[NCLUG] file system damage from dd with of=<a drive in my file system>

[Vincent Randal]

thank you for this help. NCLUG is awesome.

Vincent Randal
Longmont, Colorado

On Sun, Nov 22, 2015 at 10:07 AM, Stephen Warren <swarren at wwwdotorg.org>
wrote:

> Before you do anything, you should take an image of both drives onto a
> third unrelated drive so nothing gets worse.
>
> To find out exactly which physical volumes contain (various parts of)
> your logical volumes, you can do a couple of things:
>
> a) Run the command: "lvdisplay --maps".
>
> This will list all the LVs in your system, and for each, a list of
> segments showing where those segments are stored.
>
> b) Look at the file "/etc/lvm/backup/${vg_name}"
>
> (replace "${vg_name}" with the name of your VG)
>
> Again, the "logical_volumes" section contains an entry for each LV, and
> within each of those, there is a list of "segment" sections that
> indicates where the data is stored.
>
>
> You might be lucky; even though your VG includes PVs from both physical
> disks, unless your LV is large enough not to fit into the first PV, it's
> possible the second PV isn't used yet.
>
> Of course, hopefully you have backups just in case.
>
> On 11/22/2015 09:32 AM, Ryan Clemens wrote:
> > You've almost certainly overwritten the partition table on sdb. As long
> as
> > your system boots and starts up you probably had no real data on it
> before,
> > so you're fine to keep using your current red hat install.
> >
> > I'd recommend using "parted" (or your favorite red hat dish utility) to
> > repartition sdb however you wish and then modify your etc/fstab file (or
> > some red hat dish utility) to mount the partition at boot to be able to
> use
> > it again.
> > On Nov 22, 2015 09:17, "Ray Frush" <phred at rflm.net> wrote:
> >
> >> Well, that was unexpected.   A default Redhat install will use LVM to
> >> allocate space on /dev/sda, so that’s expected, but it’s been a while
> since
> >> I’ve installed on a system with two disks.  I didn’t expect it to use
> >> /dev/sdb as well.  (Usually, I’ll add in a second disk after the base
> >> install)   Did the disk layout get customized during install?
> >>
> >>
> >> In any case, your Volume Group is made up of physical volumes from both
> >> /dev/sda2 and /dev/sdb1, and then I’m guessing the Logical Volumes were
> >> allocated out of that combination of space.   Since you’ve overwritten
> >> /dev/sdb (and /dev/sdb1) with the contents of a large ISO file,  I
> wouldn’t
> >> expect any data on /dev/sdb1 to be recoverable.
> >>
> >> —
> >> Ray Frush
> >>
> >>
> >>> On 22 Nov 2015, at 8:50 AM, Vincent Randal <vtrandal at gmail.com> wrote:
> >>>
> >>> Thanks Ray, you given me a good idea where to look for the problem.
> >>>
> >>> sudo vgdisplay -v | tail -n 11
> >>>    Using volume group(s) on command line. # what?
> >>>  --- Physical volumes ---
> >>>  PV Name               /dev/sda2
> >>>  PV UUID               9KDSFf-xdes-deo2-18nd-Z3GW-VLlq-JMbmiL
> >>>  PV Status             allocatable
> >>>  Total PE / Free PE    59257 / 0
> >>>
> >>>  PV Name               /dev/sdb1
> >>>  PV UUID               Ceh1Cc-aGH7-voMx-rbpR-fXAj-MvOr-sWEqwn
> >>>  PV Status             allocatable
> >>>  Total PE / Free PE    121990 / 0
> >>>
> >>> sudo vgck
> >>>  Couldn't find device with uuid Ceh1Cc-aGH7-voMx-rbpR-fXAj-MvOr-sWEqwn.
> >>>  The volume group is missing 1 physical volumes.
> >>>
> >>> sudo pvck /dev/sdb1
> >>>  Could not find LVM label on /dev/sdb1
> >>>
> >>> Maybe I can fix the problem from steps described here?
> >>>
> >>
> https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/mdatarecover.html
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