Steven You

A Forged Geek.

SSH ControlMaster

Lots of people recommond using ControlMaster:

Host *
ControlMaster auto
ControlPath /tmp/%r@%h:%p

This will re-use the exiting connections instead of creating a new one, so that it can speed up the ssh connection.

To make it more convenient, this line can be added to ~/.ssh/config

ControlPersist 600

This will make the ControlMaster stay alive for 600 seconds after last existing ssh session is quit.

A regular issue I encountered using ControlMaster is that in some cases I want to kill ssh ControlMaster active connection.

For example, when I run ssh tunnel command ssh -L 8888:localhost:8888 host.com twice, the tunnel won’t work anymore.

In order to kill the active connection, use

ssh -O check host.com

to check status, and

ssh -O exit host.com

to exist the active connection.

If you want to delete all connections (not just the connection to a particular host) in one fell swoop, then fuser /tmp/ssh_mux_* or lsof /tmp/ssh_mux_* will list the ssh clients that are controlling each socket. Use fuser -HUP -k tmp/ssh_mux_* to kill them all cleanly (using SIGHUP as the signal is best as it lets the clients properly remove their socket).

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