Restore from Tape

[vaidyas]

Hi,
I had performed a full backup of my Unix system on a Tape Disk through
the cpio utility. It had taken 3 tapes to perform the backup. Recently I
had deleted an directory on the system and wanted to restore from the
tape. Accidently I kept the tape onto the drive and an automatic backup
program overwrote the contents of the tape.
My question is :
a) Is it possible to recover the data on the first tape?
b) Is it possible to list the contents of the 2nd and 3rd tapes and
recover the directory from these tapes?
I had issued the following command to write onto the tape :
"find . -print | cpio -ocvB -O /dev/rmt/c0t3d0s0"

Your comments pls.

--
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[tony@aplawrence.com]

vaidyas <member34319@dbforums.com> wrote:

>Hi,
>I had performed a full backup of my Unix system on a Tape Disk through
>the cpio utility. It had taken 3 tapes to perform the backup. Recently I
>had deleted an directory on the system and wanted to restore from the
>tape. Accidently I kept the tape onto the drive and an automatic backup
>program overwrote the contents of the tape.
>My question is :
>a) Is it possible to recover the data on the first tape?

Not with any tools or equipment you have. It is POSSIBLE for a data recovery
firm to get some of it back, or maybe even all of it if you have enough
money, but it isn't at all easy, and it wouldn't be cheap. I'm not
talking small money here.. this would be real esoteric stuff that would
be going after overwritten magnetic domains until it reached the EOT
mark. The EOT mark itself is a killer of data, and it's impossible
to move beyond it with ordinary equipment. Even writing JUST an
EOT at the beginning of a tape is a problem and of course you have done
much more.

>b) Is it possible to list the contents of the 2nd and 3rd tapes and
> recover the directory from these tapes?

Assuming what you want is there, why not?

cpio -itv < /dev/rmt/c0t3d0s0
cpio -icdumv ./desireddata < /dev/rmt/c0t3d0s0

BTW, you are doing at least two silly things:

1) not having multiple tapes
2) not using a supertar: [url]http://aplawrence.com/Reviews/supertars.html[/url]


--
[email]tony@aplawrence.com[/email] Unix/Linux/Mac OS X resources: [url]http://aplawrence.com[/url]
Get paid for writing about tech: [url]http://aplawrence.com/publish.html[/url]

[Bob Bailin]

<tony@aplawrence.com> wrote in message news:bg2ubr$u82$3@pcls4.std.com...

> vaidyas <member34319@dbforums.com> wrote:
>

> >Hi,
> >I had performed a full backup of my Unix system on a Tape Disk through
> >the cpio utility. It had taken 3 tapes to perform the backup. Recently I
> >had deleted an directory on the system and wanted to restore from the
> >tape. Accidently I kept the tape onto the drive and an automatic backup
> >program overwrote the contents of the tape.
> >My question is :
> >a) Is it possible to recover the data on the first tape?

>
> Not with any tools or equipment you have. It is POSSIBLE for a data

recovery

> firm to get some of it back, or maybe even all of it if you have enough
> money, but it isn't at all easy, and it wouldn't be cheap. I'm not
> talking small money here.. this would be real esoteric stuff that would
> be going after overwritten magnetic domains until it reached the EOT
> mark. The EOT mark itself is a killer of data, and it's impossible
> to move beyond it with ordinary equipment. Even writing JUST an
> EOT at the beginning of a tape is a problem and of course you have done
> much more.
>
>

> >b) Is it possible to list the contents of the 2nd and 3rd tapes and
> > recover the directory from these tapes?

>
> Assuming what you want is there, why not?
>
> cpio -itv < /dev/rmt/c0t3d0s0
> cpio -icdumv ./desireddata < /dev/rmt/c0t3d0s0
>
> BTW, you are doing at least two silly things:
>
> 1) not having multiple tapes
> 2) not using a supertar: [url]http://aplawrence.com/Reviews/supertars.html[/url]

3) not using the write-protect tab on the tape cartridge each & every time
you do a restore.

[Evgeniy Petrov]

I have a strimer /dev/st0 (Linux Suse 8.0)

I write to strimer using command
tar cfv /dev/st0 myfile
How can I read tape (only read)
If I write
tar tf /dev/st0
nothing happend. Is it correct syntax? Does it meen that tape is empty?

How can I restore files from tape to another location (not original)?
Should I use command mt before read from tape (or write) and what is correct
syntax?
Should I do anything with new tape before using it in my strimer?.

[Evgeniy Petrov]

> I write to strimer using command

> tar cfv /dev/st0 myfile

And is strimer understand that he should clear tape and start new session?

[K7MEM]

Evgeniy Petrov wrote:

> I have a strimer /dev/st0 (Linux Suse 8.0)
>
> I write to strimer using command
> tar cfv /dev/st0 myfile

This is correct for creating a tape.

> How can I read tape (only read)
> If I write
> tar tf /dev/st0
> nothing happend. Is it correct syntax? Does it meen that tape is empty?

However, this command is only for obtaining a table of contents
from the tape. You are missing the "v", or "verbose" option so you
probably don't see anything on the screen.

>
> How can I restore files from tape to another location (not original)?
> Should I use command mt before read from tape (or write) and what is correct
> syntax?
> Should I do anything with new tape before using it in my strimer?.
>

When you initially created the tape you probably used:

cd [some directory]
tar cfv /dev/st0 myfile

Note that if "myfile" was replaced with "mydirectory", "tar" would
transfer the directory and it's contents to tape.

To obtain a a table of contents from the tape you could use:

tar -tvf /dev/st0

Then to restore your file to another directory you could use:

cd [some other directory]
tar -xvf /dev/st0

You need to carefully read the man page. It gives you some examples
that could be useful.

--
Martin E. Meserve
[email]k7mem@myrealbox.com[/email]
[url]http://www.k7mem.150m.com[/url]

[Scott McMillan]

On Wed, 7 Jul 2004 13:39:03 +0400, "Evgeniy Petrov"
<evg@mail.wurth.ru> wrote:

>I have a strimer /dev/st0 (Linux Suse 8.0)
>
>I write to strimer using command
>tar cfv /dev/st0 myfile
>How can I read tape (only read)
>If I write
> tar tf /dev/st0
>nothing happend. Is it correct syntax? Does it meen that tape is empty?
>
>How can I restore files from tape to another location (not original)?
>Should I use command mt before read from tape (or write) and what is correct
>syntax?
>Should I do anything with new tape before using it in my strimer?.
>

Add the v option, as in
tar tvf /dev/st0

to have tar show you the file(s) on the tape. man tar for *many* more
options.


Scott McMillan

[Doug Freyburger]

Evgeniy Petrov wrote:

>
> I have a strimer /dev/st0 (Linux Suse 8.0)

Generally you should use /dev/rst0.

> I write to strimer using command
> tar cfv /dev/st0 myfile

What is the output from that command? If "myfile" is not in
the current directory, the command will write an empty file
on the tape.

> How can I read tape (only read)
> If I write
> tar tf /dev/st0
> nothing happend. Is it correct syntax? Does it meen that tape is empty?

It is correct and it does mean the tape is empty.

> How can I restore files from tape to another location (not original)?

First goal - A tape that is not blank. Locate "myfile" carefully
or spell it correctly.

> Should I use command mt before read from tape (or write) and what is correct
> syntax?

I prefer to do "mt -f /dev/rst0 rewind ; sleep 1" before each tar,
but that assumes that the definitions of /dev/rst0 and /dev/nrst0
have been combined so the automatic rewind function has been broken.
I'm paranoid that way.