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

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

hostname [-v] [-b|--boot] [-F|--file filename] [hostname]

domainname [nisdomain] [-F file]

ypdomainname [nisdomain] [-F file]

nisdomainname [nisdomain] [-F file]

dnsdomainname [-v]

Hostname is used to display the system's DNS name, and to display or set its hostname or NIS domain name.


Without any arguments, displays the current names: hostname outputs the name of the system as returned by the gethostname(2) function. domainname outputs the NIS domainname of the system. domainname uses the gethostname(2) function,
ypdomainname and nisdomainname use the yp_get_default_domain(3). dnsdomainname outputs 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 --file , 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. 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/ (normally by reading the contents of a file which contains the host name, e.g. /etc/hostname).


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.

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. 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. a machine with multiple network interfaces/addresses or is used in a mobile environment, may either have multiple FQDNs/domain names or none at all.
Avoid using hostname --fqdn, hostname --domain and dnsdomainname. hostname --ip- address
Display the alias name of the host (if used). This option is deprecated and should not be used anymore.
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 out- put may contain duplicate entries. Do not make any assumptions about the order of the output.
Always set a hostname; this allows the file specified by -F to be non-existant or empty, in which case the default host- name localhost will be used if none is yet set.
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. See the warnings in section THE FQDN above, and avoid using this option.
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.
--file filename
Read the host name from the specified file. Comments (lines starting with a `#') are ignored.
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.
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.
Display the short host name. This is the host name cut at the first dot.
Be verbose and tell what's going on.
Print version information on standard output and exit successfully.
Display the NIS domain name. If a parameter is given (or --file name ) then root can also set a new NIS domain.

The address families hostname tries when looking up the FQDN, aliases and network addresses of the host are determined by the configuration of the 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 only contained the hostname and not the full canonical FQDN. most implementations cope with a full FQDN . hostname -- set or print name of current host system

hostname [-fs] [name-of-host]

The hostname utility prints the name of the current host. The super-user can set the hostname by supplying an argument. To keep the hostname between reboots, run scutil --set HostName name-of-host.

-f Include domain information in the printed name. This is the default behavior.
-s Trim off any domain information from the printed name.
-I At aka  .4  .5  .6  .7  .8  .9      13    .15  .16  .17     .20  .21  .22    .26  .142  .175(RWS)  .176  

gethostname(3), scutil(8)