[CentOS] remote tar via ssh

Wed Sep 26 19:22:02 UTC 2007
Von Landfried <centos.list at eyestreet.com>

I copied this from <http://happygiraffe.net/copy-net> which is a nice  
little tutorial for remote copying of files.

tar is normally an archiving program for backups. But with the use of  
ssh, it can be coerced into copying large directory trees with ease.  
It has the advantage that it copies things correctly, even ACLs on  
those Unixes which have them, as well as being perfectly comfortable  
with symlinks.
The syntax, however, is slightly baroque:

tar -cf - /some/file | ssh host.name tar -xf - -C /some/place/cool
Whilst it looks complex, at heart it's quite simple: create a tar  
archive to stdout, send it across the network to another tar on the  
remote machine for unpacking.

The arguments to the first tar are -c to create a new archive and -f  
-, which tells tar to send the newly created archive to stdout.

The arguments to the second tar command are the reverse: -x to  
extract the archive and -f - to take the archive from stdin. The  
final -C /destination tells tar to change into the /destination  
directory before extracting anything.

Why should you use this method when the other two are available? For  
initial copying of large directory trees, this method can be very  
quick, because it streams. The first tar will send it's output as  
soon as it has found the first file in the source directory tree, and  
that will be extracted almost immediately afterwards by the 2nd tar.  
Meanwhile, the first tar is still finding and transmitting files.  
This pipeline works very well.

As with the other two methods, you can ask for compression of the  
data stream if your source data is amenable to it. Here, you have to  
add a -z flag to each tar:

tar -czf - /some/file | ssh host.name tar -xzf - -C /some/place/cool
In a similiar fashion, you can enable verbose mode by passing a -v  
flag to the 2nd tar. Don't pass it to the first one as well, or  
you'll get doubled output!

Why shouldn't you use this method?

The syntax is a pain to remember.
It's not as quick to type as the scp command, for small amounts of  
rsync will beat it hands down for a tree of files that already exists  
on the destination.

On Sep 26, 2007, at 3:15 PM, ann kok wrote:

> Hi all
> Can I use ssh to have remote tar files from machine A
> to machine B?
> ssh from machine A to machine B
> tar all files in machine B to exact to machine A
> Thank you
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