Removal of Software Raid-1 from disk causes linux system in to grub rescue mode

[rishi narian]

Hello,

   When i tried to removed the Raid-1 array from the Linux system which
causes  Linux system in to *grub resue* mode with lvmid/ not found error.

I am unable to recover or find out the grub configuration from the existing
system due to which i am blocked to boot in to OS.

The following is  existing configuration:

address@hidden:~# fdisk -l

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048    34613373    17305663   da  Non-FS data
/dev/sda2   *    34613374   156248189    60817408   fd  Linux raid autodetect

address@hidden:~# lsblk
NAME                    MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                       8:0    0 232.9G  0 disk
├─sda1                    8:1    0  16.5G  0 part
└─sda4                    8:4    0    58G  0 part
  └─md0                   9:0    0    58G  0 raid1
    ├─vg0-swap (dm-0)   252:0    0   1.9G  0 lvm   [SWAP]
    ├─vg0-root (dm-1)   252:1    0  19.6G  0 lvm   /
    └─vg0-backup (dm-2) 252:2    0  19.6G  0 lvm
sr0                      11:0    1   4.1G  0 rom


address@hidden:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md0 : active raid1 sda2[0]
      60801024 blocks super 1.2 [2/1] [U_]

unused devices: <none>


address@hidden:~# pvs
  PV         VG   Fmt  Attr PSize  PFree
  /dev/md0   vg0  lvm2 a--  57.98g 17.04g

address@hidden:~# lvs
  LV     VG   Attr      LSize  Pool Origin Data%  Move Log Copy%  Convert
  backup vg0  -wi-a---- 19.54g
  root   vg0  -wi-ao--- 19.54g
  swap   vg0  -wi-ao---  1.86g

address@hidden:~# vgs
  VG   #PV #LV #SN Attr   VSize  VFree
  vg0    1   3   0 wz--n- 57.98g 17.04g

address@hidden:~# cat /etc/mdadm/mdadm.conf

# definitions of existing MD arrays
ARRAY /dev/md/0 metadata=1.2 UUID=8b007464:369201ca:13634910:1d1d4bbf
name=R000001:0


address@hidden:~# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Wed Sep 23 02:59:04 2015
     Raid Level : raid1
     Array Size : 60801024 (57.98 GiB 62.26 GB)
  Used Dev Size : 60801024 (57.98 GiB 62.26 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

    Update Time : Sat Mar 18 11:49:53 2017
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

address@hidden:~# fdisk -l

Disk /dev/sda: 250.1 GB, 250059350016 bytes
255 heads, 63 sectors/track, 30401 cylinders, total 488397168 sectors

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048    34613373    17305663   da  Non-FS data
/dev/sda2   *    34613374   156248189    60817408   fd  Linux raid autodetect

address@hidden:~# lsblk
NAME                    MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                       8:0    0 232.9G  0 disk
├─sda1                    8:1    0  16.5G  0 part
└─sda4                    8:4    0    58G  0 part
  └─md0                   9:0    0    58G  0 raid1
    ├─vg0-swap (dm-0)   252:0    0   1.9G  0 lvm   [SWAP]
    ├─vg0-root (dm-1)   252:1    0  19.6G  0 lvm   /
    └─vg0-backup (dm-2) 252:2    0  19.6G  0 lvm
sr0                      11:0    1   4.1G  0 rom



address@hidden:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md0 : active raid1 sda2[0]
      60801024 blocks super 1.2 [2/1] [U_]

unused devices: <none>


address@hidden:~# pvs
  PV         VG   Fmt  Attr PSize  PFree
  /dev/md0   vg0  lvm2 a--  57.98g 17.04g

address@hidden:~# lvs
  LV     VG   Attr      LSize  Pool Origin Data%  Move Log Copy%  Convert
  backup vg0  -wi-a---- 19.54g
  root   vg0  -wi-ao--- 19.54g
  swap   vg0  -wi-ao---  1.86g

address@hidden:~# vgs
  VG   #PV #LV #SN Attr   VSize  VFree
  vg0    1   3   0 wz--n- 57.98g 17.04g

address@hidden:~# cat /etc/mdadm/mdadm.conf

# definitions of existing MD arrays
ARRAY /dev/md/0 metadata=1.2 UUID=8b007464:369201ca:13634910:1d1d4bbf
name=R000001:0


address@hidden:~# mdadm --detail /dev/md0
/dev/md0:
        Version : 1.2
  Creation Time : Wed Sep 23 02:59:04 2015
     Raid Level : raid1
     Array Size : 60801024 (57.98 GiB 62.26 GB)
  Used Dev Size : 60801024 (57.98 GiB 62.26 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

    Update Time : Sat Mar 18 11:49:53 2017
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

*Removed the RAID-1 array using Knnopix Live CD.*

   1.

   vgchange -a n vg0 -> Deactivating the volume group
   2.

   mdadm --stop /dev/md0 -> Successfully stopped
   3.

   mdadm --zero-superblock /dev/sda2 -> Meta data of mdadm array Super
   block is zerod

After doing there is no Logical Volumes and raid-1 array as expected.

*After Booting the Linux machine, the Linux system went to *

***grub rescue>**

getting error as :**lvmid/xse34fffffffffff** is not found*

I tried to update the grub using knnopix Live CD, nothing is worked out.

The below commands are executed on live CD, but the commands are not able
to execute.

Two ways i tried: -> In both the commands are failing to update grub.

Option 1 #

> update-initramfs -u,  >> Not updated
> mdadm --detail --scan > /tmp/mdadm.conf
> cp /tmp/mdadm.conf /etc/mdadm/mdadm.conf
> update-grub   >> Not updating the grub

Option 2 #

> mount /dev/sda2 /mnt -> **Not able to mount because this is linux raid 
> member**
**> error as : Mount unknown filesystem type 'linux_raid_member'**

so i can't mount the below commands:

sudo mount --bind /dev /mnt/dev &&
sudo mount --bind /dev/pts /mnt/dev/pts &&
sudo mount --bind /proc /mnt/proc &&
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt
grub-install /dev/sda2


   - Boot record is present in sda2

*Could you please help me, how to boot properly after removing the soft
raid-1 array from the LVM disk (sda2). Also, How to reload the grub
properly.*


*Thanks*


*Rishi*