dovecot - Aug 2011 - Catch22: user needs space to fix out of space condition

A mail user reported that he filled up his INBOX (despite reminders he
was approaching his filesystem quota), and furthermore, he could not
fix the situation because he couldn't expunge message he marked for
deletion.

The dovecot logs revealed the cause

 	dovecot: imap(user): Error: open(/var/mail/user.lock) failed:
 		Disc quota exceeded

This created an impasse where a user cannot free space because he needs
to create a lock file that cannot be created because he needs free
space.  Is there any way out of this without administrator intervention?

Joseph Tam <jtam.home at gmail.com>

Don't use dotlock files.

Method that generally works nice also is to start rejecting email for  
the user when they are at 99% capacity, so you leave just alittle room  
for that kind of thing left.


Quoting Joseph Tam <jtam.home at gmail.com>:
> A mail user reported that he filled up his INBOX (despite reminders he
> was approaching his filesystem quota), and furthermore, he could not
> fix the situation because he couldn't expunge message he marked for
> deletion.
>
> The dovecot logs revealed the cause
>
> 	dovecot: imap(user): Error: open(/var/mail/user.lock) failed:
> 		Disc quota exceeded
>
> This created an impasse where a user cannot free space because he needs
> to create a lock file that cannot be created because he needs free
> space.  Is there any way out of this without administrator intervention?
>
> Joseph Tam <jtam.home at gmail.com>

On Aug 24, 2011, at 5:52 PM, Joseph Tam wrote:
> 
> A mail user reported that he filled up his INBOX (despite reminders he
> was approaching his filesystem quota), and furthermore, he could not
> fix the situation because he couldn't expunge message he marked for
> deletion.
> 
> The dovecot logs revealed the cause
> 
> 	dovecot: imap(user): Error: open(/var/mail/user.lock) failed:
> 		Disc quota exceeded
> 
> This created an impasse where a user cannot free space because he needs
> to create a lock file that cannot be created because he needs free
> space.  Is there any way out of this without administrator intervention?
> 
In your mail_location you can specify a different control and index directory as
a place where the user has no quotas. I'm not quite sure which it is
(control or index) that says where the dotlock file goes but it should be one of
them. Check out the mail_location page in the wiki for more info. This
introduces more filesystem complexity (you need one tree for message files and
another for mail control/index files) but it does mean that people can log in
when they hit their quota and the storage space consumed by their dovecot
indexes won't count against them, which I personally think is more fair than
letting those things consume quota.

Also, as someone who was using dotlocks for a long time until I could make fcntl
locks work over NFS to our Netapp filers, I would strongly recommend trying to
move away from dotlocks if you can. We were seeing poor performance and some
cache corruption (mail, indexes, control all on NFS with multiple hosts possibly
accessing the same user's files) with dotlocks that went away when we
switched to native locks.
> Joseph Tam <jtam.home at gmail.com>
David Warden

Thanks to all who've made suggestions.  It seems removing dotlocks as
a locking method is the way to go.  There is another dotlock locking
variant mentioned in 10-mail.conf that seems to address this situation
for those that can't get away from dotlocks:

 	#  dotlock_try: Same as dotlock, but if it fails because of permissions or
 	#               because there isn't enough disk space, just skip it.
 	mbox_write_locks = dotlock_try fcntl

Joseph Tam <jtam.home at gmail.com>