How to read a Physical Tape outside of the NetVault Sofware by using CygWin installed on a Windows Machine (4041778)

When NetVault loads a tape and encounters a problem reading the tape, it can mark it as:

Unknown:
Foreign:
Other:
BAD:
Read-only:
Unusable:

Please consult other KBs to find the causes for NetVault marking a tape to each of the above labels.

Usually, the only thing you can do with a tape that is labeled with one of the labels above is blank them if they are NOT marked as Read-ONLY

For each condition above the KB 79596 gives steps to resolve.

A special situation is when the NV Software is able to successfully load the media onto the tape drive and successfully reads the header of the tape but marks it as OTHER.

Tapes marked as "Other"

Tapes from other backup software vendors (such as Veritas, BackupExec,etc) will show up as "other", indicating that there *is* data on the tape, but that it can't be read by NetVault.

All that NetVault can do with such tapes is blank them so that they can be used in NetVault. https://support.quest.com/SolutionDetail.aspx?id=SOL79895

Under certain conditions, you want to read at least the header of the tape to confirm if that tape was written with a different OS or if that tape was written by a different backup software.

When you need to read a tape outside of the NetVault Software, If you are using a Linux type Operating system,  you can use the native dd and mt commands that come with the OS

If the Tape Library is attached to a Windows Machine or the NetVault Backup Server software is running on a Windows machine, it becomes harder to read the tape outside of the NV software.

Here is how you use CygWin on a Windows machine to read the header of a tape that is loaded to a tape drive that is properly added to the server.

1)- Firstly you need to have the CYGWIN utility installed on the Windows Machine that has access to the tape drive and has it showing up on its Device management.

Note, you will need to make sure that you have the mt and the dd commands from CYGWIN installed to the machine.

Here is how  the mt command is installed windows machine, if they are not currently present.

a)- Plac the setup-x86_64.exe  on  C:\cygwin64\setup-x86_64.exe.

b)- Create an alias, so you can install any Cygwin package that You do not currently have.

alias cyg-get="/cygdrive/c/cygwin64/setup-x86_64.exe -q -P"

c)-Now, install any package of Cygwin on your machine by using the syntax  (cyg-get <<<<package_name>>>)

iex.   'cyg-get mt'

2)-Next, You need to determine the Windows TAPE SYMBOLIC NAME for the tape drive with the tape that you want to read with the dd command.

a) Open Device Management

b)- click on the arrow by ape Drives.

c)-All Tape Drives visible to the OS, will be under this groupt

d) Right Click on the Tape Drive that contains the tape that you want to read and select Properties.

e)- TAPE SYMBOLIC NAME is one of the tabs.

Note: make sure that the NV services is stopped and that the tape drive is not busy or locked by other software.

         If you do not see TAPE SYMBOLIC NAME as one of the options, you can try using /dev/st0 for the tape0 (the first tape drive) or /dev/st1 for second tape drive and on.

3)- Next, you need to use the Cygwin mt command to rewind the tape to the POSITION 0  (the beginning of the tape)

Note.. Remember  that CygWin is a POSIX environment and you MUST use POSIX syntax.

You MUST address a file placed into C:\cygwin64\setup-x86_64.exe  by using the corresponding POSIX syntax which is "/cygdrive/c/cygwin64/setup-x86_64.exe”

You MUST address a Tape Drive with the Symbolic Name Tape0   by using "/dev/st0”

A good way to test if you are addressing the correct Tape Drive and using the correct Cygwin (POSIX) syntax is do a Status inquire to the tape drive:

mt -f /dev/st0 status

To be able to rewind the  tape to the beginning, just issue the following command:

mt -f /dev/st0 rewind

4)- Now that your Tape Drive rewound the tape to the beginning, you are ready to read the header of the tape which are the first 32 Kbytes of the data.

dd if=/dev/st0 of=/cygdrive/c/Header.txt bs=32k count=1

Please note the POSIX address (/cygdrive/c/Header.txt) in order to save the file with the header of the tape to the root of C:\ Drive under the name Header.txt

We are only reading the header of the tape .. so using bs=32k and count=1 is what we need.

5)- Please use any Hex Editor to read the file .

HxD Hex Editor is just one of the many  that you can get from the Web.

The Tape  header contains other information but you should vbe looking for the  Word Tape starting at the address 00000000, and the word:

NetVault Domain  at the address 00000151

The result on the file C:\Header.txt will contain something like:

TAPE

..........

N.e.t.V.a.u.l.t. .D.o.m.a.i.n

From this point on, you could restore the whole tape or a group of tapes outside the NV software, but this would be much more complex and outside of the scope of this KB.