1 Smartmontools installation instructions
2 =======================================
4 $Id: INSTALL 2844 2009-07-18 12:59:21Z chrfranke $
6 Please also see the smartmontools home page:
7 http://smartmontools.sourceforge.net/
11 [1] System requirements
12 [2] Installing from SVN
13 [3] Installing from source tarball
14 [4] Guidelines for different Linux distributions
15 [5] Guidelines for FreeBSD
16 [6] Guidelines for Darwin
17 [7] Guidelines for NetBSD
18 [8] Guidelines for Solaris
19 [9] Guidelines for Cygwin
20 [10] Guidelines for Windows
21 [11] Guidelines for OS/2, eComStation
22 [12] Guidelines for OpenBSD
24 [14] Detailed description of ./configure options
26 [1] System requirements
27 =======================
31 Any Linux distribution will support smartmontools if it has a
32 kernel version greater than or equal to 2.2.14. So any recent
33 Linux distribution should support smartmontools.
35 There are two parts of smartmontools that may require a patched or
38 (1) To get the ATA RETURN SMART STATUS command, the kernel needs
39 to support the HDIO_DRIVE_TASK ioctl().
41 (2) To run Selective Self-tests, the kernel needs to support the
42 HDIO_DRIVE_TASKFILE ioctl().
44 If your kernel does not support one or both of these ioctls, then
45 smartmontools will "mostly" work. The things that don't work will
46 give you harmless warning messages.
48 Although "not officially supported" by the developers, smartmontools
49 has also been successfully build and run on a legacy Linux system
50 with kernel 2.0.33 and libc.so.5. On such systems, the restrictions
53 For item (1) above, any 2.4 or 2.6 series kernel will provide
54 HDIO_DRIVE_TASK support. Some 2.2.20 and later kernels also
55 provide this support IF they're properly patched and
56 configured. [Andre Hedrick's IDE patches may be found at
57 http://www.funet.fi/pub/linux/kernel/people/hedrick/ide-2.2.20/ or
58 are available from your local kernel.org mirror. They are not
59 updated for 2.2.21 or later, and may contain a few bugs.].
60 If the configuration option CONFIG_IDE_TASK_IOCTL
61 exists in your 2.2.X kernel source code tree, then your 2.2.X
62 kernel will probably support this ioctl. [Note that this kernel
63 configuration option does NOT need to be enabled. Its presence
64 merely indicates that the required HDIO_DRIVE_TASK ioctl() is
67 For item (2) above, your kernel must be configured with the kernel
68 configuration option CONFIG_IDE_TASKFILE_IO enabled. This
69 configuration option is present in all 2.4 and 2.6 series
70 kernels. Some 2.2.20 and later kernels also provide this support
71 IF they're properly patched and configured as described above.
73 Please see FAQ section of the URL above for additional details.
75 If you are using 3ware controllers, for full functionality you
76 must either use version 1.02.00.037 or greater of the 3w-xxxx
77 driver, or patch earlier 3ware 3w-xxxx drivers. See
78 http://smartmontools.sourceforge.net/3w-xxxx.txt
79 for the patch. The version 1.02.00.037 3w-xxxx.c driver was
80 incorporated into kernel 2.4.23-bk2 on 3 December 2003 and into
81 kernel 2.6.0-test5-bk11 on 23 September 2003.
85 For FreeBSD support, a 5-current kernel that includes ATAng is
86 required in order to support ATA drives. Even current versions of
87 ATAng will not support 100% operation, as the SMART status can not
88 be reliably retrieved. There is patch pending approval of the
89 ATAng driver maintainer that will address this issue.
93 The SCSI code has been tested on a variety of Solaris 8 and 9
94 systems. ATA/IDE code only works on SPARC platform. All tested
95 kernels worked correctly.
99 The code was tested on a 1.6ZG (i.e., 1.6-current) system. It should
100 also function under 1.6.1 and later releases (unverified). Currently
101 it doesn't support ATA devices on 3ware RAID controllers.
105 The code was tested on Cygwin 1.5.7, 1.5.11 and 1.5.18-22. It should
106 also work on other recent releases.
108 Release 1.5.15 or later is recommended for Cygwin smartd. Older versions
109 do not provide syslogd support.
111 Both Cygwin and Windows versions of smartmontools share the same code
112 to access the IDE/ATA or SCSI devices. The information in the "Windows"
113 section below also applies to the Cygwin version.
117 The code was tested on Windows 98SE, NT4(SP5,SP6), 2000(SP4),
118 XP(no SP,SP1a,SP2) and Vista RC 1. It should also work on Windows
119 95(OSR2), 98, ME and 2003.
121 On 9x/ME, only standard (legacy) IDE/ATA devices 0-3 are supported.
122 The driver SMARTVSD.VXD must be present in WINDOWS\SYSTEM\IOSUBSYS
123 to get loaded at Windows startup. The default location in a new
124 installation of some versions of Windows is the WINDOWS\SYSTEM folder.
125 In this case, move SMARTVSD.VXD to WINDOWS\SYSTEM\IOSUBSYS and reboot
126 (http://support.microsoft.com/kb/265854/en-us).
127 SMARTVSD.VXD may also be missing in a new installation
128 (http://support.microsoft.com/kb/199886/en-us).
130 SMARTVSD.VXD relies on the standard IDE port driver ESDI_506.PDR.
131 If the system uses a vendor specific driver, access of SMART data
132 is not possible on 9x/ME. This is the case if e.g. the optional
133 "IDE miniport driver" is installed on a system with VIA chipset.
135 Some ATA controllers (e.g. Promise) provided a custom SMARTVSD.VXD
136 for their Win9x/ME driver. To access SMART data from both the legacy
137 (/dev/h[a-d]) and this additional (/dev/hd[e-h]) controller, rename
138 this file to SMARTVSE.VXD. Open the file with a hex editor and replace
139 all occurrences of the string "SMARTVSD" with "SMARTVSE". Then reinstall
140 the original Windows SMARTVSD.VXD.
142 On NT4/2000/XP/2003, ATA or SATA devices are supported if the device
143 driver implements the SMART IOCTL.
145 The IDE/ATA read log command (smartctl -l, --log, -a, --all) is
146 not supported by the SMART IOCTL of NT4/2000/XP. Undocumented
147 and possibly buggy system calls are used for this purpose,
148 see WARNINGS file for details.
150 SCSI devices are supported on all versions of Windows. An installed
151 ASPI interface (WNASPI32.DLL) is required to access SCSI devices.
152 The code was tested with Adaptec Windows ASPI drivers 4.71.2.
153 (http://www.adaptec.com/en-US/support/scsi_soft/ASPI/ASPI-4.70/)
154 Links to other ASPI drivers can be found at http://www.nu2.nu/aspi/.
156 3ware 9000 RAID controllers are supported using new features available
157 in the Windows driver release 9.4.0 (3wareDrv.sys 3.0.2.70) or later.
158 Older drivers provide SMART access to the first physical drive (port)
159 of each logical drive (unit). If driver support is not available
160 (7000/8000 series, 9000 on XP 64), smartctl can be used to parse SMART
161 data output from CLI or 3DM.
165 The code was tested on MacOS 10.3.4. It should work from 10.3
166 forwards. It doesn't support 10.2.
168 It's important to know that on 10.3.x, some things don't work
169 (see WARNINGS): due to bugs in the libraries used, you cannot run
170 a short test or switch SMART support off on a drive; if you try,
171 you will just run an extended test or switch SMART support on. So
172 don't panic when your "short" test seems to be taking hours.
174 It's also not possible at present to control when the offline
175 routine runs. If your drive doesn't have it running automatically by
176 default, you can't run it at all.
178 SCSI devices are not currently supported. Detecting the power
179 status of a drive is also not currently supported.
181 To summarize this, from another point of view, the things that
182 are not supported fall into two categories:
184 * Can't be implemented easily without more kernel-level support,
186 - running immediate offline, conveyance, or selective tests
187 - running any test in captive mode
189 - switching automatic offline testing on or off
191 - checking the power mode [-n Directive of smartd] (this is not
192 completely impossible, but not by using a documented API)
194 * Work on 10.4 and later, but not on 10.3:
195 - switching off SMART (switching *on* works fine)
196 - switching off auto-save (but why would you want to?)
197 - running the short test (that leaves you with only the extended test)
199 However, some things do work well. For ATA devices, all the
200 informational output is available, unless you want something that only
201 an offline test updates. On many newer Mac OS systems, the
202 hard drive comes with the offline test switched on by default, so
207 The code was tested on eComStation 1.1, but it should work on all versions
209 Innotek LibC 0.5 runtime is required.
210 Currently only ATA disks are supported, SCSI support will be added.
212 [2] Installing from SVN
213 =======================
215 Get the sources from the SVN repository:
216 svn co https://smartmontools.svn.sourceforge.net/svnroot/smartmontools/trunk/smartmontools smartmontools
220 and continue with step [3] below, skipping the "unpack the tarball" step.
222 The autogen.sh command is ONLY required when installing from
223 SVN. You need GNU Autoconf (version 2.50 or greater), GNU Automake
224 (version 1.7 or greater) and their dependencies installed in order
225 to run it. You can get these here:
226 http://www.gnu.org/directory/GNU/autoconf.html
227 http://www.gnu.org/directory/GNU/automake.html
229 [3] Installing from the source tarball
230 ======================================
232 If you are NOT installing from SVN, then unpack the tarball:
233 tar zxvf smartmontools-5.VERSION.tar.gz
238 make install (you may need to be root to do this)
240 As shown (with no options to ./configure) this defaults to the
241 following set of installation directories:
243 --sbindir=/usr/local/sbin
244 --sysconfdir=/usr/local/etc
245 --mandir=/usr/local/share/man
246 --with-docdir=/usr/local/share/doc/smartmontools-VERSION
247 --with-initscriptdir=/usr/local/etc/rc.d/init.d
250 These will usually not overwrite existing "distribution" installations on
251 Linux Systems since the FHS reserves this area for use by the system
254 For different installation locations or distributions, simply add
255 arguments to ./configure as shown in [4] below.
257 If you wish to alter the default C compiler flags, set an
258 environment variable CFLAGS='your options' before doing
259 ./configure, or else do:
260 make CFLAGS='your options'
262 The first output line of smartctl and smartd provides information
263 about release number, last SVN checkin date and revison, platform,
264 and package. The latter defaults to "(local build)" and can be
265 changed by the variable BUILD_INFO, for example:
266 make BUILD_INFO='"(Debian 5.39-2)"'
268 [4] Guidelines for different Linux distributions
269 ================================================
271 Note: Please send corrections/additions to:
272 smartmontools-support@lists.sourceforge.net
275 If you don't want to overwrite any distribution package, use:
278 Filesystem Hierarchy Standard (FHS, http://www.pathname.com/fhs/):
279 ./configure --sbindir=/usr/local/sbin \
280 --sysconfdir=/usr/local/etc \
281 --mandir=/usr/local/man \
282 --with-initscriptdir=/usr/local/etc/rc.d/init.d \
283 --with-docdir=/usr/local/share/doc/smartmontools-VERSION
286 ./configure --sbindir=/usr/sbin \
288 --mandir=/usr/share/man \
289 --with-initscriptdir=/etc/rc.d/init.d \
290 --with-docdir=/usr/share/doc/smartmontools-VERSION
293 If you don't want to overwrite any "distribution" package, use:
297 ./configure --sbindir=/usr/sbin \
299 --mandir=/usr/share/man \
300 --with-initscriptdir=/etc/rc.d \
301 --with-docdir=/usr/share/doc/smartmontools-VERSION
304 removepkg smartmontools smartsuite (only root can do this)
307 The init script works on Slackware. You just have to add an entry like
308 the following in /etc/rc.d/rc.M or /etc/rc.d/rc.local:
310 if [ -x /etc/rc.d/smartd ]; then
311 . /etc/rc.d/smartd start
315 chmod 644 /etc/rc.d/smartd
317 For a list of options:
321 ./configure --sbindir=/usr/sbin \
323 --mandir=/usr/share/man \
324 --with-initscriptdir=/etc/init.d \
325 --with-docdir=/usr/share/doc/packages/smartmontools-VERSION
327 [5] Guidelines for FreeBSD
328 ==========================
329 To match the way it will installed when it becomes available as a PORT, use
332 ./configure --prefix=/usr/local \
333 --with-initscriptdir=/usr/local/etc/rc.d/ \
334 --with-docdir=/usr/local/share/doc/smartmontools-VERSION \
337 NOTE: --enable-sample will cause the smartd.conf and smartd RC files to
338 be installed with the string '.sample' append to the name, so you will end
339 up with the following:
340 /usr/local/etc/smartd.conf.sample
341 /usr/local/etc/rc.d/smartd.sample
344 [6] Guidelines for Darwin
345 =========================
346 ./configure --with-initscriptdir=/Library/StartupItems
348 If you'd like to build the i386 version on a powerpc machine, you can
351 CXX='g++ -isysroot /Developer/SDKs/MacOSX10.4u.sdk -arch i386' \
352 ./configure --host=i386-apple-darwin \
353 --with-initscriptdir=/Library/StartupItems
355 [7] Guidelines for NetBSD/OpenBSD
356 =================================
357 ./configure --prefix=/usr/pkg \
358 --with-docdir=/usr/pkg/share/doc/smartmontools
360 On OpenBSD, it is important that you use GNU make (gmake from
361 /usr/ports/devel/gmake) to build smartmontools, as the BSD make doesn't
362 know how to make the manpages.
364 [8] Guidelines for Solaris
365 ==========================
367 smartmontools has been partially but not completely ported to
368 Solaris. It includes complete SCSI support but no ATA or 3ware
369 support. It can be compiled with either CC (Sun's C++ compiler)
377 To compile with Sun CC:
379 env CC=cc CXX=CC ./configure [args]
382 The correct arguments [args] to configure are:
383 --sbindir=/usr/sbin \
385 --mandir=/usr/share/man \
386 --with-docdir=/usr/share/doc/smartmontools-VERSION \
387 --with-initscriptdir=/etc/init.d
389 To start the script automatically on bootup, create hardlinks that
390 indicate when to start/stop in:
392 pointing to /etc/init.d/smartd. Create:
393 K<knum>smartd in rcS.d, rc0.d, rc1.d, rc2.d
394 S<snum>smartd in rc3.d
395 where <knum> is related to <snum> such that the higher snum is the
398 On usual configuration, '95' would be suitable for <snum> and '05'
399 for <knum> respectively. If you choose these value, you can
403 sh -c 'for n in S 0 1 2; do ln init.d/smartd rc$n.d/K05smartd; done'
404 sh -c 'for n in 3 ; do ln init.d/smartd rc$n.d/S95smartd; done'
406 [9] Guidelines for Cygwin
407 =========================
410 ./configure --prefix=/usr \
412 --mandir='${prefix}/share/man'
415 ./configure --sbindir=/usr/sbin \
417 --mandir=/usr/share/man \
418 --with-initscriptdir=/etc/rc.d/init.d \
419 --with-docdir=/usr/share/doc/smartmontools-VERSION
421 Using DOS text file type as default for the working directories ("textmode"
422 mount option) is not recommended. Building the binaries and man pages using
423 "make" is possible, but "make dist" and related targets work only with UNIX
424 file type ("binmode" mount option) set. The "autogen.sh" script prints a
425 warning if DOS type is selected.
427 If installing from SVN, you may check out all files either with CR/LF
428 or LF line endings. Starting with release 3.1-7, Cygwin's bash does no
429 longer accept scripts with CR/LF by default. To run the initial script
430 ./autogen.sh checked out with CR/LF on a "binmode" mount, type:
432 bash -O igncr ./autogen.sh
434 instead. This is not necessary for the generated ./configure script.
436 [10] Guidelines for Windows
437 ==========================
439 To compile the Windows release with MinGW, use the following on Cygwin:
441 ./configure --build=mingw32
444 Instead of using "make install", copy the .exe files into
445 some directory in the PATH.
447 To build the Windows binary distribution, use:
451 This builds the distribution in directory
453 ./smartmontools-VERSION.win32/
457 ./smartmontools-VERSION.win32.zip
459 To create a Windows installer, use:
463 This builds the distribution directory and packs it into the
464 self-extracting install program
466 ./smartmontools-VERSION.win32-setup.exe
468 The installer is build using the command "makensis" from the NSIS
469 package. See http://nsis.sourceforge.net/ for documentation and
472 To both create and run the (interactive) installer, use:
476 Additional make targets are distdir-win32 to build the directory
477 only and cleandist-win32 for cleanup.
479 The binary distribution includes all documentation files converted
480 to DOS text file format and *.html and *.txt preformatted man pages.
481 The tools unix2dos.exe (package cygutils) and zip.exe (package zip
482 or a native Win32 release of Info-ZIP, http://www.info-zip.org) are
483 necessary but may be not installed by Cygwin's default settings.
485 To prepare os_win32 directory for MSVC8, use the following on Cygwin:
487 mkdir vctmp && cd vctmp
488 ../configure --build=mingw32
491 The MSVC8 project files (os_win32/smartmontools_vc8.sln,
492 os_win32/smart{ctl,d}_vc8.vcproj) are included in SVN (but not in
493 source tarball). The target config-vc8 from a Makefile configured
494 for MinGW creates os_win32/{config,svnversion}_vc8.h from
495 ./{config,svnversion}.h. The configure skript must be run outside
496 of the source directory to avoid inclusion of the original config.h.
498 Unlike MinGW, MSVC can also be used to build the syslog message file
499 tool syslogevt.exe. See smartd man page for usage information about
503 [11] Guidelines for OS/2, eComStation
504 =====================================
506 To compile the OS/2 code, please run
508 ./os_os2/configure.os2
512 [12] Guidelines for OpenBSD
513 ==========================
514 To match the way it will installed when it becomes available as a PORT, use
517 ./configure --prefix=/usr/local \
519 --with-initscriptdir=/usr/local/share/doc/smartmontools-VERSION \
520 --with-docdir=/usr/local/share/doc/smartmontools-VERSION \
523 It is important that you use GNU make (gmake from /usr/ports/devel/gmake)
524 to build smartmontools, as the default OpenBSD make doesn't know how to build
527 NOTE1: --with-initscriptdir installs a SystemV startup script. It really
528 should be --without-initscriptdir, but the Makefile code is incorrect and
529 trys to install the initscript (smartd) to /no. So, an interim fix it to
530 set the initscript dir to the doc dir.
532 NOTE2: --enable-sample will cause the smartd.conf and smartd RC files to
533 be installed with the string '.sample' append to the name, so you will end
534 up with the following:
535 /usr/local/etc/smartd.conf.sample
536 /usr/local/etc/rc.d/smartd.sample
541 To compile from another directory, you can replace the step
542 ./configure [options]
546 ../configure [options]
548 To install to another destination (used mainly by package maintainers,
549 or to examine the package contents without risk of modifying any
550 system files) you can replace the step:
553 make DESTDIR=/home/myself/smartmontools-package install
555 Use a full path. Paths like ~/smartmontools-package may not work.
557 After installing smartmontools, you can read the man pages, and try
564 /usr/sbin/smartctl -s on -o on -S on /dev/hda (only root can do this)
565 /usr/sbin/smartctl -a /dev/hda (only root can do this)
567 Note that the default location for the manual pages are
568 /usr/share/man/man5 and /usr/share/man/man8. If "man" doesn't find
569 them, you may need to add /usr/share/man to your MANPATH environment
572 Source and binary RPM packages are available at
573 http://sourceforge.net/project/showfiles.php?group_id=64297
575 Refer to http://smartmontools.sourceforge.net/index.html#howtodownload
576 for any additional download and installation instructions.
578 The following files are installed if ./configure has no options:
580 /usr/local/sbin/smartd [Executable daemon]
581 /usr/local/sbin/smartctl [Executable command-line utility]
582 /usr/local/etc/smartd.conf [Configuration file for smartd daemon]
583 /usr/local/etc/rc.d/init.d/smartd [Init/Startup script for smartd]
584 /usr/local/share/man/man5/smartd.conf.5 [Manual page]
585 /usr/local/share/man/man8/smartctl.8 [Manual page]
586 /usr/local/share/man/man8/smartd.8 [Manual page]
587 /usr/local/share/doc/smartmontools-5.X/AUTHORS [Information about the authors and developers]
588 /usr/local/share/doc/smartmontools-5.X/CHANGELOG [A log of changes. Also see SVN]
589 /usr/local/share/doc/smartmontools-5.X/COPYING [GNU General Public License Version 2]
590 /usr/local/share/doc/smartmontools-5.X/INSTALL [Installation instructions: what you're reading!]
591 /usr/local/share/doc/smartmontools-5.X/NEWS [Significant bugs discovered in old versions]
592 /usr/local/share/doc/smartmontools-5.X/README [Overview]
593 /usr/local/share/doc/smartmontools-5.X/TODO [Things that need to be done/fixed]
594 /usr/local/share/doc/smartmontools-5.X/WARNINGS [Systems where lockups or other serious problems were reported]
595 /usr/local/share/doc/smartmontools-5.X/smartd.conf [Example configuration file for smartd]
596 /usr/local/share/doc/smartmontools-5.X/examplescripts [Executable scripts for -M exec of smartd.conf (4 files)]
603 may be used to build .html and .txt preformatted man pages.
604 These are used by the dist-win32 make target to build the Windows
606 The commands also work on other operating system configurations
607 if suitable versions of man2html, groff and grotty are installed.
608 On systems without man2html, the following command should work
609 if groff is available:
611 make MAN2HTML='groff -man -Thtml' htmlman
614 Some of the source files are prepared for the documentation
615 generator Doxygen (http://www.doxygen.org/). If Doxygen is installed,
620 creates HTML documentation in doc/html and LaTeX documentation
621 in doc/latex. If TeX is installed, the following command creates
622 a documentation file doc/latex/refman.pdf:
624 ( cd doc/latex && make pdf )
627 [14] Detailed description of arguments to configure command
628 ===========================================================
631 ./configure [options]
632 there are six particularly important variables that affect where the
633 smartmontools software is installed. The variables are listed here,
634 with their default values in square brackets, and the quantities that
635 they affect described following that. This is a very wide table: please read
638 OPTIONS DEFAULT AFFECTS
639 ------- ------- -------
640 --prefix /usr/local Please see below
641 --sbindir ${prefix}/sbin Directory for smartd/smartctl executables;
642 Contents of smartd/smartctl man pages
643 --mandir ${prefix}/share/man Directory for smartctl/smartd/smartd.conf man pages
644 --sysconfdir ${prefix}/etc Directory for smartd.conf;
645 Contents of smartd executable;
646 Contents of smartd/smartd.conf man pages;
647 Directory for rc.d/init.d/smartd init script
648 --with-initscriptdir ${sysconfdir}/init.d/rc.d Location of init scripts
649 --with-docdir ${prefix}/share/doc/smartmontools-5.X Location of the documentation
650 --enable-sample --disable-sample Adds the string '.sample' to the names of the smartd.conf file and the smartd RC file
651 --with-os-deps os_<guessed>.o OS dependent module(s)
652 --with-selinux <not set> Enables SELinux support. If smartmontools has to create the /dev/tw[ae] device
653 nodes for 3ware/AMCC controllers, this option ensures that the nodes are created
654 with correct SELinux file contexts.
655 --enable-drivedb --disable-drivedb Enables default drive database file '${drivedbdir}/drivedb.h'
656 --with-drivedbdir ${prefix}/share/smartmontools/drivedb.h Directory for 'drivedb.h' (specifying this option implies --enable-drivedb)
657 --enable-savestates --disable-savestates Enables default smartd state files '${savestates}MODEL-SERIAL.ata.state'
658 --with-savestates ${prefix}/var/lib/smartmontools/smartd. Prefix for smartd state files (specifying this option implies --enable-savestates)
661 If you set --prefix=/home/joe and none of the other four
662 variables then the different directories that are used would be:
663 --sbindir /home/joe/sbin
664 --mandir /home/joe/share/man
665 --sysconfdir /home/joe/etc
666 --with-initscriptdir /home/joe/etc/init.d/rc.d
667 --with-docdir /home/joe/doc/smartmontools-5.X
669 This is useful for test installs in a harmless subdirectory somewhere.
671 Here are the four possible cases for the four variables above:
676 ===> VARIABLE gets default value above
681 ===> VARIABLE gets PREFIX/ prepended to default value above
686 ===> VARIABLE gets value that is set
691 ===> PREFIX is IGNORED, VARIABLE gets value that is set
694 Here are the differences with and without --enable-sample, assuming
695 no other options specified (see above for details)
698 --enable-sample provided
699 ==> Files installed are:
700 /usr/local/etc/smartd.conf.sample
701 /usr/local/etc/rc.d/init.d/smartd.sample
704 --disable-sample provided or parameter left out
705 ==> Files installed are:
706 /usr/local/etc/smartd.conf
707 /usr/local/etc/rc.d/init.d/smartd
709 Additional information about using configure can be found here:
710 http://www.gnu.org/software/autoconf/manual/autoconf-2.57/html_mono/autoconf.html#SEC139