10.04 w/ Ext4 Cannot boot after partition resize

[Soupcan]

Ubuntu is installed on /dev/sda1. The computer fails to boot and instead drops to an intramfs shell. The partition is still visible in gparted and fdisk, but it is unreadable. Attempting to mount it fails, and directs me to dmesg. Dmesg output:

 EXT4-fs: bad geometry: block count (large number) exceeds size of device (another large number) blocks

Output of fdisk:

 Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders total 625142448 sectors
Units = sectors of 1*512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk Identifier: 0x00013224

     Device    Boot     Start              End               Blocks     Id  System
/dev/sda1      *       2048   391134554  195566253+    83     Linux
/dev/sda2     601751550   625141759        11695105      5  Extended
/dev/sda5     601751552   625141759        11695104     82 Linux swap/Solaris

As the disk had not been written to or, to my knowledge, formatted, I was considering following this tutorial on restoring partitions to fix the problem. Would this work? Any loss of data would be a problem, as the computer is not mine and there are no backups.

[23dornot23d]

Have you had a look using Testdisk this can show you the disk partition table
and sometimes give you clues to heading in a direction for fixing it ......

[gdonwallace]

Not sure about 10.04, but i know in previous version, if You use gparted to resize your partition, it would create a new UUID for the partiion, instead of using the one that was already assigned.

I don't recall how to fix this, but search the forums and You should be able to find it.

[Soupcan]

Have you had a look using Testdisk this can show you the disk partition table
and sometimes give you clues to heading in a direction for fixing it ......

I have, but I did not finish the process. I stopped it during Deep Scan to run a few commands for a post on the GParted forum. I'll let it run all the way through and return with the results. I'd like to avoid writing anything to the drive until I get a few more opinions.

Not sure about 10.04, but i know in previous version, if You use gparted to resize your partition, it would create a new UUID for the partiion, instead of using the one that was already assigned.

I don't recall how to fix this, but search the forums and You should be able to find it.

Thanks, that's good to know. However, the partition can't be mounted, and so I cannot edit any files to point toward the new UUID. I'll be sure to check for that if I can make the drive usable again, though.

[23dornot23d]

Safest way get as much information as possible before committing to disk.

Also try to get a backup image or remove as much useful data as you can ....
photographs documents etc ..... anything thats not easily replaceable for the owner.

Photorec recovers photos without changing the drives contents as far as I know ....
this I have used to recover photos off of accidentally deleted SD cards before .......
it also worked on a hard drive I had a problem with once .....

[Soupcan]

Safest way get as much information as possible before committing to disk.

Also try to get a backup image or remove as much useful data as you can ....
photographs documents etc ..... anything thats not easily replaceable for the owner.

Photorec recovers photos without changing the drives contents as far as I know ....
this I have used to recover photos off of accidentally deleted SD cards before .......
it also worked on a hard drive I had a problem with once .....

I'll do that. Of course, the only storage I have handy is an 8gb flash drive, while the partition contained about 16gb of data.

[Soupcan]

Problem solved through the following steps:
Backup of mbr through dd:

dd if=/dev/sda of=mnt/usb bs=512 count=1

Output of dmesg showed that ext4 expected a filesystem of 601747456 sectors in size. This was determined by multiplying the value given after "block count" by 8 to convert to sectors.
dmesg output:

[ 2805.943334] EXT4-fs (sda1): bad geometry: block count 75218432 exceeds size of device (48891563 blocks)

On to repairing. Creating backup of partition table with sfdisk:

sfdisk -d /dev/sda > PT.txt

Keep an unchanged copy of PT.txt in case the next steps do not work. Edit PT.txt with any editor. In PT.txt, the line referring to /dev/sda1 was changed to the following:

/dev/sda1 : start=     2048, size=601747456, Id=83, bootable

The value of "size=" was changed from its previous value to the value expected by ext4.

Then, with the corrected PT.txt, the partition table was changed to the new values:

sudo sfdisk -f /dev/sda -O PT.save < PT.txt

After this, /dev/sda1 mounted cleanly with

sudo mount -o ro /dev/sda1 /mnt/sda1

Filesystem check showed no errors, no data was lost, and the system rebooted properly. Thanks very much to thune3, who walked me through fixing this over IRC.