hostname - show or set the systems host name
domainname - show or set the systems NIS/YP domain name
ypdomainname - show or set the systems NIS/YP domain name
nisdomainname - show or set the systems NIS/YP domain name
dnsdomainname - show the systems DNS domain name
hostname [-v] [-a|--alias] [-d|--domain] [-f|--fqdn|--long] [-A|--all-fqdns] [-i|--ip-address] [-I|--all-ip-addresses] [-s|--short] [-y|--yp|--nis]
hostname [-v] [-b|--boot] [-F|--file filename] [hostname]
hostname [-v] [-h|--help] [-V|--version]
domainname [nisdomain] [-F file]
ypdomainname [nisdomain] [-F file]
nisdomainname [nisdomain] [-F file]
Hostname is used to display the systems DNS name, and to display or set its hostname or NIS domain 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 will print the NIS domainname of the system. domainname uses the gethostname(2) function, while ypdomainname and nisdomainname use the yp_get_default_domain(3).
dnsdomainname will print the domain part of the FQDN (Fully Qualified Domain Name). The complete FQDN of the system is returned with hostname --fqdn (but see the warnings in section THE FQDN below).
When called with one argument or with the --file option, the commands set the host name or the NIS/YP domain name. hostname uses the sethostname(2) function, while all of the three domainname, ypdomainname and nisdomainname use setdomainname(2). Note, that this is effective only until the next reboot. Edit /etc/hostname for permanent change.
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/init.d/hostname.sh (normally by reading the contents of a file which contains the host name, e.g. /etc/hostname).
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 getaddrinfo(3) 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.
-a, --alias Display the alias name of the host (if used). This option is deprecated and should not be used anymore. -A, --all-fqdns Displays all FQDNs of the machine. This option enumerates all configured network addresses on all configured network interfaces, and translates them to DNS domain names. Addresses that cannot be translated (i.e. because they do not have an appropriate 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. -b, --boot Always set a hostname; this allows the file specified by -F to be non-existant or empty, in which case the default hostname localhost will be used if none is yet set. -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. See the warnings in section THE FQDN above, and avoid using this option. -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. -F, --file filename Read the host name from the specified file. Comments (lines starting with a #) are ignored. -i, --ip-address Display the network address(es) of the host name. 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 enumerates 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 resolution. Do not make any assumptions about the order of the output. -s, --short Display the short host name. This is the host name cut at the first dot. -v, --verbose Be verbose and tell whats going on. -V, --version Print version information on standard output and exit successfully. -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. -h, --help Print a usage message and exit.
The address families hostname tries when looking up the FQDN, aliases and network addresses of the host are determined by the configuration of your resolver. For instance, on GNU Libc systems, the resolver can be instructed to try IPv6 lookups first by using the inet6 option in /etc/resolv.conf.
/etc/hostname Historically this file was supposed to only contain the hostname and not the full canonical FQDN. Nowadays most software is able to cope with a full FQDN here.
Peter Tobias, <email@example.com>
Bernd Eckenfels, <firstname.lastname@example.org> (NIS and manpage).
Michael Meskes, <email@example.com>