Linux grub

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grub rescue>

The problem:

Entering rescue mode...                                                         
grub rescue>

Get into the normal grub

Find your devices:

grub rescue> ls

Find the directory where the normal.mod file resides

In this example we have LVM and the /boot/grub is in VG vg-root and the LV lv-root.

grub rescue> ls (lvm/vg--root-lv--root)/boot/grub/i386-pc
... normal.mod ...

Set the prefix to the right place

grub rescue> set prefix=(lvm/vg--root-lv--root)/boot/grub

Now you can load and start the module called "normal"

grub rescue> insmod normal
grub rescue> normal

If the menu not occurs you get something like this:

                  GNU GRUB  version 1.99,

   Minimal BASH-like line editing is supported. For the first word, TAB
   lists possible command completions. Anywhere else TAB lists possible
   device or file completions.


Normal grub is bootet, now start the Kernel

Example for LVM:

insmod gzio
insmod part_msdos
insmod lvm
insmod ext2
set root='lvmid/KAlPF4-Qb8I-Sx41-10cC-lACw-Msoh-3qEohv/pmE9Nt-rLG3-FlNM-CwOT-hy42-gSnm-fZSn3l'
linux   /boot/vmlinuz-4.4.0-53-generic root=/dev/mapper/vg--root-lv--root ro  
initrd  /boot/initrd.img-4.4.0-53-generic

Example for ZFS-Root:

insmod gzio
insmod part_msdos
insmod zfs
set root='hd0,msdos4'
linux   /ROOT/ubuntu-15.04@/boot/vmlinuz-4.4.0-57-generic root=ZFS=rpool/ROOT/ubuntu-15.04 boot=zfs zfs_force=1 ro  quiet splash nomdmonddf nomdmonisw $vt_handoff
initrd  /ROOT/ubuntu-15.04@/boot/initrd.img-4.4.0-57-generic