Question | Answer |
Is a utility that boots a Linux Kernel,or any other OS | The Grand Unified Boot Loader (GRUB) |
GRUB has 2 stages: | 1. Stage 1 is the info stored in the MBR - holds location of the boot information
2. Stage 2 is the OS software located on the Boot Patition |
GRUB uses a menu to: | allow a user to select between multiple OSs |
If no menu selection is made GRUB loads a: | Default OS after a specified time |
GRUB creates a: | GRUB root using the /boot directory -GRUB root contains the installed STAGE 2 files |
To install GRUB use command: | grub-install |
grub-install Example: To install GRUB on the second hard drive | grub-install --root-directory=/boot sd1 |
GRUB uses one of the following configuration files: | /boot/grub/menu.lst - (Suse)
/boot/grub/grub.conf - Fedora |
Common options in the GRUB configuration file; Specify the OS that boots as DEFAULT | default
default=0 boots the first OS in the menu
default=Fedora - boots the OS with Fedora as the title |
Common options in the GRUB configuration file; Set the number of seconds GRUB waits before automatically booting the default OS | timeout |
Common options in the GRUB configuration file; Specify the image file which is displayed for the Graphical Boot MENU | gfxmenu splashimage
Example: splashimage=(hd0,0)/grub/splash.xpm.gz |
Common options in the GRUB configuration file; Disable/Enable the menu that lists the OSs | hiddenmenu |
Displays the available operating systems | #hiddenmenu |
Common options in the GRUB configuration file: Specify the title a user sees in the menu | title |
Common options in the GRUB configuration file: specify the location of the root file system | root
Example: root (hd0,0) - = First partition of first hard drive |
Common options in the GRUB configuration file: Specify the kernel for the entry and kernel options | kernel
Example: kernel /vmlinuz-2.6.33.3-85.fc13.i686 |
Common options in the GRUB configuration file: Specifies the initial RAM disk (initrd image) file( the image that should be used) | initrd /vmlinuz-2.6.33.3-85.fc13.i686 |
Common options in the GRUB configuration file: Specify the number of SECTORS to be read | chainloader |
Common options in the GRUB configuration file: Prevent unauthorized boot of the OS (when set, Password is required | lock |
Common options in the GRUB configuration file: requires authentication for the options in the GRUB menu | password |
To Create an encrypted password - Requires users to have authentication for options in the GRUB menu: | 1. Type grub-md5-crypt in shell prompt
2. When prompted type and confirm password and copy the hashed output
3. Type password -md5 hashed o/p in GRUB configuration file |
Updated version of GRUB - any version of GRUB 1.98 or later | GRUB2 |
GRUB2 configuration file -do not edit directly | /boot/grub/grub.cfg |
Command to update /boot/grub/grub.cfg | update-grub |
Files update-grub uses to generate (update)the /boot/grub/grub.cfg file | 1. /etc/defualt/grub
2. /etc/grub.d/ |
Directory that holds scripts that are read by update-grub to generate the /boot/grub/grub.cfg file | /etc/grub.d |
Primary configuration file for changing GRUB2 menu display settings | /etc/defualt/grub |
Script files in /etc/grub.d/ directory: Sets initial appearance items such as Grapics Mode, Default Selection, Timeout -settings typically imported from /boot/grub/grub.cfg | 00_header |
Script files in /etc/grub.d/ directory: Sets GRUB2 background images, text colors, selection highlighting, and themes | 05_debian_theme |
Script files in /etc/grub.d/ directory: Identifies kernels on the root device for the OS in use and creates menu entries | 10_linux |
Script files in /etc/grub.d/ directory: Executes os-prober to search for other OSs (Windows, Linux etc) and lace teh results in the GRUB2 menu | 30_os-prober |
Script files in /etc/grub.d/ directory: Allows for CUSTOM menu entries which are imported directly into /boot/grub/grub.cfg without any changes | 40_custom |
/etc/default/grub configuration Options: Sets the default menu entry | GRUB_DEFAULT |
/etc/default/grub configuration Options: Automatically sets the LAST selected OS from menu as the default OS on next boot | GRUB_SAVEDEFAULT
GRUB_SAVEDEFAULT=true |
/etc/default/grub configuration Options: Determines how long a screen will be displayed | GRUB_HIDDEN_TIMEOUT
GRUB_HIDDEN_TIMEOUT=3 |
/etc/default/grub configuration Options: Displays a counter (if =false) for duration specified in GRUB_HIDDEN_TIMEOUT | GRUB_HIDDEN_TIMEOUT_QUITE |
/etc/default/grub configuration Options: Determines how long to wait for user interaction before booting into the default OS | GRUB_TIMEOUT |
/etc/default/grub configuration Options: Adds entries to the end of the 'linux' command line for both normal and recovery modes | GRUB_CMDLINE-LINUX |
/etc/default/grub configuration Options: Sets the RESOLUTION of the graphical menu | GRUB_GFXMODE |
/etc/default/grub configuration Options: Plays a single beep prior to GRUB2 menu display | GRUB_INIT_TUNE |
/etc/default/grub configuration Options: Sets the BACKGROUND image during the GRUB2 menu display (use full file path) | GRUB-BACKGROUND
GRUB-BACKGROUND=/usr/share/image/back.png |
/etc/default/grub configuration Options: Enables/Disables the os-prober check of other partitions for OSs | GRUB_DISABLE_OS_PROBER
(=true/false) |
Determine which version of GRUB2 is installed | grub-install -v
grub2-install -v |