SSH to a machine behind firewall
(This post is mostly for myself, because I know I'll forget the exact syntax next I need it)
I've recently discovered that instead of ssh to one machine and then ssh to another machine in the local network, I can configure ssh to start the proxy connection automatically. For example:
Host example-local-10 HostName 192.168.0.10 ProxyCommand ssh example.com nc %h %p 2> /dev/null
Especially useful when working with various tools that just use the ssh transport protocol, like scp or rsync.