whoisコマンドは、ドメインやIPの情報を情報を問い合せるコマンドです。
組織・登録年月日、利用しているネームサーバーなどの情報が確認できます。

whois [オプション] ドメイン|IPアドレス

# whois yahoo.co.jp
[Querying whois.jprs.jp]
[whois.jprs.jp]
[ JPRS database provides information on network administration. Its use is    ]
[ restricted to network administration purposes. For further information,     ]
[ use 'whois -h whois.jprs.jp help'. To suppress Japanese output, add'/e'     ]
[ at the end of command, e.g. 'whois -h whois.jprs.jp xxx/e'.                 ]

Domain Information:
a. [Domain Name]                YAHOO.CO.JP
g. [Organization]               Yahoo Japan Corporation
l. [Organization Type]          Corporation
m. [Administrative Contact]     HA14103JP
n. [Technical Contact]          KM43416JP
p. [Name Server]                ns01.yahoo.co.jp
p. [Name Server]                ns02.yahoo.co.jp
p. [Name Server]                ns11.yahoo.co.jp
p. [Name Server]                ns12.yahoo.co.jp
s. [Signing Key]                
[State]                         Connected (2017/11/30)
[Registered Date]               2000/11/17
[Connected Date]                2000/11/17
[Last Update]                   2017/04/20 10:09:53 (JST)

[Administrative Contact]をwhoisで確認すると、管理者情報も確認できます。

# whois HA14103JP
[Querying whois.nic.ad.jp]
[whois.nic.ad.jp]
[ JPNIC database provides information regarding IP address and ASN. Its use   ]
[ is restricted to network administration purposes. For further information,  ]
[ use 'whois -h whois.nic.ad.jp help'. To only display English output,        ]
[ add '/e' at the end of command, e.g. 'whois -h whois.nic.ad.jp xxx/e'.      ]

Contact Information: 
a. [JPNIC Handle]               HA14103JP
c. [Last, First]                Akiyoshi, Hisatsugu
d. [E-Mail]                     nic-admin@mail.yahoo.co.jp
g. [Organization]               Yahoo Japan Corporation
l. [Division]                   
n. [Title]                      
o. [TEL]                        
p. [FAX]                        
y. [Reply Mail]                 
[Last Update]                   2016/10/28 17:04:58(JST)
                                form@dom.jprs.jp