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Introduzione

Grub 2(GRand Unified Bootloader, versione 2) è la seconda versione di GNU Grub. È l'applicazione responsabile del caricamento e del trasferimento del controllo al kernel del sistema operativo durante la fase iniziale di boot.

Grub 2 è una completa riscrittura dell'interfaccia di Grub. Basato sul progetto di ricerca PUPA, Grub 2 è più modulare e portabile del suo predecessore. Alcuni miglioramenti includono:

• un'interfaccia grafica, con predisposizione all'utilizzo di temi;
• caricamento modulare;
• compatibilità multi-piattaforma;
• supporto all'utilizzo di script;
• revisione dei nomi delle partizioni.

Anchor(installazione)

Installazione e aggiornamento

Anchor(installazione_9.10)

Ubuntu 9.10 «Karmic Koala»

Grub 2 è installato di predefinito su Ubuntu 9.10. Se si ha aggiornato il proprio sistema dalla versione Ubuntu 9.04 è necessario seguire le istruzioni del [#installazione_9.04 capitolo successivo].

Anchor(installazione_9.04)

Ubuntu 9.04 «Jaunty Jackalope»

1. [:AmministrazioneSistema/InstallareProgrammi:Installare] il pacchetto [apt://grub2 grub2].

2. Selezionare Ok nel menu di configurazione di grub-pc.

3. Alla domanda «Effettuare il caricamento in cascata da menu.lst?» rispondere Sì.

4. A «Riga di comando Linux» premere Invio.

Per rendere le modifiche permanenti, eseguire la seguente procedura.

1. Da riga di comando digitare:

   sudo upgrade-from-grub-legacy

Nel caso in cui sia stato visualizzato un dispositivo di memoria di massa diverso dal proprio, qui ad esempio:

(hd0)   /dev/sda

è necessario modificare con un [:Ufficio/EditorDiTesto:editor di testo] e con i [:AmministrazioneSistema/Sudo:privilegi di amministrazione] il file /boot/grub/device.map. Successivamente digitare da riga di comando:

sudo grub-install

Grub 2 è ora installato. Il suo predecessore (Grub legacy) rimosso e fatto un backup dei suoi file di configurazione nella cartella /boot/grub con il nome di menu.lst*.

È possibile verificare la versione di Grub attualmente installata sul sistema digitato da riga di comando:

grub-install -v

Grub 2 Files & Folders

While the main grub bootloader file continues to reside in the /boot/grub folder, it is no longer Grub's familiar menu.lst. The main Grub 2 instruction file is now grub.cfg. This file is produced by various scripts run when either the "update-grub" or "update-grub2" command is executed. The files primarily responsible for the content of grub.cfg are /etc/default/grub and individual script files located in /etc/grub.d/

Many of the files in /boot/grub will not be familiar to users of Grub Legacy. Especially noticeable are the multitude of *.mod files in the /boot/grub folder. Grub 2 is modular and the *.mod files are loaded as necessary by grub. Despite the addition of these files, the total size of the /boot/grub contents is fairly close to that of Grub Legacy and should not require a larger /boot partition.

grub.cfg (/boot/grub/grub.cfg)

• grub.cfg is automatically generated or updated whenever "update-grub" or "update-grub2" is executed. The command must be run as root.

• The scripts used to generate grub.cfg include the files contained in /etc/grub.d and information gathered from /etc/default/grub

• The file is divided into sections. Each section of the file is clearly delineated and is recognizable by the section header ### BEGIN. The information on this line references the file in the /etc/grub.d folder which is used to incorporate the information into grub.cfg

• By default, and whenever the "update-grub2" command is executed, this file is made read-only. This is in keeping with the intent that the file should not be edited manually. If you must edit this file, instructions are provided later on this page.

• Sample grub.cfg including two Ubuntu kernels, memtest86+, Windows and a custom entry (41_srcd) imported from an /etc/grub.d/ script:

• #
  # DO NOT EDIT THIS FILE
  #
  # It is automatically generated by /usr/sbin/update-grub using templates
  # from /etc/grub.d and settings from /etc/default/grub
  #
  
  ### BEGIN /etc/grub.d/00_header ###
  set default=0
  set timeout=5
  set root=(hd0,5)
  search --fs-uuid --set b02e1934-12dd-418a
  if font /usr/share/grub/ascii.pff ; then
    set gfxmode=640x480
    insmod gfxterm
    insmod vbe
    terminal gfxterm
  fi
  ### END /etc/grub.d/00_header ###
  
  ### BEGIN /etc/grub.d/05_debian_theme ###
  set menu_color_normal=cyan/blue
  set menu_color_highlight=white/blue
  ### END /etc/grub.d/05_debian_theme ###
  
  ### BEGIN /etc/grub.d/10_hurd ###
  ### END /etc/grub.d/10_hurd ###
  
  ### BEGIN /etc/grub.d/10_linux ###
  set root=(hd0,5)
  search --fs-uuid --set b02e1934-12dd-418a-be3a-9ff7d3e7e7ea
  menuentry "Ubuntu, linux 2.6.28-13-generic" {
          linux   /boot/vmlinuz-2.6.28-13-generic root=UUID=b02e1934-12dd-418a ro  quiet splash vga800
          initrd  /boot/initrd.img-2.6.28-13-generic
  }
  menuentry "Ubuntu, linux 2.6.28-13-generic (single-user mode)" {
          linux   /boot/vmlinuz-2.6.28-13-generic root=UUID=b02e1934-12dd-418a ro single 
          initrd  /boot/initrd.img-2.6.28-13-generic
  }
  menuentry "Ubuntu, linux 2.6.28-11-generic" {
          linux   /boot/vmlinuz-2.6.28-11-generic root=UUID=b02e1934-12dd-418a ro  quiet splash vga800
          initrd  /boot/initrd.img-2.6.28-11-generic
  }
  menuentry "Ubuntu, linux 2.6.28-11-generic (single-user mode)" {
          linux   /boot/vmlinuz-2.6.28-11-generic root=UUID=b02e1934-12dd-418a ro single 
          initrd  /boot/initrd.img-2.6.28-11-generic
  }
  ### END /etc/grub.d/10_linux ###
  
  ### BEGIN /etc/grub.d/20_memtest86+ ###
  menuentry "Memory test (memtest86+)" {
          linux   /boot/memtest86+.bin
  }
  menuentry "Memory test (memtest86+, serial console 115200)" {
          linux   /boot/memtest86+.bin console=ttyS0,115200n8
  }
  ### END /etc/grub.d/20_memtest86+ ###
  
  ### BEGIN /etc/grub.d/30_os-prober ###
  menuentry "Microsoft Windows XP Home Edition (on /dev/sda1)" {
          set root=(hd0,1)
          chainloader +1
  }
  ### END /etc/grub.d/30_os-prober ###
  
  ### BEGIN /etc/grub.d/40_custom ###
  # This file is an example on how to add custom entries
  
  ### END /etc/grub.d/40_custom ###
  
  ### BEGIN /etc/grub.d/41_srcd ###
  menuentry "SystemRescue CD on hard drive" {
          set root=(hd0,10)
          linux   /sysrcd/rescuecd subdir=sysrcd setkmap=us
          initrd  /sysrcd/initram.igz
  } 
  ### END /etc/grub.d/41_srcd ###

grub (/etc/default/grub)

This file contains information previously found in the upper section of /boot/grub/menu.lst. It contains settings primarily affecting Grub's menu display. This file can be edited by root to make changes to these settings; they will be imported into grub.cfg when "update-grub2" is executed.

• # If you change this file, run 'update-grub' afterwards to update
  # /boot/grub/grub.cfg.
  
  GRUB_DEFAULT=0
  GRUB_HIDDEN_TIMEOUT=0
  GRUB_HIDDEN_TIMEOUT_QUIET=true
  GRUB_TIMEOUT=10
  GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
  GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
  GRUB_CMDLINE_LINUX=""
  
  # Uncomment to disable graphical terminal (grub-pc only)
  #GRUB_TERMINAL=console
  
  # The resolution used on graphical terminal
  # note that you can use only modes which your graphic card supports via VBE
  # you can see them in real GRUB with the command `vbeinfo'
  #GRUB_GFXMODE=640x480
  
  # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
  #GRUB_DISABLE_LINUX_UUID=true
  
  # Uncomment to disable generation of recovery mode menu entrys
  #GRUB_DISABLE_LINUX_RECOVERY="true"
  
  
  
  This file contains information formerly contained in the upper section of Grub Legacy's ''menu.lst'' and items contained on the end of the kernel line. The items in this file can be edited by a user with administrator (root) privileges. Grub developers have have placed explanatory comments within the file itself.

• GRUB_DEFAULT=0

  • Sets the default and pre-selected menu entry. Entries may be numeric or saved

  • GRUB_DEFAULT=0

    • Sets the default menu entry by menu position. As with Grub Legacy, the first "menuentry" in grub.cfg is 0, the second is 1, etc.

  • GRUB_DEFAULT=saved

    • Sets the default menu entry with whatever was selected on the last boot. If the menu is displayed during boot, the previously selected option will be highlighted. If no action is taken, this is selection which will be booted at the end of the timeout, or if the menu is hidden.

• GRUB_TIMEOUT=5

  • No change from Grub Legacy. This is the number of seconds before the default entry is automatically booted.

  • Setting a value of -1 will display the menu until the user makes a selection (no timeout).

• GRUB_HIDDEN_TIMEOUT=0

  • The menu will be hidden unless a # symbol is present at the beginning of this line. ( # GRUB_HIDDEN_TIMEOUT=0 )

  • The default setting initially depends on the presence of other operating systems.
    • Another OS Detected: The menu will be displayed. ( The line will begin with a # symbol. )
    • No other OS Detected: The menu will be hidden.
  • For integers greater than 0, the system will pause, but not display the menu, for the entered number of seconds.
  • 0 The menu will not be displayed. There will be no delay.
    • When this entry is set to 0:
      • The user may force displaying the menu as the computer boots by holding down the SHIFT key.
        • During boot, the system will check the SHIFT key status. If it cannot determine the key status, a short delay will enable the user to display the menu by pressing the ESC key.
      • If enabled, the splash screen designated in 05_debian_theme will be displayed even if the hidden menu feature is selected.

• GRUB_HIDDEN_MENU_QUIET=true

  • true - No countdown is displayed. The screen will be blank.
  • false - A counter will display on a blank screen for the duration of the GRUB_HIDDEN_TIMEOUT value.

• GRUB_DISTRIBUTOR=lsb_release -i -s 2> /dev/null || echo Debian

  • Determines the descriptive name in the menu entry. (Ubuntu, Xubuntu, Debian, etc.)

• GRUB_CMDLINE_LINUX

  • If it exists, this line imports any entries to the end of the linux command line (Grub Legacy's "kernel" line) for both normal and recovery modes. This is similar to the "altoptions" line in menu.lst

• GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

  • This line imports any entries to the end of the 'linux' line (Grub Legacy's "kernel" line). The entries are appended to the end of the normal mode only. This is similar to the "defoptions" line in menu.lst. If you want a black screen with scrolling boot messages, remove "quiet splash". If you want a grub splash screen with limited messages underneath the Ubuntu logo, use only "splash". < This [only "splash"]will not work in Karmic during boot as the xsplash does not display the messages , but the messages at shutdown will be displayed.

• #GRUB_TERMINAL=console

  • Uncomment to disable graphical terminal (grub-pc only).

• #GRUB_DISABLE_LINUX_UUID=true

  • Uncomment this line if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux.

• GRUB_DISABLE_LINUX_RECOVERY=true

  • Add or uncomment this line to prevent "Recovery" mode kernel options from appearing in the menu.

• GRUB_DISABLE_OS_PROBER=true

  • Enables/disables the os-prober check of other partitions for operating systems, including Windows, Linux, OSX and Hurd.

/etc/grub.d/ (folder)

The files in this folder are read during execution of '"update-grub2"'command. The scripts in these files export the information they gather into /boot/grub/grub.cfg

The files are run in sequential order - files with names starting with a numeral are run first, followed by files whose name begins with a letter. The order the file is run determines the location of items in the grub menu.

Custom entries can be added to the 40_custom file or placed in a new file.

Any file created must be executable in order to be included in the grub.cfg file during the "update-grub2" command. This can be accomplished from the terminal with "sudo chmod u+x /etc/grub.d/filename". The following is a very brief look at what the files accomplish.

• 00_header

  • Loads settings from /etc/default/grub, including visual presentations, timeout, and terminal options.

• 05_debian_theme

  • Sets background, text colors, and themes.

• 10_hurd

  • Locates hurd kernels.

• 10_linux

  • Locates kernels based on the distributor determined by the "lsb_release -i -s" results ("Ubuntu").

• 20_memtest86+

  • If the file /boot/memtest86+.bin exists, it is included as a menu item.

• 30_os-prober

  • Searches for other OS's and includes them in the menu.

• 40_custom

  • A template for adding custom menu entries which will be inserted into grub.cfg upon execution of the "update-grub2" command. This and any other custom files must be made executable to allow importation into grub.cfg. These files are placed in the Grub menu in the numerical order of the file name.

Adding Entries to Grub 2

grub.cfg is updated when update-grub or update-grub2 is run. Changes to grub.cfg should be made to the appropriate script files and not to the grub.cfg file itself.

NOTE: The first comment in grub.cfg is "DO NOT EDIT THIS FILE". The file is read-only and is returned to this status anytime update-grub is run.

Automatic Entries

• When "update-grub" is executed, Grub 2 will read /etc/default/grub and the files in contained in the /etc/grub.d folder. This combination will set the visual parameters of the grub menu (/etc/default/grub) and search for linux kernels, other operating systems, and items designated in user-created scripts in /etc/grub.d. The script files in /etc/grub.d perform the following tasks:

  • 10_linux searches for installed linux kernels.

  • 30_os-prober searches for other operating systems.

  • 40_custom and any other user-created files in the /etc/grub.d folder add menu items designated in the script files created by users.

• The name of the file determines the order in the menu. 30_os-prober entries will be placed before 40_custom entries, which will be placed before any higher-numbered entries.

• Any user-created file must be made executable. This can be done as root by running

sudo chmod u+x /etc/grub.d/filename

User-defined Entries

Users with "root" privileges can create scripts in the /etc/grub.d/ folder which will be incorporated into the grub.cfg file when update-grub is run.

• The filename should normally take the format XX_name, with XX being a number followed by an underscore and name.

• The order the entry appears on the grub menu is based on numerical ordering of the files in /etc/grub.d. Executable files in the /etc/grub.d folder beginning with an alphabetic character are placed in order following numerical entries.

• The file must be made executable by typing in a terminal

sudo chmod +x /etc/grub.d/'''filename'''

• A sample custom entry. This file creates menu items for running a SystemRescueCD installation on sdb10 and a custom kernel on sda1.

NOTE: The new partition naming convention. Devices start counting from 0 as done previously. sda is designated as "hd0", sdb is "hd1", etc. However the first partition is now designated as sda1. Counting partitions does not start with "0". The fifth partition on sda is sda5).

• echo "Adding Custom Kernel & SystemRescue" >&2
  cat << EOF
  menuentry "Ubuntu, linux 2.6.31-11-custom" {
          set root=(hd0,9)
          linux /boot/vmlinuz-2.6.31-11-custom root=UUID=c6829e27-2350-4e84-bdbb-91b83f018f98 ro 
          initrd /boot/initrd.img-2.6.28-11-generic
  }
  
  menuentry "Boot SystemRescue CD from hard drive" {
          set root=(hd1,10)
          linux   /sysrcd/rescuecd subdir=sysrcd setkmap=us
          initrd  /sysrcd/initram.igz
  } 
  EOF

• The line "echo "Adding SystemRescueCD" >&2" is not required. Including it in the file allows this line to be seen in the terminal when "update-grub2" is executed. It provides visual feedback that the entry has been found and entered. The entry, if in the correct format, will be inserted in grub.cfg whether or not this line is included in the file.

• Manual Editing of grub.cfg

  • If you must edit this file:

    sudo chmod +w /boot/grub/grub.cfg  # Remove 'read-only', necessary even for "root"
    sudo nano /boot/grub/grub.cfg      # Edit as "root"

  • Note: This file is returned to 'read-only' status and user inputs are overwritten anytime the "update-grub" command is run.

Removing Entries from Grub 2

Entries should be removed by editing or removing files in the /etc/grub.d folder. The /boot/grub/grub.cfg file is read-only and should not normally be edited directly.

• Automatically.

  • Kernels removed by Synaptic will automatically update grub.cfg and no user action is required.

  • Other operating systems which have been removed from the computer will also be removed from the menu once "update-grub2" is run as root.

• Manually.

  • To prevent a file in /etc/grub.d from adding items to the menu, remove the executable bit or remove the applicable file.

  • memtest86+: If you don't want to have memtest86+ displayed in your menu, run sudo chmod -x /etc/grub.d/20_memtest86+. The file will remain but will not be acted upon by update-grub.

  • Recovery mode: If you don't want Recovery mode entries for your linux kernels, edit /etc/default/grub and add this line:

    • GRUB_DISABLE_LINUX_RECOVERY=true

  • If a custom script in the /etc/grub.d/ folder contains multiple menu entries, individual items may be removed and others retained.

  • Tip: If the user wants his custom entries to appear at the top of the menu, the file can be named a value less than "10_linux", such as "07_custom". Check that the "DEFAULT" value in /etc/default/grub points to the correct menuentry after making this change.

  • Changes will not take effect on the Grub 2 menu until "update-grub" is run to update grub.cfg

Theming

As of version 1.96 of GRUB 2, theme support is not enabled

The GRUB graphical menu supports themes that can customize the layout and appearance of the GRUB boot menu. The theme is configured through a plain text file that specifies the layout of the various GUI components (including the boot menu, timeout progress bar, and text messages) as well as the appearance using colors, fonts, and images.

Take a look at this thread on Grub 2 Themeing

Splash Images

This is Colin Bennett's Google Summer of Code project. The GRUB 2 graphical menu project aims to create a highly customizable graphical menu system for the GNU GRUB bootloader.

Great link here.

Background Colors/Image

Background colors and images are configured in a script located in /etc/grub.d/ if you look in there you will find a file called 05_debian_theme which is the default color scheme for GRUB 2. Now to create your own color scheme you have a few options, you can copy and edit the default 05_debian_theme or create your own script.

All the files in /etc/grub.d/ are run in order, so if you have 2 theme files, 05_debian_theme and 06_mytheme, the latter (06_mytheme) will be run last, which will be the background you see.

Copy/Edit Default Colors

• Copy the default color theme

$ sudo cp /etc/grub.d/05_debian_theme /etc/grub.d/05_debian_theme.BACKUP
$ sudo nano /etc/grub.d/05_debian_theme

• Now you can edit the file to your hearts content.

Create a new theme file

• Create the new theme file

$ sudo nano /etc/grub.d/06_mytheme

• Now you can put whatever you want in here

Commands

As GRUB 2 has been totally re-written, there are now some commands you might be used to in GRUB legacy that don't exist in GRUB 2. Take a look at the Grub 2 Command's List here.

SHIFT now allows you to interrupt 'sleep --interruptible', for consistency with the quick-boot scheme.

Recover Grub 2 via LiveCD

• First, grab a copy of the latest Ubuntu LiveCD and boot it.

• Open a terminal and type

$ sudo fdisk -l

• Now, you need to remember which device listed is your linux distribution, for reference, /dev/sda1 will be used. Now we need to mount the filesystem to /mnt

$ sudo mount /dev/sda1 /mnt

• If you have /boot on a separate partition, that need's to be mounted aswell. For reference, /dev/sda2 will be used.

$ sudo mount /dev/sda2 /mnt/boot Make sure you don't mix these up, pay attention to the output of FDISK

• Now mount the rest of your devices

$ sudo mount --bind /dev /mnt/dev

• Now chroot into your system

$ sudo chroot /mnt

You should be chroot'd into your system as root, you can now run commands as root, without the need for sudo.

• Now you need to edit the /etc/default/grub file to fit your system

$ nano /etc/default/grub

• When that is done you need to run update-grub to create the configuration file.

$ update-grub

• To install GRUB 2 to the MBR, next you need to run grub-install /dev/sda

$ grub-install /dev/sda

• If you encounter any errors, try grub-install --recheck /dev/sda

$ grub-install --recheck /dev/sda

• Press Ctrl+D to exit out of the chroot.
• Once you exit back to your regular console, undo all the mounting, first the /dev

$ sudo umount /mnt/dev

• Now you can unmount the root system

$ sudo umount /mnt

• And you should be free to restart your system right into GRUB 2 and then into your system installation.

Errors

Where did my Grub2 boot menu go!?!?!

According to an email that was sent out today Monday, August 10, 2009 with the newest Grub2 update, the boot menu is hidden by default now. It's easy to get it back, just edit /etc/default/grub and comment out GRUB_HIDDEN_TIMEOUT

$ sudo nano /etc/default/grub

Make your timeout line look like this...

#GRUB_HIDDEN_TIMEOUT=3
GRUB_TIMEOUT=XXX        <---Make sure you put in a timeout value here.

Save the file and exit, then run...

$ sudo update-grub

Dual-booting

Following this thread on the forums, users have seemed to come up with a Karmic work around for fixing your dual-boot problems...

$ sudo apt-get install --reinstall libdebian-installer4
$ sudo os-prober
$ sudo update-grub

--no-floppy

It seems after an update yesterday Monday June 22, 2009 that some users are experiencing a --no-floppy error. There is a simple workaround to this. Check out this thread

• Edit your boot command with E

• Remove all entries of --no-floppy

• Boot into Ubuntu and backup your GRUB 2 configuration

$ sudo cp /etc/grub/grub.cfg /etc/grub/grub.cfg.backup

• Then edit your configuration

$ sudo nano /etc/grub/grub.cfg

• Delete all entries of --no-floppy

unkown command 'initrd'

This error came after upgrading from Jaunty 9.04 to Karmic 9.10 on June 23, 2009. The work around was to remove the search line from the boot line. Take a look here and notice the search --fs-uuid line and remove it.

• Press E to edit your boot line

• Remove the search --fs-uuid line completely

• Press Ctrl-C to enter the GRUB command line

• Type in insmod linux and press ENTER

• Press ESC to go back

• CTRL-X to boot

Once you get into your system you need to re-install grub to your device, mine was sda

• sudo grub-install /dev/sda

This fixed the problem and now booting is back to normal.

sleep 'invalid number 0.1'

***Fix released June 24, 2009***

Floating sleeps was built in, but not configured in the newest version of busybox, here's the fix.

• Add dupondje's PPA

deb http://ppa.launchpad.net/dupondje/ppa/ubuntu karmic main
deb-src http://ppa.launchpad.net/dupondje/ppa/ubuntu karmic main

• Update & Upgrade

$ sudo apt-get update && sudo apt-get upgrade

• Update initramfs

$ sudo update-initramfs -uk all

Error 11

After upgrading from GRUB Legacy

Error 11: Unrecognized device string...

• press any key to continue
• highlight "Chainload into GRUB 2"
• press e
• highlight "root xxxxxxxxxxxxxxxxxxxx"
• press e
• change "root xxxxxxxxxxxxxxxx" to "uuid xxxxxxxxxxxxxxxxxx"
• press b to boot "uuid xxxxxxxxxxxxxxxxxxx"
• load your kernel and press enter

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