openssh bugs - May 2008 - [Bug 1473] New: Add option to save PID of a backgrounded ssh process

https://bugzilla.mindrot.org/show_bug.cgi?id=1473

           Summary: Add option to save PID of a backgrounded ssh process
    Classification: Unclassified
           Product: Portable OpenSSH
           Version: 5.0p1
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: ssh
        AssignedTo: bitbucket at mindrot.org
        ReportedBy: tsteiner at nerdclub.net


When sending an ssh session to the background, there is no option to
save the forked process's PID to a file.  This would be very helpful
when writing scripts that manage ssh tunnels.  An example of such usage
would be:

ssh user at host -L 123:remote.host:456 -f /var/run/tunnel.pid -N

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473


Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org




--- Comment #1 from Damien Miller <djm at mindrot.org>  2008-05-29
05:12:16 ---
You can control a running SSH process using the control socket

ssh -nNfL 123:remote_host:456 -MS ~/.ssh/ctl-%r-%h-%p__%l user at host

You can ask the master process to exit gracefully using:

ssh -S ~/.ssh/ctl-%r-%h-%p__%l -O exit user at host

See the ControlPath and ControlMaster documentation in ssh_config(5)
for more information.

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473


Darren Tucker <dtucker at zip.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dtucker at zip.com.au




--- Comment #2 from Darren Tucker <dtucker at zip.com.au>  2008-05-29
10:10:58 ---
You can also do it with some trivial shell scripting:

#!/bin/sh
echo $$ >ssh.pid
exec ssh user at host -L 123:remote.host:456 -f -N

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473





--- Comment #3 from Tim Steiner <tsteiner at nerdclub.net>  2008-05-30
01:09:20 ---
Damien: Thanks for the tip.  I was unaware of ControlMasters.

Darren: Actually, since the ssh process is forking, the pid your script
saves is that of the parent process, and not the new child process.

I suppose something like this would work:

#!/bin/sh
echo $$ >pid.sh
exec ssh user at host -L 123:remote.host:456 -N

The downside is that you have to run it in the background, and ssh
won't be able to prompt for a password (if needed).

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473





--- Comment #4 from Tim Steiner <tsteiner at nerdclub.net>  2008-05-30
01:10:49 ---
Oops, that should have been ssh.pid above, not pid.sh!

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473

Tom Anderson <twic at urchin.earth.li> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |twic at urchin.earth.li

--- Comment #5 from Tom Anderson <twic at urchin.earth.li> 2009-12-23
06:48:06 EST ---
@Damien: The ControlMaster feature is very cool, but you can't
(currently) port-forward with the slaves, so if you're trying to set up
multiple port forwardings, it doesn't help.

@Darren: Things along this line (including ssh ... & ; echo $!) work in
many cases, but crucially, don't work with -f. -f is particularly
useful because ssh remains in the foreground until it has completed
authentication, so in a script, you can rely on a connection having
been made once it returns.

What i'd like to be able to do is to write scripts like:

echo "Starting port forwarding of A"
<SOME SSH COMMAND>
echo "Starting port forwarding of B"
<SOME SSH COMMAND>
echo "Doing lots of things using forwarded port ..."
<SOME COMMAND TO CLOSE ALL CONNECTIONS>

Whether this is using pid/kill or the ControlMaster mechanism.

I think i have an idea - mktemp a directory, then start several
independent control master connections, one for each forwarded port,
with control paths mktemp'd (or otherwise) in that directory, running
with -f. To shut them down, for-loop over the files in the directory
and do -O exit to close the connections. It's anything but pretty, but
it should work (a classic shell script, then!).

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473

--- Comment #6 from Damien Miller <djm at mindrot.org> 2009-12-26 23:41:48
EST ---
(In reply to comment #5)
> @Damien: The ControlMaster feature is very cool, but you can't
> (currently) port-forward with the slaves, so if you're trying to
> set up multiple port forwardings, it doesn't help.
You are correct that it cannot configure port-forwardings (yet - see
bug #1617. I hope to fix this before 5.4), but it does help - it gives
you exactly what a pidfile does as afar as being able to control a
running daemon.
> I think i have an idea - mktemp a directory, then start several
> independent control master connections, one for each forwarded port,
> with control paths mktemp'd (or otherwise) in that directory, running
> with -f. To shut them down, for-loop over the files in the directory
> and do -O exit to close the connections. It's anything but pretty, but
> it should work (a classic shell script, then!).
Yes, this is what I mean.

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.

https://bugzilla.mindrot.org/show_bug.cgi?id=1473

Josh Triplett <josh at joshtriplett.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mh+openssh-bugzilla at zugschl
                   |                            |us.de

--- Comment #7 from Josh Triplett <josh at joshtriplett.org> 2011-03-03
06:46:50 EST ---
*** Bug 1594 has been marked as a duplicate of this bug. ***

-- 
Configure bugmail: https://bugzilla.mindrot.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.
You are watching someone on the CC list of the bug.