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host.conf.5: Rework discussion of nospoof, spoofalert, spoof and RESOLV_SPOOF_CHECK 

The keywords and environment variables "nospoof", "spoofalert",
"spoof" and RESOLV_SPOOF_CHECK were added to glibc 2.0.7 but
never implemented

Move descriptions to historical section and reorder it for clarity

See https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=773443

Reported-by: <ygrex@ygrex.ru>
by: Stéphane Aulery <saulery@free.fr>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Stéphane Aulery 2015-03-10 00:27:28 +01:00 committed by Michael Kerrisk
parent ffb9f8b3df
commit e51f148aa1
1 changed files with 81 additions and 80 deletions
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161
man5/host.conf.5
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@ -66,6 +66,87 @@ This is
by default, as it may cause a substantial performance loss at sites
with large hosts files.
.TP
.I reorder
Valid values are
.IR on " and " off .
If set to
.IR on ,
resolv+ will attempt to reorder host addresses so that local addresses
(i.e., on the same subnet) are listed first when a
.BR gethostbyname (3)
is performed.
Reordering is done for all lookup methods.
The default value is
.IR off .
.SH ENVIRONMENT
The following environment variables can be used to allow users to
override the behavior which is configured in
.IR /etc/host.conf :
.TP
.B RESOLV_HOST_CONF
If set, this variable points to a file that should be read instead of
.IR /etc/host.conf .
.TP
.B RESOLV_MULTI
Overrides the
.I multi
command.
.TP
.B RESOLV_REORDER
Overrides the
.I reorder
command.
.TP
.B RESOLV_ADD_TRIM_DOMAINS
A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
commas (\(aq,\(aq), with the leading dot, which will be added to the list of
domains that should be trimmed.
.TP
.B RESOLV_OVERRIDE_TRIM_DOMAINS
A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
commas (\(aq,\(aq), with the leading dot, which will replace the list of
domains that should be trimmed.
Overrides the
.I trim
command.
.SH FILES
.TP
.I /etc/host.conf
Resolver configuration file
.TP
.I /etc/resolv.conf
Resolver configuration file
.TP
.I /etc/hosts
Local hosts database
.SH NOTES
The following differences exist compared to the original implementation.
A new command
.I spoof
and a new environment variable
.B RESOLV_SPOOF_CHECK
can take arguments like
.IR off ", " nowarn " and " warn .
Line comments can appear anywhere and not only at the beginning of a line.
.SS Historical
The
.BR nsswitch.conf (5)
file is the modern way of controlling the order of host lookups.
.PP
In glibc 2.4 and earlier, the following keyword is recognized:
.TP
.I order
This keyword specifies how host lookups are to be performed.
It should be followed by one or more lookup methods, separated by commas.
Valid methods are
.IR bind ", " hosts ", and " nis .
.TP
.B RESOLV_SERV_ORDER
Overrides the order command.
.PP
Since glibc 2.0.7, the following keywords and environment variable have
been recognized but never implemented:
.TP
.I nospoof
Valid values are
.IR on " and " off .
@ -112,27 +193,6 @@ enhance the security but not emit warnings via the syslog facility.
Setting this option to anything else is equal to setting it to
.IR nowarn .
.TP
.I reorder
Valid values are
.IR on " and " off .
If set to
.IR on ,
resolv+ will attempt to reorder host addresses so that local addresses
(i.e., on the same subnet) are listed first when a
.BR gethostbyname (3)
is performed.
Reordering is done for all lookup methods.
The default value is
.IR off .
.SH ENVIRONMENT
The following environment variables can be used to allow users to
override the behavior which is configured in
.IR /etc/host.conf :
.TP
.B RESOLV_HOST_CONF
If set, this variable points to a file that should be read instead of
.IR /etc/host.conf .
.TP
.B RESOLV_SPOOF_CHECK
Overrides the
.IR nospoof ", " spoofalert " and " spoof
@ -141,65 +201,6 @@ commands in the same way as the
command is parsed.
Valid values are
.IR off ", " nowarn " and " warn .
.TP
.B RESOLV_MULTI
Overrides the
.I multi
command.
.TP
.B RESOLV_REORDER
Overrides the
.I reorder
command.
.TP
.B RESOLV_ADD_TRIM_DOMAINS
A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
commas (\(aq,\(aq), with the leading dot, which will be added to the list of
domains that should be trimmed.
.TP
.B RESOLV_OVERRIDE_TRIM_DOMAINS
A list of domains, separated by colons (\(aq:\(aq), semicolons (\(aq;\(aq) or
commas (\(aq,\(aq), with the leading dot, which will replace the list of
domains that should be trimmed.
Overrides the
.I trim
command.
.SH FILES
.TP
.I /etc/host.conf
Resolver configuration file
.TP
.I /etc/resolv.conf
Resolver configuration file
.TP
.I /etc/hosts
Local hosts database
.SH NOTES
The following differences exist compared to the original implementation.
A new command
.I spoof
and a new environment variable
.B RESOLV_SPOOF_CHECK
can take arguments like
.IR off ", " nowarn " and " warn .
Line comments can appear anywhere and not only at the beginning of a line.
.SS Historical
In glibc 2.4 and earlier, the following keyword is recognized:
.TP
.I order
This keyword specifies how host lookups are to be performed.
It should be followed by one or more lookup methods, separated by commas.
Valid methods are
.IR bind ", " hosts ", and " nis .
The
.B RESOLV_SERV_ORDER
environment variable could be used to override the
.I order
command.
.PP
The
.BR nsswitch.conf (5)
file is the modern way of controlling the order of host lookups.
.SH SEE ALSO
.BR gethostbyname (3),
.BR hosts (5),