I see Timo addressed this problem with this reply ( from thread "[Dovecot] reproducible dsync backup panic (dovecot 2.2.7)/Fri Dec 20 00:37:21 EET 2013")/, but basically I don't understand how to go about doing this:
Can you get it to dump core and use
gdb /usr/bin/doveadm core bt full fr 5 p *change
/ The command I'm using to back up individual user's mail is something like: />/
/>/ sudo -u vmail dsync -v -uuser at server.com <http://dovecot.org/cgi-bin/mailman/listinfo/dovecot> -R backup ssh -i sshid-filelogin at server.com <http://dovecot.org/cgi-bin/mailman/listinfo/dovecot> sudo -u vmail dsync -v -uuser at server.com <http://dovecot.org/cgi-bin/mailman/listinfo/dovecot> / Probably an easier way would be if you could copy the local and remote mdboxes to e.g. /tmp/mdbox-local and /tmp/mdbox-remote. Then you should be able to do:
gdb --args doveadm -o mail=mdbox:/tmp/mdbox-local backup -R mdbox:/tmp/mdbox-remote run bt full fr 5 p *change