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Auteur: Dr. Nikolaus Klepp
Datum:  
Aan: dng
Onderwerp: Re: [DNG] ..should we set up our own usage policy wizard script?, was: OpenSSH: delay on beowulf
Anno domini 2019 Mon, 11 Feb 10:51:09 +0100
Didier Kryn scripsit:
> Le 10/02/2019 à 18:19, Arnt Karlsen a écrit :
> >>
> >> There's nothing in the logs. It just takes verry long to start.
>
>
>     Tried to set LogLevel in sshd_config?
>
>     or launch sshd with the -d option ?
>
>
>             Didier


Hi!

The problem only exists if all of these conditions are met:

- kernel 4.19. from beowulf
- network up, but DNS of ISP not reacting in time or dhcpcd did not get a lease
- sshd_config has "UseDNS yes"
- first try to start sshd after boot

The problem is solved by "UseDNS no" in sshd_config.

Now that sshd uses DNS on first startup is quite surprising - at least it was for me.

The other anoying thing is, that networking is not started in background and there is no option to force it to start in background. Desktop users usually prefer their GUI up and running, no matter if the network is ready or not. I had a pre-up script referenced in /etc/network/interfaces on ascii:

allow-hotplug eth0
iface eth0 inet dhcp
pre-up /home/nik/bin/pre-up

That script checked /sys/class/net/$IFACE/carrier to detect the precence of the carrier signal on eth0. Now with the new kernel that file is not readable when eth0 is brought up and the pre-up script is executed, so I cannot check the presence of the carrier any more. A minute or two later - when /etc/init.d/networking failed - the said file readable, but not earlier.

My workaround is to modify /etc/init.d/networking so that the "start)"-part is executed in background:

122c122
<     process_options
---

> (    process_options

143a144
> ) &


Maybe not the best idea, but it definitly works reliably for desktop users.

Nik









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