# Creating and working with a names (DNS) server

A Names server can be perform three basic operations:

- act as a recursive server, forwarding queries to other servers
- perform local caching of recursively discovered records
- act as the authoritative server for a domain

### Creating a non-authoritative server

The first two of these are easy, and you can create a server that performs them with the command `twistd -n dns --recursive --cache`. You may wish to run this as root since it will try to bind to UDP port 53. Try performing a lookup with it, `dig twistedmatrix.com @127.0.0.1`.

### Creating an authoritative server

To act as the authority for a domain, two things are necessary: the address of the machine on which the domain name server will run must be registered as a nameserver for the domain; and the domain name server must be configured to act as the authority. The first requirement is beyond the scope of this howto and will not be covered.

To configure Names to act as the authority for `example-domain.com`, we first create a zone file for this domain.

    zone = [
        SOA(
            # For whom we are the authority
            'example-domain.com',

            # This nameserver's name
            mname = "ns1.example-domain.com",

            # Mailbox of individual who handles this
            rname = "root.example-domain.com",

            # Unique serial identifying this SOA data
            serial = 2003010601,

            # Time interval before zone should be refreshed
            refresh = "1H",

            # Interval before failed refresh should be retried
            retry = "1H",

            # Upper limit on time interval before expiry
            expire = "1H",

            # Minimum TTL
            minimum = "1H"
        ),

        A('example-domain.com', '127.0.0.1'),
        NS('example-domain.com', 'ns1.example-domain.com'),

        CNAME('www.example-domain.com', 'example-domain.com'),
        CNAME('ftp.example-domain.com', 'example-domain.com'),

        MX('example-domain.com', 0, 'mail.example-domain.com'),
        A('mail.example-domain.com', '123.0.16.43')
    ]

Zone file - listings/names/example-domain.com

Next, run the command `twistd -n dns --pyzone example-domain.com`. Now try querying the domain locally (again, with dig): `dig -t any example-domain.com @127.0.0.1`.

Names can also read a traditional, BIND-syntax zone file. Specify these with the `--bindzone` parameter. The $GENERATE and $INCLUDE directives are not yet supported.

Index

Version: 8.2.0