Common DNS Resource Records

Each DNS zone in a DNS server has a zone file.
A DNS zone is usually a single domain (though not always).
A zone file is composed of many DNS resource records (RRs).
There are many different types of RRs.
Let’s record some common ones.

A record

Maps a hostname to an IPv4 address. (32-bit)

hostname IN A xxx.xxx.xxx.xxx

AAAA record

Maps a hostname to an IPv6 address. (128-bit)

hostname IN AAAA xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx

CNAME record

An alias for a hostname.

alias IN CNAME hostname

Note that an alias cannot have other A records or MX records.

MX record

Mail exchanger record.
The email server’s domain name, priority, and hostname.
Note that it must be a hostname, not directly an IP address,
and it cannot be a CNAME alias.
Therefore, an additional RR (A or AAAA record) must be set up for the IP.
A lower priority number indicates higher priority (mail is delivered to higher priority servers first).

mail_domain_name IN MX priority hostname

Example:

example.com. IN MX 10 mailserver.example.com