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@@ -0,0 +1,165 @@ +Installation + +The software is distributed as source code which has to be compiled. The source +code is supplied in the form of a gzipped tar file, which unpacks to a +subdirectory identifying the name and version of the program. + +A C compiler (e.g. gcc or clang) and GNU Make are needed to build chrony. The +following libraries with their development files, and programs, are needed to +enable optional features: + + o pkg-config: detection of development libraries + + o Nettle, GnuTLS, NSS, or LibTomCrypt: secure hash functions (SECHASH) + + o libcap: dropping root privileges on Linux (DROPROOT) + + o libseccomp: system call filter on Linux (SCFILTER) + + o GnuTLS and Nettle: Network Time Security (NTS) + + o Editline: line editing in chronyc (READLINE) + + o timepps.h header: PPS reference clock + + o Asciidoctor: documentation in HTML format + + o Bash: test suite + +The following programs are needed when building chrony from the git repository +instead of a released tar file: + + o Asciidoctor: manual pages + + o Bison: parser for chronyc settime command + +After unpacking the source code, change directory into it, and type + +./configure + +This is a shell script that automatically determines the system type. There is +an optional parameter --prefix, which indicates the directory tree where the +software should be installed. For example, + +./configure --prefix=/opt/free + +will install the chronyd daemon into /opt/free/sbin and the chronyc control +program into /opt/free/bin. The default value for the prefix is /usr/local. + +The configure script assumes you want to use gcc as your compiler. If you want +to use a different compiler, you can configure this way: + +CC=cc ./configure --prefix=/opt/free + +for Bourne-family shells, or + +setenv CC cc +setenv CFLAGS -O +./configure --prefix=/opt/free + +for C-family shells. + +If the software cannot (yet) be built on your system, an error message will be +shown. Otherwise, Makefile will be generated. + +On Linux, if development files for the libcap library are available, chronyd +will be built with support for dropping root privileges. On other systems no +extra library is needed. The default user which chronyd should run as can be +specified with the --with-user option of the configure script. + +If development files for the POSIX threads library are available, chronyd will +be built with support for asynchronous resolving of hostnames specified in the +server, peer, and pool directives. This allows chronyd operating as a server to +respond to client requests when resolving a hostname. If you don't want to +enable the support, specify the --disable-asyncdns flag to configure. + +If development files for the Nettle, NSS, or libtomcrypt library are available, +chronyd will be built with support for other cryptographic hash functions than +MD5, which can be used for NTP authentication with a symmetric key. If you +don't want to enable the support, specify the --disable-sechash flag to +configure. + +If development files for the editline library are available, chronyc will be +built with line editing support. If you don't want this, specify the +--disable-readline flag to configure. + +If a timepps.h header is available (e.g. from the LinuxPPS project), chronyd +will be built with PPS API reference clock driver. If the header is installed +in a location that isn't normally searched by the compiler, you can add it to +the searched locations by setting the CPPFLAGS variable to -I/path/to/timepps. + +The --help option can be specified to configure to print all options supported +by the script. + +Now type + +make + +to build the programs. + +If you want to build the manual in HTML, type + +make docs + +Once the programs have been successfully compiled, they need to be installed in +their target locations. This step normally needs to be performed by the +superuser, and requires the following command to be entered. + +make install + +This will install the binaries and man pages. + +To install the HTML version of the manual, enter the command + +make install-docs + +Now that the software is successfully installed, the next step is to set up a +configuration file. The default location of the file is /etc/chrony.conf. +Several examples of configuration with comments are included in the examples +directory. Suppose you want to use public NTP servers from the pool.ntp.org +project as your time reference. A minimal useful configuration file could be + +pool pool.ntp.org iburst +makestep 1.0 3 +rtcsync + +Then, chronyd can be run. For security reasons, it's recommended to create an +unprivileged user for chronyd and specify it with the -u command-line option or +the user directive in the configuration file, or set the default user with the +--with-user configure option before building. + +Support for system call filtering + +chronyd can be built with support for the Linux secure computing (seccomp) +facility. This requires development files for the libseccomp library and the +--enable-scfilter option specified to configure. The -F option of chronyd will +enable a system call filter, which should significantly reduce the kernel +attack surface and possibly prevent kernel exploits from chronyd if it is +compromised. + +Extra options for package builders + +The configure and make procedures have some extra options that may be useful if +you are building a distribution package for chrony. + +The --mandir=DIR option to configure specifies an installation directory for +the man pages. This overrides the man subdirectory of the argument to the +--prefix option. + +./configure --prefix=/usr --mandir=/usr/share/man + +to set both options together. + +The final option is the DESTDIR option to the make command. For example, you +could use the commands + +./configure --prefix=/usr --mandir=/usr/share/man +make all docs +make install DESTDIR=./tmp +cd tmp +tar cvf - . | gzip -9 > chrony.tar.gz + +to build a package. When untarred within the root directory, this will install +the files to the intended final locations. + +Last updated 2022-08-29 15:04:33 +0200 |