DNS server on Linux (2)


Configuring the client

Configuring the DNS client is to configure the client's /etc/resolv.conf file. . The specific options are as follows:
1. Domain + domain name
is used to specify the local domain name of this host.
2. Search + Domain Name
Used to list the domain name to be resolved when the domain name is not included in the host name.
3. Nameserver +IP address
is used to specify the DNS server. Note that you must use the IP address here, but you cannot use the host name of the DNS server, otherwise DNS queries will not be possible. This setting can be repeated, but up to three DNS servers can be pointed out. The priority of use is from high to low in the order of appearance. It is recommended not to specify only one DNS server, because it will inevitably fail, there is a second The road and the third road are always good.

V. Classification of DNS Servers

DNS servers can be divided into three categories: Primary DNS Server, Secondary DNS Server, and Cached DNS Server. DNS Server). The relationship and role of the primary and secondary DNS servers is the same as the PDC and BDC in the NT domain. The primary DNS server can provide the latest query, and the secondary DNS server shares the burden of the query for the primary DNS server, but the secondary DNS server is not as fast as the primary DNS server. The principle of a cached DNS server is to provide a history of queries and use these records to improve the efficiency of the query. When a query is sent to the cached DNS server for the first time, the cached DNS server records the entire process of the query and uses it to answer all the same queries for a certain period of time, thereby reducing the overall DNS system. The burden and increase the speed of the query.

Sixth, configure the DNS server

1. About the named daemon
The named process is the main process of DNS. It is usually started at system startup. After startup, it reads its configuration information from a corresponding set of configuration files. 2. Configuration of the /etc/named.boot file
The named.boot file is the first configuration file read by the named process at startup. It contains pointers to other configuration files and other domain name servers, so it is very important. The comment line begins with a semicolon in the file. Some of the frequently used options have the following meanings:

(1) directory
is used to notify the named process that all the files involved in this file are in the system and can be reused.

(2) cache
The file following the cache contains a list of existing root DNS servers on the Internet. The latest list is available at ftp://rs.internic.net/domain/named.cache. This item must be there, otherwise it will cause serious performance problems.

(3) primary
primary has a domain name and a file name, which identifies the local DNS server of the specified domain, and the file name that follows contains the entry of this server.

(4) secondary
This item causes the named process to run as a secondary DNS server. It has three parameters: the domain name, the IP address of the primary DNS server, and the file name. The file name here specifies a file that holds the content retrieved from the primary DNS server.

(5) forwarders
This item is used to indicate a list of DNS servers, that is, the location where this query is forwarded when the local named process cannot be parsed. (If the machine is a caching DNS server, then it should indicate the primary or secondary DNS server of the domain; if the local is a secondary DNS server, it should point to the primary server; if the local is already the primary DNS server, it should point to the Internet access ISP's DNS server.)

It is used to designate this machine as a secondary server. At this time, all the queries are forwarded by the server according to the server indicated by the forwarders item.

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