sda2 is corrupted

[Jim]

On 07/06/2012 12:02 PM, Michael Schwendt wrote:
> On Fri, 06 Jul 2012 11:22:55 -0400, Jim wrote:
>
>>>> /dev/sdb1 is now a blockwise copy of /dev/sda2
>>> On 05.07.2012, Jim wrote:
>>>
>>>> There are some important data files  I must save off of sda2
>>> Before you start any rescueing, take a full snapshot of the partition,
>>> e.g. "dd if=/dev/sda2 of=/dev/on_an_external_disk"
>>>
>>>
>>>
>> that is exactly what I did but nothing shows up on /dev/sdb1 external
>> drive after dd has completed .
> That makes no sense. If /dev/sdb1 points at a corrupted filesystem,
> above "dd" command will copy the same corrupted filesystem to /dev/sda2.
> That's expected and okay, if you only want to keep that one read-only as
> a backup of the originally corrupted filesystem. Then you can play with
> rescueing sdb1 - but be careful and remember that sda2 is supposed to be
> your backup of a corrupted filesystem. Don't mess with that one.
>
> Better would have been to copy sdb1 to an image file instead of another
> partition device.
>
sda2 is the corrupted file system.
I'm trying to send a img of the sda2 to backup hard drive sdb1 .
I' running into a read-only filisystem on sda3 , but :

# mount | grep sda3

/dev/sda3 on / type ext4 (rw,relatime,seclabel,data=ordered)

it say it is rw but when i run the dd command i get a read-only filesystem.