Grub2 keeps rebooting without showing menu

[CtrlSPATIE]

Dear all,

Right after passing the BIOS, at the moment Grub is supposed to show it’s menu, my Debian Linux (Jessie/sid) system reboots.

I have been googling and testing for hours and can’t seem to find a way around the issue.

How do I solve this?

All testing and installing is done using Debian from 7.5 LIVE CD, command line only.

I have set up my RAID as follows:

Code:
root#debian:~# cat /proc/mdstat
Personalities : [raid1]
md3 : active raid1 sda4[0]
1458608960 blocks super 1.2 [2/1] [U_]

md2 : active raid1 sda3[0]
5238720 blocks super 1.2 [2/1] [U_]

md0 : active raid1 sda1[0]
102336 blocks [2/1] [U_]

unused devices: <none>
Partition table of running 4TB disk (only 1.5TB is currently used):

Code:
root#debian:~# parted /dev/sda
GNU Parted 2.3
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Model: ATA WDC WD40EFRX-68W (scsi)
Disk /dev/sda: 4001GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number Start End Size File system Name Flags
1 1049kB 106MB 105MB ext3 boot bios_grub
2 106MB 1180MB 1074MB swap
3 1180MB 6548MB 5369MB ext4 system
4 6548MB 1500GB 1494GB ext4 data
Mountpoints are set:

Code:
root#debian:/mnt/etc# cat fstab
# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
/dev/md2 / ext3 defaults,errors=remount-ro 0 1
/dev/sda2 none swap sw 0 0
/dev/md0 /boot ext4 defaults 0 1
/dev/md3 /data ext4 defaults 0 1
#
/dev/cdrom /media/cdrom0 udf,iso9660 user,noauto 0 0
After chrooting /mnt I run grub-install:

Code:
root#debian:/# grub-install /dev/sda
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
Installation finished. No error reported.
Code:
root#debian:/# update-grub
Generating grub.cfg ...
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
/usr/sbin/grub-probe: warning: Couldn't find physical volume `(null)'. Some modules may be missing from core image..
done

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