Linux Domain Name Service DNS

Posted by gojiita on Tue, 27 Aug 2019 04:46:02 +0200

What is DNS

The full name of DNS is Domain Name System, which means Domain Name Resolution System. It is the responsibility of translating a domain name into a recognizable IP for connecting different computer devices.

linux Configuration and Files for DNS Resolution

There are three files in linux about dns parsing:

/etc/hosts Records ip address corresponding to hostname
/etc/resolv.conf Set ip address of DNS server
/etc/host.conf Specifies the order in which domain names are resolved (from local hosts files or from DNS)

The existence of /etc/hosts is that the early network is not very developed. It is just necessary to keep the corresponding relationship between hostname and ip address in hosts. With the development of network, distributed DNS services gradually appear, but the form of /etc/hosts remains.

/etc/resolv.conf is configured with a DNS domain name and an ip address. There is a lot of information on the Internet to refer to.

How a domain name is resolved

How the Domain Name System (DNS) Works This article roughly explains the process of domain name resolution, which can be divided into:

Request the Domain Name Service where the top-level domain name is located from the Root Domain Name Service
Request secondary domain name service from top-level domain name service
Request a specific ip address from the secondary domain name service

Simple DNS configuration case (based on entOs7)

Server Side

1. Install bind

yum install bind

2. Modify/etc/named.conf configuration file

vim /etc/named.conf

options {
        listen-on port 53 { any; };    //Open listening port 53 and accept any IP connection
        listen-on-v6 port 53 { ::1; };    //Support IP V6
        directory       "/var/named";    //All forward and reverse zone files are created in this directory
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        allow-query     { 0.0.0.0/0; };    //Allow any IP query

        recursion yes;
        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;
        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";
        managed-keys-directory "/var/named/dynamic";

};

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};

zone "." IN {
        type hint;
        file "named.ca";
};

include "/etc/named.rfc1912.zones";    //Main Profile
include "/etc/named.root.key";

3. Modify the/etc/named.rfc1912.zones file to add a forward zone for duiyi.com

vim /etc/ named.rfc1912.zones

zone "localhost.localdomain" IN {
        type master;
        file "named.localhost";
        allow-update { none; };
};

zone "localhost" IN {
        type master;
        file "named.localhost";
        allow-update { none; };
};

zone "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa" IN {
        type master;
        file "named.loopback";
        allow-update { none; };
};

zone "1.0.0.127.in-addr.arpa" IN {
        type master;
        file "named.loopback";
        allow-update { none; };
};
zone "0.in-addr.arpa" IN {
        type master;
        file "named.empty";
        allow-update { none; };
};

//Forward Zone of duiyi.com
zone "duiyi.com" IN {
        type master;
        file "duiyi.com.zone";
        allow-update { none; };
};

4. Create a forward zone resource file

vim /var/named/duiyi.com.zone

$TTL 1D
@    IN SOA  duiyi.com. rname.invalid. (
                                        0       ; serial
                                        1D      ; refresh
                                        1H      ; retry
                                        1W      ; expire
                                        3H )    ; minimum
        NS      @
        A       127.0.0.1
        AAAA    ::1
www    IN A 192.168.81.1
mail    IN A 192.168.81.2
ftp    IN A 192.168.81.3

5. Start the name service

systemctl start named

6. Start-up self-start

systemctl enable named

##Client
Operating system: both windows and linux
IP address: The IP (192.168.81.133) that can ping through the DNS server is fine.
Role: Tests whether the DNS server is functioning properly.

1. Modify DNS:

2.ping server ip(192.168.81.133), test access to the server

3. Use the nslookup command to test whether three DNS resolves successfully

As shown, DNS forward resolution succeeded

Linux as a client test:

1. Install the bind-utils package so that you can use the nslookup, dig, and host tools

yum install bind-utils

2. Modify DNS configuration to use our DNS server

vim /etc/resolv.conf

nameserver 192.168.81.133
nameserver 114.114.114.114
nameserver 8.8.8.8

3. Forward parsing test, using nslookup command (same as windows test)

nslookup

Topics: Linux DNS vim network

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