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

[Andrei Borzenkov]

20.03.2017 19:06, rishi narian пишет:
> 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

This does not match. Where partition 4 comes from?
...
> address@hidden:~# mdadm --detail /dev/md0
> /dev/md0:
>         Version : 1.2
...
> 
> *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*
> 

Of course. Your grub was instructed to access /boot/grub on LV on MD.
Now LV on MD is gone, so it cannot load itself.

> 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
> 

I have no idea what update-grub does. Unless someone else chimes in, you
are better off asking your distribution help channels.

> 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'**
> 

You cannot mount partition directly if it was used with mdadm 1.2
metadata. Content is offset from the beginning of partition. Your best
bet is to setup MD/LVM again, copy data away from this partition, change
your disk setup and copy data back. This is rather way off-topic on this
list. Once you have done it, you will need to reinstall grub - then you
may ask for help here :)