[Dovecot] Odd ownership of the dovecot-uidlist file

Steffen Kaiser skdovecot at smail.inf.fh-brs.de
Wed Jun 4 06:52:51 UTC 2014

Hash: SHA1

On Wed, 4 Jun 2014, Bruce wrote:

> Please see my responses below,

I dislike top posting anyway :-)

> On 04/06/14 01:35, dovecot-request at dovecot.org wrote:
>> Message: 4
>> Date: Tue, 3 Jun 2014 09:33:48 +0200 (CEST)
>> From: Steffen Kaiser
>>> >Jun 3 11:38:51 brio dovecot: Dovecot postlogin.sh running as hamish at XXXXX
>>> >(/mnt/spool/keepers/h/XXXXX/hamish) userid = 7053 (7053) - uidlist = 
>>> 26624
>>> >Jun 3 11:38:51 brio dovecot: Dovecot for hamish at XXXXX finished, uidlist 
>>> now =
>>> >26624
>> who is user 26624? Is the uid valid at all? If it is invalid, are there
>> other files owned by this uid? Maybe only one of your NFS server has this
>> uid in its /etc/passwd? Is user "hamish" shared to another user somehow,
>> either via symlinks, ACLs, ...?
> UID 26624 is a valid user ('info' of domain14552) but under a compleltly 
> different domain name (hamish is under domain25367). However that user has 
> also not logged in around the time the ownership was changed. There is no 
> relevance to the two users, except that they exist on the system and for some 
> reason this issue happened to the hamish user.

That means: no sharing, right ?

> The NFS server does not know about the UIDs, it just provides the numeric IDs 
> which is translated on the dovecot/exim servers by NSS and Dovecotr using the 
> replicated MySQL database. Additionally both users have existed for some time 
> and the databases are in sync. Customers also do not have any access to the 
> file system so there will be no symlinks in place.
> Its also not a single server that we are seeing the issue on, it maybe one 
> Dovecot server accessing one NFS server. Then the next time its a different 
> Dovecot server accessing a different NFS server.

Because it's NFS, any server accessing this NFS export may alter the 
ownership, because I still do not believe it's a Dovecot IMAP/POP issue 

>>> >the logs for that time which is abnormal (a whole bunch of other logins 
>>> from
>>> >other customers but nothing from those two users and no errors)
>> What about cron jobs, message delivery, backups, ... anything that
>> possibly can alter that file. I don't think, it's a Dovecot issue, unless
>> the uid 26624 is valid and hamish is shared with that user.
> Nothing besides Courier being replaced by Dovecot has changed in the server 
> setup (although I could be wrong there, but we are going through one 
> component at a time and until this issue is resolved we are not moving onto 
> the next), and the only file which is being modified is a file which only 
> Dovecot maintains.

Could there be Courier-related left-over scripts running?

> There are hourly backups which do an rsync to another server in case of 
> hardware failure, there are scripts which move mailboxes between NFS servers 
> but they show up in logs. Exim has no need to touch a dovecot controlled 
> file, and when it writes mail into the maildir its writing as the correct 
> user.

How does exim deliver the messages to the user storage? Via 
Dovecot-Deliver or directly. I interprete your sentence, that the messages 
are dropped directly.
> It also seem odd that one login is fine then randomly the next login the file 
> ownership has changed, nothing happens in between the two logins which are in 
> some cases only 5 to 10 minutes apart.
> All I am really looking for is ideas on where to look, as it seems odd that 
> nobody else is reporting this, and since its a reasonably new setup its

That's why I point to non-Dovecot things.

> possibly something we have done in the config (which I posted in my first 
> email). Is there a reliable way to run a script directly when a dovecot 
> session starts and finishes so we could output the ownership before and after 
> which may also help eliminate the session itself.

Your post-login script does exactly that. That leaves the message 
delivery, if you do so via Dovecot deliver. LMTP seems to be off.

I'm not sure if inotify works via NFS as Peter suggested, but that would 
my next idea as well. Let inotify wait for changes on that file, then fire 
up a script to capture "ps gaux" and maybe more.

If you have SELinux running, maybe you can trigger a warning there? I 
don't know much about SELinux.

- -- 
Steffen Kaiser
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