Using Netcat for Backup

Using Netcat for Backup

Providing you have netcat installed, on the destination machine execute the following command:

nc -l -p 6666 > filename.tar.bz2

This creates a listening socket on port 6666 with the filename specified above.

We now need to setup the source machine to dump whatever directories or filesystems you want to send to the destination machine.

So on the source you can issue the following command:

tar jlcvPpf - / > /dev/tcp/192.168.0.2/6666

In the example above 192.168.0.2 is the address of the destination address and the forward slash indicates that it is the entire filesystem to be backed up. You can easily change this for example to tar jlcvPpf - /var/www > /dev/tcp/192.168.0.2/6666 to backup the /var/www directory.

If there is no /dev/tcp it is possible to use netcat on both ends

tar jlcPpf - / | nc 192.168.0.2 6666

The options for the tar command are as follows:

• j - do bzip2 compression on the archive
• l - one file system (more on this later)
• c - create archive
• v - be verbose about it
• P - don't strip leading / from pathnames
• p - preserve permissions
• f - the file name to write, which in this case is - which means standard output.

Sending back the compressed archive

There is no need to send the whole archive back to the client, and then decompress it. This can all be done at once

• On host machine

nc -l -p 6666 < foo.tar.bz2

• On client machine

nc 192.168.0.2 6666 | tar -xj

If the client is a very slow machine it might be faster to decompress on the host

(Host)

bzip2 -d --stdout foo.tar.bz2 | nc -l -p 6666

(Client)

nc 192.168.0.2 6666 | tar -x