Tip: Faster remote shells with multiplexed SSH

Edit ~/.ssh/config (or /etc/ssh/ssh_config for sitewide configuration) and add the following snippet:

Host *
   ControlMaster auto
   ControlPath ~/.ssh/socket-%r@%h:%p

This will create a socket for each set (user, machine, port) when the first SSH session is opened. Further sessions will see the socket and use it instead of opening a new connection, multiplexing all concurrent connections via the same connection. The same goes for scp and sftp.

Nice side-effects of this:

  • No functionality is lost at all.
  • SSH sessions will open faster, as there is no need to establish a connection.
  • You will not need to enter you password everytime (but note that maybe you should be using public-key authentication).
  • You can open several sessions to servers which put a limit on the number of simultaneous connections.
  • If you are a sysadmin, you can limit the number of SSH connections to exactly one per user :-)

Hope you find this tip useful :-P

This entry was posted on Thursday, June 26th, 2008 at 7:37 pm and is filed under Toolchain. You can follow any comments to this entry through the RSS 2.0 feed. You can leave a comment, or trackback from your own site.

3 comments

  1. Sergio
    July 3, 2008 at 2:17 pm

    Wow, very useful tip, thx. The speed up is really great.

    Reply
  2. aklis
    August 12, 2008 at 1:05 am

    Nice tip.

    As counterpart, if someone logged in your machine can read the ~/.ssh/socket-*,he could login to hosts using those credentials.

    Reply
  3. aperez
    August 12, 2008 at 2:23 am

    @aklis: You are right. Fortunately OpenSSH is very picky regarding permissions of the ~/.ssh directory and will print a big warning if its permissions are different from 0700. That’s the reason why I always put session sockets in that directory ;-) . Thanks for pointing out that issue.

    Reply

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