How to reuse an ssh connection

user_115025 0
Viewed 20618

I'm creating a small script to update some remote servers (2+)
I am making multiple connects to each server; is there a way I can reuse the SSH connections so I don't have to open too many at once?

ssh
4 Answers

If you open the first connection with -M:

ssh -M $REMOTEHOST

subsequent connections to $REMOTEHOST will "piggyback" on the connection established by the master ssh. Most noticeably, further authentication is not required. See man ssh_config under "ControlMaster" for more details. Use -S to specify the path to the shared socket; I'm not sure what the default is, because I configure connection sharing using the configuration file instead.

In my .ssh/config file, I have the following lines:

host *
  ControlMaster auto
  ControlPath ~/.ssh/ssh_mux_%h_%p_%r

This way, I don't have to remember to use -M or -S; ssh figures out if a sharable connection already exists for the host/port/username combination and uses that if possible.

This option is available in OpenSSH since 2004.

user_11268410

For modern-distro setups that have a /run/user/$UID/ for just-this-boot runtime stuff,

controlmaster auto
controlpath /run/user/%i/ssh-%C
controlpersist 900

at the top of the config (where no match or host restrictions are in effect) will set all ssh sessions that share hosts, port and remote username to use a single connection. I keep addkeystoagent yes and identityfile ~/.ssh/id_ed25519 up there too so ssh doesn't offer all my keys for every host.

user_12907310
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