Package: isc-dhcp-client
Version: 4.4.3-P1-5+b1
Severity: minor
Tags: patch
* What led up to the situation?
Checking for defects with a new version
test-[g|n]roff -mandoc -t -K utf8 -rF0 -rHY=0 -rCHECKSTYLE=10 -ww -z < "man
page"
[Use "groff -e ' $' -e '\\~$' <file>" to find obvious trailing spaces.]
["test-groff" is a script in the repository for "groff"; is not shipped]
(local copy and "troff" slightly changed by me).
[The fate of "test-nroff" was decided in groff bug #55941.]
* What was the outcome of this action?
an.tmac:<stdin>:27: style: .TH missing third argument; consider document
modification date in ISO 8601 format (YYYY-MM-DD)
an.tmac:<stdin>:27: style: .TH missing fourth argument; consider
package/project name and version (e.g., "groff 1.23.0")
an.tmac:<stdin>:32: misuse, warning: .IR is for at least 2 arguments, got 1
Use macro '.I' for one argument or split argument.
an.tmac:<stdin>:65: style: 1 leading space(s) on input line
an.tmac:<stdin>:85: style: 1 leading space(s) on input line
an.tmac:<stdin>:97: style: 1 leading space(s) on input line
an.tmac:<stdin>:122: style: 1 leading space(s) on input line
an.tmac:<stdin>:137: style: 1 leading space(s) on input line
an.tmac:<stdin>:152: style: 1 leading space(s) on input line
an.tmac:<stdin>:166: style: 1 leading space(s) on input line
an.tmac:<stdin>:218: style: 1 leading space(s) on input line
an.tmac:<stdin>:224: style: 1 leading space(s) on input line
an.tmac:<stdin>:256: style: 1 leading space(s) on input line
an.tmac:<stdin>:274: style: 1 leading space(s) on input line
an.tmac:<stdin>:314: style: 1 leading space(s) on input line
an.tmac:<stdin>:337: style: 1 leading space(s) on input line
an.tmac:<stdin>:349: style: 1 leading space(s) on input line
an.tmac:<stdin>:361: style: 1 leading space(s) on input line
an.tmac:<stdin>:377: style: 1 leading space(s) on input line
an.tmac:<stdin>:394: style: 1 leading space(s) on input line
an.tmac:<stdin>:419: style: 1 leading space(s) on input line
an.tmac:<stdin>:428: style: 1 leading space(s) on input line
an.tmac:<stdin>:439: style: 1 leading space(s) on input line
an.tmac:<stdin>:447: style: 1 leading space(s) on input line
an.tmac:<stdin>:455: style: 1 leading space(s) on input line
an.tmac:<stdin>:462: style: 1 leading space(s) on input line
an.tmac:<stdin>:471: style: 1 leading space(s) on input line
an.tmac:<stdin>:485: style: 1 leading space(s) on input line
an.tmac:<stdin>:496: style: 1 leading space(s) on input line
an.tmac:<stdin>:515: style: 1 leading space(s) on input line
an.tmac:<stdin>:517: style: 1 leading space(s) on input line
an.tmac:<stdin>:519: style: 1 leading space(s) on input line
an.tmac:<stdin>:540: style: 1 leading space(s) on input line
an.tmac:<stdin>:556: style: 1 leading space(s) on input line
an.tmac:<stdin>:572: style: 1 leading space(s) on input line
an.tmac:<stdin>:592: style: 1 leading space(s) on input line
an.tmac:<stdin>:623: style: 1 leading space(s) on input line
an.tmac:<stdin>:645: style: 1 leading space(s) on input line
an.tmac:<stdin>:665: style: 1 leading space(s) on input line
an.tmac:<stdin>:695: style: 1 leading space(s) on input line
an.tmac:<stdin>:716: style: 1 leading space(s) on input line
an.tmac:<stdin>:727: style: 1 leading space(s) on input line
* What outcome did you expect instead?
No output (no warnings).
-.-
General remarks and further material, if a diff-file exist, are in the
attachments.
-- System Information:
Debian Release: trixie/sid
APT prefers testing
APT policy: (500, 'testing')
Architecture: amd64 (x86_64)
Kernel: Linux 6.12.12-amd64 (SMP w/2 CPU threads; PREEMPT)
Locale: LANG=is_IS.iso88591, LC_CTYPE=is_IS.iso88591 (charmap=ISO-8859-1),
LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: sysvinit (via /sbin/init)
Versions of packages isc-dhcp-client depends on:
ii debianutils 5.21
ii iproute2 6.13.0-1
ii libc6 2.40-6
Versions of packages isc-dhcp-client recommends:
ii isc-dhcp-common 4.4.3-P1-5+b1
Versions of packages isc-dhcp-client suggests:
ii dhcpcd-base [avahi-autoipd] 1:10.1.0-3
pn isc-dhcp-client-ddns <none>
pn resolvconf <none>
-- no debconf information
Input file is dhclient.conf.5
Output from "mandoc -T lint dhclient.conf.5": (shortened list)
1 missing date, using "": TH
1 skipping paragraph macro: PP after SH
1 skipping paragraph macro: PP empty
-.-.
Output from "test-groff -mandoc -t -ww -z dhclient.conf.5": (shortened list)
1 Use macro '.I' for one argument or split argument.
1 .IR is for at least 2 arguments, got 1
-.-.
Wrong distance between sentences in the input file.
Separate the sentences and subordinate clauses; each begins on a new
line. See man-pages(7) ("Conventions for source file layout") and
"info groff" ("Input Conventions").
The best procedure is to always start a new sentence on a new line,
at least, if you are typing on a computer.
Remember coding: Only one command ("sentence") on each (logical) line.
E-mail: Easier to quote exactly the relevant lines.
Generally: Easier to edit the sentence.
Patches: Less unaffected text.
Search for two adjacent words is easier, when they belong to the same line,
and the same phrase.
The amount of space between sentences in the output can then be
controlled with the ".ss" request.
Mark a final abbreviation point as such by suffixing it with "\&".
Some sentences (etc.) do not begin on a new line.
172:startup and the actual first transmission. Previous versions of ISC DHCP
174:due to impact on startup time. As such, new versions have the default
175:initial delay set to 0. To restore old behavior, please set initial-delay
610:files. With the default format, octal, values are written as quoted strings
in
620:string if contains only printable characters. This is done to maintain
backward
-.-.
Test nr. 38:
Use \(en (en-dash) for a dash at the beginning (en) of a line,
or between space characters,
not a minus (\-) or a hyphen (-), except in the NAME section.
dhclient.conf.5:29:dhclient.conf - DHCP client configuration file
dhclient.conf.5:53:reasonable timing behaviour will be used by default - one
which
dhclient.conf.5:115:By default, the select-timeout is zero seconds - that is,
the client
dhclient.conf.5:229:statement - not option parameters. By default, the DHCPv4
client
dhclient.conf.5:371:enforced - if you ignore it, the behaviour will be
unpredictable.
dhclient.conf.5:387:enforced - if you ignore it, the behaviour will be
unpredictable.
dhclient.conf.5:530:DHCP client, but must also be configured in predefined
leases - a
dhclient.conf.5:544:lease expires - it's specified as a number from zero to
six, with zero
dhclient.conf.5:611:which non-printable characters are represented as octal
escapes -
dhclient.conf.5:630:misconfigured dhcp servers, although it should be a last
resort -
dhclient.conf.5:690:interface up or down - essentially, all it needs to handle
are the
dhclient.conf.5:704:capable of sensing the media type unaided - whichever media
type
dhclient.conf.5:777:This is a very complicated dhclient.conf file - in general,
yours
dhclient.conf.5:779:create an empty dhclient.conf file - the defaults are
usually fine.
-.-.
Split a punctuation mark from a single argument for a two-font macro
32:.IR dhclient,
-.-.
Test nr. 45:
The name of a man page is typeset in bold and the section in roman
(see man-pages(7)).
218: \fBdhcp-options(5)\fR.
278:declaration as described in \fBdhcp-options(5)\fR. Options that are
317:script (see \fBdhclient-script(8)\fR) rather than having the
483:.B dhclient-script(8).
493:.B dhcp-options(5)
692:where a lease has expired. See \fBdhclient-script(8)\fR for more
781:dhcp-options(5), dhcp-eval(5), dhclient.leases(5), dhcpd(8), dhcpd.conf(5),
784:.B dhclient(8)
-.-.
Test nr. 46:
Name of a manual is set in bold, the section in roman.
See man-pages(7).
493:.B dhcp-options(5)
784:.B dhclient(8)
-.-.
Split a punctuation from a single argument, if a two-font macro is meant.
483:.B dhclient-script(8).
786:.B https://www.isc.org.
-.-.
Test nr. 69:
Put a parenthetical sentence, phrase on a separate line,
if not part of a code.
See man-pages(7), item "semantic newline".
Not considered in a patch, too many lines.
dhclient.conf.5:39:file (except within quotes). Comments begin with the #
character and
dhclient.conf.5:99:It is possible (some might say desirable) for there to be
more than
dhclient.conf.5:295:server (see \fBdhcpd.conf\fR(5) for details). You also
need to
dhclient.conf.5:317:script (see \fBdhclient-script(8)\fR) rather than having the
dhclient.conf.5:445:specified as a dotted quad (e.g., 12.34.56.78).
dhclient.conf.5:617:and the IAID value (DHCPv6 only). The client automatically
reads the values
dhclient.conf.5:706:probably right (no guarantees).
dhclient.conf.5:709:acquisition (the DHCPDISCOVER and DHCPOFFER packets). Once
an
dhclient.conf.5:724:link layer type (example: \'ethernet\'), while the
\fImac-address\fR is
dhclient.conf.5:743:interface, ep0 (a 3com 3C589C). Booting intervals have been
-.-.
Output from "test-groff -mandoc -t -K utf8 -rF0 -rHY=0 -rCHECKSTYLE=10 -ww -z
":
an.tmac:<stdin>:27: style: .TH missing third argument; consider document
modification date in ISO 8601 format (YYYY-MM-DD)
an.tmac:<stdin>:27: style: .TH missing fourth argument; consider
package/project name and version (e.g., "groff 1.23.0")
an.tmac:<stdin>:32: misuse, warning: .IR is for at least 2 arguments, got 1
Use macro '.I' for one argument or split argument.
an.tmac:<stdin>:65: style: 1 leading space(s) on input line
an.tmac:<stdin>:85: style: 1 leading space(s) on input line
an.tmac:<stdin>:97: style: 1 leading space(s) on input line
an.tmac:<stdin>:122: style: 1 leading space(s) on input line
an.tmac:<stdin>:137: style: 1 leading space(s) on input line
an.tmac:<stdin>:152: style: 1 leading space(s) on input line
an.tmac:<stdin>:166: style: 1 leading space(s) on input line
an.tmac:<stdin>:218: style: 1 leading space(s) on input line
an.tmac:<stdin>:224: style: 1 leading space(s) on input line
an.tmac:<stdin>:256: style: 1 leading space(s) on input line
an.tmac:<stdin>:274: style: 1 leading space(s) on input line
an.tmac:<stdin>:314: style: 1 leading space(s) on input line
an.tmac:<stdin>:337: style: 1 leading space(s) on input line
an.tmac:<stdin>:349: style: 1 leading space(s) on input line
an.tmac:<stdin>:361: style: 1 leading space(s) on input line
an.tmac:<stdin>:377: style: 1 leading space(s) on input line
an.tmac:<stdin>:394: style: 1 leading space(s) on input line
an.tmac:<stdin>:419: style: 1 leading space(s) on input line
an.tmac:<stdin>:428: style: 1 leading space(s) on input line
an.tmac:<stdin>:439: style: 1 leading space(s) on input line
an.tmac:<stdin>:447: style: 1 leading space(s) on input line
an.tmac:<stdin>:455: style: 1 leading space(s) on input line
an.tmac:<stdin>:462: style: 1 leading space(s) on input line
an.tmac:<stdin>:471: style: 1 leading space(s) on input line
an.tmac:<stdin>:485: style: 1 leading space(s) on input line
an.tmac:<stdin>:496: style: 1 leading space(s) on input line
an.tmac:<stdin>:515: style: 1 leading space(s) on input line
an.tmac:<stdin>:517: style: 1 leading space(s) on input line
an.tmac:<stdin>:519: style: 1 leading space(s) on input line
an.tmac:<stdin>:540: style: 1 leading space(s) on input line
an.tmac:<stdin>:556: style: 1 leading space(s) on input line
an.tmac:<stdin>:572: style: 1 leading space(s) on input line
an.tmac:<stdin>:592: style: 1 leading space(s) on input line
an.tmac:<stdin>:623: style: 1 leading space(s) on input line
an.tmac:<stdin>:645: style: 1 leading space(s) on input line
an.tmac:<stdin>:665: style: 1 leading space(s) on input line
an.tmac:<stdin>:695: style: 1 leading space(s) on input line
an.tmac:<stdin>:716: style: 1 leading space(s) on input line
an.tmac:<stdin>:727: style: 1 leading space(s) on input line
an-end-check:<stdin>: Warning: Different number of .RS and .RE calls,
an-RS-open=1 at end of file
--- dhclient.conf.5 2025-02-09 17:44:49.161373555 +0000
+++ dhclient.conf.5.new 2025-02-09 20:09:10.017771619 +0000
@@ -9,7 +9,8 @@
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
-.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
+.\" MERCHANTABILITY AND FITNESS.
+.\" IN NO EVENT SHALL ISC BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
@@ -26,37 +27,47 @@
.\"
.TH dhclient.conf 5
.SH NAME
-dhclient.conf - DHCP client configuration file
+dhclient.conf \- DHCP client configuration file
.SH DESCRIPTION
The dhclient.conf file contains configuration information for
-.IR dhclient,
+.IR dhclient ,
the Internet Systems Consortium DHCP Client.
.PP
-The dhclient.conf file is a free-form ASCII text file. It is parsed by
-the recursive-descent parser built into dhclient. The file may contain
-extra tabs and newlines for formatting purposes. Keywords in the file
-are case-insensitive. Comments may be placed anywhere within the
-file (except within quotes). Comments begin with the # character and
-end at the end of the line.
+The dhclient.conf file is a free-form ASCII text file.
+It is parsed by the recursive-descent parser built into dhclient.
+The file may contain extra tabs
+and newlines for formatting purposes.
+Keywords in the file are case-insensitive.
+Comments may be placed anywhere within the file
+(except within quotes).
+Comments begin with the # character
+and end at the end of the line.
.PP
The dhclient.conf file can be used to configure the behaviour of the
-client in a wide variety of ways: protocol timing, information
-requested from the server, information required of the server,
-defaults to use if the server does not provide certain information,
-values with which to override information provided by the server, or
-values to prepend or append to information provided by the server.
+client in a wide variety of ways:
+protocol timing,
+information requested from the server,
+information required of the server,
+defaults to use
+if the server does not provide certain information,
+values with which to override information provided by the server,
+or values to prepend
+or append to information provided by the server.
The configuration file can also be preinitialized with addresses to
-use on networks that don't have DHCP servers.
+use on networks
+that don't have DHCP servers.
.SH PROTOCOL TIMING
The timing behaviour of the client need not be configured by the user.
-If no timing configuration is provided by the user, a fairly
-reasonable timing behaviour will be used by default - one which
-results in fairly timely updates without placing an inordinate load on
-the server.
-.PP
-If required the following statements can be used to adjust the timing
-behaviour of the DHCPv4 client. The DHCPv6 protocol provides values
-to use and they are not currently configurable.
+If no timing configuration is provided by the user,
+a fairly reasonable timing behaviour will be used by default
+\(en one which results in fairly timely updates
+without placing an inordinate load on the server.
+.PP
+If required
+the following statements can be used to adjust the timing behaviour of
+the DHCPv4 client.
+The DHCPv6 protocol provides values to use
+and they are not currently configurable.
.PP
.I The
.B timeout
@@ -66,17 +77,25 @@ to use and they are not currently config
.PP
The
.I timeout
-statement determines the amount of time that must pass between the
-time that the client begins to try to determine its address and the
-time that it decides that it's not going to be able to contact a
-server. By default, this timeout is sixty seconds. After the
-timeout has passed, if there are any static leases defined in the
-configuration file, or any leases remaining in the lease database that
-have not yet expired, the client will loop through these leases
-attempting to validate them, and if it finds one that appears to be
-valid, it will use that lease's address. If there are no valid
-static leases or unexpired leases in the lease database, the client
-will restart the protocol after the defined retry interval.
+statement determines the amount of time
+that must pass between the time
+that the client begins to try to determine its address
+and the time
+that it decides
+that it's not going to be able to contact a server.
+By default,
+this timeout is sixty seconds.
+After the timeout has passed,
+if there are any static leases defined in the configuration file,
+or any leases remaining in the lease database
+that have not yet expired,
+the client will loop through these leases attempting to validate them,
+and if it finds one
+that appears to be valid,
+it will use that lease's address.
+If there are no valid static leases
+or unexpired leases in the lease database,
+the client will restart the protocol after the defined retry interval.
.PP
.I The
.B retry
@@ -86,9 +105,12 @@ will restart the protocol after the defi
.PP
The
.I retry
-statement determines the time that must pass after the client has
-determined that there is no DHCP server present before it tries again
-to contact a DHCP server. By default, this is five minutes.
+statement determines the time
+that must pass after the client has determined
+that there is no DHCP server present
+before it tries again to contact a DHCP server.
+By default,
+this is five minutes.
.PP
.I The
.B select-timeout
@@ -96,24 +118,33 @@ to contact a DHCP server. By default, t
.PP
\fBselect-timeout \fItime\fR\fB;\fR
.PP
-It is possible (some might say desirable) for there to be more than
-one DHCP server serving any given network. In this case, it is
-possible that a client may be sent more than one offer in response to
-its initial lease discovery message. It may be that one of these
-offers is preferable to the other (e.g., one offer may have the
-address the client previously used, and the other may not).
+It is possible
+(some might say desirable)
+for there to be more than one DHCP server serving any given network.
+In this case,
+it is possible
+that a client may be sent more than one offer in response to
+its initial lease discovery message.
+It may be
+that one of these offers is preferable to the other
+(e.g., one offer may have the
+address the client previously used,
+and the other may not).
.PP
The
.I select-timeout
is the time after the client sends its first lease discovery request
-at which it stops waiting for offers from servers, assuming that it
-has received at least one such offer. If no offers have been
-received by the time the
+at which it stops waiting for offers from servers,
+assuming
+that it has received at least one such offer.
+If no offers have been received by the time the
.I select-timeout
-has expired, the client will accept the first offer that arrives.
+has expired,
+the client will accept the first offer that arrives.
.PP
-By default, the select-timeout is zero seconds - that is, the client
-will take the first offer it sees.
+By default,
+the select-timeout is zero seconds \(en that is,
+the client will take the first offer it sees.
.PP
.I The
.B reboot
@@ -121,14 +152,20 @@ will take the first offer it sees.
.PP
\fBreboot \fItime\fR\fB;\fR
.PP
-When the client is restarted, it first tries to reacquire the last
-address it had. This is called the INIT-REBOOT state. If it is
-still attached to the same network it was attached to when it last
-ran, this is the quickest way to get started. The
+When the client is restarted,
+it first tries to reacquire the last address it had.
+This is called the INIT-REBOOT state.
+If it is still attached to the same network
+it was attached to
+when it last ran,
+this is the quickest way to get started.
+The
.I reboot
-statement sets the time that must elapse after the client first tries
-to reacquire its old address before it gives up and tries to discover
-a new address. By default, the reboot timeout is ten seconds.
+statement sets the time
+that must elapse after the client first tries to reacquire its old address
+before it gives up and tries to discover
+a new address.
+By default, the reboot timeout is ten seconds.
.PP
.I The
.B backoff-cutoff
@@ -138,11 +175,13 @@ a new address. By default, the reboot t
.PP
The client uses an exponential backoff algorithm with some randomness,
so that if many clients try to configure themselves at the same time,
-they will not make their requests in lockstep. The
+they will not make their requests in lockstep.
+The
.I backoff-cutoff
statement determines the maximum amount of time that the client is
allowed to back off, the actual value will be evaluated randomly between
-1/2 to 1 1/2 times the \fItime\fR specified. It defaults to fifteen
+1/2 to 1 1/2 times the \fItime\fR specified.
+It defaults to fifteen
seconds.
.PP
.I The
@@ -154,11 +193,13 @@ seconds.
The
.I initial-interval
statement sets the amount of time between the first attempt to reach a
-server and the second attempt to reach a server. Each time a message
+server and the second attempt to reach a server.
+Each time a message
is sent, the interval between messages is incremented by twice the
current interval multiplied by a random number between zero and one.
If it is greater than the backoff-cutoff amount, it is set to that
-amount. It defaults to ten seconds.
+amount.
+It defaults to ten seconds.
.PP
.I The initial-delay
.I statement
@@ -169,53 +210,67 @@ amount. It defaults to ten seconds.
parameter sets the maximum time client can wait after start before
commencing first transmission.
According to RFC2131 Section 4.4.1, client should wait a random time between
-startup and the actual first transmission. Previous versions of ISC DHCP
+startup and the actual first transmission.
+Previous versions of ISC DHCP
client used to wait random time up to 5 seconds, but that was unwanted
-due to impact on startup time. As such, new versions have the default
-initial delay set to 0. To restore old behavior, please set initial-delay
+due to impact on startup time.
+As such, new versions have the default
+initial delay set to 0.
+To restore old behavior, please set initial-delay
to 5.
.SH DHCPv6 LEASE SELECTION
In the DHCPv6 protocol the client will wait a small amount of time to
-allow ADVERTISE messages from multiple servers to arrive. It will then
+allow ADVERTISE messages from multiple servers to arrive.
+It will then
need to choose from all of the messages that may have arrived before
proceeding to making a request of the selected server.
The first selection criteria is the set of options and addresses
-in the message. Messages that don't include an option specified
-as required will be given a score of 0 and not used. If the
+in the message.
+Messages that don't include an option specified
+as required will be given a score of 0 and not used.
+If the
\fI-R\fR option is given on the command line then messages that
don't include the correct number of bindings (IA-NA, IA-TA or
IA-PD) will be discarded.
-The next criteria is the preference value from the message. With
+The next criteria is the preference value from the message.
+With
the highest preference value being used even if leases with better
addresses or options are available.
Finally the lease is scored and the lease with the highest score
-is selected. A lease's score is based on the number of bindings,
+is selected.
+A lease's score is based on the number of bindings,
number of addresses and number of options it contains:
.nf
bindings * X + addresses * Y + options
.fi
By default X = 10000 and Y = 100, this will cause the client to
select a lease with more bindings over a lease with less bindings
-but more addresses. The weightings were changed as part of
-implementing RFC 7550. Previously they were X = 50 and Y = 100
-meaning more addresses were preferred over more bindings. If
+but more addresses.
+The weightings were changed as part of
+implementing RFC 7550.
+Previously they were X = 50 and Y = 100
+meaning more addresses were preferred over more bindings.
+If
you wish to continue using the old style you may do so by editing
the file includes/site.h and uncommenting the define for
USE_ORIGINAL_CLIENT_LEASE_WEIGHTS.
.SH LEASE REQUIREMENTS AND REQUESTS
The DHCP protocol allows the client to request that the server send it
specific information, and not send it other information that it is not
-prepared to accept. The protocol also allows the client to reject
+prepared to accept.
+The protocol also allows the client to reject
offers from servers if they don't contain information the client
needs, or if the information provided is not satisfactory.
.PP
There is a variety of data contained in offers that DHCP servers send
-to DHCP clients. The data that can be specifically requested is what
-are called \fIDHCP Options\fR. DHCP Options are defined in
- \fBdhcp-options(5)\fR.
+to DHCP clients.
+The data that can be specifically requested is what
+are called \fIDHCP Options\fR.
+DHCP Options are defined in
+\fBdhcp-options\fR(5).
.PP
.I The
.B request
@@ -225,16 +280,20 @@ are called \fIDHCP Options\fR. DHCP Opt
.PP
The request statement causes the client to request that any server
responding to the client send the client its values for the specified
-options. Only the option names should be specified in the request
-statement - not option parameters. By default, the DHCPv4 client
+options.
+Only the option names should be specified in the request
+statement \(en not option parameters.
+By default, the DHCPv4 client
requests the subnet-mask, broadcast-address, time-offset, routers,
domain-name, domain-name-servers and host-name options while the DHCPv6
-client requests the dhcp6 name-servers and domain-search options. Note
+client requests the dhcp6 name-servers and domain-search options.
+Note
that if you enter a \'request\' statement, you over-ride these defaults
and these options will not be requested.
.PP
In some cases, it may be desirable to send no parameter request list
-at all. To do this, simply write the request statement but specify
+at all.
+To do this, simply write the request statement but specify
no parameters:
.PP
.nf
@@ -242,7 +301,8 @@ no parameters:
.fi
.PP
In most cases, it is desirable to simply add one option to the request
-list which is of interest to the client in question. In this case, it
+list which is of interest to the client in question.
+In this case, it
is best to \'also request\' the additional options:
.PP
.nf
@@ -256,8 +316,10 @@ is best to \'also request\' the addition
\fB[ also ] require [ [ \fIoption-space\fR . ] \fIoption\fR ] [\fB,\fI ...
]\fB;\fR
.PP
The require statement lists options that must be sent in order for an
-offer to be accepted. Offers that do not contain all the listed
-options will be ignored. There is no default require list.
+offer to be accepted.
+Offers that do not contain all the listed
+options will be ignored.
+There is no default require list.
.PP
.nf
require name-servers;
@@ -274,25 +336,33 @@ options will be ignored. There is no de
\fBsend [ \fIoption declaration\fR ] \fB;\fR
.PP
The send statement causes the client to send the specified option to
-the server with the specified value. This is a full option
-declaration as described in \fBdhcp-options(5)\fR. Options that are
+the server with the specified value.
+This is a full option
+declaration as described in \fBdhcp-options\fR(5).
+Options that are
always sent in the DHCP protocol should not be specified here, except
that the client can specify a requested \fBdhcp-lease-time\fR option other
-than the default requested lease time, which is two hours. The other
+than the default requested lease time, which is two hours.
+The other
obvious use for this statement is to send information to the server
that will allow it to differentiate between this client and other
clients or kinds of clients.
.SH DYNAMIC DNS
The client now has some very limited support for doing DNS updates
-when a lease is acquired. This is prototypical, and probably doesn't
-do what you want. It also only works if you happen to have control
+when a lease is acquired.
+This is prototypical, and probably doesn't
+do what you want.
+It also only works if you happen to have control
over your DNS server, which isn't very likely.
.PP
Note that everything in this section is true whether you are using DHCPv4
-or DHCPv6. The exact same syntax is used for both.
+or DHCPv6.
+The exact same syntax is used for both.
.PP
To make it work, you have to declare a key and zone as in the DHCP
-server (see \fBdhcpd.conf\fR(5) for details). You also need to
+server
+(see \fBdhcpd.conf\fR(5) for details).
+You also need to
configure the \fIfqdn\fR option on the client, as follows:
.PP
.nf
@@ -303,8 +373,10 @@ configure the \fIfqdn\fR option on the c
.fi
.PP
The \fIfqdn.fqdn\fR option \fBMUST\fR be a fully-qualified domain
-name. You \fBMUST\fR define a zone statement for the zone to be
-updated. The \fIfqdn.encoded\fR option may need to be set to
+name.
+You \fBMUST\fR define a zone statement for the zone to be
+updated.
+The \fIfqdn.encoded\fR option may need to be set to
\fIon\fR or \fIoff\fR, depending on the DHCP server you are using.
.PP
.I The
@@ -314,20 +386,26 @@ updated. The \fIfqdn.encoded\fR option
\fBdo-forward-updates [ \fIflag\fR ] \fB;\fR
.PP
If you want to do DNS updates in the DHCP client
-script (see \fBdhclient-script(8)\fR) rather than having the
+script
+(see \fBdhclient-script\fR(8))
+rather than having the
DHCP client do the update directly (for example, if you want to
use SIG(0) authentication, which is not supported directly by the
DHCP client, you can instruct the client not to do the update using
-the \fBdo-forward-updates\fR statement. \fIFlag\fR should be \fBtrue\fR
+the \fBdo-forward-updates\fR statement.
+\fIFlag\fR should be \fBtrue\fR
if you want the DHCP client to do the update, and \fBfalse\fR if
-you don't want the DHCP client to do the update. By default, the DHCP
+you don't want the DHCP client to do the update.
+By default, the DHCP
client will do the DNS update.
.SH OPTION MODIFIERS
In some cases, a client may receive option data from the server which
is not really appropriate for that client, or may not receive
information that it needs, and for which a useful default value
-exists. It may also receive information which is useful, but which
-needs to be supplemented with local information. To handle these
+exists.
+It may also receive information which is useful, but which
+needs to be supplemented with local information.
+To handle these
needs, several option modifiers are available.
.PP
.I The
@@ -364,11 +442,13 @@ If for some set of options the client sh
supply, and then use the values supplied by
the server, if any, these values can be defined in the
.B prepend
-statement. The
+statement.
+The
.B prepend
statement can only be used for options which
-allow more than one value to be given. This restriction is not
-enforced - if you ignore it, the behaviour will be unpredictable.
+allow more than one value to be given.
+This restriction is not
+enforced \(en if you ignore it, the behaviour will be unpredictable.
.PP
.I The
.B append
@@ -380,13 +460,14 @@ If for some set of options the client sh
supplied by the server, if any, and then use values you supply, these
values can be defined in the
.B append
-statement. The
+statement.
+The
.B append
statement can only be used for options which
-allow more than one value to be given. This restriction is not
-enforced - if you ignore it, the behaviour will be unpredictable.
+allow more than one value to be given.
+This restriction is not
+enforced \(en if you ignore it, the behaviour will be unpredictable.
.SH LEASE DECLARATIONS
-.PP
.I The
.B lease
.I declaration
@@ -395,12 +476,15 @@ enforced - if you ignore it, the behavio
.PP
The DHCP client may decide after some period of time (see \fBPROTOCOL
TIMING\fR) that it is not going to succeed in contacting a
-server. At that time, it consults its own database of old leases and
+server.
+At that time, it consults its own database of old leases and
tests each one that has not yet timed out by pinging the listed router
-for that lease to see if that lease could work. It is possible to
+for that lease to see if that lease could work.
+It is possible to
define one or more \fIfixed\fR leases in the client configuration file
for networks where there is no DHCP or BOOTP service, so that the
-client can still automatically configure its address. This is done
+client can still automatically configure its address.
+This is done
with the
.B lease
statement.
@@ -408,12 +492,14 @@ statement.
NOTE: the lease statement is also used in the dhclient.leases file in
order to record leases that have been received from DHCP servers.
Some of the syntax for leases as described below is only needed in the
-dhclient.leases file. Such syntax is documented here for
+dhclient.leases file.
+Such syntax is documented here for
completeness.
.PP
A lease statement consists of the lease keyword, followed by a left
curly brace, followed by one or more lease declaration statements,
-followed by a right curly brace. The following lease declarations
+followed by a right curly brace.
+The following lease declarations
are possible:
.PP
\fBbootp;\fR
@@ -421,8 +507,10 @@ are possible:
The
.B bootp
statement is used to indicate that the lease was acquired using the
-BOOTP protocol rather than the DHCP protocol. It is never necessary
-to specify this in the client configuration file. The client uses
+BOOTP protocol rather than the DHCP protocol.
+It is never necessary
+to specify this in the client configuration file.
+The client uses
this syntax in its lease database file.
.PP
\fBinterface\fR \fB"\fR\fIstring\fR\fB";\fR
@@ -430,8 +518,10 @@ this syntax in its lease database file.
The
.B interface
lease statement is used to indicate the interface on which the lease
-is valid. If set, this lease will only be tried on a particular
-interface. When the client receives a lease from a server, it always
+is valid.
+If set, this lease will only be tried on a particular
+interface.
+When the client receives a lease from a server, it always
records the interface number on which it received that lease.
If predefined leases are specified in the dhclient.conf file, the
interface should also be specified, although this is not required.
@@ -440,15 +530,19 @@ interface should also be specified, alth
.PP
The
.B fixed-address
-statement is used to set the ip address of a particular lease. This
-is required for all lease statements. The IP address must be
-specified as a dotted quad (e.g., 12.34.56.78).
+statement is used to set the ip address of a particular lease.
+This
+is required for all lease statements.
+The IP address must be
+specified as a dotted quad
+(e.g., 12.34.56.78).
.PP
\fBfilename "\fR\fIstring\fR\fB";\fR
.PP
The
.B filename
-statement specifies the name of the boot filename to use. This is
+statement specifies the name of the boot filename to use.
+This is
not used by the standard client configuration script, but is included
for completeness.
.PP
@@ -456,7 +550,8 @@ for completeness.
.PP
The
.B server-name
-statement specifies the name of the boot server name to use. This is
+statement specifies the name of the boot server name to use.
+This is
also not used by the standard client configuration script.
.PP
\fBoption\fR \fIoption-declaration\fR\fB;\fR
@@ -473,14 +568,17 @@ script to use if the predefined lease is
The
.B script
statement is used to specify the pathname of the dhcp client
-configuration script. This script is used by the dhcp client to set
+configuration script.
+This script is used by the dhcp client to set
each interface's initial configuration prior to requesting an address,
to test the address once it has been offered, and to set the
-interface's final configuration once a lease has been acquired. If
+interface's final configuration once a lease has been acquired.
+If
no lease is acquired, the script is used to test predefined leases, if
-any, and also called once if no valid lease can be identified. For
+any, and also called once if no valid lease can be identified.
+For
more information, see
-.B dhclient-script(8).
+.BR dhclient-script (8).
.PP
\fBvendor option space "\fIname\fB";\fR
.PP
@@ -489,8 +587,9 @@ The
statement is used to specify which option space should be used for
decoding the vendor-encapsulate-options option if one is received.
The \fIdhcp-vendor-identifier\fR can be used to request a specific
-class of vendor options from the server. See
-.B dhcp-options(5)
+class of vendor options from the server.
+See
+.BR dhcp-options (5)
for details.
.PP
\fBmedium "\fImedia setup\fB";\fR
@@ -499,9 +598,11 @@ The
.B medium
statement can be used on systems where network interfaces cannot
automatically determine the type of network to which they are
-connected. The media setup string is a system-dependent parameter
+connected.
+The media setup string is a system-dependent parameter
which is passed to the dhcp client configuration script when
-initializing the interface. On Unix and Unix-like systems, the
+initializing the interface.
+On Unix and Unix-like systems, the
argument is passed on the ifconfig command line when configuring the
interface.
.PP
@@ -520,18 +621,21 @@ interface requires media type configurat
.PP
The \fBrenew\fR statement defines the time at which the dhcp client
should begin trying to contact its server to renew a lease that it is
-using. The \fBrebind\fR statement defines the time at which the dhcp
+using.
+The \fBrebind\fR statement defines the time at which the dhcp
client should begin to try to contact \fIany\fR dhcp server in order
-to renew its lease. The \fBexpire\fR statement defines the time at
+to renew its lease.
+The \fBexpire\fR statement defines the time at
which the dhcp client must stop using a lease if it has not been able
to contact a server in order to renew it.
.PP
These declarations are automatically set in leases acquired by the
-DHCP client, but must also be configured in predefined leases - a
+DHCP client, but must also be configured in predefined leases \(en a
predefined lease whose expiry time has passed will not be used by the
DHCP client.
.PP
-Dates are specified in one of two ways. The software will output times in
+Dates are specified in one of two ways.
+The software will output times in
these two formats depending on if the \fBdb-time-format\fR configuration
parameter has been set to \fIdefault\fR or \fIlocal\fR.
.PP
@@ -541,12 +645,17 @@ If it is set to \fIdefault\fR, then \fId
<hour>\fB:\fI<minute>\fB:\fI<second>\fR
.PP
The weekday is present to make it easy for a human to tell when a
-lease expires - it's specified as a number from zero to six, with zero
-being Sunday. When declaring a predefined lease, it can always be
-specified as zero. The year is specified with the century, so it
-should generally be four digits except for really long leases. The
-month is specified as a number starting with 1 for January. The day
-of the month is likewise specified starting with 1. The hour is a
+lease expires \(en it's specified as a number from zero to six, with zero
+being Sunday.
+When declaring a predefined lease, it can always be
+specified as zero.
+The year is specified with the century, so it
+should generally be four digits except for really long leases.
+The
+month is specified as a number starting with 1 for January.
+The day
+of the month is likewise specified starting with 1.
+The hour is a
number between 0 and 23, the minute a number between 0 and 59, and the
second also a number between 0 and 59.
.PP
@@ -557,9 +666,11 @@ the \fIdate\fR values appear as follows:
<day-number> <hours>\fR\fB:\fR\fI<minutes>\fR\fB:\fR\fI<seconds> <year>\fR
.PP
The \fIseconds-since-epoch\fR is as according to the system's local clock
(often
-referred to as "unix time"). The \fB#\fR symbol supplies a comment that
+referred to as "unix time").
+The \fB#\fR symbol supplies a comment that
describes what actual time this is as according to the system's configured
-timezone, at the time the value was written. It is provided only for human
+timezone, at the time the value was written.
+It is provided only for human
inspection, the epoch time is the only recommended value for machine
inspection.
.PP
@@ -574,7 +685,8 @@ instead of an actual date.
Some DHCP clients running TCP/IP roaming protocols may require that in
addition to the lease they may acquire via DHCP, their interface also
be configured with a predefined IP alias so that they can have a
-permanent IP address even while roaming. The Internet Systems
+permanent IP address even while roaming.
+The Internet Systems
Consortium DHCP client doesn't support roaming with fixed addresses
directly, but in order to facilitate such experimentation, the dhcp
client can be set up to configure an IP alias using the
@@ -583,19 +695,23 @@ declaration.
.PP
The alias declaration resembles a lease declaration, except that
options other than the subnet-mask option are ignored by the standard
-client configuration script, and expiry times are ignored. A typical
+client configuration script, and expiry times are ignored.
+A typical
alias declaration includes an interface declaration, a fixed-address
declaration for the IP alias address, and a subnet-mask option
-declaration. A medium statement should never be included in an alias
+declaration.
+A medium statement should never be included in an alias
declaration.
.SH OTHER DECLARATIONS
\fBdb-time-format\fR [ \fIdefault\fR | \fIlocal\fR ] \fB;\fR
.PP
The \fBdb-time-format\fR option determines which of two output methods are
-used for printing times in leases files. The \fIdefault\fR format provides
+used for printing times in leases files.
+The \fIdefault\fR format provides
day-and-time in UTC, whereas \fIlocal\fR uses a seconds-since-epoch to store
the time value, and helpfully places a local timezone time in a comment on
-the same line. The formats are described in detail in this manpage, within
+the same line.
+The formats are described in detail in this manpage, within
the LEASE DECLARATIONS section.
.PP
The
@@ -607,17 +723,22 @@ parameter
.PP
The \fIformat\fR parameter must be either \fBoctal\fR or \fBhex\fR.
This parameter governs the format used to write certain values to lease
-files. With the default format, octal, values are written as quoted strings in
+files.
+With the default format, octal, values are written as quoted strings in
which non-printable characters are represented as octal escapes -
-a backslash character followed by three octal digits. When the hex format
+a backslash character followed by three octal digits.
+When the hex format
is specified, values are written as an unquoted series of hexadecimal digit
pairs, separated by colons.
Currently, the values written out based on lease-id-format are the default-duid
-and the IAID value (DHCPv6 only). The client automatically reads the values
-in either format. Note that when the format is octal, rather than as an octal
+and the IAID value (DHCPv6 only).
+The client automatically reads the values
+in either format.
+Note that when the format is octal, rather than as an octal
string, IAID is output as hex if it contains no printable characters or as a
-string if contains only printable characters. This is done to maintain backward
+string if contains only printable characters.
+This is done to maintain backward
compatibility.
.PP
\fBreject \fIcidr-ip-address\fR [\fB,\fR \fI...\fB \fIcidr-ip-address\fR ]
\fB;\fR
@@ -626,7 +747,8 @@ The
.B reject
statement causes the DHCP client to reject offers from
servers whose server identifier matches any of the specified hosts or
-subnets. This can be used to avoid being configured by rogue or
+subnets.
+This can be used to avoid being configured by rogue or
misconfigured dhcp servers, although it should be a last resort -
better to track down the bad DHCP server and fix it.
.PP
@@ -634,7 +756,8 @@ The \fIcidr-ip-address\fR configuration
form \fIip-address\fR[\fB/\fIprefixlen\fR], where \fIip-address\fR is a
dotted quad IP address, and \fRprefixlen\fR is the CIDR prefix length of
the subnet, counting the number of significant bits in the netmask starting
-from the leftmost end. Example configuration syntax:
+from the leftmost end.
+Example configuration syntax:
.PP
.I \fIreject\fR 192.168.0.0\fB/\fR16\fB,\fR 10.0.0.5\fB;\fR
.PP
@@ -645,21 +768,26 @@ single address 10.0.0.5, to be rejected.
\fBinterface "\fIname\fB" { \fIdeclarations ... \fB }
.PP
A client with more than one network interface may require different
-behaviour depending on which interface is being configured. All
+behaviour depending on which interface is being configured.
+All
timing parameters and declarations other than lease and alias
declarations can be enclosed in an interface declaration, and those
parameters will then be used only for the interface that matches the
-specified name. Interfaces for which there is no interface
+specified name.
+Interfaces for which there is no interface
declaration will use the parameters declared outside of any interface
declaration, or the default settings.
.PP
.B Note well:
ISC dhclient only maintains one list of interfaces, which is either
determined at startup from command line arguments, or otherwise is
-autodetected. If you supplied the list of interfaces on the command
+autodetected.
+If you supplied the list of interfaces on the command
line, this configuration clause will add the named interface to the
-list in such a way that will cause it to be configured by DHCP. Which
-may not be the result you had intended. This is an undesirable side
+list in such a way that will cause it to be configured by DHCP.
+Which
+may not be the result you had intended.
+This is an undesirable side
effect that will be addressed in a future release.
.PP
\fBpseudo "\fIname\fR" "\fIreal-name\fB" { \fIdeclarations ... \fB }
@@ -670,11 +798,14 @@ Each interface that the DHCP client is s
client state machine running on it to acquire and maintain its lease.
A pseudo-interface is just another state machine running on the
interface named \fIreal-name\fR, with its own lease and its own
-state. If you use this feature, you must provide a client identifier
+state.
+If you use this feature, you must provide a client identifier
for both the pseudo-interface and the actual interface, and the two
-identifiers must be different. You must also provide a separate
+identifiers must be different.
+You must also provide a separate
client script for the pseudo-interface to do what you want with the IP
-address. For example:
+address.
+For example:
.PP
.nf
interface "ep0" {
@@ -687,9 +818,10 @@ address. For example:
.fi
.PP
The client script for the pseudo-interface should not configure the
-interface up or down - essentially, all it needs to handle are the
+interface up or down \(en essentially, all it needs to handle are the
states where a lease has been acquired or renewed, and the states
-where a lease has expired. See \fBdhclient-script(8)\fR for more
+where a lease has expired.
+See \fBdhclient-script\fR(8) for more
information.
.PP
\fBmedia "\fImedia setup\fB"\fI [ \fB, "\fImedia setup\fB", \fI... ]\fB;\fR
@@ -697,20 +829,25 @@ information.
The
.B media
statement defines one or more media configuration parameters which may
-be tried while attempting to acquire an IP address. The dhcp client
+be tried while attempting to acquire an IP address.
+The dhcp client
will cycle through each media setup string on the list, configuring
the interface using that setup and attempting to boot, and then trying
-the next one. This can be used for network interfaces which aren't
-capable of sensing the media type unaided - whichever media type
+the next one.
+This can be used for network interfaces which aren't
+capable of sensing the media type unaided \(en whichever media type
succeeds in getting a request to the server and hearing the reply is
-probably right (no guarantees).
+probably right
+(no guarantees).
.PP
The media setup is only used for the initial phase of address
-acquisition (the DHCPDISCOVER and DHCPOFFER packets). Once an
+acquisition (the DHCPDISCOVER and DHCPOFFER packets).
+Once an
address has been acquired, the dhcp client will record it in its lease
database and will record the media type used to acquire the address.
Whenever the client tries to renew the lease, it will use that same
-media type. The lease must expire before the client will go back to
+media type.
+The lease must expire before the client will go back to
cycling through media types.
.PP
\fBhardware\fR \fIlink-type mac-address\fR\fB;\fR
@@ -718,10 +855,14 @@ cycling through media types.
The
.B hardware
statement defines the hardware MAC address to use for this interface,
-for DHCP servers or relays to direct their replies. dhclient will determine
+for DHCP servers or relays to direct their replies.
+dhclient will determine
the interface's MAC address automatically, so use of this parameter
-is not recommended. The \fIlink-type\fR corresponds to the interface's
-link layer type (example: \'ethernet\'), while the \fImac-address\fR is
+is not recommended.
+The \fIlink-type\fR corresponds to the interface's
+link layer type
+(example: \'ethernet\'),
+while the \fImac-address\fR is
a string of colon-separated hexadecimal values for octets.
.PP
\fBanycast-mac\fR \fIlink-type mac-address\fR\fB;\fR
@@ -730,19 +871,22 @@ The
.B anycast-mac
statement over-rides the all-ones broadcast MAC address dhclient will use
when it is transmitting packets to the all-ones limited broadcast IPv4
-address. This configuration parameter is useful to reduce the number of
+address.
+This configuration parameter is useful to reduce the number of
broadcast packets transmitted by DHCP clients, but is only useful if you
know the DHCP service(s) anycast MAC address prior to configuring your
-client. The \fIlink-type\fR and \fImac-address\fR parameters are configured
+client.
+The \fIlink-type\fR and \fImac-address\fR parameters are configured
in a similar manner to the \fBhardware\fR statement.
-.PP
.SH SAMPLE
The following configuration file was used on a laptop running NetBSD
1.3, though the domains have been modified.
The laptop has an IP alias of 192.5.5.213, and has one
-interface, ep0 (a 3com 3C589C). Booting intervals have been
+interface, ep0 (a 3com 3C589C).
+Booting intervals have been
shortened somewhat from the default, because the client is known to
-spend most of its time on networks with little DHCP activity. The
+spend most of its time on networks with little DHCP activity.
+The
laptop does roam to multiple networks.
.nf
@@ -774,13 +918,14 @@ alias {
option subnet-mask 255.255.255.255;
}
.fi
-This is a very complicated dhclient.conf file - in general, yours
-should be much simpler. In many cases, it's sufficient to just
-create an empty dhclient.conf file - the defaults are usually fine.
+This is a very complicated dhclient.conf file \(en in general, yours
+should be much simpler.
+In many cases, it's sufficient to just
+create an empty dhclient.conf file \(en the defaults are usually fine.
.SH SEE ALSO
-dhcp-options(5), dhcp-eval(5), dhclient.leases(5), dhcpd(8), dhcpd.conf(5),
-RFC2132, RFC2131.
+.BR dhcp-options "(5), " dhcp-eval "(5), " dhclient.leases "(5), " \
+dhcpd "(8), " dhcpd.conf "(5), " RFC2132 ", " RFC2131 .
.SH AUTHOR
-.B dhclient(8)
+.BR dhclient (8)
Information about Internet Systems Consortium can be found at
-.B https://www.isc.org.
+.BR https://www.isc.org .
Any program (person), that produces man pages, should check the output
for defects by using (both groff and nroff)
[gn]roff -mandoc -t -ww -b -z -K utf8 <man page>
The same goes for man pages that are used as an input.
For a style guide use
mandoc -T lint
-.-
Any "autogenerator" should check its products with the above mentioned
'groff', 'mandoc', and additionally with 'nroff ...'.
It should also check its input files for too long (> 80) lines.
This is just a simple quality control measure.
The "autogenerator" may have to be corrected to get a better man page,
the source file may, and any additional file may.
Common defects:
Not removing trailing spaces (in in- and output).
The reason for these trailing spaces should be found and eliminated.
Not beginning each input sentence on a new line.
Line length should thus be reduced.
The script "reportbug" uses 'quoted-printable' encoding when a line is
longer than 1024 characters in an 'ascii' file.
See man-pages(7), item "semantic newline".
-.-
The difference between the formatted output of the original and patched file
can be seen with:
nroff -mandoc <file1> > <out1>
nroff -mandoc <file2> > <out2>
diff -d -u <out1> <out2>
and for groff, using
\"printf '%s\n%s\n' '.kern 0' '.ss 12 0' | groff -mandoc -Z - \"
instead of 'nroff -mandoc'
Add the option '-t', if the file contains a table.
Read the output from 'diff -d -u ...' with 'less -R' or similar.
-.-.
If 'man' (man-db) is used to check the manual for warnings,
the following must be set:
The option \"-warnings=w\"
The environmental variable:
export MAN_KEEP_STDERR=yes (or any non-empty value)
or
(produce only warnings):
export MANROFFOPT=\"-ww -b -z\"
export MAN_KEEP_STDERR=yes (or any non-empty value)
-.-
