f0a33e7b28
GNU readline switched to GPLv3+ in version 6.0, which is incompatible with the chrony's GPLv2 license. Drop support for the readline library. Only editline is supported now.
200 lines
6.9 KiB
Text
200 lines
6.9 KiB
Text
// This file is part of chrony
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//
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// Copyright (C) Richard P. Curnow 1997-2003
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// Copyright (C) Miroslav Lichvar 2009-2016
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//
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of version 2 of the GNU General Public License as
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// published by the Free Software Foundation.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License along
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// with this program; if not, write to the Free Software Foundation, Inc.,
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// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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= Installation
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The software is distributed as source code which has to be compiled. The source
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code is supplied in the form of a gzipped tar file, which unpacks to a
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subdirectory identifying the name and version of the program.
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A C compiler (e.g. `gcc` or `clang`) and GNU Make are needed to build `chrony`.
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The following libraries with their development files, and programs, are needed
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to enable optional features:
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* pkg-config: detection of development libraries
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* Nettle, NSS, or LibTomCrypt: secure hash functions (`SECHASH`)
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* libcap: dropping root privileges on Linux (`DROPROOT`)
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* libseccomp: system call filter on Linux (`SCFILTER`)
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* GnuTLS and Nettle: Network Time Security (`NTS`)
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* Editline: line editing in `chronyc` (`READLINE`)
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* timepps.h header: PPS reference clock
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* Asciidoctor: documentation in HTML format
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* Bash: test suite
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The following programs are needed when building `chrony` from the git
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repository instead of a released tar file:
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* Asciidoctor: manual pages
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* Bison: parser for chronyc settime command
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After unpacking the source code, change directory into it, and type
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----
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./configure
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----
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This is a shell script that automatically determines the system type. There is
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an optional parameter `--prefix`, which indicates the directory tree where the
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software should be installed. For example,
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----
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./configure --prefix=/opt/free
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----
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will install the `chronyd` daemon into `/opt/free/sbin` and the `chronyc`
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control program into `/opt/free/bin`. The default value for the prefix is
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`/usr/local`.
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The `configure` script assumes you want to use `gcc` as your compiler. If you
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want to use a different compiler, you can configure this way:
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----
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CC=cc ./configure --prefix=/opt/free
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----
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for Bourne-family shells, or
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----
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setenv CC cc
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setenv CFLAGS -O
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./configure --prefix=/opt/free
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----
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for C-family shells.
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If the software cannot (yet) be built on your system, an error message will be
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shown. Otherwise, `Makefile` will be generated.
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On Linux, if development files for the libcap library are available, `chronyd`
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will be built with support for dropping root privileges. On other systems no
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extra library is needed. The default user which `chronyd` should run as can be
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specified with the `--with-user` option of the `configure` script.
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If development files for the POSIX threads library are available, `chronyd`
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will be built with support for asynchronous resolving of hostnames specified in
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the `server`, `peer`, and `pool` directives. This allows `chronyd` operating as
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a server to respond to client requests when resolving a hostname. If you don't
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want to enable the support, specify the `--disable-asyncdns` flag to
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`configure`.
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If development files for the https://www.lysator.liu.se/~nisse/nettle/[Nettle],
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https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS[NSS], or
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http://www.libtom.net/LibTomCrypt/[libtomcrypt] library are available,
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`chronyd` will be built with support for other cryptographic hash functions
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than MD5, which can be used for NTP authentication with a symmetric key. If you
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don't want to enable the support, specify the `--disable-sechash` flag to
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`configure`.
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If development files for the editline library are available,
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`chronyc` will be built with line editing support. If you don't want this,
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specify the `--disable-readline` flag to `configure`.
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If a `timepps.h` header is available (e.g. from the
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http://linuxpps.org[LinuxPPS project]), `chronyd` will be built with PPS API
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reference clock driver. If the header is installed in a location that isn't
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normally searched by the compiler, you can add it to the searched locations by
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setting the `CPPFLAGS` variable to `-I/path/to/timepps`.
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The `--help` option can be specified to `configure` to print all options
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supported by the script.
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Now type
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----
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make
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----
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to build the programs.
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If you want to build the manual in HTML, type
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----
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make docs
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----
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Once the programs have been successfully compiled, they need to be installed in
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their target locations. This step normally needs to be performed by the
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superuser, and requires the following command to be entered.
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----
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make install
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----
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This will install the binaries and man pages.
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To install the HTML version of the manual, enter the command
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----
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make install-docs
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----
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Now that the software is successfully installed, the next step is to set up a
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configuration file. The default location of the file is _/etc/chrony.conf_.
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Several examples of configuration with comments are included in the examples
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directory. Suppose you want to use public NTP servers from the pool.ntp.org
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project as your time reference. A minimal useful configuration file could be
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----
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pool pool.ntp.org iburst
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makestep 1.0 3
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rtcsync
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----
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Then, `chronyd` can be run. For security reasons, it's recommended to create an
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unprivileged user for `chronyd` and specify it with the `-u` command-line
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option or the `user` directive in the configuration file, or set the default
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user with the `--with-user` configure option before building.
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== Support for system call filtering
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`chronyd` can be built with support for the Linux secure computing (seccomp)
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facility. This requires development files for the
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https://github.com/seccomp/libseccomp[libseccomp] library and the
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`--enable-scfilter` option specified to `configure`. The `-F` option of
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`chronyd` will enable a system call filter, which should significantly reduce
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the kernel attack surface and possibly prevent kernel exploits from `chronyd`
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if it is compromised.
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== Extra options for package builders
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The `configure` and `make` procedures have some extra options that may be
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useful if you are building a distribution package for `chrony`.
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The `--mandir=DIR` option to `configure` specifies an installation directory
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for the man pages. This overrides the `man` subdirectory of the argument to the
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`--prefix` option.
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----
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./configure --prefix=/usr --mandir=/usr/share/man
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----
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to set both options together.
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The final option is the `DESTDIR` option to the `make` command. For example,
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you could use the commands
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----
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./configure --prefix=/usr --mandir=/usr/share/man
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make all docs
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make install DESTDIR=./tmp
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cd tmp
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tar cvf - . | gzip -9 > chrony.tar.gz
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----
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to build a package. When untarred within the root directory, this will install
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the files to the intended final locations.
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