Comments on: Smart Tricks with ssh

By: ssh with unstable and mobile clients | Software Cooperative News

ssh with unstable and mobile clients | Software Cooperative News — Sat, 21 Nov 2009 07:14:17 +0000

[...] Smart Tricks with ssh mentioned ServerAliveInterval 3600 and the page I referenced for it mentions ClientAliveInterval on the server-side. Is there any reason not to use that? [...]

By: MJ Ray

MJ Ray — Tue, 20 Jan 2009 12:27:44 +0000

Pete Savage: SSH tunneling :: The next step http://www.progbox.co.uk/wordpress/?p=580 describes the -w flag which was a new one on me, setting up tun network devices.

By: daFux

daFux — Sun, 14 Dec 2008 20:02:07 +0000

Portforwarding (or rather the lack of it in the non-master sessions) is a serious issue. “ssh -S none” is your friend in such a situation.

By: Philipp K.

Philipp K. — Sat, 13 Dec 2008 11:59:06 +0000

Port forwarding only works in the master session, but since most of my port forwardings are setup in .ssh/config anyway, that doesn’t bother me too much.
More annoying is IMHO that agent- and X-forwarding also only works when you thought of it at the time of establishing the master session. I often have to go through my tabs to find and kill the master session to a particular host, because the need for remote X or key forwarding only came up later.
Even so, I’m still staying with “ControlMaster auto”, as it certainly causes more convenience than harm for me.

By: Matt Simmons

Matt Simmons — Fri, 12 Dec 2008 00:41:23 +0000

Hi! Thanks a lot for the link to Standalone Sysadmin. I’m glad you found the series useful. Most of the credit goes to the other people who have been writing the other entries, but I’m happy to point to them!

Take care!

By: Np237

Np237 — Thu, 11 Dec 2008 16:59:23 +0000

I have noticed two major issues while using ControlMaster already:
– port forwarding only seems to work in the master session
– after some time, new connections are rejected, and I have yet to understand why.

By: Michal Čihař

Michal Čihař — Thu, 11 Dec 2008 12:55:39 +0000

Thanks for noticing typo, fixed .

By: Josh Triplett

Josh Triplett — Thu, 11 Dec 2008 12:44:35 +0000

Yes, ControlMaster auto does have one major disadvantage: the first SSH session you start to a new system becomes the control master, and thus it can’t exit until all other SSH sessions using that same control master exit. So if you go to a terminal, run SSH, and then in another window do something else that opens an SSH session to the same host, the SSH in your original terminal will not exit after you quit.

However, if you set ControlPath but not ControlMaster, you can still enable ControlMaster for a specific SSH connection with the -M option to ssh. That way, you can control which instance of SSH becomes the control master.

Personally, I wish SSH had the ability to fork off a new control master in the background if one doesn’t already exist, and then that control master could automatically exit if a given amount of time passes since the last connection.