SSH Multiplexing: a faster way to SSH
How it works:
By changing the way you ssh to a machine, you can reuse your initial ssh connection to save time when connecting.
Edit your ~/.ssh/config file to have this:
Host *
ControlMaster auto
ControlPath ~/.ssh/sockets/%r@%h:%p
We avoid problems of reusing the default /tmp but storing our connections in their own directory.
Be sure to create the directory:
mkdir -m 700 -p ~/.ssh/sockets
When was it available:
The functionality has been available since OpenSSH 3.9.
Usefulness:
I has come in handy for those hard to type passwords. Once in, a repeat ssh on another (local) terminal to the same machine will take just a few miliseconds and you have a command prompt to work with.
Security:
One caveat is that this is on a per-user basis, so if you want to connect with a different username then you will have to initialize a new connection. This also means that anyone using your machine can then reuse your connection to log into the remote machine. This could be a security issue for you.