[Dovecot] realtime backup with LDA?

[Steffen Kaiser]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Mon, 24 Feb 2014, Charles Marcus wrote:

> On 2/24/2014 3:58 AM, Steffen Kaiser <skdovecot at smail.inf.fh-brs.de> wrote:
>> I would add a BCC recipient in the MTA. It's more save in such situation. 
>> See the thread about qmail and multiple recipients for one mail address. 
>
> The only downside to this is all of the original headers are *not* preserved 
> in the BCC copy.

Er, I don't know what you mean with "all of the original headers". There 
are no headers of the delivery process to user, that's right. Everything 
else should be untouchted. Or in other words, the backup copy does not 
"backup" the delivery process.

> On 2/24/2014 3:58 AM, Steffen Kaiser <skdovecot at smail.inf.fh-brs.de> wrote:
>> If posting (appending a new message) would be OK: Add a global Sieve script 
>> and let each message: fileinto :copy "backup";
>
> So... it looks like this would work as I described above? An identical copy, 
> preserving all of the original headers?

The other one would be the wrapper method. I just looked into the man page 
of dovecot-lda:

        -p path
               Path  to  the  mail to be delivered instead of reading from stdin.  If using maildir
               the file is hard linked to the destination if possible.  This allows a  single  mail
               to  be  delivered to multiple users using hard links, but currently it also prevents
               deliver from updating cache file so it shouldn't be used unless really necessary.

So Dovecot LDA seems to keep its virtual fingers off the message and
you don't need to redirect all the time and you can get hard links,
if you use the same uid/gid for both users, 100% identical then e.g.:

#!/bin/bash

user=$...
f=/path/to/dir/on/same/mountpoint/as/user/and/user_backup/$$.tmp
cat - > $f
dovecot-lda .... -d ${user} -p $f
rc=$?
if test $rc -gt 0; then
 	rm -f $f
 	exit $rc
fi
dovecot-lda .... -d ${user}_backup -p $f
rm -f $f
# ignore errors to prevent re-delivery to user
exit 0


- -- 
Steffen Kaiser
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (GNU/Linux)

iQEVAwUBUwtWUXD1/YhP6VMHAQKHXgf/Z1h23FhLvd5KfHjb90neguH7p7ZoEL9t
YyX52w8GCSkPXCvDkJ6Nc/iAi54TqkVzv7VERXODWDiMeB/rmXSg/OnWMo5s2cSO
AnV19SP6OPkmRcxPulOz1dp3uQoDUDbwW6iDf9EGaV3MzfNC6fBiOGUXeTDAbBa9
k6z6W1wwvqQ192/gkb6pkzw8wpL48zxurSPkquMH6hqB1MwfnQmS6J0cG3TY1+QP
7HbpvDaqJ4KPhlJk7DnIKk+78/pc04GnuAFqo/+JXDchNBgSSk7FzHys3/irLGLU
BkyZ+kDfGNBklsH4Zzwb7L5soryDa5HAfgEZSydK404O3BtnMR2iVA==
=P93w
-----END PGP SIGNATURE-----