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# hostname - Unix, Linux Command

# NAME

hostname - show or set the system’s host name
domainname - show or set the system’s NIS/YP domain name
dnsdomainname - show the system’s DNS domain name
nisdomainname - show or set system’s NIS/YP domain name
ypdomainname - show or set the system’s NIS/YP domain name

# SYNOPSIS

hostname [-v] [-a] [--alias] [-d] [--domain] [-f] [--fqdn] [-i] [--ip-address] [--long] [-s] [--short] [-y] [--yp] [--nis] [-n] [--node]

hostname [-v] [-F filename] [--file filename] [hostname]

domainname [-v] [-F filename] [--file filename] [name]

nodename [-v] [-F filename] [--file filename] [name]

hostname [-v] [-h] [--help] [-V] [--version]

dnsdomainname [-v]
nisdomainname [-v]
ypdomainname [-v]

# DESCRIPTION

Hostname is the program that is used to either set or display the current host, domain or node name of the system. These names are used by many of the networking programs to identify the machine. The domain name is also used by NIS/YP.

## GET NAME

When called without any arguments, the program displays the current names:

hostname will print the name of the system as returned by the gethostname(2) function.

domainname, nisdomainname, ypdomainname will print the name of the system as returned by the getdomainname(2) function. This is also known as the YP/NIS domain name of the system.

dnsdomainname will print the domain part of the FQDN (Fully Qualified Domain Name). The complete FQDN of the system is returned with hostname --fqdn.

The function gethostname(2) is used to get the hostname. Only when the hostname -s is called will gethostbyname(3) be called. The difference in gethostname(2) and gethostbyname(3) is that gethostbyname(3) is network aware, so it consults /etc/nsswitch.conf and /etc/host.conf to decide whether to read information in /etc/sysconfig/network or /etc/hosts
.To add another dimension to this, the hostname is also set when the network interface is brought up.

## SET NAME

When called with one argument or with the --file option, the commands set the host name, the NIS/YP domain name or the node name.

Note, that only the super-user can change the names.

It is not possible to set the FQDN or the DNS domain name with the dnsdomainname command (see THE FQDN below).

The host name is usually set once at system startup in /etc/rc.d/rc.inet1 or /etc/init.d/boot (normally by reading the contents of a file which contains the host name, e.g. /etc/hostname).

## THE FQDN

You can’t change the FQDN (as returned by hostname --fqdn) or the DNS domain name (as returned by dnsdomainname) with this command. The FQDN of the system is the name that the resolver(3) returns for the host name.

Technically: The FQDN is the name gethostbyname(2) returns for the host name returned by gethostname(2). The DNS domain name is the part after the first dot.

Therefore it depends on the configuration (usually in /etc/host.conf) how you can change it. Usually (if the hosts file is parsed before DNS or NIS) you can change it in /etc/hosts.

# OPTIONS

Tag | Description
--- | ---
-a, --alias
| Display the alias name of the host (if used).
-d, --domain
| Display the name of the DNS domain. Don’t use the command domainname to get the DNS domain name because it will show the NIS domain name and not the DNS domain name. Use dnsdomainname instead.
-F, --file filename
| Read the host name from the specified file. Comments (lines starting with a ‘#’) are ignored.
-f, --fqdn, --long
| Display the FQDN (Fully Qualified Domain Name). A FQDN consists of a short host name and the DNS domain name. Unless you are using bind or NIS for host lookups you can change the FQDN and the DNS domain name (which is part of the FQDN) in the /etc/hosts file.
-h, --help
| Print a usage message and exit.
-i, --ip-address
| Display the IP address(es) of the host.
-s, --short
| Display the short host name. This is the host name cut at the first dot.
-V, --version
| Print version information on standard output and exit successfully.
-v, --verbose
| Be verbose and tell what’s going on.
-y, --yp, --nis
| Display the NIS domain name. If a parameter is given (or --file name ) then root can also set a new NIS domain.

# FILES

/etc/hosts /etc/sysconfig/network

# NOTE

Note that hostname doesn’t change anything permanently. After reboot original names from /etc/hosts are used again.

# AUTHOR

Peter Tobias, <tobias@et-inf.fho-emden.de>
Bernd Eckenfels, <net-tools@lina.inka.de> (NIS and manpage).
Steve Whitehouse, <SteveW@ACM.org> (DECnet support and manpage).

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