domainname Man page

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 gethost‐
name(2) function.

domainname will print the NIS domainname of the system. domainname
uses the gethostname 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).

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 function, while all of the three domainname, ypdomain‐
name and nisdomainname use setdomainname. 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 dns‐
domainname 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).

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.example.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 returns for the host
name returned by gethostname. 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 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 IP 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. 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 und
use hostname –all-fqdns instead wherever possible.

-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 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.

-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,
Bernd Eckenfels, (NIS and manpage).
Michael Meskes,

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