which are the exact effects of MaxSessions

Jakub Jelen jjelen at redhat.com
Fri Feb 20 18:09:27 AEDT 2015

According my observation, MaxSessions 1 works for opening only one 
session through multiplexed channel, which degrades multiplexed 
connection back to only one session. MaxSessions 0 doesn't make much sense.

I don't know if you use openssh from some distribution, but in RHEL we 
had recently one bug in audit which looks similar like your issue -- 
with MaxSessions 1 sshd was preventing to log you in.

On 02/20/2015 02:51 AM, Christoph Anton Mitterer wrote:
> Hey.
> I wondered a bit which the exact effects of MaxSessions are.
> The documentation says:
>          Specifies the maximum number of open sessions permitted per net‐
>          work connection.  The default is 10.
> And it apparently seems that setting e.g. the following in sshd_config:
>    MaxSessions 0
>       => no logins possible at all
>    MaxSessions 1
>       => control channel muxing basically forbidden from the server side
>    MaxSessions n
>       => at most n sessions may use a mux, including the one which
>          initiated it
>          but further muxes (with again n session) may be created by that
>          client
> Is it just that? Or are there any other side effects which I can't see?
Yes, it should be like this. Basically it is meant to have max N 
interactive sessions in that connection initiated by mux. If you try to 
connect using "ssh -T", pty is not allocated and this doesn't count as a 
session (not sure if it is bug or feature -- reproducible with vanilla 
sources). Damien?

> Thanks,
> Chris.
> btw: Would be nice if something like the above could be added to the
> manpage for clraification :)
> _______________________________________________
> openssh-unix-dev mailing list
> openssh-unix-dev at mindrot.org
> https://lists.mindrot.org/mailman/listinfo/openssh-unix-dev

More information about the openssh-unix-dev mailing list