Bootloader

GRUB Legacy

GRUB Legacy is no longer being developed, but let's mention it for historical purposes.

/boot/grub/menu.lst

title           GNU/Linux
root            (hd0,0)
kernel          /boot/vmlinuz root=/dev/hda1 ro
initrd          /boot/initrd.img

title		Windows NT
root		(hd1,0)
makeactive                                            # Makes hd1,0 active, i.e. it modifies hd1!
chainloader	+1

GRUB 2

GRUB 2 has really replaced #GRUB Legacy now. The configuration is built by grub2-mkconfig from the configuration files in /etc/grub.d. A few defaults can be set in /etc/default/grub

/etc/default/grub

# Boot first entry per default
GRUB_DEFAULT=0

# Disable the submenu, so that GRUB_DEFAULT can address each boot entry more easily.
GRUB_DISABLE_SUBMENU=y

# Wait this many seconds for the user to press a key
GRUB_HIDDEN_TIMEOUT=0

# No countdown is displayed
GRUB_HIDDEN_TIMEOUT_QUIET=true

# Seconds to display the boot menu before booting
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`

# Boot parameters
GRUB_CMDLINE_LINUX=""

# Special boot parameters for the GRUB_DEFAULT entry
GRUB_CMDLINE_LINUX_DEFAULT=""

# Select output device
GRUB_TERMINAL=console

# Disable "root=UUID=xxx" parameters
# GRUB_DISABLE_LINUX_UUID=true

# Disable recovery mode menu entries
GRUB_DISABLE_RECOVERY="true"

Notes:

• GRUB_DISABLE_SUBMENU may not be available in earlier GRUB versions.
• GRUB_DEFAULT setting can also be used to boot nested configuration items. For example, let's assume the following boot menu:

0) Linux
1) Previous Versions >
        1.0) Linux_2
        2.1) Linux_3

To boot "Linux_3", set GRUB_DEFAULT to "Previous Versions>Linux_3". Numbers can also be used ("1>1"), but using the exact menu entry names may be more easy to read.

To activate the configuration:

sudo update-grub                                      # Debian, Ubuntu
sudo grub-mkconfig -o /boot/grub/grub.cfg             # Fedora, Arch Linux

/boot/grub/grub.cfg

 menuentry 'Debian GNU/Linux' --class debian --class gnu-linux --class gnu --class os {
        insmod part_gpt
        insmod ext2
        set root='(hd0,gpt1)'
        search --no-floppy --fs-uuid --set 92ed9f74-dd26-4750-9e10-d376214ab13f
        echo    'Loading Linux...'
        linux   /boot/vmlinuz-2.6.32-5-amd64 root=UUID=92ed9f74-dd26-4750-9e10-d376214ab13f ro  
        echo    'Loading initial ramdisk...'
        initrd  /boot/initrd.img-2.6.32-5-amd64
}

LiLo

/etc/lilo.conf

  # global
  lba32
  large-memory       # allow for initrds larger than 15MB
  map=/boot/lilo/map
  backup=/boot/lilo/boot.NNNN
  install=menu       # text, menu, bmp
  prompt
  timeout=100        # 10s timeout for 'prompt'
  boot=/dev/hda
  default=Linux
  # serial=0,115200n8
  # disk=/dev/sda
  # bios=0x80
  # disk=/dev/hda
  # disk=0x81

  # linux
  image=/boot/vmlinuz-2.6.26
  label="Linux"
  root=/dev/hda1
  append=""
  read-only
  
  # bsd/windows
  other=/dev/hda3
  label="FreeBSD"
  optional

• LILO Bootloader for GNU/Linux

FreeBSD Boot Manager

tbd

• The Boot Manager and Boot Stages

Windows NTLDR

C:\boot.ini

  [boot loader]
  timeout=30
  default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
  
  [operating systems]
  multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect

• NTLDR
• How to edit the Boot.ini file in Windows XP

Links

• Classic SysAdmin: How to Rescue a Non-booting GRUB 2 on Linux