How I fix my Ubuntu with iRST(Intel Rapid Start Technology) Raid

2016-12-29 by terryoy, in tricks

I have bought a Haier X3 laptop with a 500GB hard disk and a 32GB SSD with which you could use to boot and cache disk rapidly for Windows via Intel's technology. However, I'm a Linux fan, so I also need to install Ubuntu on my computer.

At first, the Windows 7 system was pre-installed. When I installed Ubuntu it failed at booting if the Windows 7 had enabled iRST. I cannot find any working solution to fix the Ubuntu problem at the time, so I just disabled Win 7's iRST, and then use the SSD as normal disk. Later I had a very good time with the Linux environment.

Recently, I'm going to refresh the whole system and make both clean again. So I give a second try to enable Windows 7's iRST and make Ubuntu boot correctly, and I succeeded after two days hard work!

The root cause is that the raid management tool on Linux will assemble the partitions as RAID and then the initramds cannot find the partition with UUID. It fails like this:

Gave up waiting for root device. Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
   - Check root= (did the system wait for the right device?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT! /dev/disk/by-uuid/52152d36-9dc4-42a6-8be1-3966bf397b09 does not exist. Dropping to a shell!

BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)
Enter 'help' for a lost of built-in commands.
(initramfs)

I have searched on the internet about it, finding that it's related to the block id that generated for the partitions are missing:

(initramfs) blkid
/dev/sda: TYPE="isw_raid_member"
/dev/sdb: TYPE="isw_raid_member"

(initramfs) ls /dev/md*
md/  md126  md127

While the partitions of /dev/sda/ are supposed to be recognized by UUIDs, but it is created as a software RAID device(md126), so the partitions of it cannot be accessed at boot time. I have tried to install Ubuntu via my usb disk again and again, also try to use chroot to update the grub record and the initramfs on the partiion, and I still don't have luck. After a long frustrating period, I suddenly come up the idea: why not just disable the raid array at boot time?

After I tried the below two commands in initramfs, it come back to normal boot after I exit the initramfs mode!

(initramfs) mdadm --stop --scan

(initramfs) blockdev --rereadpt /dev/sda

The first command scan all the RAID array entries and close them. The second command re-read the partitions with UUIDs so you get the UUID entries for initramfs to boot.

This time I have confident to make the solution permanent. First of all, I will need to use my Ubuntu usb boot disk to enter the shell('Go Back' in the first step of the installation, then you find a choice for executing a shell) and mount the partition. (My target Ubuntu parition is /dev/sda3)

$ mount /dev/sda3 /mnt
$ mount -t proc /proc /mnt/proc
$ mount -t sysfs /sys /mnt/sys
$ mount -o bind /dev /mnt/dev
$ chroot /mnt /bin/bash

This allow me to mount the partition just as I've booted into it. Then I will update it's boot process(e.g. grub & initramfs).

$ grub-install /dev/sda
$ update-grub

$ vi /etc/initramfs-tools/script/local-top/mdadm
mdadm --stop --scan
blockdev --rereadpt /dev/sda

$ chmod +x /etc/initramfs-tools/script/local-top/mdadm
$ update-initramfs -u

Voilà! My Ubuntu's back!…wait, my Windows 7 has gone! It seems that GRUB has erase my Windows 7 boot entry. This doesn't stop me now. It's easy to get Windows back.

I tried to run update-grub again, but it doesn't recognize the Windows boot entry even though os-prober is enabled. So I need to add it manually:

# check the Windows partition UUID
$ blkid

$ vi /boot/grub/grub.cfg
# (look for the section of "/etc/grub.d/40_custom" and add the content below)
menuentry "Windows 7" {
    insmod ntfs
    set root='(hd0,1)'
    search --no-floppy --fs-uuid --set 76B0EE43B0EE0987
    chainloader +1
}

Then reboot. It is finally OK.

Tags: linux