HP-UX HB v13.00 Ch-10 - Network Services

HP-UX Handbook – Rev 13.00 Page 5 (of 26)
Chapter 10 Network Services
October 29, 2013
Name Service Switching
Most, if not all, network services are designed to be Name Service Switch (NSS) aware.
For instance, the telnetd daemon in the process of setting up an incoming telnet connection, will
as part of the program logic, verify the source IP address on the incoming request. To do this the
telnetd program opens /etc/nsswitch.conf if it is present and follows the instructions for ipnodes
first and then hosts. In the case below, /etc/hosts (files) will be searched first and then dns.
passwd: files ldap
group: files ldap
hosts: files [NOTFOUND=continue] dns
ipnodes: files
services: files
networks: files
protocols: files
rpc: files
publickey: files
netgroup: files
automount: files
aliases: files
If there is no /etc/nsswitch.conf configured then the choices provided in the file are made by the
program. The /etc/nsswitch.hp_defaults lists the following as the default for hostname
resolution:
hosts: dns [NOTFOUND=return] nis [NOTFOUND=return] files
ipnodes: dns [NOTFOUND=return] nis [NOTFOUND=return] files
ADVICE: It is essential that /etc/nsswitch.conf be configured to safeguard against unintended
and undesirable resolution behavior. A poor design (resulting from blindly taking the defaults)
can cause performance problems for applications.
Example:
Environment: DNS caching-only nameserver with no /etc/nsswitch.conf and application using
loopback for inter process communication (IPC).
Default /etc/nsswitch.conf values: