Linux – SCP transfer only modified files

centoslinuxrsyncscp

I'm using below command to transfer files cross server

scp -rc blowfish /source/directory/* username@domain.net:/destination/directory

Is there a way to transfer only files modified files just like update command for cp?

rsync is your friend.

rsync -ru /source/directory/* username@domain.net:/destination/directory

If you want it to delete files at the destination that no longer exist at the source, add the --delete option.

You can add -o options to scp instead of .ssh/config.

scp -o ProxyCommand="ssh $jump_host nc $host 22" $local_path $host:$destination_path

$jump_host is your "server B" in this case.

DEPRECATED: Please note the following answer is out of date. rssh is no longer maintained and is no longer a secure method.

rssh shell (http://pizzashack.org/rssh/) is designed for precisely this purpose.

Since RHEL/CentOS 5.2 doesn't include a package for rssh, you might look here to obtain an RPM: http://dag.wieers.com/rpm/packages/rssh/

To use it just set it as a shell for a new user like this:

useradd -m -d /home/scpuser1 -s /usr/bin/rssh scpuser1
passwd scpuser1

..or change the shell for an existing one like this:

chsh -s /usr/bin/rssh scpuser1

..and edit /etc/rssh.conf to configure rssh shell - especially uncomment allowscp line to enable SCP access for all rssh users.

(You may also want to use chroot to keep the users contained in their homes but that's another story.)