Re: Remote backup using GNU tar doesn't work

[Colin S. Miller]

Saurabh Barve wrote:
> Hi,
>
> I'm trying to do a remote backup of system to a tape drive connected to 
> another system. I have set up public key authentication between the 
> systems, so that I can log in as root without passwords. The setup is 
> like this:
>
>
> Tape Drive----System A<----->System B
>
> I want to write data from System B on to tape in the tape drive 
> connected to System A.
> To test the connection, I do:
>
> [System A]# ssh System B tar -b 512 --rsh-command=/usr/bin/ssh -tvf 
> System A:/dev/nst0
>
> However, this gives me an error:
>
> ---
> Permission denied, please try again.
> Permission denied, please try again.
> Permission denied (publickey,gssapi-with-mic,password).
> tar: SystemA\:/dev/nst0: Cannot open: Input/output error
> tar: Error is not recoverable: exiting now
> ---
>
> Allocating a pseudo-TTY helps in getting the remote tar command to work. 
> But I'm prompted to enter my key passphrase:
>
> ---
> [System A]# ssh -t System B tar -b 512 --rsh-command=/usr/bin/ssh -tvf 
> System A:/dev/nst0
>
> Enter passphrase for key '/root/.ssh/id_rsa':
> ---
>
> However, I want this to be non-interactive. I can run the tar command 
> locally on System B and it works fine.
> I am running tar-1.15 on both machines. On System A, I'm running OpenSSH 
> 4.2p1, and on System B I'm running OpenSSH 3.6.1p2
>
> Is there a way to do what I want?
>
> Thanks,
> Saurabh

It looks like you have set up a ssh keypair (ssh-keygen).
If you set the key's password to the empty string,
you won't be prompted for a password.

If this is too much for a security risk, you can set up a
'tar' user on the remote machine, and use sudo to run tar.
You then set up a passwordless keypair for the 'tar' user.


HTH,
Colin S. Miller





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