On Mon, Feb 11, 2019 at 11:25:03AM +0100, Dr. Nikolaus Klepp wrote:
> 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.


This is something you must have specified in your sshd_config, since
the default for sshd is to *not* UseDNS. From `man sshd_config`:

     UseDNS  Specifies whether sshd(8) should look up the remote host name, and to check that the resolved host name for the re‐
                  mote IP address maps back to the very same IP address.

             If this option is set to no (the default) then only addresses and not host names may be used in
                      ~/.ssh/authorized_keys from and sshd_config Match Host directives.

            
So sshd is trying to make sure that the IP it is listening on actually
maps back to the hostname.

My2Cents

KatolaZ

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