hostname and nodename

[Shivkumar]

Hi,

hostname and nodename "uname -n" are stored in which files ?

Thanks,
Shiv

[A. Clay Stephenson · Accepted solution]

HOSTNAME is stored in /etc/rc.config.d/netconf. If NODENAME is not defined or is null then the NODENAME is set to HOSTNAME.

Examine /sbin/init.d/hostname and you will see how this works.

[Shivkumar]

What is the purpose of having hostname and nodename defined separately ? I mean why same server is known 2 names by hostname and by nodename ?

Thanks,
Shiv

[John Kittel]

the man page for the hostname command explains some of the reasons, such as they are...

- John

[A. Clay Stephenson]

Essentially because there were nodenames long before there were hostnames. UNIX goes back to a time before Ethernet and TCP/IP and the main mechanism for transferring files and logging in remotely was uucp (Unix to Unix copy) using dial-up connections. There are also two distinct sets of system calls (getuname,setuname) and (gethostname,sethostname) that deal with these different identifiers. Normally, these are set to the same value. Things get a bit confusing when a machine has multiple network cards , each with a different IP address and possibly a different entry in /etc/hostnames (or DNS, NIS, NIS+, or LDAP) but these entries really only coincidentally have any connection to the names defined by the system calls.

[Bill Hassell]

And to expand on Clay's explanation:

HP-UX is a standards-based system and uname must remain consistent with the standards. uname is defined as an 8-character (max) name as stated in the man page for hostname. Once a standard is changed, all sorts of problems with compatibility start showing up. Each man page documents the applicable standard(s) at the bottom.

NOTE: hostname is limited to 64 characters but nodename (the value reported by uname) is limited to 8 characters. BOTH can be set by editing the /etc/rc.conig.d/netconf file and entering separate values for HOSTNAME and NODENAME. If you must use a long hostname, then set NODENAME *and* HOSTNAME in the netconf file:

NODENAME="shorty"
HOSTNAME="shortstuffismyname"

A lot of mixed system managers will be tempted to change HOSTNAME to a long network name, not knowing that the network name (NODENAME) gets the same string and creates problems with uname.

So, if you can keep 8-character names for your servers, just set HOSTNAME and you're set. Otherwise, define NODENAME as the uname/8char-name and HOSTNAME as the network name.

[James R. Ferguson]

Hi Shiv:

To add to both Clay and Bill's information, on 11iv2 (11.23) there is an *optional* bundle that will allow you to use up to 255 characters for both the nodename and the hostname.

This package is available for download but should be entertained only after very *careful* analysis of your needs. The documentation surrounding this can be seen, along with the download depot, here:

http://docs.hp.com/en/5991-1101/ch05s16.html

http://h20293.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=NodeHostNameXpnd

Regards!

...JRF...

[Arunvijai_4]

Hi Shiv,

Some more information on Wikipedia.,

http://en.wikipedia.org/wiki/Hostname

-Arun

[Shivkumar]

If a machine has (1) multiple LAN cards and or (2) multiple virtual network interface on a single lan card then how to decide which is the real nodename and hostname ?

Regards,
Shiv

[Bill Hassell]

The 'real' names are associated with a specific LAN card via the IP address. You assign the HOSTNAME/NODENAME variables and in /etc/hosts, the IP address which has $NODENAME is associated with a specific LAN instance in /etc/rc.config.d/netconf.

[James R. Ferguson]

Hi (again) Shiv:

You asked, "If a machine has (1) multiple LAN cards and or (2) multiple virtual network interface on a single lan card then how to decide which is the real nodename and hostname?"

The HOSTNAME and/or NODENAME apply system-wide. Look at '/etc/rc.config.d/netconf'. Therein, you will see your hostname set:

# HOSTNAME="abcdef"

As Bill notes, you can specify the NODENAME variable and value in this file too.

During startup, '/sbin/rc' runs and causes the various configuration files in '/etc/rc.config.d/' to be sourced (read) thus collecting the various configuration variables (HOSTNAME, NODENAME, etc. etc.) into the running environment. [See the manpages for 'rc(1M)' for more information on this process].

When 'sbin/init.d/hostname' executes, the HOSTNAME and NODENAME for the server are set using '/usr/bin/hostname' and '/usr/bin/uname', respectively. You can easily see from this script that if NODENAME is empty (undefined), then the HOSTNAME is used to set the NODENAME.

Regards!

...JRF...