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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.
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 or readline 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.
Support for line editing libraries
chronyc can be built with support for line editing, this allows you to use the
cursor keys to replay and edit old commands. Two libraries are supported which
provide such functionality, editline and GNU readline.
Please note that readline since version 6.0 is licensed under GPLv3+ which is
incompatible with chrony's license GPLv2. You should use editline instead if
you don't want to use older readline versions.
The configure script will automatically enable the line editing support if one
of the supported libraries is available. If they are both available, the
editline library will be used.
If you don't want to use it (in which case chronyc will use a minimal command
line interface), invoke configure like this:
./configure --disable-readline other-options...
If you have editline, readline or ncurses installed in locations that aren't
normally searched by the compiler and linker, you need to use extra options:
--with-readline-includes=directory_name
This defines the name of the directory above the one where readline.h is.
readline.h is assumed to be in editline or readline subdirectory of the
named directory.
--with-readline-library=directory_name
This defines the directory containing the libedit.a or libedit.so file, or
libreadline.a or libreadline.so file.
--with-ncurses-library=directory_name
This defines the directory containing the libncurses.a or libncurses.so
file.
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 2018-09-19 16:38:15 CEST
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