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
$Id$
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.com
Where 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>
Example 21.1. dnsquery
[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 199.183.24.251
Where <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 207.175.42.154
Where <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 >
Example 21.3. Using host
[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 199.183.24.251
This 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 208.164.186.3
This 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.