The commands listed belows are some that we use often, but many more exist. Check the man pages and documentation for more details and information.
nslookup The nslookup program allows the user to query Internet domain name servers interactively or non-interactively. In interactive mode the user can query name servers for information about various hosts and domains, and print a list of hosts in a domain. In non-interactive mode the user can just print the name and request information for a host or domain. Interactive mode has a lot of options and commands; it is recommended that you see the man page for nslookup, or the help under nslookup Interactive mode.
To enter under nslookup Interactive mode, use the command:
[root@deep] /# nslookup
Default Server: deep.openna.com Address: 208.164.186.1 > help $Id: nslookup.help,v 8.4 1996/10/25 18:09:41 vixie Exp $ Commands: (identifiers are shown in uppercase, [] means optional) NAME - print info about the host/domain NAME using default server NAME1 NAME2 - as above, but use NAME2 as server help or ? - print info on common commands; see nslookup(1) for details set OPTION - set an option all - print options, current server and host [no]debug - print debugging information [no]d2 - print exhaustive debugging information
To run in non-interactive mode, use the command:
[root@deep] /# nslookup www.redhat.com
Server: deep.openna.com Address: 208.164.186.1 Non-authoritative answer: Name: www.portal.redhat.com Addresses: 206.132.41.202, 206.132.41.203 Aliases: www.redhat.comWhere www.redhat.com is the host name or Internet address of the name server to be looked up.
dnsquery The dnsquery program queries domain name servers via the resolver library calls /etc/resolv.conf. To query domain name servers using resolver, use the command:
[root@deep] /# dnsquery <host>
[root@deep] /# dnsquery www.redhat.com
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 40803 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4 ;; www.redhat.com, type = ANY, class = IN www.redhat.com. 2h19m46s IN CNAME www.portal.redhat.com. redhat.com. 2h18m13s IN NS ns.redhat.com. redhat.com. 2h18m13s IN NS ns2.redhat.com. redhat.com. 2h18m13s IN NS ns3.redhat.com. redhat.com. 2h18m13s IN NS speedy.redhat.com. ns.redhat.com. 1d2h18m8s IN A 207.175.42.153 ns2.redhat.com. 1d2h18m8s IN A 208.178.165.229 ns3.redhat.com. 1d2h18m8s IN A 206.132.41.213 speedy.redhat.com. 2h18m13s IN A 199.183.24.251Where <host> is the name of the host you want to query.
host The host program looks up host names using DNS. To look up host names using domain server, use the command:
[root@deep] /# host <FQDN, domain names, host names, or host numbers>
Example 21.2. Look up host names
[root@deep] /# host redhat.com
redhat.com has address 207.175.42.154Where <FQDN, domain names, host names, or host numbers> is either FDQN www.redhat.com, domain names redhat.com, host names www or host numbers 207.175.42.154.
To find all of the information about a host maintained by the DNS, use the command:
[root@deep] /# host -a <domain names >
[root@deep] /# host -a redhat.com
Trying null domain rcode = 0 (Success), ancount=6 The following answer is not authoritative: The following answer is not verified as authentic by the server: redhat.com 8112 IN NS ns.redhat.com redhat.com 8112 IN NS ns2.redhat.com redhat.com 8112 IN NS ns3.redhat.com redhat.com 8112 IN NS speedy.redhat.com redhat.com 8112 IN A 207.175.42.154 redhat.com 11891 IN SOA ns.redhat.com noc.redhat.com( 2000021402 ;serial (version) 3600 ;refresh period 1800 ;retry refresh this often 604800 ;expiration period 86400 ;minimum TTL ) For authoritative answers, see: redhat.com 8112 IN NS ns.redhat.com redhat.com 8112 IN NS ns2.redhat.com redhat.com 8112 IN NS ns3.redhat.com redhat.com 8112 IN NS speedy.redhat.com Additional information: ns.redhat.com 94507 IN A 207.175.42.153 ns2.redhat.com 94507 IN A 208.178.165.229 ns3.redhat.com 94507 IN A 206.132.41.213 speedy.redhat.com 8112 IN A 199.183.24.251This option can be used to find all of the information that is maintained by the domain server about this host, in our example redhat.com.
To list a complete domain, use the command:
[root@deep] /# host -l <domain names >
Example 21.4. List a complete domain
[root@deep] /# host -l openna.com
openna.com name server deep.openna.com openna.com name server mail.openna.com localhost.openna.com has address 127.0.0.1 deep.openna.com has address 208.164.186.1 mail.openna.com has address 208.164.186.2 www.openna.com has address 208.164.186.3This option, in the official master file format, will give a complete download of the zone data for the domain name openna.com. This command should be used only if it is absolutely necessary.