Page 178 - DCAP106_OPERATING_SYSTEM_TOOLS

Unit 10: Servers

Notes
Table 10.1: Keywords in /etc/resolv.conf
Keyword Value
Nameserver IP address of your DNS nameserver. There should be only one entry per
"nameserver" keyword. If there is more than one nameserver, you’ll need to
have multiple "nameserver" lines.
Domain The local domain name to be used by default. If the server is bigboy.my-web-
site.org, then the entry would just be my-web-site.org
Search If you refer to another server just by its name without the domain added on,
DNS on your client will append the server name to each domain in this list and
do a DNS lookup on each to get the remote servers’ IP address. This is a handy
time saving feature to have so that you can refer to servers in the same domain
by only their server name without having to specify the domain. The domains
in this list must separated by spaces.

Obtain a sample configuration in which the client server’s main domain is my-site.com, but it also
is a member of domains my-site.net and my-site.org, which should be searched for shorthand
references to other servers. Two name servers, 192.168.1.100 and 192.168.1.102, provide DNS
name resolution:

search my-site.com my-site.net my-site.org
nameserver 192.168.1.100
nameserver 192.168.1.102
The first domain scheduled after the search directive must be the home domain of your network,
in our case ignou.ac.in. Placing a domain and search entry in the /etc/resolv.conf is redundant,
therefore.

Important File Locations

The locations of the BIND configuration files vary by Linux distribution, as you will soon see.

z z RedHat/Fedora:
RedHat/Fedora BIND normally runs as the named process owned by the unprivileged
named user.
Sometimes BIND is also installed using Linux’s chroot characteristic to not only run named
as user named, but also to limit the files named can see. When installed, named is fooled
into thinking that the directory /var/named/chroot is actually the root or / directory.
Therefore, named files normally found in the /etc directory are found in /var/named/
chroot/etc directory instead, and those you’d expect to find in /var/named are actually
located in /var/named/chroot/var/named.
The benefit of the chroot feature is that if a hacker enters your system via a BIND exploit, the
hacker’s access to the rest of your system is isolated to the files under the chroot directory
and nothing else. This type of security is also known as a chroot jail.
You can determine whether you have the chroot add-on RPM by using this command,
which returns the name of the RPM.
[root@bigboy tmp]# rpm -q bind-chroot
bind-chroot-9.2.3-13
[root@bigboy tmp]#

LOVELY PROFESSIONAL UNIVERSITY 171