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Installation instructions


This software should build on any operating system conformant to POSIX.1-2001 and ISO/IEC 9899:1999 (C99). In addition, the operating system must have an ntp_adjtime(2) call. Also, it must support the IPv6 API defined in RFC 2493 and RFC 2553. Finally, it must support iterating over active UDP interfaces via getifaddrs(3) or some equivalent facility.

You can browse a summary of differences from legacy NTP here:

There are some prerequisites. Libraries need the binary installed to run and in addition, the development headers installed to build.

We need pthreads (It’s optional in POSIX) We need OpenSSL >= 1.0.1 NTS needs TLS1.2 or newer.

The short version

If you are on a Debian or Ubuntu distribution that uses apt-get, or on a Fedora or RedHat distribution that uses yum or dnf, or a Suse distribution that uses yast or zypper, or Gentoo, you can use the ./buildprep script.

In that case, run ./buildprep -n to see what needs to be installed as prerequisites on your system. In order that we have a single point of truth about package requirements, much information about installable-package names that used to live in this file has moved to that script.

If you are using other distributions or OSes, such as macOS, Solaris, or *BSD, you will have to install the build prerequisites by hand on your system. Read the buildprep script to get an idea what packages are required.

buildprep does not attempt to install dependencies for optional components like ntpviz or building documentation unless asked. See buildprep --help for details on available options. asciidoc has a huge tail of dependencies and you probably don’t want it unless you’re planning to modify the documentation. psutil may require different packages depending on whether your base Python version is 2 or 3.


Python 2.x, x >= 6, or Python 3.x, x >= 3

Required to build, and for various scripts such as ntpviz (but see the guidance for packagers in devel/packaging.adoc). Our Python code has been written polyglot to also run with production versions of Python 3. Note that you will need both the ordinary Python installation and Python dev tools, if your OS makes such a distinction.

Some OS distros won't find our installed python libraries.
More info in README-PYTHON.

Required for ntpviz when using Python version 2.6 Install with pip: pip install argparse


Optional for ntpviz. Allows running with ionice() Debian: python-psutil or python3-psutil Ubuntu: python-psutil or python3-psutil Fedora/CentOS: python-psutil CentOS 6: python-psutil in epel ("Extra Packages for Enterprise Linux"). Gentoo: dev-python/psutil SLES: python-psutil


If you are building to supply Stratum 1 time service (that is, with refclocks linked in) you may find that you need the sys/timepps.h file to be installed, depending on which refclocks you enable. This won’t be necessary for pure client (Stratum 2 or higher) installations.

asciidoc, a2x

You will need asciidoc to make HTML and a2x to make manual pages from the documentation masters. Only required if you configured with --enable-doc. Note, you need asciidoc 8.6.0 at minimum. Debian/Ubuntu: asciidoc Fedora/CentOS: asciidoc (CentOS/RHEL6 has only 8.4.5, you must upgrade) Gentoo: app-text/asciidoc SLES: asciidoc

Local copy of DocBook stylesheets: Optional: Prevents documentation build failures when your Internet is down Debian/Ubuntu: docbook-xsl Fedora/CentOS: docbook-xsl-stylesheets Gentoo: app-text/docbook-xsl-stylesheets SLES: docbook-xsl-stylesheets - pulled in by asciidoc

wget: Optional, used by ntpleapfetch

Basic Installation

These are generic Unix installation instructions. Some notes on specific platforms follow this section.

Under Unix, the simplest way to compile this package is:

  1. cd to the directory containing the package’s source code.

  2. Run ./buildprep as root to get your prerequisites installed.

  3. Run ./waf configure to configure the package for your system. You may want to add configuration options after the verb 'configure'; see below. NOTE: if you will be using any local reference clocks (GPS, PTP, SHM, etc.) then you need to configure for them by running the command: ./waf configure --refclock=all.

  4. Run ./waf build to compile the package.

  5. Run ./waf install to install the programs and any data files and documentation.

  6. You can uninstall cleanly by running ./waf uninstall as root.

  7. Look under "Boot script setup" in wscript for how to set up boot time startup of ntpd; this will vary according to your init system.

  8. You can remove the program binaries and object files from the source code directory by running ./waf clean.

  9. To also remove the files that ./waf configure created (so you can configure and compile the package for a different kind of computer), run ./waf distclean.


When building the NTPsec suite using gcc under Solaris, you may see prototype-mismatch warnings involving adjtime(2). These warnings are functionally harmless and can be ignored. They reflect an unfortunate choice by Solaris not to const the function’s first argument as do other implementations.

Build Bugs

The configuration system occasionally acts up during builds on new platforms. If you see the message "Compilation check failed but include exists!" this means that an attempt to compile a small test program using the include header mentioned on the previous line failed, but waf configure then found that despite this the header file exists on your system.

When this happens, it is likely that the header has prerequisites on your system that waf configure doesn’t know about - that is, other headers always need to be included before it in C programs. Please report this as a bug, along with your platform details.

Source build limitations

When you do an install from source, no attempt is made to generate an /etc/ntp.conf for you. The reason is that we, the maintainers, can’t know what pool host you are authorized to use. If you have an existing ntp.conf from a legacy version, you can expect it to work.

Due to a limitation of the Python distutils library, if you install from the source distribution with prefix set to a value other than /usr (in particular, if it’s the default value /usr/local), that prefix will be honored only if the corresponding Python library directory already exists. Otherwise, under Linux, the install will drop the ntp Python library in /usr/lib. This layout may violate the Linux File Hierarchy Standard.

You should have neither issue if you install from an OS distribution’s binary package.

Installation Names

By default, waf install will install the package’s files in /usr/local/bin, /usr/local/man, etc. You can specify an installation prefix other than /usr/local by giving waf the option --prefix=PATH.

You should read the section "Path problems with the test tools" in devel/testing.adoc before setting a non-default prefix.

There is a separate --destdir option that changes the root of the entire installation hierarchy, prepending all paths. It defaults to /. You might, say, use --destdir=/tmp/ntp for a test install to see what the installation paths look like without running as root or touching system directories.

NB: --destdir is specified at install time, --prefix is specified at configure time and saved until install time.

Qualification testing

Details on how to qualify NTPsec if you’ve never used it before are at devel/testing.adoc.

Strict compatibility mode

There have been a handful of forward-incompatible changes from NTP Classic. These are unlikely to affect normal operation. However, there is a configure operation, --enable-classic-mode, that restores certain legacy behaviors. This is not recommended, as it makes the code a little bulkier and slower.

Here’s what it currently does:

  • Reverts logging to the old format that designates clocks with magic addresses rather than the driver shortname and unit number.

  • Enables declaring generic-driver refclocks with the old magic-address syntax (but the new syntax won’t work for these, though it will for other driver types).

  • Reverts the default baudrate of the NMEA driver to 4800 (from 9600).

  • Restores the old (non-RFC 3339) format of logfile timestamps.

Other behaviors may be added in future releases.

Optional Features

The waf builder accepts --enable-FEATURE options to where FEATURE indicates an optional part of the package. Do waf --help for a list of options.

refclocks are enabled with --refclock=<n1,n2,n3..> or --refclock=all waf configure --list will print a list of available refclocks.


Drop root privileges as early as possible. This requires the refclock devices to be owned by the same owner or group that ntpd will be running under (most likely that group will be named "ntp") so that it can still open the devices. This can be accomplished by adding GROUP="ntp" or OWNER="ntp" to the udev rules that create the device symlinks for the refclocks.

Developer options


Enable GDB debugging symbols.

Operation Controls

The waf builder recognizes the following options to control how it operates.


Print a summary of the options to waf configure, and exit.


Print the version of waf used to generate the configure script, and exit.


Set up a cross-compile environment for the target architecture. At minimum it will need OpenSSL headers/libraries and Python headers/libraries.

Configure NTPSec with:

PYTHON_VERSION=2.7 PYTAG=cpython27 pyext_PATTERN="" PYTHON_LDFLAGS='-lpthread -ldl' \
./waf configure --cross-compiler=/path/to/your/cross/cc \
--pythondir=/usr/local/lib/python2.7/dist-packages --pythonarchdir=/usr/local/lib/python2.7/dist-packages

There are also --cross-cflags and --cross-ldflags to supply the cross compiler with appropriate values.


If you want to generate the ntpviz graphs regularly, add these lines to your root crontab:

53 * * * * cd /usr/local/src/NTP/ntpsec/ntpstats; ./ntpviz -p 1 -o day
45 11,23 * * * cd /usr/local/src/NTP/ntpsec/ntpstats; ./ntpviz -p 7 -o week
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