failed: read(/var/run/dovecot/dns-client)

[Laura Smith]

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, April 10, 2019 8:20 PM, Aki Tuomi <aki.tuomi at open-xchange.com> wrote:

> > On 10 April 2019 22:13 Laura Smith via dovecot dovecot at dovecot.org wrote:
> > On Wednesday, April 10, 2019 7:57 PM, Aki Tuomi aki.tuomi at open-xchange.com wrote:
> >
> > > > On 10 April 2019 21:26 Laura Smith via dovecot dovecot at dovecot.org wrote:
> > > >
> > > > ==========================================================================
> > > >
> > > > dsync(foobar at example.com): Error: imapc(foobar.example.com:993): dns_lookup(foobar.example.com) failed: read(/var/run/dovecot/dns-client) failed: read(size=512) failed: Connection reset by peer
> > >
> > > This is dovecot's internal dns-client, and something goes wrong when talking to the service.
> > >
> > > > dsync(foobar at example.com): Error: Failed to initialize user: imapc: Login to foobar.example.com failed: Disconnected from server
> > >
> > > This is btw dsync service, not imap service.
> > >
> > > > ===
> > > > Initially I thought "oh no, not another AppArmor block".
> > > > But then surely the second message would not appear if the DNS lookup was not successful ?
> > > > Also "dig foobar.example.com" works fine.
> > > > How should I be troubleshooting this ? And if it is still likely to be AppArmor, what is calling it ? "doveadm" itself or something else ? What does "/var/run/dovecot/dns-client" do and why doesn't dovecot use standard OS calls like everyone else ?
> > >
> > > Because the "standard OS call" is blocking and we would prefer it to not block everything else.
> > >
> > > > So many questions !
> > >
> > > Aki
> >
> > Thanks for your reply, but both those message are generated from a simple :
> > doveadm -v -o mail_fsync=never backup -R -u foobar at example.com imapc:
> > So I don't know what you mean about dsync service failing ? Surely the DNS lookup succeeded if the 'dsync service' failed due to remote disconnect ?
> > I'm still none the wiser as to where to start looking for troubleshoting ?
>
> Did you check dovecot logs? Maybe there is something useful?
>
> Aki


Only the same old cryptic message about dns-client ?
master: Fatal: execv(/usr/lib/dovecot/dns-client) failed: Permission denied
master: Error: service(dns_client): command startup failed, throttling for 16 secs
dns_client: Fatal: master: service(dns_client): child 14293 returned error 84 (exec() failed)