= GPSD Installation Instructions
:author: Eric S. Raymond
:date: 24 August 2021
:description: Steps for installing GPSD and verifying its performance.
:docinfodir: www
:email: <esr@thyrsus.com>
:keywords: GPSD, GPS, installation
:robots: index,follow
:sectlinks:
:toc: macro

include::www/inc-menu.adoc[]

Here are the steps for installing GPSD and verifying its performance.
They assume you have GPSD available as an installable binary package.

Most of these installation instructions are generic to POSIX.

Instructions for building GPSD from source (including cross-building), and
some special notes on installation on *BSD, WSL, OS X, macOS, and the
Raspberry Pi are in the file "build.adoc" in the source distribution.

== Check that your GPS is live and you can get data from it

Start by making sure you can get data from your GPS, otherwise the later
steps will be very frustrating.  In this command:

      stty -F /dev/ttyXXX ispeed 4800 && cat </dev/ttyXXX

replace ttyXXX with the filename of the port.  This will probably be
either /dev/ttyUSB0 or /dev/ttyS0. If you are on a *BSD Unix or MacOS X,
replace -F with -f.

When you run this command, you should see text lines beginning with $
come to stdout (possibly after a short initial burst of binary
garbage).  If you don't see this, you may have OS-level problems with
your serial support, but more likely have the wrong device.  Look
again.

If you have trouble with the preceding step, check your cabling
first.  Verify that the device is connected and that its power LED
(if it has one) is lit.

If you seem to have some sort of serial-device problem, check that
your kernel properly supports the device you are using.  For GPSes
using an RS-232 port (which is no longer common) you will need
serial-port support compiled into your kernel.  Various USB-to-serial
adapter chips found in GPSes require specific drivers.

Under a stock Linux kernel these will all be loaded on demand when
the USB system sees the appropriate vendor/product ID combinations.
See build.adoc for instructions relating to custom kernels.

== Check that your system configuration will allow GPSD to work

Ensure that device permissions will enable gpsd to read from and write
to GPS devices even after it drops root privileges.  If you are
running Fedora Core, Ubuntu, or stock Debian you can skip this step,
as the stock configuration has the right properties.

gpsd requires two things: (1) that GPS devices have group read and
write enabled, and (2) all of them have the same group ID as a
prototypical device, typically /dev/ttyS0 under Linux or /dev/tty00
under *BSD. It does not actually matter what the owning group is, as
gpsd will look this up on startup.  Alternatively, (3), you can set a
fallback group with the gpsd-group option in case the prototype is not
found: this should be the group that has write access to serial
devices.  On Debian and derivatives including Ubuntu this is "dialout";
on Gentoo/Fedora/openSuse it is "uucp".

Before dropping privileges, gpsd will ensure that it has access to
devices given to it on the command line by forcing their group read
and write permissions on.

On a Linux with udev, check the files in /etc/udev/permissions.d to
ensure that /dev/tty* devices are all created with the same group
and with 0660 permissions.

When gpsd drops privileges, its default is to set uid to 'nobody' and
group to the owning group of the prototype device (the configure
option gpsd-user=foo will cause gpsd to change to 'foo'
instead).

If your system has the Linux hotplug facility installed you can skip
the permission-setting part; the hotplug scripts will force the
permissions for you.  You still have to make sure all the tty devices
are in the same group.

== Check your installation prerequisites

A minimum build of GPSD can run pretty close to the metal; all it
absolutely needs is the C runtime support. The test clients and
various additional features have additional prerequisites:

|===============================================================================
|asciidoctor                  | to build the documentation and www
|dbus                         | gpsd will issue DBUS notifications
|gnuplot                      | to plot gpsprof output.
|GTK                          | for python-GI
|libtinfo5                    | low-level terminfo library (see below)
|libusb-1.0.x or later        | for older Garmin USB devices
|ncurses                      | for cgps and gpsmon clients
|pps-tools                    | for PPS time keeping
|PyGObject                    | for xps and xgpsspeed clients (see below)
|pyserial                     | for ubxtool and zerk in direct-serial mode
|python2.x(x>=6) or 3.y(y>=2) | required for various clients and utilities
|python-cairo                 | for python-GI
|Qt                           | libQgpsmm depends on this
|===============================================================================

Some ncurses packages contain the terminfo library; some break it out
separately as libtinfo5 or libtinfo.

The PyGObject package goes by several names, and is split up into sub
packages different ways, depending on the distribution.  Sometimes
python-gi, python-gobject, python-cairo, etc.  The packages also need
the underlying system libraries (GTK, GLib, etc.)

The asynchronous python module (gps/aiogps.py) and its example client
(example_aiogps.py) require Python 3.6+.

See below for more specific module requirements in the individual
distribution instructions.

== Installing gpsd

Before installing gpsd on your system, make sure that all parts of any
previous installation have been removed.  Do not mix gpsd parts from
different sources.  The gpsd clients and the server must be of the same
version.

=== Install your distributions package(s)

Up-to-date gpsd packages are generally available for Linux distributions
including Debian and derivatives (including Ubuntu and Mint), Fedora and
derivatives (including CentOS), openSUSE, PCLinuxOS, Mageia, Gentoo, and
Slackware.  In the embedded space, CeroWRT and Yocto carry GPSD. The
GPSD package in the FreeBSD ports tree is also reliably up to date.
Even if your distribution is not on this list, it is quite likely GPSD
has already been packaged for it.

Whatever distribution you are running, the name of the core GPSD
package containing the service daemon is almost certainly "gpsd".
However, many distributions break up GPSD into separate installable
packages for the core daemon and clients; you should search your
repository index for anything with gpsd as a prefix.

== How to test the software

1. You should start gpsd while running as root.  Starting as a normal
user will cause some loss of functionality.  Starting with sudo will cause
a different loss of functionality.

2. Start gpsd.  You'll need to give it as an argument a path to
a serial or USB port with a GPS attached to it.  Your test command
should look something like this:

       gpsd -D 5 -N -n /dev/ttyUSB0

3. Once gpsd is running, telnet to port 2947. You should see a
greeting line that's a JSON object describing GPSD's version.
Now plug in your GPS (or AIS receiver, or RTCM2 receiver).

4. Type '?WATCH={"enable":true,"json":true};' to start raw and
watcher modes.  You should see lines beginning with '{' that are
JSON objects representing reports from your GPS; these are reports
in GPSD protocol.

5. Start the xgps or cgps client.  Calling it with no arguments
should do the right thing.  You should see a display panel with
position/velocity-time information, and a satellite display.  The
displays won't look very interesting until the GPS acquires satellite
lock.

6. Have patience.  If you are cold-starting a new GPS, it may take 15-20
minutes after it gets a good skyview for it to download an ephemeris
for each satellites in view, and the current almanac.  Only then can it
deliver the best quality fixes.

7. A FAQ and troubleshooting instructions can be found at the GPSD
project site.

== Once you have verified correct operation

1. If you installed from a '.deb' package under Debian or a
Debian-derived system, you may need to `dpkg-reconfigure -plow gpsd' to
enable the hotplug magic ("Start gpsd automatically").

2. Check out the list of supported hardware at the Hardware page on
the GPSD project's website. If your GPS isn't on the list, please send
us information to add a new line to the table.  Directions are
included on that page. We can also use updates of the latest version
number known to work with hardware already supported.

3. GPSD includes gpsd.php, a PHP script, that you can use to generate
a PHP status page for your GPS if you wish. (It may not be in the
core package.)  It should be manually copied to your HTTP document
directory.  The first time it's invoked, it will generate a file
called 'gpsd_config.inc' in that directory containing configuration
information; edit to taste.

4. There are other non-essential scripts that may be useful; these
are in the contrib/ directory of the source.  They may not be available
in the packages available from distributions.

For special instructions related to using GPSD for time service, see the
GPSD Time Service HOWTO in the distribution or on the web.

== Raspberry Pi tips

Any USB connected GPS that is known to work with gpsd will work fine on
the RasPi.  No special instructions apply.

A very popular option is to install the AdaFruit Ultimate GPS HAT.  With
this GPS you also get a good 1PPS signal.  This works as any other GPS
with gpsd, but there are two things to note.  The GPS takes over the
serial console: /dev/ttyAMA0.  The PPS signal will be on GPIO Pin #4.

Only three specific changes need to be made to make the HAT work.  First
in the file /boot/cmdline.txt, remove this part "console=ttyAMA0,115200
kgdboc=ttyAMA0,115200".  That frees the serial port from console use so
the GPS can use it.

Second you need to tell the boot process to load the pps_gpio module
and attach /dev/pps0 to GPIO pin 4.  Do that by adding this line
to the bottom of /boot/config.txt: dtoverlay=pps-gpio,gpiopin=4

Reboot so those changes take effect.

Run gpsd like this:

--------------------------------------------------------------
~ # gpsd -D 5 -N -n /dev/ttyAMA0 /dev/pps0
--------------------------------------------------------------

If you are on the RasPi with gpsd version 3.17, or above, /dev/pps0 can
be autodetected, and used for PPS if available.

gpsd 3.17 and up only:

--------------------------------------------------------------
~ # gpsd -D 5 -N -n /dev/ttyAMA0
--------------------------------------------------------------

You can verify gpsd is using the PPS by running ntpshmmon:

--------------------------------------------------------------
~ # ntpshmmon
#      Name   Seen@                Clock                Real               L Prec
sample NTP0 1461619703.641899335 1461619703.445224418 1461619703.000000000 0  -1
sample NTP2 1461619703.642203397 1461619702.999262204 1461619703.000000000 0 -20
sample NTP0 1461619704.142097363 1461619703.445224418 1461619703.000000000 0  -1
sample NTP2 1461619704.142204134 1461619703.999258157 1461619704.000000000 0 -20
--------------------------------------------------------------

If you do not see NTP2 then you misconfigured the pps_gpio driver.

The serial time is provided to ntpd on NTP0, the PPS time is on NTP2, not
on NTP1 like described earlier.  So your ntp.conf will need to be adjusted
from:

--------------------------------------------------------------
# GPS PPS reference (NTP1)
server 127.127.28.1 prefer
fudge 127.127.28.1 refid PPS
--------------------------------------------------------------

To:

--------------------------------------------------------------
# GPS PPS reference (NTP2)
server 127.127.28.2 prefer
fudge 127.127.28.2 refid PPS
--------------------------------------------------------------

Now proceed as for any other operating system to use gpsd.

Be sure to validate that your PPS signal is not offset by the pulse
width.  That would mean gpsd is using the wrong edge.

Detailed instructions are available from their website:
https://learn.adafruit.com/adafruit-ultimate-gps-hat-for-raspberry-pi/

You will need to dig deeper to make the PPS work, here is a good reference:
http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

== Special Notes for Windows

Only Windows Subsystem for Linux 1 provides a reasonable means
of running gpsd at this time. WSL2 lacks a GUI, USB and serial
support making it unsuitable at this time.

=== About WSL 1

WSL 1 is  a component of Microsoft
Windows that implements an alternate kernel. Linux
distributions, notably Alpine, Debian, Kali, OpenSUSE, and
Ubuntu may run on top of it.

There are some issues known which affect gpsd.

* /dev/ttyS* nodes have a 1 indexed number, like in MS Windows.
* Windows 10 may attempt to use your GPS itself.
* Older pl2303 (knockoff) serial chipsets are no longer supported \
  in Windows 10

=== Installing a Linux distribution on WSL 1 or WSL 2

1. Install a Linux distribution by clicking on the `Microsoft Store` \
Icon in the taskbar.
2. Click on the search icon (it is a magnifying glass).
3. Type in 'Linux' or the name of a supported distribution. (see list)
4. Click on the icon of your chosen Linux Distribution
5. Click 'Get' then click 'Install' and busy-wait.
6. Click on the start menu and scroll to your Linux distribution and \
click it.
7. Follow the distribution-specific on-screen instructions to finish \
installing your Linux distribution.

=== Recommended packages

Due to current WSL limitations, it is recommended at this time that you
only install the equivalent of the following packages on your distribution.

----
Python
SCons (preferably 3.0+)
ncurses-dev (to build/run cgps and gpsmon)
asciidoctor (to build the documentation)
----

Optionally, the following packages might also be installed
----
pyserial (for direct control of UBlox GPS and GREIS devices)
gnuplot (to generate graphs of gpsprof data)
libusb-dev (to possibly use crusty old Garmin GPS receivers)
git (if building from the development sources)
----

=== Building on WSL 1 or WSL 2

Follow instructions in the distro-specific section in the file
*build.adoc*.
