![variable.jp [データベース,パフォーマンス,運用]](https://variable.jp/wp-content/uploads/2013/09/cropped-variable.jp_.jpg)
Windowsでは名前解決したアドレスはローカルキャッシュに残っているが、
Linuxではローカルキャッシュに残って無いので場合によっては、
名前解決の処理やネットワークの負荷を軽減する為にLinuxでも利用した方が良い場合がある。
但し、便利な反面ローカルにキャッシュが残っている事を認識してないと問題解決に
時間がかかる場合があるので、運用者は常に認識しておいた方が良いかと。
DNSMASQのインストール
[root@HOME001 htop-0.8.3]# yum install dnsmasq Loaded plugins: fastestmirror, security Loading mirror speeds from cached hostfile * base: ftp.iij.ad.jp * extras: ftp.iij.ad.jp * updates: ftp.iij.ad.jp Setting up Install Process Resolving Dependencies --> Running transaction check ---> Package dnsmasq.i686 0:2.48-6.el6 will be installed --> Finished Dependency Resolution Dependencies Resolved ======================================================================================================================================================================== Package Arch Version Repository Size ======================================================================================================================================================================== Installing: dnsmasq i686 2.48-6.el6 base 144 k Transaction Summary ======================================================================================================================================================================== Install 1 Package(s) Total download size: 144 k Installed size: 281 k Is this ok [y/N]: y Downloading Packages: dnsmasq-2.48-6.el6.i686.rpm | 144 kB 00:00 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Installing : dnsmasq-2.48-6.el6.i686 1/1 Verifying : dnsmasq-2.48-6.el6.i686 1/1 Installed: dnsmasq.i686 0:2.48-6.el6 Complete! [root@HOME001 htop-0.8.3]# /sbin/chkconfig --list dnsmasq dnsmasq 0:off 1:off 2:off 3:off 4:off 5:off 6:off [root@HOME001 htop-0.8.3]#
自動起動する場合は、chkconfigにて自動起動設定して下さい。
ローカルからDNSを利用出来るように設定ファイルの編集
/etc/dnsmasq.conf
[root@HOME001 htop-0.8.3]# cat /etc/dnsmasq.conf | grep "127.0.0.1" | egrep -i -v ^# listen-address=127.0.0.1 [root@HOME001 htop-0.8.3]#
/etc/resolv.conf
[root@HOME001 htop-0.8.3]# cat /etc/resolv.conf | grep "127.0.0.1" | egrep -i -v ^# nameserver 127.0.0.1 [root@HOME001 htop-0.8.3]#
サービスの再起動
[root@HOME001 htop-0.8.3]# /etc/init.d/dnsmasq restart Shutting down dnsmasq: [ OK ] Starting dnsmasq: [ OK ] [root@HOME001 htop-0.8.3]#
ローカルで名前解決が出来るか確認
[root@HOME001 htop-0.8.3]# dig @127.0.0.1 kakaku.com ; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> @127.0.0.1 kakaku.com ; (1 server found) ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 37234 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;kakaku.com. IN A ;; ANSWER SECTION: kakaku.com. 411 IN A 210.129.151.129 ;; Query time: 9 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Sun Dec 30 13:53:28 2012 ;; MSG SIZE rcvd: 44 [root@HOME001 htop-0.8.3]# [/SHELL] <a href="http://variable.jp/2012/12/30/linux%e3%81%ab%e3%81%8a%e3%81%91%e3%82%8bdns-cache/dig/" rel="attachment wp-att-2450"><img src="http://variable.jp/wp-content/uploads/2012/12/dig.jpg" alt="dig" width="624" height="351" /></a> <a href="http://variable.jp/2012/12/30/linux%e3%81%ab%e3%81%8a%e3%81%91%e3%82%8bdns-cache/dig-grep/" rel="attachment wp-att-2452"><img src="http://variable.jp/wp-content/uploads/2012/12/dig-grep.jpg" alt="dig-grep" width="442" height="80" /></a> <strong>ローカルキャッシュのリフレッシュ</strong> [SHELL] [root@HOME001 htop-0.8.3]# /etc/init.d/dnsmasq force-reload Shutting down dnsmasq: [ OK ] Starting dnsmasq: [ OK ] [root@HOME001 htop-0.8.3]#
参考