Two files from the same source

Let's begin with an example for distributing two files from the same source. At the Network Division we run the University's primary nameservers. But we also give support to people that run secondary servers. In one of our primary servers, we also wanted to publish the configuration file needed to run a secondary server. We wanted to use the same source to keep both files consistent. This apparently simple task has created a lot of problems with other tools we have used. With PICA the solution is simple:

In the case of the masters, we have to install one version for production (the master server file) and one for documentation (the slave DNS server file). Thus, we defined, in hosts.conf, the following:

hostgroup dnsservers {
    members { fobos, deimos, mercurio, ulpnet, ulpnet2 }
}
hostgroup dnsmaster {
    members { ulpnet, ulpnet2 }
}
hostgroup doc {
    members { ulpnet, ulpnet2 }
}

This way we can differentiate between documentation, DNS master and DNS slave servers. Thus, in objects.conf, we can define the relevant files as:

#if (ingroup('dnsservers'))
group DNS {
    file named.conf {
         path = '/etc/named.conf';
         source = "DNS/named_conf.cfg";
    }

    ## Documentation for this Service
#  if (ingroup('doc'))
    # ...
    file named.conf.sample {
       path = '<#$docdir#>/Servicios/DNS/named.conf.sample';
       source = 'DNS/named_conf.cfg';
    }
#  fi
}
#fi

The only thing left to do is defining the named.conf file contents. The trick is checking the name of the object: if it ends with ``.sample'', it's a slave sample file; it not, then it's a master file.

# ...
zone "ulpgc.es" {
#if ((ingroup('dnsmaster')) && ($picaobject !~ /\.sample$/))
   type master;
   file "mydb.db";
   also-notify {
      # ...
   };
#else
   type slave;
   file "mydb.db.bak";
   masters {
      # ...
   };
#fi
};
# ...

This shows the power of using arbitrary perl code in PICA conditions.