ubuntu用dnsmasq、nscd解析还是慢的解决办法

1.缘起

好吧,ubuntu下面打开oschina.net,打开linux.cn等等都很慢,根源在于dns解析很慢,那怎么解决呢?

2.网上常用解决办法及存在问题

  • dnsmasq

使用dnsmasq可以缓存一段时间的dns到本机,但是过上3、5分钟又得重新到互联网上取一遍dns,然后又慢得要死。

  • nscd

理论上装了nscd后,在/var/db/下有nscd相关的缓存文件,但不知道为啥,我安装了nscd之后,然后启动了nscd,但是/var/db/下不存在nscd相关的缓存文件,然后每次nslookup oschina.net都会去114.114.114.114查询,慢死了。

3.ubuntu14.04 解决办法

(1)卸载dnsmasq、nscd

  • 正常ubuntu不会安装这两个东西,如果安装了就记得卸载掉,卸载命令
sudo apt-get purge dnsmasq nscd

(2)注销networkmanager的dnsmasq功能

  • 打开 /etc/NetworkManager/NetworkManager.conf
  • 删除dns=dnsmasq

(3)安装、配置pdnsd

1)安装

sudo apt-get install pdnsd

安装时选择resolv.conf,不要选择manual

2)配置

  • 修改/etc/defaults/pdnsd

将其中的START_DAEMON=no改为yes

  • 修改/etc/pdnsd.conf

修改global里面的min_ttl=1d;修改完成后的结果见下

global {
    perm_cache=2048;
    cache_dir="/var/cache/pdnsd";
    run_as="pdnsd";
    server_ip = 127.0.0.1;  // Use eth0 here if you want to allow other
                // machines on your network to query pdnsd.
    status_ctl = on;
    paranoid=on;
//  query_method=tcp_udp;   // pdnsd must be compiled with tcp
                // query support for this to work.
    min_ttl=1d;       // Retain cached entries at least 15 minutes.
    max_ttl=1w;    // One week.
    timeout=10;        // Global timeout option (10 seconds).

        // Don't enable if you don't recurse yourself, can lead to problems
        // delegation_only="com","net";
}

修改server的ip,修改完成后的结果见下

server {
    label = "root-servers";
    root_server=on;
    ip =    114.114.114.114
    ,   8.8.8.8
    ;
    timeout = 5;
    uptest = query;
    interval = 30m;      // Test every half hour.
    ping_timeout = 300;  // 30 seconds.
    purge_cache = off;
    exclude = .localdomain;
    policy = included;
    preset = off;
}
  • 修改/etc/resolv.conf

修改完成后的结果见下

nameserver 127.0.0.1
nameserver 114.114.114.114
nameserver 8.8.8.8
  • 设置/etc/resolv.conf的不可更改属性
sudo chattr +i resolv.conf
  • 上述命令如果报错:chattr: Operation not supported while reading flags on /etc/resolv.conf
  • 则执行下述命令并重启,然后重新建立resolv.conf
sudo apt-get purge resolvconf

4 ubuntu16.04解决办法

不知道为啥,16.04安装了pdnsd之后无法cache,du -h /var/cache/pdnsd 一直返回8k,然后,发现16.04如果修改了某些东西后解析dns好像还是蛮快的

(1)卸载resolvconf和avahi-daemon(可能有的没有安装,就不用卸载了)

sudo apt-get purge resolvconf avahi-daemon

(2)修改/etc/NetworkManager/NetworkManager.conf

原始值:dns=dnsmasq
修改后:dns=none

(3)/etc/resolv.conf里写上阿里dns、114dns、googledns

sudo rm -rfv /etc/resolv.conf
sudo touch /etc/resolv.conf

修改后的/etc/resolv.conf

nameserver 223.5.5.5
nameserver 114.114.114.114
nameserver 8.8.8.8
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