5 This document describes installation on all supported operating
6 systems (the Linux/Unix family, OpenVMS and Windows)
8 To install OpenSSL, you will need:
10 * A make implementation
11 * Perl 5 with core modules (please read NOTES.PERL)
12 * The perl module Text::Template (please read NOTES.PERL)
14 * a development environment in the form of development libraries and C
16 * a supported operating system
18 For additional platform specific requirements, solutions to specific
19 issues and other details, please read one of these:
22 * NOTES.WIN (any supported Windows)
23 * NOTES.DJGPP (DOS platform with DJGPP)
25 Notational conventions in this document
26 ---------------------------------------
28 Throughout this document, we use the following conventions in command
31 $ command Any line starting with a dollar sign
32 ($) is a command line.
34 { word1 | word2 | word3 } This denotes a mandatory choice, to be
35 replaced with one of the given words.
36 A simple example would be this:
38 $ echo { FOO | BAR | COOKIE }
40 which is to be understood as one of
49 [ word1 | word2 | word3 ] Similar to { word1 | word2 | word3 }
50 except it's optional to give any of
51 those. In addition to the examples
52 above, this would also be valid:
56 {{ target }} This denotes a mandatory word or
57 sequence of words of some sort. A
58 simple example would be this:
62 which is to be understood to use the
63 command 'type' on some file name
64 determined by the user.
66 [[ options ]] Similar to {{ target }}, but is
69 Note that the notation assumes spaces around {, }, [, ], {{, }} and
70 [[, ]]. This is to differentiate from OpenVMS directory
71 specifications, which also use [ and ], but without spaces.
76 If you want to just get on with it, do:
92 on Windows (only pick one of the targets for configuration):
94 $ perl Configure { VC-WIN32 | VC-WIN64A | VC-WIN64I | VC-CE }
99 If any of these steps fails, see section Installation in Detail below.
101 This will build and install OpenSSL in the default location, which is:
103 Unix: normal installation directories under /usr/local
104 OpenVMS: SYS$COMMON:[OPENSSL-'version'...], where 'version' is the
105 OpenSSL version number with underscores instead of periods.
106 Windows: C:\Program Files\OpenSSL or C:\Program Files (x86)\OpenSSL
108 If you want to install it anywhere else, run config like this:
112 $ ./config --prefix=/opt/openssl --openssldir=/usr/local/ssl
116 $ @config --prefix=PROGRAM:[INSTALLS] --openssldir=SYS$MANAGER:[OPENSSL]
119 Configuration Options
120 ---------------------
122 There are several options to ./config (or ./Configure) to customize
123 the build (note that for Windows, the defaults for --prefix and
124 --openssldir depend in what configuration is used and what Windows
125 implementation OpenSSL is built on. More notes on this in NOTES.WIN):
128 Don't build with support for deprecated APIs below the
129 specified version number. For example "--api=1.1.0" will
130 remove support for all APIS that were deprecated in OpenSSL
131 version 1.1.0 or below.
133 --cross-compile-prefix=PREFIX
134 The PREFIX to include in front of commands for your
135 toolchain. It's likely to have to end with dash, e.g.
136 a-b-c- would invoke GNU compiler as a-b-c-gcc, etc.
137 Unfortunately cross-compiling is too case-specific to
138 put together one-size-fits-all instructions. You might
139 have to pass more flags or set up environment variables
140 to actually make it work. Android and iOS cases are
141 discussed in corresponding Configurations/10-main.cf
142 sections. But there are cases when this option alone is
143 sufficient. For example to build the mingw64 target on
144 Linux "--cross-compile-prefix=x86_64-w64-mingw32-"
145 works. Naturally provided that mingw packages are
146 installed. Today Debian and Ubuntu users have option to
147 install a number of prepackaged cross-compilers along
148 with corresponding run-time and development packages for
149 "alien" hardware. To give another example
150 "--cross-compile-prefix=mipsel-linux-gnu-" suffices
151 in such case. Needless to mention that you have to
152 invoke ./Configure, not ./config, and pass your target
156 Build OpenSSL with debugging symbols.
159 The name of the directory under the top of the installation
160 directory tree (see the --prefix option) where libraries will
161 be installed. By default this is "lib". Note that on Windows
162 only ".lib" files will be stored in this location. dll files
163 will always be installed to the "bin" directory.
166 Directory for OpenSSL configuration files, and also the
167 default certificate and key store. Defaults are:
170 Windows: C:\Program Files\Common Files\SSL
171 or C:\Program Files (x86)\Common Files\SSL
172 OpenVMS: SYS$COMMON:[OPENSSL-COMMON]
175 The top of the installation directory tree. Defaults are:
178 Windows: C:\Program Files\OpenSSL
179 or C:\Program Files (x86)\OpenSSL
180 OpenVMS: SYS$COMMON:[OPENSSL-'version']
183 Build OpenSSL without debugging symbols. This is the default.
186 This is a developer flag that switches on various compiler
187 options recommended for OpenSSL development. It only works
188 when using gcc or clang as the compiler. If you are
189 developing a patch for OpenSSL then it is recommended that
190 you use this option where possible.
192 --with-zlib-include=DIR
193 The directory for the location of the zlib include file. This
194 option is only necessary if enable-zlib (see below) is used
195 and the include file is not already on the system include
199 On Unix: this is the directory containing the zlib library.
200 If not provided the system library path will be used.
201 On Windows: this is the filename of the zlib library (with or
202 without a path). This flag must be provided if the
203 zlib-dynamic option is not also used. If zlib-dynamic is used
204 then this flag is optional and a default value ("ZLIB1") is
205 used if not provided.
206 On VMS: this is the filename of the zlib library (with or
207 without a path). This flag is optional and if not provided
208 then "GNV$LIBZSHR", "GNV$LIBZSHR32" or "GNV$LIBZSHR64" is
209 used by default depending on the pointer size chosen.
212 Don't build the AFALG engine. This option will be forced if
213 on a platform that does not support AFALG.
216 Build with the Address sanitiser. This is a developer option
217 only. It may not work on all platforms and should never be
218 used in production environments. It will only work when used
219 with gcc or clang and should be used in conjunction with the
223 Do not use assembler code. On some platforms a small amount
224 of assembler code may still be used.
227 Do not build support for async operations.
230 Don't automatically load all supported ciphers and digests.
231 Typically OpenSSL will make available all of its supported
232 ciphers and digests. For a statically linked application this
233 may be undesirable if small executable size is an objective.
234 This only affects libcrypto. Ciphers and digests will have to
235 be loaded manually using EVP_add_cipher() and
236 EVP_add_digest() if this option is used. This option will
237 force a non-shared build.
240 Don't automatically load all libcrypto/libssl error strings.
241 Typically OpenSSL will automatically load human readable
242 error strings. For a statically linked application this may
243 be undesirable if small executable size is an objective.
247 Don't build the CAPI engine. This option will be forced if
248 on a platform that does not support CAPI.
251 Don't build support for CMS features
254 Don't build support for SSL/TLS compression. If this option
255 is left enabled (the default), then compression will only
256 work if the zlib or zlib-dynamic options are also chosen.
259 Build support for debugging memory allocated via
260 OPENSSL_malloc() or OPENSSL_zalloc().
262 enable-crypto-mdebug-backtrace
263 As for crypto-mdebug, but additionally provide backtrace
264 information for allocated memory.
265 TO BE USED WITH CARE: this uses GNU C functionality, and
266 is therefore not usable for non-GNU config targets. If
267 your build complains about the use of '-rdynamic' or the
268 lack of header file execinfo.h, this option is not for you.
269 ALSO NOTE that even though execinfo.h is available on your
270 system (through Gnulib), the functions might just be stubs
274 Don't build support for Certificate Transparency.
277 Don't build with support for any deprecated APIs. This is the
278 same as using "--api" and supplying the latest version
282 Don't build support for datagram based BIOs. Selecting this
283 option will also force the disabling of DTLS.
286 Don't build support for loading Dynamic Shared Objects.
289 Don't build the dynamically loaded engines. This only has an
290 effect in a "shared" build
293 Don't build support for Elliptic Curves.
296 Don't build support for binary Elliptic Curves
298 enable-ec_nistp_64_gcc_128
299 Enable support for optimised implementations of some commonly
300 used NIST elliptic curves. This is only supported on some
304 Build support for gathering entropy from EGD (Entropy
308 Don't build support for loading engines.
311 Don't compile in any error strings.
314 Don't compile in filename and line number information (e.g.
315 for errors and memory allocation).
317 enable-fuzz-libfuzzer, enable-fuzz-afl
318 Build with support for fuzzing using either libfuzzer or AFL.
319 These are developer options only. They may not work on all
320 platforms and should never be used in production environments.
321 See the file fuzz/README.md for further details.
324 Don't build support for GOST based ciphersuites. Note that
325 if this feature is enabled then GOST ciphersuites are only
326 available if the GOST algorithms are also available through
327 loading an externally supplied engine.
330 Build support for DTLS heartbeats.
333 Don't build the padlock engine.
336 Don't generate dependencies.
339 Don't build support for writing multiple records in one
340 go in libssl (Note: this is a different capability to the
341 pipelining functionality).
344 Don't build support for the NPN TLS extension.
347 Don't build support for OCSP.
350 Don't build with support for Position Independent Code.
353 Don't use POSIX IO capabilities.
356 Don't build support for Pre-Shared Key based ciphersuites.
359 Don't use hardware RDRAND capabilities.
362 Don't build support for RFC3779 ("X.509 Extensions for IP
363 Addresses and AS Identifiers")
366 Build support for SCTP
369 Do not create shared libraries, only static ones. See "Note
370 on shared libraries" below.
373 Don't build support for socket BIOs
376 Don't build support for SRP or SRP based ciphersuites.
379 Don't build SRTP support
382 Exclude SSE2 code paths. Normally SSE2 extension is
383 detected at run-time, but the decision whether or not the
384 machine code will be executed is taken solely on CPU
385 capability vector. This means that if you happen to run OS
386 kernel which does not support SSE2 extension on Intel P4
387 processor, then your application might be exposed to
388 "illegal instruction" exception. There might be a way
389 to enable support in kernel, e.g. FreeBSD kernel can be
390 compiled with CPU_ENABLE_SSE, and there is a way to
391 disengage SSE2 code paths upon application start-up,
392 but if you aim for wider "audience" running such kernel,
393 consider no-sse2. Both the 386 and no-asm options imply
397 Build with the SSL Trace capabilities (adds the "-trace"
398 option to s_client and s_server).
401 Don't build the statically linked engines. This only
402 has an impact when not built "shared".
405 Don't use any C "stdio" features. Only libcrypto and libssl
406 can be built in this way. Using this option will suppress
407 building the command line applications. Additionally since
408 the OpenSSL tests also use the command line applications the
409 tests will also be skipped.
412 Don't try to build with support for multi-threaded
416 Build with support for multi-threaded applications. Most
417 platforms will enable this by default. However if on a
418 platform where this is not the case then this will usually
419 require additional system-dependent options! See "Note on
420 multi-threading" below.
423 Don't build Time Stamping Authority support.
426 Build with the Undefined Behaviour sanitiser. This is a
427 developer option only. It may not work on all platforms and
428 should never be used in production environments. It will only
429 work when used with gcc or clang and should be used in
430 conjunction with the "-DPEDANTIC" option (or the
431 --strict-warnings option).
434 Don't build with the "UI" capability (i.e. the set of
435 features enabling text based prompts).
438 Enable additional unit test APIs. This should not typically
439 be used in production deployments.
441 enable-weak-ssl-ciphers
442 Build support for SSL/TLS ciphers that are considered "weak"
443 (e.g. RC4 based ciphersuites).
446 Build with support for zlib compression/decompression.
449 Like "zlib", but has OpenSSL load the zlib library
450 dynamically when needed. This is only supported on systems
451 where loading of shared libraries is supported.
454 On Intel hardware, use the 80386 instruction set only
455 (the default x86 code is more efficient, but requires at
456 least a 486). Note: Use compiler flags for any other CPU
457 specific configuration, e.g. "-m32" to build x86 code on
461 Don't build support for negotiating the specified SSL/TLS
462 protocol (one of ssl, ssl3, tls, tls1, tls1_1, tls1_2, dtls,
463 dtls1 or dtls1_2). If "no-tls" is selected then all of tls1,
464 tls1_1 and tls1_2 are disabled. Similarly "no-dtls" will
465 disable dtls1 and dtls1_2. The "no-ssl" option is synonymous
466 with "no-ssl3". Note this only affects version negotiation.
467 OpenSSL will still provide the methods for applications to
468 explicitly select the individual protocol versions.
471 As for no-<prot> but in addition do not build the methods for
472 applications to explicitly select individual protocol
476 Build with support for the specified algorithm, where <alg>
477 is one of: md2 or rc5.
480 Build without support for the specified algorithm, where
481 <alg> is one of: bf, blake2, camellia, cast, chacha, cmac,
482 des, dh, dsa, ecdh, ecdsa, idea, md4, mdc2, ocb, poly1305,
483 rc2, rc4, rmd160, scrypt, seed or whirlpool. The "ripemd"
484 algorithm is deprecated and if used is synonymous with rmd160.
486 -Dxxx, -lxxx, -Lxxx, -fxxx, -mXXX, -Kxxx
487 These system specific options will be passed through to the
488 compiler to allow you to define preprocessor symbols, specify
489 additional libraries, library directories or other compiler
493 Installation in Detail
494 ----------------------
496 1a. Configure OpenSSL for your operation system automatically:
498 NOTE: This is not available on Windows.
500 $ ./config [[ options ]] # Unix
504 $ @config [[ options ]] ! OpenVMS
506 For the remainder of this text, the Unix form will be used in all
507 examples, please use the appropriate form for your platform.
509 This guesses at your operating system (and compiler, if necessary) and
510 configures OpenSSL based on this guess. Run ./config -t to see
511 if it guessed correctly. If you want to use a different compiler, you
512 are cross-compiling for another platform, or the ./config guess was
513 wrong for other reasons, go to step 1b. Otherwise go to step 2.
515 On some systems, you can include debugging information as follows:
517 $ ./config -d [[ options ]]
519 1b. Configure OpenSSL for your operating system manually
521 OpenSSL knows about a range of different operating system, hardware and
522 compiler combinations. To see the ones it knows about, run
528 $ perl Configure # All other platforms
530 For the remainder of this text, the Unix form will be used in all
531 examples, please use the appropriate form for your platform.
533 Pick a suitable name from the list that matches your system. For most
534 operating systems there is a choice between using "cc" or "gcc". When
535 you have identified your system (and if necessary compiler) use this name
536 as the argument to Configure. For example, a "linux-elf" user would
539 $ ./Configure linux-elf [[ options ]]
541 If your system isn't listed, you will have to create a configuration
542 file named Configurations/{{ something }}.conf and add the correct
543 configuration for your system. See the available configs as examples
544 and read Configurations/README and Configurations/README.design for
547 The generic configurations "cc" or "gcc" should usually work on 32 bit
550 Configure creates a build file ("Makefile" on Unix, "makefile" on Windows
551 and "descrip.mms" on OpenVMS) from a suitable template in Configurations,
552 and defines various macros in include/openssl/opensslconf.h (generated from
553 include/openssl/opensslconf.h.in).
555 1c. Configure OpenSSL for building outside of the source tree.
557 OpenSSL can be configured to build in a build directory separate from
558 the directory with the source code. It's done by placing yourself in
559 some other directory and invoking the configuration commands from
564 $ mkdir /var/tmp/openssl-build
565 $ cd /var/tmp/openssl-build
566 $ /PATH/TO/OPENSSL/SOURCE/config [[ options ]]
570 $ /PATH/TO/OPENSSL/SOURCE/Configure {{ target }} [[ options ]]
574 $ set default sys$login:
575 $ create/dir [.tmp.openssl-build]
576 $ set default [.tmp.openssl-build]
577 $ @[PATH.TO.OPENSSL.SOURCE]config [[ options ]]
581 $ @[PATH.TO.OPENSSL.SOURCE]Configure {{ target }} [[ options ]]
586 $ mkdir \temp-openssl
588 $ perl d:\PATH\TO\OPENSSL\SOURCE\Configure {{ target }} [[ options ]]
590 Paths can be relative just as well as absolute. Configure will
591 do its best to translate them to relative paths whenever possible.
593 2. Build OpenSSL by running:
596 $ mms ! (or mmk) OpenVMS
599 This will build the OpenSSL libraries (libcrypto.a and libssl.a on
600 Unix, corresponding on other platforms) and the OpenSSL binary
601 ("openssl"). The libraries will be built in the top-level directory,
602 and the binary will be in the "apps" subdirectory.
604 If the build fails, look at the output. There may be reasons for
605 the failure that aren't problems in OpenSSL itself (like missing
606 standard headers). If you are having problems you can get help by
607 sending an email to the openssl-users email list (see
608 https://www.openssl.org/community/mailinglists.html for details). If it
609 is a bug with OpenSSL itself, please report the problem to
610 <rt@openssl.org> (note that your message will be recorded in the request
611 tracker publicly readable at
612 https://www.openssl.org/community/index.html#bugs and will be
613 forwarded to a public mailing list). Please check out the request
614 tracker. Maybe the bug was already reported or has already been
617 (If you encounter assembler error messages, try the "no-asm"
618 configuration option as an immediate fix.)
620 Compiling parts of OpenSSL with gcc and others with the system
621 compiler will result in unresolved symbols on some systems.
623 3. After a successful build, the libraries should be tested. Run:
627 $ nmake test # Windows
629 NOTE: you MUST run the tests from an unprivileged account (or
630 disable your privileges temporarily if your platform allows it).
632 If some tests fail, look at the output. There may be reasons for
633 the failure that isn't a problem in OpenSSL itself (like a
634 malfunction with Perl). You may want increased verbosity, that
635 can be accomplished like this:
637 $ make VERBOSE=1 test # Unix
639 $ mms /macro=(VERBOSE=1) test ! OpenVMS
641 $ nmake VERBOSE=1 test # Windows
643 If you want to run just one or a few specific tests, you can use
644 the make variable TESTS to specify them, like this:
646 $ make TESTS='test_rsa test_dsa' test # Unix
647 $ mms/macro="TESTS=test_rsa test_dsa" test ! OpenVMS
648 $ nmake TESTS='test_rsa test_dsa' test # Windows
650 And of course, you can combine (Unix example shown):
652 $ make VERBOSE=1 TESTS='test_rsa test_dsa' test
654 You can find the list of available tests like this:
656 $ make list-tests # Unix
657 $ mms list-tests ! OpenVMS
658 $ nmake list-tests # Windows
660 Have a look at the manual for the perl module Test::Harness to
661 see what other HARNESS_* variables there are.
663 If you find a problem with OpenSSL itself, try removing any
664 compiler optimization flags from the CFLAGS line in Makefile and
665 run "make clean; make" or corresponding.
667 Please send bug reports to <rt@openssl.org>.
669 4. If everything tests ok, install OpenSSL with
671 $ make install # Unix
672 $ mms install ! OpenVMS
673 $ nmake install # Windows
675 This will install all the software components in this directory
676 tree under PREFIX (the directory given with --prefix or its
681 bin/ Contains the openssl binary and a few other
684 Contains the header files needed if you want
685 to build your own programs that use libcrypto
687 lib Contains the OpenSSL library files.
688 lib/engines Contains the OpenSSL dynamically loadable engines.
690 share/man/man1 Contains the OpenSSL command line man-pages.
691 share/man/man3 Contains the OpenSSL library calls man-pages.
692 share/man/man5 Contains the OpenSSL configuration format man-pages.
693 share/man/man7 Contains the OpenSSL other misc man-pages.
695 share/doc/openssl/html/man1
696 share/doc/openssl/html/man3
697 share/doc/openssl/html/man5
698 share/doc/openssl/html/man7
699 Contains the HTML rendition of the man-pages.
701 OpenVMS ('arch' is replaced with the architecture name, "Alpha"
702 or "ia64", 'sover' is replaced with the shared library version
703 (0101 for 1.1), and 'pz' is replaced with the pointer size
704 OpenSSL was built with):
706 [.EXE.'arch'] Contains the openssl binary.
707 [.EXE] Contains a few utility scripts.
709 Contains the header files needed if you want
710 to build your own programs that use libcrypto
712 [.LIB.'arch'] Contains the OpenSSL library files.
713 [.ENGINES'sover''pz'.'arch']
714 Contains the OpenSSL dynamically loadable engines.
715 [.SYS$STARTUP] Contains startup, login and shutdown scripts.
716 These define appropriate logical names and
718 [.SYSTEST] Contains the installation verification procedure.
719 [.HTML] Contains the HTML rendition of the manual pages.
722 Additionally, install will add the following directories under
723 OPENSSLDIR (the directory given with --openssldir or its default)
726 certs Initially empty, this is the default location
727 for certificate files.
728 private Initially empty, this is the default location
729 for private key files.
730 misc Various scripts.
732 Package builders who want to configure the library for standard
733 locations, but have the package installed somewhere else so that
734 it can easily be packaged, can use
736 $ make DESTDIR=/tmp/package-root install # Unix
737 $ mms/macro="DESTDIR=TMP:[PACKAGE-ROOT]" install ! OpenVMS
739 The specified destination directory will be prepended to all
740 installation target paths.
742 Compatibility issues with previous OpenSSL versions:
744 * COMPILING existing applications
746 OpenSSL 1.1.0 hides a number of structures that were previously
747 open. This includes all internal libssl structures and a number
748 of EVP types. Accessor functions have been added to allow
749 controlled access to the structures' data.
751 This means that some software needs to be rewritten to adapt to
752 the new ways of doing things. This often amounts to allocating
753 an instance of a structure explicitly where you could previously
754 allocate them on the stack as automatic variables, and using the
755 provided accessor functions where you would previously access a
756 structure's field directly.
758 Some APIs have changed as well. However, older APIs have been
759 preserved when possible.
761 Environment Variables
762 ---------------------
764 A number of environment variables can be used to provide additional control
765 over the build process. Typically these should be defined prior to running
766 config or Configure. Not all environment variables are relevant to all
770 The name of the ar executable to use.
773 Use a different build file name than the platform default
774 ("Makefile" on Unixly platforms, "makefile" on native Windows,
775 "descrip.mms" on OpenVMS). This requires that there is a
776 corresponding build file template. See Configurations/README
777 for further information.
780 The compiler to use. Configure will attempt to pick a default
781 compiler for your platform but this choice can be overridden
782 using this variable. Set it to the compiler executable you wish
783 to use, e.g. "gcc" or "clang".
786 This environment variable has the same meaning as for the
787 "--cross-compile-prefix" Configure flag described above. If both
788 are set then the Configure flag takes precedence.
791 The name of the nm executable to use.
793 OPENSSL_LOCAL_CONFIG_DIR
794 OpenSSL comes with a database of information about how it
795 should be built on different platforms as well as build file
796 templates for those platforms. The database is comprised of
797 ".conf" files in the Configurations directory. The build
798 file templates reside there as well as ".tmpl" files. See the
799 file Configurations/README for further information about the
800 format of ".conf" files as well as information on the ".tmpl"
802 In addition to the standard ".conf" and ".tmpl" files, it is
803 possible to create your own ".conf" and ".tmpl" files and store
804 them locally, outside the OpenSSL source tree. This environment
805 variable can be set to the directory where these files are held
806 and will have Configure to consider them in addition to the
810 The name of the Perl executable to use when building OpenSSL.
813 The command string for the Perl executable to insert in the
814 #! line of perl scripts that will be publically installed.
815 Default: /usr/bin/env perl
816 Note: the value of this variable is added to the same scripts
817 on all platforms, but it's only relevant on Unix-like platforms.
820 The name of the rc executable to use. The default will be as
821 defined for the target platform in the ".conf" file. If not
822 defined then "windres" will be used. The WINDRES environment
823 variable is synonymous to this. If both are defined then RC
827 The name of the ranlib executable to use.
835 The Configure script generates a Makefile in a format relevant to the specific
836 platform. The Makefiles provide a number of targets that can be used. Not all
837 targets may be available on all platforms. Only the most common targets are
838 described here. Examine the Makefiles themselves for the full list.
841 The default target to build all the software components.
844 Remove all build artefacts and return the directory to a "clean"
848 Rebuild the dependencies in the Makefiles. This is a legacy
849 option that no longer needs to be used in OpenSSL 1.1.0.
852 Install all OpenSSL components.
855 Only install the OpenSSL software components.
858 Only install the OpenSSL documentation components.
861 Only install the OpenSSL man pages (Unix only).
864 Only install the OpenSSL html documentation.
867 Prints a list of all the self test names.
870 Build and run the OpenSSL self tests.
873 Uninstall all OpenSSL components.
876 This is a developer option. If you are developing a patch for
877 OpenSSL you may need to use this if you want to update
878 automatically generated files; add new error codes or add new
879 (or change the visibility of) public API functions. (Unix only).
881 Note on multi-threading
882 -----------------------
884 For some systems, the OpenSSL Configure script knows what compiler options
885 are needed to generate a library that is suitable for multi-threaded
886 applications. On these systems, support for multi-threading is enabled
887 by default; use the "no-threads" option to disable (this should never be
890 On other systems, to enable support for multi-threading, you will have
891 to specify at least two options: "threads", and a system-dependent option.
892 (The latter is "-D_REENTRANT" on various systems.) The default in this
893 case, obviously, is not to include support for multi-threading (but
894 you can still use "no-threads" to suppress an annoying warning message
895 from the Configure script.)
897 OpenSSL provides built-in support for two threading models: pthreads (found on
898 most UNIX/Linux systems), and Windows threads. No other threading models are
899 supported. If your platform does not provide pthreads or Windows threads then
900 you should Configure with the "no-threads" option.
902 Note on shared libraries
903 ------------------------
905 For most systems the OpenSSL Configure script knows what is needed to
906 build shared libraries for libcrypto and libssl. On these systems
907 the shared libraries will be created by default. This can be suppressed and
908 only static libraries created by using the "no-shared" option. On systems
909 where OpenSSL does not know how to build shared libraries the "no-shared"
910 option will be forced and only static libraries will be created.
912 Note on random number generation
913 --------------------------------
915 Availability of cryptographically secure random numbers is required for
916 secret key generation. OpenSSL provides several options to seed the
917 internal PRNG. If not properly seeded, the internal PRNG will refuse
918 to deliver random bytes and a "PRNG not seeded error" will occur.
919 On systems without /dev/urandom (or similar) device, it may be necessary
920 to install additional support software to obtain a random seed.
921 Please check out the manual pages for RAND_add(), RAND_bytes(), RAND_egd(),
922 and the FAQ for more information.
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