How to kill an unresponsive SSH session

Read the SSH man pages every so often, even if you think you know how to use it. There's a lot of features in there. Don't miss the "AUTHORIZED_KEYS FILE FORMAT" in sshd's man page for the uber-cool "command='command'" options for authorized keys (restricts a given key to just be able to run a certain command, very useful). See also SSH's port forwarding, -D, learn how to use ssh-agent, and "man ssh_config".

Or use mosh[1] on top of SSH and stop worrying about that stuff.<p>It works much better over high-latency links (mobile). It is not bothered by saturated links, tolerates IP changes and losing the underlying connection like when you suspend your laptop and take it elsewhere.<p>I now have mosh connect to several servers in tabs when I run gnome-terminal the first time, and only disconnect on reboot. I also run a mosh-capable Irssi Connectbot fork on the phone[2].<p>It&#x27;s a massive improvement, fixing many of the little annoyances of ssh.<p>[1] <a href="http://mosh.mit.edu/" rel="nofollow">http:&#x2F;&#x2F;mosh.mit.edu&#x2F;</a><p>[2] <a href="http://dan.drown.org/android/mosh/" rel="nofollow">http:&#x2F;&#x2F;dan.drown.org&#x2F;android&#x2F;mosh&#x2F;</a>

The default escape character ~ does not work if the tilde key in your keyboard layout is a dead key [1], like it is in many European layouts. It can be changed via the EscapeChar config option or the -e command line parameter. It seems, though, that not just any old character is accepted - I tried to use §, which, in the Finnish layout, is in the same physical position as ~ is in the US version, but ssh complains about &quot;bad escape character&quot;.<p>EDIT - I suppose it must be an ASCII character, which is not an entirely unreasonable requirement.<p>[1] <a href="http://en.wikipedia.org/wiki/Dead_key" rel="nofollow">http:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Dead_key</a>

enter-tilde-dot<p>It is useful, yes. Here&#x27;s another thing I picked up last week - how do you reboot a remote linux box that&#x27;s somehow lost its root drive but you still have a shell open (because you left ssh running on another machine)?<p><pre><code> echo 1 &gt; &#x2F;proc&#x2F;sys&#x2F;kernel&#x2F;sysrq echo b &gt; &#x2F;proc&#x2F;sysrq-trigger</code></pre>

Another useful trick to remember if you&#x27;re using Putty and you ever accidentally hit Ctrl-S and find that you&#x27;ve frozen the terminal.<p>Just type Ctrl-Q and you will unfreeze the connection.<p>Credit due to: <a href="http://raamdev.com/2007/recovering-from-ctrls-in-putty/" rel="nofollow">http:&#x2F;&#x2F;raamdev.com&#x2F;2007&#x2F;recovering-from-ctrls-in-putty&#x2F;</a>

&lt;enter&gt;~Ctrl-Z will suspend the ssh session, too.<p>I&#x27;ve also found it useful to do &lt;enter&gt;~C - then you can configure port forwarding without having to open a new ssh session.<p>(~C opens a command line, enter &quot;help&quot; for available commands.)

Please don&#x27;t let HN become a substitute for RTFM. This should be known by all SSH users who have skimmed the man page. Fair enough as a blog post but for this trivia to get 46 points so far is deeply depressing.<p>Maybe I should write a blog post about the use of CTRL-Z in the shell and post that here, should get me Kilo-karma points if this is anything to go by.

If you happen to be a few sessions deep, ~~ will send ~ to the next session along. A casual ~~~~~~~~~~~. or so later and everything is wonderful again!

In case anyone is having difficulty with the font used on the page, the escape sequence is: newline followed by tilde (~) and then period (.).

The thing that amazes me about this is that people don&#x27;t realise that this comes from BSD 4.2 rsh released in 1983.

I&#x27;m a little surprised this is on HN? To me this is the equivalent of a blog post about using %d with printf.<p>Not complaining, just a little surprised something so novice would get attention...

Another great solution is to just use the ServerAliveInterval option.

While I&#x27;ve frequently used this to kill connections, my favorite thing I&#x27;ve done with it is to list existing and dynamically add new forwarding ports through SSH.

Hitting &#x27;.&#x27; at a prompt used to be a common idiom for exiting a program. I first saw it when I was a kid working on an HP-3000 system where the system programming language was BASIC and all programs followed this convention. Don&#x27;t know where it came from originally, but you can still see it in places like rsh&#x2F;SSH etc.

Does it work too with ctrl-\ ? This has been my process killer recently and it&#x27;s powerful (and the only way I know to get out of xtail.)

On a side note, does anyone know what ~B actually does? Does it send a SIGINT to the remote terminal? What does ssh mean by the phrase &quot;send a BREAK to a remote system&quot;?<p>I&#x27;ve tried to use it without success to kill a runaway listing of megabytes of scrolling text, but frantically hitting ctrl-C seems to work much better.

This usually doesn&#x27;t work for me. Perhaps it&#x27;s because my sessions are usually multiplexed via &quot;ControlMaster auto&quot;?

[Enter] Shift+~ .

I&#x27;m surprised&#x2F;apalled at how many people upvote this, considering how this place is supposed to be &quot;hacker news&quot;...