LinuxQuestions.org - Need help identifying the lines of Grub.conf file

Quote:

Originally Posted by Sarge_P

I am new to Linux and need some help! Would someone pllease explain what each line of the grub.conf file means, and what the initrd is? Thanks for any help, Sarge_P

Code:

>$ cat /boot/grub/menu.lst

# menu.lst - See: grub(8), info grub, update-grub(8)

#            grub-install(8), grub-floppy(8),

#            grub-md5-crypt, /usr/share/doc/grub

#            and /usr/share/doc/grub-doc/.



## default num

# Set the default entry to the entry number NUM. Numbering starts from 0, and

# the entry number 0 is the default if the command is not used.

#

# You can specify 'saved' instead of a number. In this case, the default entry

# is the entry saved with the command 'savedefault'.

default        0

The default line does what the comments say the 0 (zero which is what grub starts counting with instead of 1) tells it to boot the first entry of the menu image configuration and save here boots the last used option if the section for it contained the savedefault in it.

Code:

## timeout sec

# Set a timeout, in SEC seconds, before automatically booting the default entry

# (normally the first entry defined).

timeout        5

How long to wait before booting the default image.

Code:

# Pretty colours

color cyan/blue white/blue

Customize colours of boot splash screen.

Code:

## password ['--md5'] passwd

# If used in the first section of a menu file, disable all interactive editing

# control (menu entry editor and command-line)  and entries protected by the

# command 'lock'

# e.g. password topsecret

#      password --md5 $1$gLhU0/$aW78kHK1QfV3P2b2znUoe/

# password topsecret

Using password to protect the boot options.

Code:

#

# examples

#

# title        Windows 95/98/NT/2000

# root          (hd0,0)

# makeactive

# chainloader  +1

#

# title        Linux

# root          (hd0,1)

# kernel        /vmlinuz root=/dev/hda2 ro

#

Examples to help you configure your own entries.

Code:

#

# Put static boot stanzas before and/or after AUTOMAGIC KERNEL LIST



### BEGIN AUTOMAGIC KERNELS LIST

## lines between the AUTOMAGIC KERNELS LIST markers will be modified

## by the debian update-grub script except for the default options below



## DO NOT UNCOMMENT THEM, Just edit them to your needs



## ## Start Default Options ##

## default kernel options

## default kernel options for automagic boot options

## If you want special options for specific kernels use kopt_x_y_z

## where x.y.z is kernel version. Minor versions can be omitted.

## e.g. kopt=root=/dev/hda1 ro

##      kopt_2_6_8=root=/dev/hdc1 ro

##      kopt_2_6_8_2_686=root=/dev/hdc2 ro

# kopt=root=/dev/sda2 ro

The kopt= tells update-grub where your root file system is located for menu entry additions.

Code:

## default grub root device

## e.g. groot=(hd0,0)

# groot=(hd0,1)

This tells update-grub where the grub root device is located in its terms for example my /dev/sda2 above gets translated to hd0 first hard drive in system ,1 second partition.

Code:

## should update-grub create alternative automagic boot options

## e.g. alternative=true

##      alternative=false

# alternative=true

Exactly what it says should grub make alternative boot entries other than a main menu entry.

Code:

## should update-grub lock alternative automagic boot options

## e.g. lockalternative=true

##      lockalternative=false

# lockalternative=false

Should the entry be locked.

Code:

## additional options to use with the default boot option, but not with the

## alternatives

## e.g. defoptions=vga=791 resume=/dev/hda5

# defoptions=

Extra options to add to main boot menu entries.

Code:

## should update-grub lock old automagic boot options

## e.g. lockold=false

##      lockold=true

# lockold=false

Lock the old entries when updating to new.

Code:

## Xen hypervisor options to use with the default Xen boot option

# xenhopt=

Options when using Xen to boot.

Code:

## Xen Linux kernel options to use with the default Xen boot option

# xenkopt=console=tty0

More Xen options.

Code:

## altoption boot targets option

## multiple altoptions lines are allowed

## e.g. altoptions=(extra menu suffix) extra boot options

##      altoptions=(single-user) single

# altoptions=(recovery mode) single

The options to add when making the alternative boot menu entries.

Code:

## controls how many kernels should be put into the menu.lst

## only counts the first occurence of a kernel, not the

## alternative kernel options

## e.g. howmany=all

##      howmany=7

# howmany=all

How many kernel you want to be able to boot from the menu.

Code:

## should update-grub create memtest86 boot option

## e.g. memtest86=true

##      memtest86=false

# memtest86=true

Create memtest86 entry if the program is installed so you can test your ram.

Code:

## should update-grub adjust the value of the default booted system

## can be true or false

# updatedefaultentry=false

Not sure.

Code:

## ## End Default Options ##



title          Debian GNU/Linux, kernel 2.6.18-ck1-smp Default

root            (hd0,1)

kernel          /boot/vmlinuz root=/dev/sda2 ro

savedefault

A menu entry for boot the title part is what is displayed on the menu, the root is the location of the root partition that grub will boot, the kernel line is the location of the kernel image that will be booted and savedefault tells grub that this will be the default option when booting next time if specified to do so above in default save instead of using number (0) entry.

Code:

title          Debian GNU/Linux, kernel 2.6.18-ck1-smp Default (recovery mode)

root            (hd0,1)

kernel          /boot/vmlinuz root=/dev/sda2 ro single

savedefault

Example of the alternative entry created with the options specified in the # altoptions=(recovery mode) single configuration item.

Code:

title          Debian GNU/Linux, kernel 2.6.17-ck1-1-smp Previous

root            (hd0,1)

kernel          /boot/vmlinuz.old root=/dev/sda2 ro

initrd          /boot/initrd.img.old

savedefault



title          Debian GNU/Linux, kernel 2.6.17-ck1-1-smp Previous (recovery mode)

root            (hd0,1)

kernel          /boot/vmlinuz.old root=/dev/sda2 ro single

initrd          /boot/initrd.img.old

savedefault

Examples of the previous installed kernel.

Code:

title          Debian GNU/Linux, kernel 2.6.8-11-amd64-generic

root            (hd0,1)

kernel          /boot/vmlinuz-2.6.8-11-amd64-generic root=/dev/sda2 ro

initrd          /boot/initrd.img-2.6.8-11-amd64-generic

savedefault



title          Debian GNU/Linux, kernel 2.6.8-11-amd64-generic (recovery mode)

root            (hd0,1)

kernel          /boot/vmlinuz-2.6.8-11-amd64-generic root=/dev/sda2 ro single

initrd          /boot/initrd.img-2.6.8-11-amd64-generic

savedefault

Original install kernel which shows the use of an initrd line when using that type of kernel.

Code:

### END DEBIAN AUTOMAGIC KERNELS LIST



# This is a divider, added to separate the menu items below from the Debian

# ones.

title          Other operating systems:

root





# This entry automatically added by the Debian installer for a non-linux OS

# on /dev/hda1

title          Microsoft Windows XP Professional

root            (hd0,0)

savedefault

makeactive

chainloader    +1

Example of menu item to boot windows on the first (hd0) hard drive first partition (0).