Grub fails to install - Debian Wheezy with mdadm RAID1 and GPT partition table

Question

I've been trying all day to get my new Wheezy install completed but it fail to install Grub every time. I'm using x64 netinstall iso.

Here is my partition table:

Model: ATA ST3000DM001-1CH1 (scsi)
Disk /dev/sda: 5860533168s
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags: 

Number  Start      End          Size         File system  Name  Flags
 1      2048s      6143s        4096s                     grub  bios_grub
 2      6144s      1953791s     1947648s                  boot  raid
 3      1953792s   31250431s    29296640s                 root  raid
 4      31250432s  5860532223s  5829281792s               home  raid

Disk /dev/sdb has the same partition table. You can see I've added that infamous small partition and marked it as bios_grub to give Grub space because GPT takes more than legacy msdos table.

Error message I get from installer is "Failed to install Grub to /dev/sda" (or similar).

Partitions 2, 3 and 4 make three RAID1 partitions for /boot, /, and /home. All properly selected and formatted in Debian installer.

Please help!

Answer 1

Looks like somehow Debian installer screws up the partition table. The "bios_grub" flag gets removed and becomes "raid" flag. The fix is to rework the partition table again with parted and set it back.

parted /dev/sda
set 1 bios_grub on
quit

Same for /dev/sdb, and then chrooting and installing grub with answer from this question: How can I fix/install/reinstall grub?

Answer 2

you can also set grub partition with gdisk(8)

Command (? for help): t
Partition number (1-4): 1
Current type is 'BIOS boot partition'
Hex code or GUID (L to show codes, Enter = 8300): EF02
Changed type of partition to 'BIOS boot partition'

Important thing to note is that you CANNOT reuse your existing /boot or any other partition for this - 64KB might be enough (it should be just big enough to fit your /boot/grub/i386-pc/*.img files), but there is usually about 1MB free which is way more than enough.

If the partition was missing instead, you could have create New one, there is even usually enough space free before your first partition. For example, then it would be like:

# gdisk /dev/sdb

Command (? for help): p
Disk /dev/sdb: 7814037168 sectors, 3.6 TiB
Logical sector size: 512 bytes
Disk identifier (GUID): CEFE1861-C13E-4E30-AEC4-0037CA6CBE8D
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 7814037134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         3893247   1.9 GiB     0700  Microsoft basic data
   2         3893248        12281855   4.0 GiB     8200  Linux swap
   3        12281856        12806143   256.0 MiB   FD00  Linux RAID
   4        12806144      7814037134   3.6 TiB     FD00  Linux RAID

Command (? for help): n
Partition number (5-128, default 5):
First sector (34-2047, default = 34) or {+-}size{KMGTP}: 34
Last sector (40-2047, default = 2047) or {+-}size{KMGTP}:
Current type is 'Linux filesystem'
Hex code or GUID (L to show codes, Enter = 8300): EF02
Changed type of partition to 'BIOS boot partition'

Command (? for help): p
Disk /dev/sdb: 7814037168 sectors, 3.6 TiB
Logical sector size: 512 bytes
Disk identifier (GUID): CEFE1861-C13E-4E30-AEC4-0037CA6CBE8D
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 7814037134
Partitions will be aligned on 2048-sector boundaries
Total free space is 6 sectors (3.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         3893247   1.9 GiB     0700  Microsoft basic data
   2         3893248        12281855   4.0 GiB     8200  Linux swap
   3        12281856        12806143   256.0 MiB   FD00  Linux RAID
   4        12806144      7814037134   3.6 TiB     FD00  Linux RAID
   5              40            2047   1004.0 KiB  EF02  BIOS boot partition

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): y
OK; writing new GUID partition table (GPT) to /dev/sdb.
Warning: The kernel is still using the old partition table.
The new table will be used at the next reboot.
The operation has completed successfully.