GNU'S Not Unix- GRand Unified Bootloader...

GNU-GRUB

What will we be covering?

Introduction to GRUB

Installing GRUB

Exploring GRUB

Customizing GRUB

GRUB Error Recovery

Introduction...err...Features

Many features and lot of flexibility

Supports booting multiple operating systems

Support for many boot devicesHard disk (of course), cd-rom(El-Torito), network(tftp)

Support for many file systems (ext2/3, xfs, jfs,reiserfs, dos, fat16, fat32...)

Configuration File

Features (continued)

Support for network cards (etherboot)

Menu Interfaces for regular and command interface for advanced users

Remote control from serial console.

Supports multiple executable formats

Can uncompress compressed files.

Installing GRUB

From Scratch (i.e. on a blank disk)Do it from a host with GNU/GRUB installed.

Create a partition on disk fdisk /dev/sda

Format and mount this partition:mkfs.ext3 /dev/sda1sudo mount /dev/sda1 /mnt/sda1

Installation....(Continued)

Download grub tarball ftp://ftp.gnu.org/gnu/grub

Compiling :)

Install grub:grub-install root-directory=/mnt/sda1 /dev/sda

grub-mkconfig -o /boot/grub/grub.cfg

A secret:The grub-install (Just a shell script !!! :-O)The real heroes are :'grub-mkimage' and

'grub-setup'

Exploring(The quest to learn GRUB-fu)

Changes???/boot/grub

/etc/grub.d

/etc/default/grub

Other places: /usr/lib/grub(Modules)| /usr/bin or /bin (Binaries),Docs

Exploring....(Digging In)

Scanning grub.cfg(/boot/grub/grub.cfg) Phew!!.....looks complicated....(actually non-editable)we'll come back later.

Peeking in /etc/grub.d00_* contains header info

10_* Native boot entries

20_* Third party apps

30_osprobe :Scans for other O.S.

40_custom : Custom templates for additional entries

Looking at /etc/default/grub....Hmmm....looks interesting.!!! :)

Customizing GRUB

Some Theory:

/etc/default/grub

/etc/grub.d//boot/grub/grub.cfg

Custom Settings

Custom Scripts

What can we do?

Making Custom Settings

We change the /etc/default/grub file.

Some of the configurations are:GRUB_DEFAULT,

GRUB_TIMEOUT,

GRUB_HIDDEN_TIMEOUT,

GRUB_DISABLE_RECOVERY,

GRUB_BACKGROUND,

GRUB_THEME,

.....AND MANY MORE.

Making Custom Scripts

Can be done by adding scripts in /etc/default/grub

Sample:

echo "Some string" cat