Ubuntu
grub2 package

Can't find / after upgrade

Asked by alan@alandbell.co.uk

Hi, I just did an upgrade from V10 to 12.04. Everything seemed to go well and at the end of the installation I was asked to re-start. I did a re-start but all I can get is a wait screen with the following message:

"Can't find /"

It also asked if I want to quite or manually boot by pressing 'M'. If I press 'M' and get to a terminal screen what do I do then?

Many thanks

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actionparsnip (andrew-woodhead666) said : 		#1

Boot to liveCD/USB and run:

sudo blkid

You can then see the UUIDs of the devices. If you then mount your installed OS and read the etc/fstab file there, you can make sure the UUIDs match.

You can also fsck the partitions (unmounted) to make sure they are healthy

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alan@alandbell.co.uk (alan-alandbell) said : 		#2

Hi, I don't have a disk though. I've been running this install of Ubuntu since V7 and just updating ever since. It was working just fine until this update.

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alan@alandbell.co.uk (alan-alandbell) said : 		#3

Ok, in the fstab I have the following:

/dev/sdb1 /media/400GB ext3 defaults 0 0
/dev.sda5 swap swap sw 0 0
/dev/sdb2 /media/prive ext4 0 0
/dev/sda1 / ext4 defaults 0 1

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actionparsnip (andrew-woodhead666) said : 		#4

I suggest you use UUIDs instead of /dev/sdaX

The sdXY may change at boot if other devices are inserted at boot. The UUIDs never change.

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alan@alandbell.co.uk (alan-alandbell) said : 		#5

Ok, I'll try that. Thanks.

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alan@alandbell.co.uk (alan-alandbell) said : 		#6

Ok, running up against some issues here. Can you tell what the easiest way is to change the fstab to use UUIDs. Is there a command line I can issue to do that or will have to manually type in the ID?

Many thanks.

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actionparsnip (andrew-woodhead666) said : 		#7

Mount the internal partition and run:

gksudo gedit

You can then open the fstab file in /media/[something]/etc/fstab and change the /dev/sdaX to the UUIDs output in:

sudo blkid

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alan@alandbell.co.uk (alan-alandbell) said : 		#8

Brilliant, I'll try that. Can i copy from one file to the other or do I have to type the UUIDs in manually?

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actionparsnip (andrew-woodhead666) said : 		#9

You can copy and paste the UUIDs from the terminal. The resulting file will look similar to this:

# / was on /dev/sda2 during installation
UUID=6d091c3b-bae2-4e35-9fcf-59b4e0c25cfd / ext4 noatime,errors=remount-ro 0 1
# /home was on /dev/sda5 during installation
UUID=29454e63-47c8-435c-b00e-3abcaa4ad68e /home ext4 noatime,defaults 0 2
# swap was on /dev/sda1 during installation
UUID=38555e5a-b592-4727-b821-b17b80d2efd5 none swap sw 0 0

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alan@alandbell.co.uk (alan-alandbell) said : 		#10

Is there a command to copy the contents of blkid to fstab?

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alan@alandbell.co.uk (alan-alandbell) said : 		#11

Hmmm, it's saying that fstab is read only

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actionparsnip (andrew-woodhead666) said : 		#12

What is the output of:

mount

Thanks

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actionparsnip (andrew-woodhead666) said : 		#13

Basically you'll want to run:

sudo mount -o remount,rw /media/something

change /media/something to the mount point of the system partition on the installed OS. The fact it is read only may point to the fact that the partition isn't healthy and should be fsck'd

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