HOSTNAME(1) Linux Programmer s Manual HOSTNAME(1)

NAME hostname - show or set the systems host name domainname - show or set the systems NIS/YP domain name dnsdomainname - show the systems DNS domain name nisdomainname - show or set systems NIS/YP domain name ypdomainname - show or set the systems NIS/YP domain name

SYNOPSIS hostname [-v] [-a] [--alias] [-d] [--domain] [-f] [--fqdn] [-A] [--all- fqdns] [-i] [--ip-address] [-I] [--all-ip-addresses] [--long] [-s] [--short] [-y] [--yp] [--nis]

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 cur- rent 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 gethost- name(2) function.

domainname, nisdomainname, ypdomainname will print the name of the sys- tem 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. When the hostname -a, -d, -f or -i is called will gethostbyname(3) be called. The difference in gethostname(2) and gethostbyname(3) is that gethost- byname(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 dns- domainname 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 con- tents of a file which contains the host name, e.g. /etc/hostname).

THE FQDN You cant 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.

If a machine has multiple network interfaces/addresses or is used in a mobile environment, then it may either have multiple FQDNs/domain names or none at all. Therefore avoid using hostname --fqdn, hostname --domain and dnsdomainname. hostname --ip-address is subject to the same limitations so it should be avoided as well.

OPTIONS -a, --alias Display the alias name of the host (if used).

-d, --domain Display the name of the DNS domain. Dont 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. See the warnings in section THE FQDN above, and avoid using this option; use hostname --all-fqdns instead.

-A, --all-fqdns Displays all FQDNs of the machine. This option enumerates all configured network addresses on all configured network inter- faces, and translates them to DNS domain names. Addresses that cannot be translated (i.e. because they do not have an appropri- ate reverse DNS entry) are skipped. Note that different addresses may resolve to the same name, therefore the output may contain duplicate entries. Do not make any assumptions about the order of the output.

-h, --help Print a usage message and exit.

-i, --ip-address Display the IP address(es) of the host. Note that this works only if the host name can be resolved. Avoid using this option; use hostname --all-ip-addresses instead.

-I, --all-ip-addresses Display all network addresses of the host. This option enumer- ates all configured addresses on all network interfaces. The loopback interface and IPv6 link-local addresses are omitted. Contrary to option -i, this option does not depend on name reso- lution. Do not make any assumptions about the order of the out- put.

-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 success- fully.

-v, --verbose Be verbose and tell whats 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 doesnt change anything permanently. After reboot original names from /etc/hosts are used again.

AUTHOR Peter Tobias, <> Bernd Eckenfels, <> (NIS and manpage). Steve Whitehouse, <> (DECnet support and manpage).

net-tools 28 Jan 1996 HOSTNAME(1)