Reuben, could you try this:

service auth-worker {
  executable = /usr/bin/strace -o /tmp/out /usr/libexec/dovecot/auth -w
}

and send the out file to me? I wasn't able to reproduce your problem with glibc-2.28.

Aki

On 31.08.2018 21:30, Aki Tuomi wrote:
Ah. Thanks for the pointer.

---
Aki Tuomi
Dovecot oy

-------- Original message --------
From: Michael Marley <michael@michaelmarley.com>
Date: 31/08/2018 21:17 (GMT+02:00)
To: dovecot@dovecot.org
Subject: Re: Dovecot User Listing Error - getpwent() failed: Invalid Argument

I think this might be caused by glibc 2.28.  I saw a similar error with the "doveadm purge" command after upgrading my system to that version.

Michael Marley

On 2018-08-31 13:10, Aki Tuomi wrote:

I'll see if this is reproducible
 
 
 
---
Aki Tuomi
Dovecot oy
 
-------- Original message --------
From: Reuben Farrelly <reuben-dovecot@reub.net>
Date: 31/08/2018 17:41 (GMT+02:00)
To: Aki Tuomi <aki.tuomi@dovecot.fi>, Dovecot Mailing List <dovecot@dovecot.org>
Subject: Re: Dovecot User Listing Error - getpwent() failed: Invalid Argument
 
Sure:

https://www.reub.net/files/dovecot/lightning-dovecot.conf
https://www.reub.net/files/dovecot/thunderstorm-dovecot.conf

Updated nightly.

Reuben


On 1/09/2018 12:26 am, Aki Tuomi wrote:
> Can you provide doveconf -n?
>
>
>
> ---
> Aki Tuomi
> Dovecot oy
>
> -------- Original message --------
> From: Reuben Farrelly <reuben-dovecot@reub.net>
> Date: 31/08/2018 17:12 (GMT+02:00)
> To: Aki Tuomi <aki.tuomi@dovecot.fi>, Dovecot Mailing List
> <dovecot@dovecot.org>
> Subject: Re: Dovecot User Listing Error - getpwent() failed: Invalid
> Argument
>
> No.  Neither of those are installed on either system.
>
> Reuben
>
> On 1/09/2018 12:09 am, Aki Tuomi wrote:
>  > Could apparmor or selinux be causing this!
>  >
>  >
>  >
>  > ---
>  > Aki Tuomi
>  > Dovecot oy
>  >
>  > -------- Original message --------
>  > From: Reuben Farrelly <reuben-dovecot@reub.net>
>  > Date: 31/08/2018 16:50 (GMT+02:00)
>  > To: Dovecot Mailing List <dovecot@dovecot.org>
>  > Subject: Dovecot User Listing Error - getpwent() failed: Invalid Argument
>  >
>  > Hi,
>  >
>  > I'm running dovecot-2.3 git and seeing on 2 of my Dovecot installations,
>  > the following message logged quite frequently:
>  >
>  > Aug 31 16:55:53 lightning.reub.net dovecot[7698]: auth-worker(7707):
>  > Error: getpwent() failed: Invalid argument
>  > Aug 31 16:55:53 lightning.reub.net dovecot[7698]: replicator: Error:
>  > User listing returned failure
>  > Aug 31 16:55:53 lightning.reub.net dovecot[7698]: replicator: Error:
>  > listing users failed, can't replicate existing data
>  >
>  > It appears that this could be having an effect on replication, but it's
>  > unclear because the secondary/replica doesn't see much traffic.
>  >
>  > Authentication is via PAM and the system is Gentoo Linux x86_64. passb
>  > driver = pam, userdb driver = static .
>  >
>  > doveadm user -u '*' shows the system users listed twice like this (is
>  > this a problem?) and then prints:
>  >
>  > ----
>  > reuben
>  > liam
>  > reuben
>  > liam
>  > <some other users>
>  > Error: User listing returned failure
>  > Fatal: user listing failed
>  > ----
>  >
>  > To me that doesn't look right.
>  >
>  > Can anyone suggest what could be causing this?  I don't recall seeing
>  > this message some time ago so I suspect it's a recent change in either
>  > dovecot, or pam or glibc etc..
>  >
>  > Thanks,
>  > Reuben