Networking Guide
Chapter 6, Configuring the Domain Name Service

Special resource record characters

Special resource record characters

These characters have special meanings in resource records:

.
A free-standing dot in the ``name'' field refers to the current zone.

@
A free-standing ``@'' in the ``name'' field denotes the current origin. You can use origins within configuration files as a shorthand for fully qualified domain names.

..
Two free-standing dots represent the null domain name of the root when used in the ``name'' field.

\X
Here X is any character other than a digit (0-9), and \X escapes that character so that its special meaning does not apply. For example, \. can be used to place a dot character in a label.

\DDD
Here each D is a digit, and \DDD is the octet corresponding to the decimal number described by DDD. The resulting octet is assumed to be text and is not checked for special meaning.

()
Parentheses are used to group data that crosses a line. In effect, line terminations are not recognized within parentheses.

;
A semicolon starts a comment; the remainder of the line is ignored.

*
An asterisk signifies a wildcard. Wildcarding is only meaningful for some resource record types, notably MX, and then only in the ``name'' field. Do not use an asterisk in the data field.

Anywhere a name appears, either in the ``name'' field or in a data field defined to contained names, the current origin is appended if the name does not end with a ''.''. This is useful for appending the current zone name to the data, such as machine names, but can cause problems when you do not want this to happen. The following rule helps avoid this problem: if the name is not in the zone for which you are creating the data file, end the name with a ``.''.