Linux Cloud Automation Operations Basics (DNS service)

I. DNS Overview
Role: Provide domain name Resolution service
Forward parsing: domain name--IP eg: (www.baidu.com--220.181.111.188)
Reverse parsing: ip--domain name eg: (220.181.111.188--www.baidu.com)
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How DNS is queried
Recursive query: How the client requests resolution from its own DNS server.
Iterative query: How the server queries the server.


Precedence of DNS resolution (determined by configuration file/etc/nsswitch.comf)
1. Native cache
2. Native/etc/hosts files
Format:
3. Specify the DNS server cache
Empty cache: RHDC Flush
4. Specified DNS server (/etc/resolve.conf)


DNS Query commands
1.gethostip It is the composition of the Syslinux package, through the Hosts file and DNS resolution host name to IP, the IP is calculated as 8-bit 16 binary in PXE has a special purpose.

2.host only through DNS query, query host name to IP resolution.

3.nslookup Windows Parsing tool, common in Linux, currently less used, provides simple forward and reverse parsing queries

4.dig Linux Powerful query tool, can query more detailed information, the most widely used, can be traced to non-authoritative DNS


Two. Setting up a DNS service
1. Configuring Cache DNS
(1). Modify the Ip,hostname, and adjust the firewall policy to configure the Yum source.

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(2). Install BIND server and turn on BIND service, generate Rndc.key

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(3). Edit the DNS configuration file/etc/resolve.conf

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(4). Modify the configuration file vim/etc/named.conf of the bind service and restart the service

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(5). Query Port Status Netstat-antple | grep named

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(6). Test: Dig the target domain name twice to see the change in response time

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Set authoritative DNS
1. Forward parsing: domain name--IP eg: (www.baidu.com--220.181.111.188)
(1) Edit the configuration file of the bind service/etc/named.conf
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(2) Edit File Vim/etc/named.rfc1912.zones
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(3) Cd/var/named/cp-p Name.localhost Westos.com.zone

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(4) Edit File Vim/var/named/westos.com.zone
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(5) Restart service Systemctl restart named

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(6) Testing Service dig domain name

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2. Round call mechanism
Edit File Vim/var/named/westos.com.zone
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3. Reverse parsing: ip--domain name eg: (220.181.111.188--www.baidu.com)

(1) Edit the configuration file of the bind service/etc/named.rfc1912.zones

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(2) Cp-p/var/named/named.lookback/var/named/westos.com.ptr Copy configuration file template

(3) Vim Westos.com.ptr

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(4) Restart the service

Systemctl Restart named

(5) Testing Service: Dig-x address

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4. Bidirectional parsing
(1) vim/etc/named.conf

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(2) Cp-p/etc/name.rfc1912.zone/etc/name.rfc1913.zone

(3) Edit/etc/name.rfc1912.zone Separately,/etc/name.rfc1913.zone note that since 1913 when copying 1912 of the content, should be 1912 of the point of the file that the block commented out

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(4) Cp-p/var/named/westos.com.zone/var/named/westos.com.inter

(5) Edit the/var/named/westos.com.zone separately,/var/named/westos.com.inter set the IP that the intranet user obtains, set up the IP that the extranet user obtains

Intranet

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(External network)

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(6) Restart service

(7) Testing Services
Set the DNS of another host to the IP of the service host

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5. Master-Slave DNS server settings
Because a single DNS server resolves too many times when the load becomes larger, set the pressure from the DNS server to mitigate the primary DNS server.
(1) Modify the Ip,hostname, and adjust the firewall policy to configure the Yum source. (same as previous operation)
(2) Install BIND server and turn on BIND service, generate Rndc.key
(3) Edit the DNS configuration file/etc/resolve.conf Here DNS is the DNS from the server, which is used to relieve the stress of the primary DNS server.

Add nameserver 172.25.254.124 to the file

(4) Modify the configuration file vim/etc/named.conf of the bind service and restart the service # #开启53端口

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(6) Test: Perform dig from the DNS server 172.25.254.124 www.westos.com from the results can be seen from the service 172.25.254.124, is from the server, showing the burden of sharing the primary DNS server from the server.


Master-Slave DNS server synchronization
If the parsing file on the primary DNS server is modified but not received from the server in a timely manner, it resolves 2 addresses, so in order to maintain the accuracy of the DNS server cluster, the modified information on the primary DNS server needs to be modified synchronously to the slave server.

1. The/etc/named.rfc1912.zones and/etc/named.rfc1913.zones files need to be configured on the primary DNS server.

1912

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1913

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2. Outside the network users to do the example

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Linux Cloud Automation Operations Basics (DNS service)