Detailed dns settings under Linux

Introduction DNS is the Domain Name System, which can convert a domain name such as www.haoxiai.net to an IP address such as 211.152.50.35. Without DNS, you must use 211.2152.50.35 when browsing the 21php.com website. So hard to remember the numbers to visit. It is the DNS server that provides DNS services. The DNS server can be divided into three types, a cache server (Cache-only server), a primary server (Primary Name server), and a secondary server (Second Name Server).

The detailed principles, workflows, terminology, and concepts of DNS are limited by space, so I won't say it here. You can read a special article, such as DNS-HOWTO to understand.

2Configure the primary DNS server

First, we make the following assumptions: The A server is the primary domain name server of 21php.com, its IP address is 11.0.0.1, and the B server is the assistant of 21php.com. The domain name server, its IP address is 11.0.0.2;

Below we configure the server 11.0.0.1 as the primary DNS server of 21PHP.COM

The dns function under Linux is implemented by bind software. After the bind software is installed, several intrinsic files are generated, which are divided into two categories. One is the configuration file in the /etc directory, and the other is the dns record file in the /var/named directory. Together with other related documents, set up the dns server together. Below is a list and description of all the files related to the dns settings.

Located in the /etc directory are: hosts, host.conf, resolv.conf, named.boot, named.conf.

1, "hosts", file, defines the correspondence between the host name and ip address, which also has the ip address and host name of the computer that will run dns. Content:

127.0.0.1 localhost.localdomain localhost

2, “host.conf” file [Boban Note: originally mistakenly written as hosts.conf], "order hosts bind" statement, The order in which the host names are resolved is first searched in the hosts, and then found in the records of the dns server. “multi on" is to allow a host name to correspond to multiple ip addresses. Content:

order hosts, bind

multi on

nospoof on

3,“resolv.conf”file,“nameserver 10.0.0.211 ” specifies the address of the dns server. Note that this file is essential for normal non-dns server computers (non-windows systems; Windows systems are set up in "Network Properties"). If you have not set up this machine as a dns server, and you have to be able to resolve the domain name, you must specify the address of a dns server. You can write up to three addresses as a candidate dns server for the previous failure. “domain zrs.com” specifies the default domain. File Content:

domain 21php.com

nameserver 11.0.0.1

4,“named.boot” file is the configuration file used by the earlier version of the bind software, now The new version has given way to “named.conf”. Named.conf is the core file of the dns server configuration. Let's explain it for a while.

# named.conf - configuration for bind

#

# Generated automatically by bindconf, alchemist et al.

controls {

inet 127.0.0.1 allow { localhost; } keys { rndckey; };

};

include "/etc/rndc.key";options {

directory "/var/named/";

};

zone "." {

type hint;

file "named .ca";

};

zone "0.0.127.in-addr.arpa" {

type master;

file " 0.0.127.in-addr.arpa.zone";

};

zone "localhost" {

type master;

file " ;localhost.zone";

};

zone "21php.com" {

type master;

notify yes;

file "21php.com";

};

The above # is a comment symbol, and the other lines have the following meanings:

direto Ry /var/named

Specify named to read DNS data files from the /var/named directory. This directory can be specified and created by the user. All specified DNS data files are stored. In this directory;

zone "." {

type hint;

file "named.ca";

};< Br>

Specifies that named gets the top level of the Internet from the named.ca file.

zone "0.0.127.in-addr.arpa" {

type master;

file "0.0.127.in-addr.arpa.zone" ;

};

Specify named as the 127.0.0 network segment address translation master server, the named.local file contains the conversion data from the address to the domain name of 127.0.0.* (127.0) .0 network segment address is the internal loopback address of the LAN interface);

zone "localhost" {

type master;

file "localhost.zone";< Br>

};

Specify DNS file data containing localhost to be stored in /var/named/localhost.zone;

zone "21php.com" {

type master;

notify yes;

file "21php.com.zone";

};

The above statement indicates the domain 21php. The com DNS data is stored in 21php.com.zone in the /var/named/directory;

We can open /var/named/21php.com.zone with a text editor, the contents of which are as follows: Br>

$TTL 86400 @ IN SOA @ root.localhost (

2 ;serial

28800 ;refresh

7200 ;retry

604800 ;expire

86400 ;ttl

)

@ IN NS localhost

www IN A 11.0.0.233

www2 IN A 11.0.0.23

forum IN A 11.0.0.10

@ IN MX 5 mail.21php.com.

The first part of the file is the corresponding parameter settings, this part does not need to be changed, the latter part is the specific DNS data;

For example: < Br>

www IN A 11.0.0.233

Resolve www.21php.com to address 11.0.0.233;

www2 IN A 11.0.0.23

will be www2 .21php.com resolves to address 11.0.0.23;

club IN A 11.0.0.10

resolves club.21php.com to address 11.0.0.10;

3 configuration Secondary DNS Server

Configure Server 11.05.2 as 21php.com Secondary dns Server

A secondary DNS server that can transfer a complete set of domain information from the primary server. The zone file is transferred from the primary server and stored as a local disk file on the secondary server. There is a full copy of the domain information in the secondary server, so it is also possible to answer queries for this domain. The configuration of this part is as follows:

zone "21php.com" IN {

type slave;

file "21php.com.zone";

masters { 11.0.0.1; };

};

As you can see, the difference from the primary DNS server is: "type” changed to “slave”, then specified The address of the primary DNS server “masters { 11.0.0.1; };”. When the DNS service starts, it will automatically connect to 11.0.0.1, read the information of the 21php.com domain, and save it to the 21php.com.zone file of this machine.

4Test DNS Server

Change the corresponding file of DNS, restart the service with the “ndc restart” command, use the command in redhat 7.1 or later:

/Etc/rc.d/init.d/named restart

or

/etc/rc.d/init.d/named reload

Make the changes take effect.

To test DNS, you can find a client, set its DNS address to the newly created DNS server address, and then try to access the Internet, receive, download, and so on. You can also use the nslookup command: run nslookup, enter the host name to be queried to see if it returns the correct ip address, and use the dig command in redhat 7.1 or later.