Linux优化DNS配置方法

Step 1 配置冗余DNS Server地址

可防止DNS Server单点故障后，域名无法解析的情况。

以CentOS为例：

打开主机内/etc/resolv.conf文件，

若文件中只配置了1个IP，根据如下列表，替换为以下2个IP：

Step 2 开启NSCD服务

在Linux中开启NSCD服务可在本地缓存DNS解析结果。在TTL时间内，无需去DNS服务器重复解析，从而加快DNS的解析速度，也缓解DNS服务器的压力。

以CentOS为例：

1、安装

yum install nscd

2、增加配置文件 /etc/nscd.conf

内容如下：

#
# /etc/nscd.conf
#
# An example Name Service Cache config file.  This file is needed by nscd.
#
# Legal entries are:
#
#       logfile                 <file>
#       debug-level             <level>
#       threads                 <initial #threads to use>
#       max-threads             <maximum #threads to use>
#       server-user             <user to run server as instead of root>
#               server-user is ignored if nscd is started with -S parameters
#       stat-user               <user who is allowed to request statistics>
#       reload-count            unlimited|<number>
#       paranoia                <yes|no>
#       restart-interval        <time in seconds>
#
#       enable-cache            <service> <yes|no>
#       positive-time-to-live   <service> <time in seconds>
#       negative-time-to-live   <service> <time in seconds>
#       suggested-size          <service> <prime number>
#       check-files             <service> <yes|no>
#       persistent              <service> <yes|no>
#       shared                  <service> <yes|no>
#       max-db-size             <service> <number bytes>
#       auto-propagate          <service> <yes|no>
#
# Currently supported cache names (services): passwd, group, hosts, services
#
#   logfile                 /var/log/nscd.log
    threads                 4
    max-threads             32
    server-user             nscd
    stat-user               somebody
    debug-level             5
    reload-count            5
    paranoia                no
    restart-interval        3600


    enable-cache            hosts           yes
    enable-cache            passwd          no
    enable-cache            group           no
    enable-cache            services        no
    positive-time-to-live   hosts           5
    negative-time-to-live   hosts           20
    suggested-size          hosts           211
    check-files             hosts           yes
    persistent              hosts           yes
    shared                  hosts           yes
    max-db-size             hosts           33554432

3、启动服务

service nscd start

4、添加开机自启动

chkconfig nscd on

5、如需要停止服务

service nscd stop