はじめに
CentOS 6をminimalインストールすると、デフォルトではDNS名前解決テスト用のdig,nslookup,hostコマンドがインストールされていません。
[root@example-CentOS-6 ~]# which host
/usr/bin/which: no host in (/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin)
[root@example-CentOS-6 ~]# which dig
/usr/bin/which: no dig in (/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin)
[root@example-CentOS-6 ~]# which nslookup
/usr/bin/which: no nslookup in (/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin)
[root@example-CentOS-6 ~]#
CentOS 6にdig,nslookup,hostコマンドをインストールしたい場合、bind-utilsをインストールします。
[root@example-CentOS-6 ~]# yum -y install bind-utils
対象環境
・CentOS release 6.6 (2.6.32-504.8.1.el6.x86_64)
bind-utilsのインストール
・bind-utilsをインストールします。
[root@example-CentOS-6 ~]# yum -y install bind-utils
・bind-utilsインストールにより、dig,nslookup,hostコマンドがインストールされます。
[root@example-CentOS-6 ~]# which dig
/usr/bin/dig
[root@example-CentOS-6 ~]# which host
/usr/bin/host
[root@example-CentOS-6 ~]# which nslookup
/usr/bin/nslookup
[root@example-CentOS-6 ~]#
・dig,nslookup,hostコマンドによるDNS名前解決テストが可能になります。
[root@example-CentOS-6 ~]# dig www.example.com +trace
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.30.rc1.el6_6.1 <<>> www.example.com +trace
;; global options: +cmd
. 518400 IN NS M.ROOT-SERVERS.NET.
. 518400 IN NS A.ROOT-SERVERS.NET.
. 518400 IN NS B.ROOT-SERVERS.NET.
. 518400 IN NS C.ROOT-SERVERS.NET.
. 518400 IN NS D.ROOT-SERVERS.NET.
. 518400 IN NS E.ROOT-SERVERS.NET.
. 518400 IN NS F.ROOT-SERVERS.NET.
. 518400 IN NS G.ROOT-SERVERS.NET.
. 518400 IN NS H.ROOT-SERVERS.NET.
. 518400 IN NS I.ROOT-SERVERS.NET.
. 518400 IN NS J.ROOT-SERVERS.NET.
. 518400 IN NS K.ROOT-SERVERS.NET.
. 518400 IN NS L.ROOT-SERVERS.NET.
;; Received 496 bytes from 172.31.0.2#53(172.31.0.2) in 9 ms
com. 172800 IN NS i.gtld-servers.net.
com. 172800 IN NS e.gtld-servers.net.
com. 172800 IN NS a.gtld-servers.net.
com. 172800 IN NS g.gtld-servers.net.
com. 172800 IN NS c.gtld-servers.net.
com. 172800 IN NS l.gtld-servers.net.
com. 172800 IN NS k.gtld-servers.net.
com. 172800 IN NS h.gtld-servers.net.
com. 172800 IN NS m.gtld-servers.net.
com. 172800 IN NS j.gtld-servers.net.
com. 172800 IN NS f.gtld-servers.net.
com. 172800 IN NS d.gtld-servers.net.
com. 172800 IN NS b.gtld-servers.net.
;; Received 493 bytes from 192.112.36.4#53(192.112.36.4) in 79 ms
example.com. 172800 IN NS a.iana-servers.net.
example.com. 172800 IN NS b.iana-servers.net.
;; Received 169 bytes from 192.48.79.30#53(192.48.79.30) in 143 ms
www.example.com. 86400 IN A 93.184.216.34
example.com. 172800 IN NS b.iana-servers.net.
example.com. 172800 IN NS a.iana-servers.net.
;; Received 185 bytes from 199.43.133.53#53(199.43.133.53) in 125 ms
[root@example-CentOS-6 ~]#
[root@example-CentOS-6 ~]# host -t ns example.com b.iana-servers.net
Using domain server:
Name: b.iana-servers.net
Address: 199.43.133.53#53
Aliases:
example.com name server b.iana-servers.net.
example.com name server a.iana-servers.net.
[root@example-CentOS-6 ~]#
[root@example-CentOS-6 ~]# nslookup a.iana-servers.net.
Server: XX.XX.XX.XX
Address: XX.XX.XX.XX#53
Non-authoritative answer:
Name: a.iana-servers.net
Address: 199.43.132.53
[root@example-CentOS-6 ~]#
以上になります。