Getting Started
===============

Selecting the right version
---------------------------

Gluon's releases are managed using `Git tags`_. If you are just getting
started with Gluon we recommend to use the latest stable release of Gluon.

Take a look at the `list of gluon releases`_ and notice the latest release,
e.g. *v2021.1*. Always get Gluon using git and don't try to download it
as a Zip archive as the archive will be missing version information.

Please keep in mind that there is no "default Gluon" build; a site configuration
is required to adjust Gluon to your needs. Due to new features being added (or
sometimes being removed) the format of the site configuration changes slightly
between releases. Please refer to our release notes for instructions to update
an old site configuration to a newer release of Gluon.

An example configuration can be found in the Gluon repository at *docs/site-example/*.

.. _Git tags: https://git-scm.com/book/en/v2/Git-Basics-Tagging
.. _list of gluon releases: https://github.com/freifunk-gluon/gluon/releases

Dependencies
------------
To build Gluon, several packages need to be installed on the system. On a
freshly installed Debian Stretch system the following packages are required:

* `git` (to get Gluon and other dependencies)
* `subversion`
* `python3`
* `build-essential`
* `gawk`
* `unzip`
* `libncurses-dev` (actually `libncurses5-dev`)
* `libz-dev` (actually `zlib1g-dev`)
* `libssl-dev`
* `wget`
* `time` (built-in `time` doesn't work)
* `qemu-utils`

We also provide a container environment that already tracks all these dependencies. It quickly gets you up and running, if you already have either Docker or Podman installed locally.

::

  ./scripts/container.sh

Building the images
-------------------

To build Gluon, first check out the repository. Replace *RELEASE* with the
version you'd like to checkout, e.g. *v2021.1*.

::

  git clone https://github.com/freifunk-gluon/gluon.git gluon -b RELEASE

This command will create a directory named *gluon/*.
It might also tell a scary message about being in a *detached state*.
**Don't panic!** Everything's fine.
Now, enter the freshly created directory::

  cd gluon

It's time to add (or create) your site configuration. If you already
have a site repository, just clone it::

  git clone https://github.com/freifunk-alpha-centauri/site-ffac.git site

If you want to build a new site, create a new git repository *site/*::

  mkdir site
  cd site
  git init

Copy *site.conf*, *site.mk* and *i18n* from *docs/site-example*::

  cp ../docs/site-example/site.conf .
  cp ../docs/site-example/site.mk .
  cp -r ../docs/site-example/i18n .

Edit these files as you see fit and commit them into the site repository.
Extensive documentation about the site configuration can be found at:
:doc:`site`. The
site directory should always be a git repository by itself; committing site-specific files
to the Gluon main repository should be avoided, as it will make updates more complicated.

Next go back to the top-level Gluon directory and build Gluon\ [#make_update]_::

  cd ..
  make update                       # Get other repositories used by Gluon
  make GLUON_TARGET=ath79-generic   # Build Gluon

In case of errors read the messages carefully and try to fix the stated issues
(e.g. install missing tools not available or look for Troubleshooting_ in the wiki.

.. _Troubleshooting: https://github.com/freifunk-gluon/gluon/wiki/Troubleshooting

``ath79-generic`` is the most common target and will generate images for most of the supported hardware.
To see a complete list of supported targets, call ``make`` without setting ``GLUON_TARGET``.

To build all targets use a loop like this::

  for TARGET in $(make list-targets); do
    make GLUON_TARGET=$TARGET
  done

You should generally reserve 5GB of disk space and additionally about 10GB for each `GLUON_TARGET`.

The built images can be found in the directory `output/images`. Of these, the `factory`
images are to be used when flashing from the original firmware a device came with,
and `sysupgrade` is to upgrade from other versions of Gluon or any other OpenWrt-based
system.

**Note:** The images for some models are identical; to save disk space, symlinks are generated instead
of multiple copies of the same image. If your webserver's configuration prohibits following
symlinks, you can use the following command to resolve these links while copying the images::

  cp -rL output/images /var/www

The directory `output/debug` contains a compressed kernel image for each
architecture.
These can be used for debugging and should be stored along with the images to
allow debugging of kernel problems on devices in the field.
See :ref:`Debugging <dev-debugging-kernel-oops>` for more information.

.. rubric:: Footnotes

.. [#make_update] ``make update`` only needs to be called again after updating the
  Gluon repository (using ``git pull`` or similar) or after changing branches,
  not for each build. Running it more often than necessary is undesirable, as
  the update will take some time, and may undo manual modifications of the
  external repositories while developing on Gluon.

  See :ref:`working-with-repositories` for more information.

Cleaning the build tree
.......................

There are two levels of `make clean`::

  make clean GLUON_TARGET=ath79-generic

will ensure all packages are rebuilt for a single target. This is usually not
necessary, but may fix certain kinds of build failures.

::

  make dirclean

will clean the entire tree, so the toolchain will be rebuilt as well, which will take a while.

opkg repositories
-----------------

Gluon is mostly compatible with OpenWrt, so the normal OpenWrt package repositories
can be used for Gluon as well.

This is not true for kernel modules; the Gluon kernel is incompatible with the
kernel of the default OpenWrt images. Therefore, Gluon will not only generate images,
but also an opkg repository containing all core packages provided by OpenWrt,
including modules for the kernel of the generated images.

Signing keys
............

Gluon does not support HTTPS for downloading packages; fortunately, opkg deploys
public-key cryptography to ensure package integrity.

The Gluon images will contain public keys from two sources: the official OpenWrt keyring
(to allow installing userspace packages) and a Gluon-specific key (which is used
to sign the generated package repository).

OpenWrt will handle the generation and handling of the keys itself.
When making firmware releases based on Gluon, it might make sense to store
the keypair, so updating the module repository later is possible.
In fact you should take care to reuse the same opkg keypair, so you don't pollute the key
store (see ``/etc/opkg/keys``) on the node.

The signing-key is stored at ``openwrt/key-build.pub``, ``openwrt/key-build``,
``key-build.ucert`` and  ``key-build.ucert.revoke``.

The ``openwrt`` directory is the Git checkout, that gets created after calling ``make update``.
After making a fresh clone copy the key files to the aforementioned locations.

.. _getting-started-make-variables:

Make variables
--------------

Gluon's build process can be controlled by various variables. They can
usually be set on the command line or in ``site.mk``.

Common variables
................

GLUON_AUTOUPDATER_BRANCH
  Overrides the default branch of the autoupdater set in ``site.conf``. For the ``make manifest`` command,
  ``GLUON_AUTOUPDATER_BRANCH`` defines the branch to generate a manifest for.

GLUON_AUTOUPDATER_ENABLED
  Set to ``1`` to enable the autoupdater by default for newly installed nodes.

GLUON_DEPRECATED
  Controls whether images for deprecated devices should be built. The following
  values are supported:

  - ``0``: Do not build any images for deprecated devices.
  - ``upgrade``: Only build sysupgrade images for deprecated devices.
  - ``full``: Build both sysupgrade and factory images for deprecated devices.

  Usually, devices are deprecated because their flash size is insufficient to
  support future Gluon versions. The recommended setting is ``0`` for new sites,
  and ``upgrade`` for existing configurations (where upgrades for existing
  deployments of low-flash devices are required).

GLUON_LANGS
  Space-separated list of languages to include for the config mode/advanced settings. Defaults to ``en``.
  ``en`` should always be included, other supported languages are ``de`` and ``fr``.

GLUON_PRIORITY
  Defines the priority of an automatic update in ``make manifest``. See :doc:`../features/autoupdater` for
  a detailed description of this value.

GLUON_REGION
  Some devices (at the moment the TP-Link Archer C7) contain a region code that restricts
  firmware installations. Set GLUON_REGION to ``eu`` or ``us`` to make the resulting
  images installable from the respective stock firmware.

GLUON_RELEASE
  Firmware release number: This string is displayed in the config mode, announced
  via respondd/alfred and used by the autoupdater to decide if a newer version
  is available. The same GLUON_RELEASE has to be passed to ``make`` and ``make manifest``
  to generate a correct manifest.

GLUON_TARGET
  Target architecture to build.

Special variables
.................

GLUON_AUTOREMOVE
  Setting ``GLUON_AUTOREMOVE=1`` enables the ``CONFIG_AUTOREMOVE`` OpenWrt setting, which will delete package build
  directories after a package build has finished to save space. This is mostly useful for CI builds from scratch. Do
  not set this flag during development (or generally, when you want you reuse your build tree for subsequent builds),
  as it significantly increases incremental build times.

GLUON_DEBUG
  Setting ``GLUON_DEBUG=1`` will provide firmware images including debugging symbols usable with GDB or
  similar tools. Requires a device or target with at least 16 MB of flash space, e.g. `x86-64`. Unset by default.

GLUON_MINIFY
  Setting ``GLUON_MINIFY=0`` will omit the minification of scripts during the build process. By
  default the flag is set to ``1``. Disabling the flag is handy if human readable scripts on the
  devices are desired for development purposes. Be aware that this will increase the size of the
  resulting images and is therefore not suitable for devices with small flash chips.

GLUON_DEVICES
  List of devices to build. The list contains the Gluon profile name of a device, the profile
  name is the first parameter of the ``device`` command in a target file.
  e.g. ``GLUON_DEVICES="avm-fritz-box-4020 tp-link-tl-wdr4300-v1"``.
  Empty by default to build all devices of a target.

GLUON_IMAGEDIR
  Path where images will be stored. Defaults to ``$(GLUON_OUTPUTDIR)/images``.

GLUON_PACKAGEDIR
  Path where the opkg package repository will be stored. Defaults to ``$(GLUON_OUTPUTDIR)/packages``.

GLUON_OUTPUTDIR
  Path where output files will be stored. Defaults to ``output``.

GLUON_SITEDIR
  Path to the site configuration. Defaults to ``site``.
