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Diff for /src/share/man/man7/hostname.7 between version 1.10 and 1.11

version 1.10, 2010/09/29 13:44:33

version 1.11, 2010/09/29 14:34:07

Line 1

.\" $NetBSD$

.\"

.\" Permission to use, copy, modify, and distribute this software for any

Line 31

Line 33

.\"

.Dd February 16, 1994

.Dt HOSTNAME 7

.Os BSD 4

.Os

.Sh NAME

.Nm hostname

.Nd host name resolution description

.Sh DESCRIPTION

Hostnames are domains. A domain is a hierarchical, dot-separated list

Hostnames are domains.

of subdomains. For example, the machine

A domain is a hierarchical, dot-separated list of subdomains.

.Dq Li monet ,

For example, the machine

in the

.Dq Li monet ,

in the

.Dq Li Berkeley

subdomain of the

.Dq Li EDU

subdomain of the Internet Domain Name System would be represented as

.Pp

Line 54 which must generally translate the name

Line 57 which must generally translate the name

(This task is usually performed by the library routine

.Xr gethostbyname 3 . )

The default method for resolving hostnames by the Internet name resolver is

to follow RFC 1535's security recommendations. Actions can be taken

to follow RFC 1535's security recommendations.

by the administrator to override these recommendations and to have the

Actions can be taken by the administrator to override these

resolver behave the same as earlier, non-RFC 1535

recommendations and to have the resolver behave the same as earlier,

resolvers.

non-RFC 1535 resolvers.

.Pp

The default method (using RFC 1535 guidelines) follows:

.Pp

If the name consists of a single component, i.e. contains no dot, and if the

environment variable

.Dq Ev HOSTALIASES

is set to the name of a file,

that file is searched for a string matching the input hostname. The file

that file is searched for a string matching the input hostname.

The file

should consist of lines made up of two strings separated by white-space, the

first of which is the hostname alias, and the second of which is the complete

hostname to be substituted for that alias. If a case-insensitive match is

hostname to be substituted for that alias.

If a case-insensitive match is

found between the hostname to be resolved and the first field of a line in

the file, the substituted name is looked up with no further processing.

.Pp

If there is at least one dot in the name, then the name is first tried

.Dq as-is .

The number of dots to cause this action is configurable by setting the

threshold using the

.Dq Li ndots

option in

.Pa /etc/resolv.conf

(default: 1). If the name ends with a dot, the trailing dot is

(default: 1).

If the name ends with a dot, the trailing dot is

removed, and the remaining name is looked up (regardless of the setting of

the

.Li ndots

option), without further processing.

.Pp

If the input name does not end with a trailing dot, it is looked up by

searching through a list of domains until a match is found. If neither the

searching through a list of domains until a match is found.

search option in the

If neither the search option in the

.Pa /etc/resolv.conf

file or the

.Dq Ev LOCALDOMAIN

environment variable is used, then the

search list of domains contains only the full domain specified by the

.Li domain

option (in

.Pa /etc/resolv.conf )

or the domain used in the local hostname. For example, if the

or the domain used in the local hostname.

.Dq Li domain

For example, if the

option is set to

.Dq Li domain

option is set to

.Li CS.Berkeley.EDU ,

then only

.Li CS.Berkeley.EDU

will be in the search list, and this will be the only

domain appended to the partial hostname. For example, if

domain appended to the partial hostname.

.Dq Li lithium

For example, if

.Dq Li lithium

is the name to be resolved, this would make

.Li lithium.CS.Berkeley.EDU

the only name to be tried using the search list.

.Pp

If the

.Li search

option is used in

.Pa /etc/resolv.conf

or the environment variable

.Dq Ev LOCALDOMAIN

is set by the user, then

the search list will include what is set by these methods. For

the search list will include what is set by these methods.

example, if the

For example, if the

.Dq Li search

option contained

.Pp

.Dl CS.Berkeley.EDU CChem.Berkeley.EDU Berkeley.EDU

.Pp

then the partial hostname (e.g.,

.Dq Li lithium )

will be tried with

.Em each

domain name appended (in the same order specified); the resulting hostnames

that would be tried are:

.Bd -literal -offset indent

lithium.CS.Berkeley.EDU

Line 135 lithium.CChem.Berkeley.EDU

Line 143 lithium.CChem.Berkeley.EDU

lithium.Berkeley.EDU

.Ed

.Pp

The environment variable

.Dq Ev LOCALDOMAIN

overrides the

.Dq Li search

and

.Dq Li domain

options, and if both

.Li search

and

.Li domain

options are present in the resolver configuration file, then only the

.Em last

one listed is used (see

.Xr resolver 5 ) .

.Pp

If the name was not previously tried

.Dq as-is

(i.e., it fell below the

.Dq Li ndots

threshold or did not contain a dot), then the name as

originally provided is attempted.

.Sh ENVIRONMENT

.Bl -tag -width "/etc/resolv.conf "

.It Ev LOCALDOMAIN

Affects domains appended to partial hostnames.

.It Ev HOSTALIASES

Name of file containing

Line 169 pairs.

Line 177 pairs.

.Bl -tag -width "/etc/resolv.conf " -compact

.It Pa /etc/resolv.conf

See

.Xr resolve 5 .

.Xr resolver 5 .

.El

.Sh SEE ALSO

.Xr gethostbyname 3 ,

.Xr resolver 5 ,

.Xr mailaddr 7 ,

.Xr mailaddr 7

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