changes in secondary zone records in ispconfig are not written to slave files in '/etc/bind/slave'. this is a rather strange problem for me, as this was working before !! and the server is still serving as a secondary DNS server. Bind is updating slave files from primary server, all slave files have recent dates. so there is no problem with existing slave zone files. Just, I cannot add new secondary zones or edit existing ones with ISPConfig. I tried to resync DNS records, only the primary records are resynced and they are updated in '/etc/bind/'. no information about slave zones. I changed the permissions of slave directory, tried to resync again nothing changed. I guess, this is related to an update, but I cannot find any clues to solve it.