HP OpenView System Administration Handbook [Electronic resources] : Network Node Manager, Customer Views, Service Information Portal, HP OpenView Operations نسخه متنی

B.2 SETTING A SYSTEMS HOSTNAME

The hostname is set by the operating system. In HP-UX, the hostname is set at boot time by the startup script /sbin/init.d/hostname using the HOSTNAME variable set in the file /etc/rc.config.d/netconf. The IP addresses for all Ethernet interfaces are defined in /etc/rc.config.d/netconf. Each Ethernet interface name and its associated subnet mask, IP address, Broadcast address, and Interface state is assigned the same unique index number for that Interface Name/IP address combination. All Ethernet interfaces defined in /etc/rc.config.d/netconf are set at boot time by the startup script /sbin/init.d/net. The interfaces themselves are configured by the "ifconfiging," the interface with its associated IP address in /etc/rc.config.d/netconf, and not by resolving an alias to its IP.

In Solaris, the hostname is configured in the file /etc/nodename and is set at boot time by the /etc/rcS.d/S30rootusr.sh script. It is not set by using the

hostname command, but by using the

uname command with the S option which sets both the

uname and the

hostname to the same name simultaneously. The IP addresses are configured for each interface by placing the hostname alias for an interface within the appropriate configuration file in /etc/hostname. <interface_type>0-9. The IP addresses are set at boot time by the /etc/rcS.d/S30rootusr.sh by retrieving the hostname alias from each file, resolving that hostname to the IP address, retrieving the IP netmask from /etc/netmasks file, and configuring the associated IP and netmask to the appropriate interface. Many times, the hostname alias in each /etc/hostname.<interface_type>0-9 is incorrectly inserted into hostname naming services (/etc/hosts, NIS hosts map, and the DNS) as an official hostname for resolution, such as the second column of the hosts file or file used to create the NIS hosts map. The S30rootusr.sh file will function properly with the hostname alias in the third or fourth column of the /etc/hosts file.

This hostname returned by the

hostname command is commonly known as the

short hostname, meaning that it is unqualified, or has no DNS domain attached to it. It should not be set to an FQDN. The UNIX operating system and subsequent programs retrieve the hostname of the current host with the

gethostname() system call. Many products will then try to fully qualify the hostname to find what is commonly known as the official hostname from a naming service such as /etc/hosts, NIS, or DNS. The official hostname is the second column of the /etc/hosts file or file used to create the NIS hosts map. It should always be the FQDN. The DNS always returns a FQDN.

B.2.1 Incorrect /etc/hosts, NIS, and DNS Configuration

"My hostnames in one product don't match those within Network Node Manager." "The hostnames in all my NMS products come up differently in each products database." "I can only remsh or rcp from specific hosts." or "When Network Node Manager does a configuration check, hostnames for the map icons get changed, so I turn the configuration check off."

Do these comments sound familiar? It is because each product uses a different algorithm for retrieving the hostname for a multi-homed system, and the naming service it used for obtaining the hostname from the IP did not resolve to the same fully qualified (with domain) hostname, or FQDN, as another product.

To prevent this from occurring, the entries within /etc/hosts, NIS, and the DNS for a particular host and IP address must match each other. Each IP must resolve to an FQDN. Each IP on a multi-homed host must resolve to the same FQDN. The DNS always returns an FQDN and the /etc/hosts and NIS should as well. Everything else is an alias (/etc/hosts, NIS) or an additional address record (DNS). The

pointer records (PTR), or address-to-name records, within DNS must all "point" to the same official hostname for a multi-homed host. The PTR records should not point to an alias.

The network and systems management products, even ARPA services, benefit from a correct configuration of each naming service. It prevents one from turning off processes, such as NNM's configuration check, that are designed to help give a snapshot of how a particular host is configured within the network. It makes administration of UNIX and authentication simpler and easier.