domainname
show the system’s DNS domain name
Synopsis
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]
dnsdomainname
[-v]
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examples
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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 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(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).
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(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 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, 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
what’s 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.
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.
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.
authors
Peter Tobias,
<tobias@et-inf.fho-emden.de>
Bernd Eckenfels, <net-tools[:at:]lina.inka[:dot:]de> (NIS and
manpage).
Michael Meskes, <meskes[:at:]debian[:dot:]org>