tweaking max sessions / scaling

Mike Tancsa mike at
Thu Sep 28 00:44:38 AEST 2017

On 9/26/2017 9:07 PM, Peter Stuge wrote:
> Mike Tancsa wrote:
>> Without leaving the server at debug2 logging level, is there a way
>> to find out if I am hitting application limits vs OS limits ?
> If you run sshd under ktrace maybe you can spot resource limit errors
> for relevant syscalls in the kdump output.

Thanks! Although in this case, the measurement seems pretty resource
intensive.  I increased the MaxSessions and as well as MaxStartups and I
have the failure rate down to under 10 per day.  So it seems based on
changing that, it is application limits ?

I added

MaxSessions 920
ClientAliveInterval 15 # get rid of procs sitting arround
MaxStartups 30:50:500

Most of the clients come behind a single natted IP.


Mike Tancsa, tel +1 519 651 3400
Sentex Communications, mike at
Providing Internet services since 1994
Cambridge, Ontario Canada

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