GRUB

Grub 2

• command that generates and prints out configuration:

grub2-mkconfig

• save configuration

grub2-mkconfig -o /boot/grub/grub.cfg

• regenerate EFI file

mv /boot/efi/EFI/fedora/grub.cfg /tmp/grub.cfg
dnf reinstall grub2-common

• get OS's list of labels

grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2
Fedora
Ubuntu 12.04.2 LTS (12.04)
Gentoo Base System release 2.1

• show actual default entry

grub2-editenv list
saved_entry=Fedora Linux, with Linux 3.6.6-1.fc17.i686.PAE

• alter default entry

grub2-set-default "Gentoo Base System release 2.1"

• check...

grub2-editenv list
saved_entry=Gentoo Base System release 2.1

Other Operative Systems disappeared

From debian 12, an option in grub config will disable the scan for other OS's thus making impossible to boot from them. how to fix:

• open the config

vi /etc/default/grub

• un-comment or add this line:

GRUB_DISABLE_OS_PROBER=false

• regenerate grub config:

update-grub

Boot after update

ALERT! /dev/mapper/ubuntu--vg-root does npt exist. Dropping to a shell!

(initram-fs)# vgchange -ay

Grub 1.X

Link a una documentazione...

Installing GRUB in the Master Boot Record

• Con grub-install

grub-install /dev/hda

o meglio... (se si sta installando il sistema)

chroot /mnt/sysimage/

• • con la directory boot sta nella /

/sbin/grub-install --root-directory=/boot /dev/md1

• • con la directory boot è una partizione

/sbin/grub-install --root-directory=/ /dev/md0

• find grub copies:

grub> find /grub/stage1

• or...

grub> find /boot/grub/stage1

• grub (/usr/sbin/grub)

grub> device (hd0) /dev/sdb (/dev/hdb for ide)
grub> root (hd0,0)          (La partizione di boot, Disco 0 Partizione 0)
grub> setup (hd0)           (Installa GRUB nel MBR)
grub> quit                  (Esci dalla shell GRUB)

Immagine sfondo grub

   1. xpm.gz file
   2. 640x480
   3. 14 colors
   4. copiare in /boot/grub
   5. gzip myfile.xpm

VGA modes

| 640x480 800x600 1024x768 1280x1024
----+-------------------------------------
256 | 0x301 0x303 0x305 0x307
32k | 0x310 0x313 0x316 0x319
64k | 0x311 0x314 0x317 0x31A
16M | 0x312 0x315 0x318 0x31B