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Old 03-20-2015, 03:47 PM   #1
mzzxx11
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Recovering after windows 7 install: rescue cannot mount root


I have a dual boot laptop with debian stable & Windows 7.

The HD partitions are:
sda1: NTFS for W7
sda2: FAT32 (currently unused)
sda3: linux /boot
sda4: linux ext4, which is LVM with encryption

I've re-installed W7 and now need to recover the MBR & grub menu.

I've booted with the netinst usb in rescue mode, but it fails to mount the root partition /sda4:
"An error occured while mounting the device you entered for your root file system (/dev/sda4) on /target"

and /var/syslog shows:
Code:
rescue-mode: selected root device '/dev/sda4'
umount: cant umount /target: Invalid argument
isofs_fill_super: bread failed, dev=sda4, iso_blknum=16, block=32
EXT2-fs (sda4): error: unable to readsuperblock
EXT3-fs (sda4): error: unable to readsuperblock
rescue: mount: mounting /dev/sda4 on /target failed: Invalid argument
So it seems like something is wrong with the mount command?

Would appreciate suggestions how to solve this.

Thanks
 
Old 03-20-2015, 04:51 PM   #2
TobiSGD
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If sda4 is a LVM you can't mount it directly, you have to mount the logical volume that is part volume group which resides on sda4. If LVM is started and has scanned the disk you should find logical volumes under /dev/mapper/.
 
Old 03-20-2015, 08:19 PM   #3
syg00
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... and after that, open the (presumably) LUKS container, then maybe you might be able to mount it.
 
Old 03-21-2015, 05:36 AM   #4
mzzxx11
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tnx for the replies.

how do I manually mount the LVM and LUKS containers?

when I did the same thing (re-installing W7) on my desktop machine, all I had to do was:
mount /dev/sda3 /boot
to mount partition 3 which is /boot, and then
grub-install /dev/sda

so I'm assuming the root partition was mounted without any issues, but if I remember correctly I had to type my passphrase somewhere during boot.

this time the rescue mode didnt ask me for the passphrase - I'm puzzled

Thanks
 
Old 03-22-2015, 06:32 AM   #5
mzzxx11
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bump

anyone?
 
Old 03-22-2015, 07:08 AM   #6
TobiSGD
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To see if LVM is working let the system show the infor for logical volumes with
Code:
lvdisplay
It will show you all logical volumes on the system, including the path to the device descriptor that can be used for mounting. I am not that familiar with encrypted partitions, someone else will have to help here.
 
Old 03-22-2015, 07:43 PM   #7
syg00
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Similar thread - see the link in this reply; seems to cover the situation.
 
Old 03-23-2015, 12:03 PM   #8
mzzxx11
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tnx for the replies.

I've solved it as follows:
booted up with "boot repair disk"
sourceforge.net/projects/boot-repair-cd/

opened a terminal->
mounted the boot partition (unencrypted) manually: sudo mount /dev/sda3 /boot
then:
sudo grub-install /dev/sda
reboot
everything works
 
  


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