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Two classic tools are nslookup and dig.
Although dig is more convenient, you can get a version of a nameserver using nslookup:
> set q=txt
> set class=chaos
VERSION.BIND text = "8.2.2-P7"
Queries Internet domain name servers.
nslookup [ -Option ... ] [ Host ] [ -NameServer ]
The nslookup command queries Internet domain name servers in two modes. Interactive mode allows you to query name servers for information about various hosts and domains, or to print a list of the hosts in a domain. In noninteractive mode, the names and requested information are printed for a specified host or domain.
The nslookup command enters interactive mode when no arguments are given, or when the first argument is a - (minus sign) and the second argument is the host name or Internet address of a name server. When no arguments are given, the command queries the default name server. The - (minus sign) invokes an optional subcommand (-Option... variable). With the exception of the set command, these subcommands are specified on the command line and must precede the nslookup command arguments. The set subcommand options can alternatively be specified in the .nslookuprc file in the user's home directory.
The nslookup command executes in noninteractive mode when the first argument is the name or Internet address of the host being searched for. In this case, the host name or Internet address of the name server is optional.
The noninteractive command looks up information for the specified Host using the default name server or the name server specified by the NameServer parameter. If the Host parameter specifies an Internet address and the query type is A or PTR, the name of the host is returned. If the Host parameter specifies a name and the name does not have a trailing period, the default domain name is appended to the name. To look up a host not in the current domain, append a single period to the name.
Note: If they are specified in the .nslookuprc file of the user's home directory, the set subcommand's domain, srchlist, defname, and search options can affect the behavior of the noninteractive command.
The following commands can be interrupted at any time by entering a Ctrl-C key sequence. To exit, enter a Ctrl-D key sequence or type exit. To treat a built-in command as a host name, precede it with an escape character, which is a \. Unrecognized commands are interpreted as host names.
The following subcommands are recognized by the nslookup command:
finger [Name] [>> FileName]
|Connects with the finger daemon server on the current host. The current host is defined when a previous lookup for a host was successful and returned address information, such as that returned with the set querytype=A command. The Name parameter, which specifies a user name, is optional. The > and >> characters can be used to redirect output to a new or existing file.|
|Changes the default server to the value specified by the Domain parameter. The lserver subcommand uses the initial server to look up information about the domain. The server subcommand uses the current default server. If an authoritative answer cannot be found, the names of any additional servers that might have the answer are returned.|
|root||Changes the default server to the server for the root of the domain name space. Currently, the host ns.nic.ddn.mil is used. The name of the root server can be changed with the set root subcommand. (The root subcommand is synonymous with the lserver ns.nic.ddn.mil subcommand.)|
ls [Option] Domain [>> FileName]
|Lists the information available for the
Domain specified, optionally creating
or appending the output to the file specified by the
FileName parameter. The default
output contains host names and their Internet addresses. Possible
values for the Option parameter
Note: When output is redirected to a file, hash marks are printed for every 50 records received from the server.
|view FileName||Sorts the output of previous ls commands and lists them using the more command.|
|?||Prints a brief summary of commands.|
|exit||Exits the program.|
|set Keyword[=Value]||Changes state information that affects lookups. This subcommand
can be specified on the command line or optionally included
in the .nslookuprc file in the user's
home directory. Valid keywords are:
|type=Value||Changes the information query to one of the following values.
The default is A.
nslookup -query=hinfo -timeout=10
nslookup -set srchlist=lcs.MIT.EDU/ai.MIT.EDU/MIT.EDU
This command overrides the default domain name and search list of the set domain command. Use the set all command to display the list.
nslookup -querytype=ANY austin.ibm.com
The nslookup command returns all available information about the name austin.ibm.com, including Statement of Authority (SOA), name server, mail exchanger, and host Internet address information, as follows:
Server: benames.austin.ibm.com Address: 126.96.36.199 austin.ibm.com origin = ausname1.austin.ibm.com mail addr = brian.chriss.austin.ibm.com serial=1993081210,refresh=3600,retry=300,expire=604800, min=86400 austin.ibm.com nameserver = ausname1.austin.ibm.com austin.ibm.com nameserver = bb3names.austin.ibm.com austin.ibm.com nameserver = benames.austin.ibm.com austin.ibm.com nameserver = b45names.austin.ibm.com austin.ibm.com nameserver = bbcnames.austin.ibm.com austin.ibm.com nameserver = netmail.austin.ibm.com austin.ibm.com preference = 10, mail exchanger = netmail.austin.ibm.com austin.ibm.com inet address = 188.8.131.52 ausname1.austin.ibm.com inet address = 184.108.40.206 bb3names.austin.ibm.com inet address = 220.127.116.11 benames.austin.ibm.com inet address = 18.104.22.168 b45names.austin.ibm.com inet address = 22.214.171.124 bbcnames.austin.ibm.com inet address = 126.96.36.199 netmail.austin.ibm.com inet address = 188.8.131.52
The nslookup command responds similarly to the host command. The command returns the domain name and Internet address of host opus, as follows:
Name: opus.austin.ibm.com Address: 184.108.40.206
If host opus had been a name server (a host running the named daemon with an empty /etc/resolv.conf file), the following information would have been displayed:
Server: loopback Address: 0.0.0.0
When a lookup request is not successful, the nslookup command returns one of the following error messages:
|Timed Out||Indicates the server did not respond to the request after the specified number of retries.|
|No Response from Server||Indicates that a name server is not running on the server machine.|
|No Records||Indicates the server does not have the resource records of the specified query type for the host, although the host name is valid.|
|Non-Existent Domain||Indicates the host or domain name does not exist.|
|Connection Refused||Indicates the connection to the name or finger server could not be made at the time of the inquiry. This error is typically associated with ls and finger requests.|
|Network Is Unreachable||Indicates the connection to the name or finger server could not be made at the time of the inquiry. This error is typically associated with ls and finger requests.|
|Server Failure||Indicates the name server encountered an internal inconsistency and could not return a valid answer.|
|Refused||Indicates the name server refused to service the request.|
|Format Error||Indicates the name server refused the request packet because it was not in the proper format.|
|/usr/bin/nslookup||Contains the nslookup command.|
|/etc/resolv.conf||Contains the initial domain name and nameserver addresses.|
|$HOME/.nslookuprc||Contains the user's initial options.|
|HOSTALIASES||Contains the host aliases.|
|LOCALDOMAIN||Contains the override default domain.|
namerslv command, traceroute command.
res_query subroutine, res_search subroutine.
resolv.conf file format for TCP/IP.
TCP/IP Name Resolution in AIX 5L Version 5.3 System Management Guide: Communications and Networks.
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