18.4. Configuration Examples

18.4.1. Dynamic DNS

BIND allows hosts to update their records in DNS and zone files dynamically. This is used when a host computer's IP address changes frequently and the DNS record requires real-time modification.
Use the /var/named/dynamic/ directory for zone files you want updated by dynamic DNS. Files created in or copied into this directory inherit Linux permissions that allow named to write to them. As such files are labeled with the named_cache_t type, SELinux allows named to write to them.
If a zone file in /var/named/dynamic/ is labeled with the named_zone_t type, dynamic DNS updates may not be successful for a certain period of time as the update needs to be written to a journal first before being merged. If the zone file is labeled with the named_zone_t type when the journal attempts to be merged, an error such as the following is logged:
named[PID]: dumping master file: rename: /var/named/dynamic/zone-name: permission denied
Also, the following SELinux denial message is logged:
setroubleshoot: SELinux is preventing named (named_t) "unlink" to zone-name (named_zone_t)
To resolve this labeling issue, use the restorecon utility as root:
~]# restorecon -R -v /var/named/dynamic