How to build a DNS auxiliary server? Deployment and configuration full process guide

in the domain name resolution system, the DNS secondary server is an important part of ensuring the high availability of resolution services. It can synchronize domain name data from the primary server. When the primary server fails, it can temporarily take over the resolution work to avoid business interruption. When many operation and maintenance personnel build DNS secondary servers, synchronization failures or service abnormalities are often caused by unfamiliarity with configuration details. This article will dismantle the complete process of DNS secondary server construction for you from multiple dimensions such as pre-preparation, configuration operation, verification and maintenance, and help you complete the deployment efficiently.

, build DNS server before the preparation?

the preparation work before the formal establishment directly affects the deployment efficiency and stability of the DNS auxiliary server, and it is necessary to confirm whether the prerequisites are met one by one.

1, determine the primary and secondary server network environment

first make sure that the DNS secondary server and the primary server are in the same interoperable network environment, and the primary server has opened the UDP and TCP protocols of port 53, because DNS data synchronization depends on these two ports to transmit data. At the same time, it is necessary to configure a fixed Internet Protocol Address for the DNS secondary server to avoid synchronization failure due to IP changes.

2, install DNS service software

mainstream Linux system can choose BIND9 as the DNS service software, through the system package management tool to complete the installation, such as CentOS system using yum install bind-utils command, Ubuntu system using apt install bind9 bind9-utils command. After the installation is completed, it is necessary to confirm that the service can be started normally to lay a good foundation for subsequent DNS secondary server configuration.

3, obtain the main server authorization information

need to add the Internet Protocol Address of the DNS secondary server in the domain name zone configuration file of the primary server in advance to authorize it to synchronize the resolution data of the domain name. Only with the authorization of the primary server can the DNS secondary server initiate a synchronization request and obtain a complete domain name resolution record.

2. Core configuration steps of DNS secondary server?

after completing the preliminary preparation, enter the core configuration of the DNS secondary server, which is a key step in determining whether the service can operate normally.

1, configure the main configuration file named conf

open BIND's main configuration file named.conf, add a zone declaration to the file, specifying the domain name to be synchronized, the primary server Internet Protocol Address, and the path to store the synchronization data locally. For example, add zone "example.com" {type slave; file "/var/named/slaves/example.com.zone"; masters {192.168.1.10 ; }; };， where type slave indicates that the server is a DNS secondary server, and the masters field is followed by the master server IP.

2, configure area profile permissions

need to ensure that the directory where the synchronization data is stored on the DNS secondary server has the read and write permissions of the BIND service process. For example, the default permissions of the/var/named/slaves directory in the CentOS system meet the requirements. If you create a directory by yourself, you need to use the chown named: named command to modify the user group to which you belong. To avoid insufficient permissions to synchronize data cannot be written.

3, restart the DNS service and load the configuration

configuration is complete, restart the BIND service with the systemctl restart named command to let the new configuration take effect. After restart, you can check the service status through the systemctl status named command to confirm whether the service is running normally. If the startup fails, you need to check the syntax error of the configuration file.

3. Data synchronization verification method of DNS auxiliary server?

configuration is completed, it is necessary to verify whether the DNS secondary server successfully synchronizes data from the primary server to ensure that the resolution service can be provided normally.

1 View synchronized area files

enter the zone file storage directory of the DNS secondary server to check whether the zone file corresponding to the domain name is generated, and the file content is consistent with the zone file of the primary server. If the file exists and the content matches, it means that the DNS secondary server has completed the first data synchronization.

2, use the dig command to test the parsing

use the dig command on the local or other client side to specify the Internet Protocol Address of the DNS secondary server to test the domain name resolution, such as dig @192.168.1.20 example.com A. If the correct resolution record is returned, it means that the DNS secondary server can provide resolution services normally. At the same time, different types of records can be tested, such as MX, NS records, to ensure that all resolution data is synchronized completely.

3, check the main server synchronization log

check the system log of the DNS secondary server, such as/var/log/messages or/var/log/syslog, to confirm whether there is a log information of successful synchronization. At the same time, you can check whether there is a record of synchronization requests from the DNS secondary server in the log of the primary server to verify the integrity of the synchronization process in both directions.

4, DNS auxiliary server daily maintenance points?

DNS auxiliary server is completed, daily maintenance is the key to ensure its long-term stable operation, and various maintenance operations need to be performed regularly.

1, regularly check the synchronization status

can check the synchronization status of the DNS secondary server through the rndc command that comes with BIND, such as the rndc status command to confirm whether the regional data is in the latest state. At the same time, you can set a scheduled task to regularly check the update time of the regional file to ensure that the data changes of the main server can be synchronized to the DNS secondary server in time.

2, monitoring service operation status

with the help of monitoring tools such as Zabbix, Prometheus, real-time monitoring of DNS secondary server service status, CPU and memory usage, network traffic and other indicators, when the service is abnormal or the resource occupation is too high to issue an alarm in time, so that the operation and maintenance personnel can quickly troubleshoot the problem.

3, timely update of software version

regularly pay attention to the official updates of BIND software, upgrade to the latest stable version in time, fix known security bugs and functional defects, and avoid attacks on DNS secondary servers or service abnormalities due to software vulnerabilities.

To sum up, the construction of DNS auxiliary server needs to complete four key links: pre-preparation, core configuration, synchronization verification and daily maintenance. From network environment confirmation to service software installation, from configuration file writing to data synchronization verification, each step needs to pay attention to details. During daily maintenance, it is necessary to regularly check the synchronization status and service operation to ensure the continuous and stable operation of DNS auxiliary server and provide reliable redundancy support for domain name resolution system.