Information Technology Reference
In-Depth Information
23.9 Domain name server
Each institution on the Internet has a host that runs a process called the domain name server
(DNS). The DNS maintains a database called the directory information base (DIB) which
contains directory information for that institution. When a new host is added, the system
manager adds its name and its IP address. It can then access the Internet.
23.9.1 DNS program
The DNS program is typically run on a Linux-based PC with a program called
named
(lo-
cated in
/usr/sbin
) with an information file of
named.boot
. To run the program the fol-
lowing is used:
/usr/bin/named -b /usr/local/adm/named/named.boot
The following shows that the DNS program is currently running.
$ ps -ax
PID TTY STAT TIME COMMAND
295 con S 0:00 bootpd
35 con S 0:00 /usr/sbin/lpd
272 con S 0:00 /usr/sbin/named -b /usr/local/adm/named/named.boot
264 p 1 S 0:01 bash
306 pp0 R 0:00 ps -ax
In this case the data file
named.boot
is located in the
/usr/local/adm/named
directory.
A sample
named.boot
file is
/usr/local/adm/named - soabasefile
eece.napier.ac.uk -main record of computer names
net/net144 -reverse look-up database
net/net145
“ “
net/net146
“ “
net/net147
“ “
net/net150
“ “
net/net151
“ “
This file specifies that the reverse look-up information on computers on the subnets 144,
145, 146, 147, 150 and 151 is contained in the
net144
,
net145
,
net146
,
net147
,
net150
and
net151
files, respectively. These are stored in the
net
subdirectory. The main file
which contains the DNS information is, in this case,
eece.napier.ac.uk
.
Whenever a new computer is added onto a network, in this case, the
eece.napier.ac.uk
file and the
net/net1
**
(where
**
is the relevant subnet name) are
updated to reflect the changes. Finally, the serial number at the top of these data files is up-
dated to reflect the current date, such as 19970321 (for 21st March 1997).
The DNS program can then be tested using
nslookup
;
For example,
$ nslookup
Default Server: ees99.eece.napier.ac.uk
Address: 146.176.151.99
> src.doc.ic.ac.uk
Server: ees99.eece.napier.ac.uk
Address: 146.176.151.99
Non-authoritative answer:
