centos man page for domainname

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

NAME
       hostname - show or set the system's host 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
       dnsdomainname - show the system's DNS domain name

SYNOPSIS
       hostname   [-a|--alias]	 [-d|--domain]	 [-f|--fqdn|--long]   [-A|--all-fqdns]	 [-i|--ip-address]   [-I|--all-ip-addresses]  [-s|--short]
       [-y|--yp|--nis]
       hostname [-b|--boot] [-F|--file filename] [hostname]
       hostname [-h|--help] [-V|--version]

       domainname [nisdomain] [-F file]
       ypdomainname [nisdomain] [-F file]
       nisdomainname [nisdomain] [-F file]

       dnsdomainname

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

   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 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 host-
       name --fqdn (but see the warnings in section THE FQDN below).

       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 gethostbyname(3) is network aware, so it consults /etc/nsswitch.conf and
       /etc/host.conf to decide whether to read information in /etc/hostname or /etc/hosts

   SET NAME
       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 effec-
       tive 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 (normally by reading the contents  of  a  file  which  contains  the  host  name,  e.g.
       /etc/hostname).

   THE FQDN
       The  FQDN  (Fully  Qualified  Domain  Name) of the system is the name that the resolver(3) returns for the host name, such as, ursula.exam-
       ple.com.  It is usually the hostname followed by the DNS domain name (the part after the first dot).  You can check the FQDN using hostname
       --fqdn or the domain name using dnsdomainname.

       You cannot change the FQDN with hostname or dnsdomainname.

       The  recommended method of setting the FQDN is to make the hostname be an alias for the fully qualified name using /etc/hosts, DNS, or NIS.
       For example, if the hostname was "ursula", one might have a line in /etc/hosts which reads

	      127.0.1.1    ursula.example.com ursula

       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 of the resolver (usually in /etc/host.conf) how you can change it. Usually the hosts file is
       parsed before DNS or NIS, so it is most common to change the FQDN 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). 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 local-
	      host will be used if none is yet set.

       -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. 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, --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.

NOTES
       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.

FILES
       /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. This file is read at boot time by the system initialization scripts to set the hostname.

       /etc/hosts Usually, this is where one sets the domain name by aliasing the host name to the FQDN.

AUTHORS
       Peter Tobias, <tobias@et-inf.fho-emden.de>
       Bernd Eckenfels, <net-tools@lina.inka.de> (NIS and manpage).
       Michael Meskes, <meskes@debian.org>

net-tools							    2009-09-16							       HOSTNAME(1)