Why can't named update secondary zone database files, secondary journal files and primary zones from journals?

This is a problem that has been reported when running BIND 9 on Red Hat Enterprise Linux or Fedora Core. Specifically, problems are encountered with updating secondary zone database files, creating DDNS journal files, and updating primary zones from journals. It also manifests itself as named being unable to create custom log files.

Red Hat Security Enhanced Linux (SELinux) policy security protections:

Red Hat has adopted the National Security Agency's SELinux security policy and recommendations for BIND security, which are more secure than running named in a chroot and make use of the bind-chroot environment unnecessary.

By default, named is not allowed by the SELinux policy to write, create, or delete any files EXCEPT in these directories:

$ROOTDIR/var/named/slaves$ROOTDIR/var/named/data$ROOTDIR/var/tmp

where $ROOTDIR may be set in /etc/sysconfig/named if bind-chroot is installed.

The SELinux policy particularly does NOT allow named to modify the $ROOTDIR/var/named directory, the default location for primary zone database files.

SELinux policy overrules file access permissions, so even if all the files under /var/named have ownership named:named and mode rw-rw-r--, named will still not be able to write or create files except in the directories above, with SELinux in Enforcing mode. So, to allow named to update secondary or DDNS zone files, it is best to locate them in $ROOTDIR/var/named/secondaries, with named.conf zone statements such as:

zone "secondary.zone." IN { type secondary; file "secondaries/secondary.zone.db"; ...};   zone "ddns.zone." IN  { type primary; allow-updates {...}; file "secondaries/ddns.zone.db";};

To allow named to create its cache dump and statistics files, for example, you could use named.conf options statements such as:

options { ... dump-file "/var/named/data/cache_dump.db"; statistics-file "/var/named/data/named_stats.txt"; ...};

You can also tell SELinux to allow named to update any zone database files, by setting the SELinux tunable boolean parameter named_write_primary_zones=1, using the system-config-securitylevel GUI, using the setsebool command, or in /etc/selinux/targeted/booleans.

You can disable SELinux protection for named entirely by setting the named_disable_trans=1 SELinux tunable boolean parameter.

The SELinux named policy defines these SELinux contexts for named:

named_zone_t : for zone database files - $ROOTDIR/var/named/*named_conf_t : for named configuration files - $ROOTDIR/etc/{named,rndc}.*named_cache_t: for files modifiable by named - $ROOTDIR/var/{tmp,named/{slaves,data}}

If you want to retain use of the SELinux policy for named, and put named files in different locations, you can do so by changing the context of the custom file locations.

To create a custom configuration file location, e.g. /root/named.conf, to use with the named -c option, do:

# chcon system_u:object_r:named_conf_t /root/named.conf

To create a custom modifiable named data location, e.g. /var/log/named for a log file, do:

# chcon system_u:object_r:named_cache_t /var/log/named

To create a custom zone file location, e.g. /root/zones/, do:

# chcon system_u:object_r:named_zone_t /root/zones/{.,*}

See these man-pages for more information: selinux(8), named_selinux(8), chcon(1), setsebool(8)