTION 4. To get the details of the menuentry for the new OS for the existing grub.cfg, you might have to boot
into the new OS and copy details from its grub.cfg. Or, simply boot your new OS using symlinks or chainloader (from
another OS's boot menu), for which you do not need any details specific to the new OS. See SECTION 4, "4 Ways to
boot an OS."
= = = = = = = = = = = = = = = = = = = =
Working as root
Opening a text editor (e.g., Kate, Kwrite, etc.) to see the file and/or to edit it:
kdesudo kate path-to-file
Example: kdesudo kate /etc/fstab
Opening an empty text document as root:
kdesudo kate
(then File > Save As)
Opening a file manager as root:
in 8.10 and after: kdesudo konqueror (or dolphin)
in 8.04: kdesu konqueror (dolphin)
Opening a terminal as root:
sudo i (to get a root terminal)
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http://www.gnu.org/software/grub/grub-2.en.html
GNU GRUB, main site, Legacy GRUB
http://www.gnu.org/software/grub/
GRUB Wiki: grub.cfg
http://grub.enbug.org/grub.cfg
GRUB 2 Commands, GRUB Wiki
http://grub.enbug.org/CommandListCompares GRUB Legacy to GRUB 2 commands.
GRUB 2: Live CD Install Guide
http://grub.enbug.org/Grub2LiveCdInstallGuide
StartUp-Manager
https://help.ubuntu.com/community/StartUpManager
GRUB & GRUB 2 Boot Process
http://www.pixelbeat.org/docs/disk/
Bootloaderhttp://en.wikipedia.org/wiki/Boot_loader
GNU GRUB
http://en.wikipedia.org/wiki/GRUB
Boot Options
https://help.ubuntu.com/community/BootOptions
Kernel Parameters
http://www.kernel.org/doc/Documentation/kernel-parameters.txt
Grub Legacy-- How To GRUB Methods - Toolkit
http://kubuntuforums.net/forums/index.php?topic=3081671.0
GParted Live CD
http://gparted.sourceforge.net/livecd.php
For partitioning, formatting your hard drive.
Super Grub Disk
http://www.supergrubdisk.org/
Will boot you into your OS when you can't do it alone.
Arch Linux, ArchWiki GRUB 2http://wiki.archlinux.org/index.php/GRUB2
Experiences in the Community, Jaunty and GRUB2
http://flossexperiences.wordpress.com/2008/11/19/jaunty-and-grub2/
GRUB 2 installation
http://www.techenclave.com/guides-and-tutorials/grub-2-installation-92883.html
GRUB2 Theming
http://ubuntuforums.org/showthread.php?t=1182436
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KernelTeam/Grub2Testing
https://wiki.ubuntu.com/KernelTeam/Grub2Testing
Using UUID
https://help.ubuntu.com/community/UsingUUID
BIOS Boot Partition, and what does GRUB use it for?
http://grub.enbug.org/BIOS_Boot_Partition
GUID Partition Tablehttp://en.wikipedia.org/wiki/GUID_Partition_Table
Technical Note TN2166, Secrets of the GPT
http://developer.apple.com/mac/library/technotes/tn2006/tn2166.html
HOWTO: Booting LiveCD ISOs from USB flash drive with Grub2, by JustRon.
http://ubuntuforums.org/showthread.php?t=1288604
Booting LiveCD from HD ISO
http://ubuntuforums.org/showthread.php?t=1295506
Boot an iso via Grub 2http://michael-prokop.at/blog/2009/05/25/boot-an-iso-via-grub2/
MultiBoot USB with Grub2 (boot directly from iso files)
http://www.panticz.de/MultiBootUSB
GRUB Graphical Menu Development Journal
http://grub.gibibit.com/Journal
Debian Wiki, GRUB, grub.cfg
http://wiki.debian.org/Grub/grub.cfg.manpage
As of 9-9-09, it doesn't exist.
Tweaking GRUB 2
http://www.drlock.com/blog/2008/07/11/tweaking-grub-2/
GRUB 2 configuration, shirish
http://www.techenclave.com/guides-and-tutorials/grub-2-configuration-93512.html
How To Install GRUB 2 On Ubuntu 9.04
http://www.linuxtoday.com/news_story.php3?ltsn=2009-09-02-005-35-OS-HL-SM