looking for thread about backup using ssh -T

[Bill Davidsen]

Cameron Simpson wrote:
> On 12Apr2008 13:15, Mike Wright <mike.wright at mailinator.com> wrote:
>> Hi all,
>>
>> There was a fascinating thread about using ssh to do backups to a remote 
>> host without using a term.  Something like:
>>
>>     "tar jc some_dir | ssh -T user at remote cat > backup"
>>
>> Tried the examples and then some --- works great!
>>
>> I seem to have fat-fingered the delete key and have lost that email thread 
>> and try for the life of me can't find it again.
> 
> Get rid of the -T. The "cat >backup" needs to be executed by the shell
> at the far end, so quote it:
> 
>   tar cf - some_dir | ssh user at remote 'cat >backup'
> 
I don't think you totally understand -T, should be used whenever the 
stdin is not a tty. Failure to do so can cause some issues with binary 
files being transferred, from memory the binary can contain the escape 
character.

 From the man page:

"If no pseudo-tty has been allocated, the session is transparent and can 
be used to reliably transfer binary data."

Mike - please ignore the advice to drop -T, it is not correct!!

> Without the quotes your local shell takes the ">backup" and funnels the
> data to the _local_ file "backup". So you pump the backup over the net
> via ssh, and _back_ again, landing locally.

That advice is exactly correct. You can also use dd instead of cat, some 
people claim that the buffering helps. I don't see it myself. ;-)


-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot