[ILUG] disk recovery

[Vicente Werner]

You can try using testdisk (http://www.cgsecurity.org/wiki/TestDisk) to
recover the main partition, BUT, if the logical structure has been
garbled... it might not be possible to recover the data you had inside.

On Tue, May 12, 2009 at 1:33 PM, Kae Verens <kae at verens.com> wrote:

> hi all,
>
> two days ago, I went to read a file on one of my archive disks, shared
> through NFS by a machine in the attic. the root directory showed the right
> number of files, but most of the file names were garbled.
>
> I didn't spot that for a moment, and tried to go into the directory I
> wanted ('/b'), but it claimed it was a file. then I noticed the garbled
> files.
>
> restarted the machine in case it was something simple. drive didn't turn
> up.
>
> went upstairs and checked. the drive was very hot, so I guess that was the
> culprit. turned it off and left it over night.
>
> next day, checked, and the main partition was missing (/dev/sdc did not
> have child /dev/sdc1 node), and fdisk claimed the drive was 80GB, even
> though it's actually 200GB.
>
> today, I check again, and fdisk claims it's 200GB, but the partitions are
> still missing.
>
> went into fdisk to rebuild them:
>
> > [root at localhost ~]# fdisk /dev/sdc
> > Device contains neither a valid DOS partition table, nor Sun, SGI or OSF
> disklabel
> > Building a new DOS disklabel with disk identifier 0xb97626c7.
> > Changes will remain in memory only, until you decide to write them.
> > After that, of course, the previous content won't be recoverable.
> >
> >
> > The number of cylinders for this disk is set to 24792.
> > There is nothing wrong with that, but this is larger than 1024,
> > and could in certain setups cause problems with:
> > 1) software that runs at boot time (e.g., old versions of LILO)
> > 2) booting and partitioning software from other OSs
> >    (e.g., DOS FDISK, OS/2 FDISK)
> > Warning: invalid flag 0x0000 of partition table 4 will be corrected by
> w(rite)
> >
> > Command (m for help): p
> >
> > Disk /dev/sdc: 203.9 GB, 203928109056 bytes
> > 255 heads, 63 sectors/track, 24792 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> > Disk identifier: 0xb97626c7
> >
> >    Device Boot      Start         End      Blocks   Id  System
> >
>
> no partitions.
>
> so rebuilt and saved:
>
> > Command (m for help): n
> > Command action
> >    e   extended
> >    p   primary partition (1-4)
> > p
> > Partition number (1-4): 1
> > First cylinder (1-24792, default 1):
> > Using default value 1
> > Last cylinder, +cylinders or +size{K,M,G} (1-24792, default 24792):
> > Using default value 24792
> >
> > Command (m for help): p
> >
> > Disk /dev/sdc: 203.9 GB, 203928109056 bytes
> > 255 heads, 63 sectors/track, 24792 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> > Disk identifier: 0xb97626c7
> >
> >    Device Boot      Start         End      Blocks   Id  System
> > /dev/sdc1               1       24792   199141708+  83  Linux
> >
> > Command (m for help): w
> > The partition table has been altered!
> >
> > Calling ioctl() to re-read partition table.
> > Syncing disks.
> > [root at localhost ~]#
>
> fine enough. now let's look again:
>
> > [root at localhost ~]# fdisk /dev/sdc
> > Device contains neither a valid DOS partition table, nor Sun, SGI or OSF
> disklabel
> > Building a new DOS disklabel with disk identifier 0x4de23cfd.
> > Changes will remain in memory only, until you decide to write them.
> > After that, of course, the previous content won't be recoverable.
> >
> >
> > The number of cylinders for this disk is set to 24792.
> > There is nothing wrong with that, but this is larger than 1024,
> > and could in certain setups cause problems with:
> > 1) software that runs at boot time (e.g., old versions of LILO)
> > 2) booting and partitioning software from other OSs
> >    (e.g., DOS FDISK, OS/2 FDISK)
> > Warning: invalid flag 0x0000 of partition table 4 will be corrected by
> w(rite)
> >
> > Command (m for help): p
> >
> > Disk /dev/sdc: 203.9 GB, 203928109056 bytes
> > 255 heads, 63 sectors/track, 24792 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> > Disk identifier: 0x4de23cfd
> >
> >    Device Boot      Start         End      Blocks   Id  System
> >
> > Command (m for help):
>
> still no partitions. nothing else I can think of until I can at least
> rebuilt the partition table.
>
> any ideas? it's a Maxtor DiamondMax 10, 200GB PATA133 HDD, held in a Canyon
> external USB caddy.
>
> kae
>
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-- 
Vicente Werner y Sánchez