path: root/README-Guide.md

# Installing and Maintaining the Yocto Autobuilder 2

This guide will walk through how to install a stand-alone autobuilder controller and
worker, and then reconfigure it with new builds, etc.  The guide was written with the
help of Richard Purdie under the context of a headless Ubuntu 18.04.02 Server installation.

## 1) Stand-alone Installation

### 1.1) Basic Requirements

The final outputs of this section are a controller and worker installed in the same
server, ready for trimming back to an individual organization's needs.

 > NOTE: The guide assumes that your host OS has the packages installed to support
 > BitBake for the release(s) you are targeting.  Please refer to the Yocto manual
 > for those packages:
 > https://docs.yoctoproject.org/ref-manual/system-requirements.html#ubuntu-and-debian

The latest version of BuildBot is written in Python 3, so installation via pip3:

```
apt install git build-essential python3-pip virtualenv enchant npm
sudo pip3 install buildbot buildbot-www buildbot-waterfall-view buildbot-console-view buildbot-grid-view buildbot-worker
```

It is recommended to also install `testtools` and `libccpunit-subunit-dev` (via
apt, in this case) on the worker in order for certain image tests to work
correctly (e.g., `core-image-sato-sdk:do_testimage`).

### 1.2) Creating the Autobuilder User's Directory

For a new installation you will need a system user that can run Autobuilder2 as
well as a couple of repositories: Autobuilder2 itself and a helper plugin.  As
root:

```
useradd -m --system pokybuild
cd /home/pokybuild
buildbot create-master -r yocto-controller
buildbot-worker create-worker -r --umask=0o22 yocto-worker localhost example-worker pass
cd yocto-controller
git clone https://git.yoctoproject.org/git/yocto-autobuilder2 yoctoabb
ln -rs yoctoabb/master.cfg master.cfg
cd -
git clone https://git.yoctoproject.org/git/yocto-autobuilder-helper
chown -R pokybuild:nogroup /home/pokybuild
```

Note: depending on the configuration of your system, you may need to
replace "nogroup" with "pokybuild" for the last command to work.

 > **IMPORTANT:** In the above command you created a controller and a worker,
 > which will attempt to join the controller using `pass` as the password.  Feel
 > free to change this, knowing that if you do, you must change the controller's
 > master configuration file to match.

At the end of this, your build user's home directory (e.g., `/home/pokybuild`)
should look like this:

```
yocto-autobuilder-helper
yocto-controller
yocto-controller/yoctoabb
yocto-worker
```

Before proceeding, make sure that the following is added to the
pokybuild user's exports (e.g. in .bashrc), or builds will fail after
being triggered:

```
export LANG=en_US.UTF-8
```

### 1.3) Customizing the Autobuilder Configuration

Next, we need to update the `yocto-controller/yoctoabb/master.cfg` towards the
bottom where the `title`, `titleURL`, and `buildbotURL` are all set.  This is
also where you would specify a different password for binding workers to the
master.

Then, we need to update the `yocto-controller/yoctoabb/config.py` to include our
worker.  In that file, find the line where `workers` is set and
add: ["example-worker"].  _NOTE:_ if your worker's name is different, use that
here.  Section 3.1 discusses how to further refine this list of workers.

 > **IMPORTANT:** You should also take this time to edit the `sharedrepodir`
 > and `publish_dest` variables to be in your build user's home as well.  You
 > will need to create these directories since the related code that will check
 > for if they exist _will not_ also attempt to create them (and the server will
 > crash on start).

Next, if you do not want to edit the original
`yocto-autobuilder-helper/config.json`, you can overlay your own by creating,
for instance, `yocto-autobuilder-helper/config-local.json`.  _NOTE:_ there is no
way for your overlay to _remove_ builders or other attributes, so this route is
really more about extenending the original set of builders.

Here are some suggestions for the sake of :

 1. In the original `config.json`, find all instances of whatever
    `BASE_HOMEDIR` was set to, for example `/home/pokybuild`.  Copy those
    variables to your `config-local.json` replace `/home/pokybuild`
    with `${BASE_HOMEDIR}`.  These will be variables
    like `BUILDPERF_STATEDIR` and `EXTRAPLAINCMDS`.  Set `BASE_HOMEDIR` should
    be your build user's home directory.  (There are shell scripts where this is
    assumed.)
 2. Add `BASE_SHAREDDIR` and `BASE_PUBLISHDIR` such that they are subtrees of
    your `BASE_HOMEDIR`, e.g., `${BASE_HOMEDIR}/srv/autobuilder.yoursite.com`.
 3. Change your `WEBPUBLISH_URL` to match your `config.py` definition
    for `buildbotURL`.
 4. In order for this to work, you must export `ABHELPER_JSON="config.json
    config-local.json"` into the environment of the controller and janitor
    services (the example service scripts included below already have this).

 > NOTE: The way the build step is written, the worker will pull a fresh copy of
 > the helper from the server.  Therefore these configuration files must be
 > committed to the `yocto-autobuilder-helper` repo location you have specified
 > in `yoctoabb/config.py` because the worker is given a build step that pulls
 > from that repo (see `yoctoabb/builders.py`).

Finally, it is time to start the Autobuilder. There are two ways to do this:

### 1.4) Starting the Autobuilder

At this point, you can start your Autobuilder controller, worker, and
janitor in one of two ways: using buildbot manually, or by creating
systemd service files.

#### 1.4.1) Manually Starting the Autobuilder

Run the following from the pokybuild directory:

 1. yocto-autobuilder-helper/janitor/ab-janitor&
 2. buildbot start yocto-controller
 3. buildbot-worker start yocto-worker

#### 1.4.2) Creating Service Files

 1. As root, add the `yocto-*.service` files to `/lib/systemd/system` (See
    Appendix A).
 2. Run: `systemctl daemon-reload`.
 3. You should now be able to successfully start these services (e.g., `sudo
    systemctl start yocto-*`). The controller may take up to 15 seconds to
    start.

### 1.5) Configuring the Worker's Hash Equivalency Server

A key part of the autobuilder setup is the use of a hash equivalency server,
which is started manually on the Yocto hosts. By default, the config.json file
that is pulled along with yocto-autobuilder-helper contains "BB_HASHSERVE =
'typhoon.yocto.io:8686'", which will likely cause a custom autobuilder instance
to hang while trying to communicate with the hash equivalency server. As
mentioned in the previous section, any configuration changes made need to be
committed to the yocto-autobuilder-helper repo that your worker will pull from.
A simple way to start the hash equivalency server and properly configure your
workers is done with the following steps:

1. Clone a copy of the poky distribution repo from
   https://git.yoctoproject.org/cgit/cgit.cgi/poky/
2. Source the oe-init-build-env script into your build directory
3. Run "bitbake-hashserv --bind <PORT>:<IP>" from the build directory
4. Clone a copy of
   https://git.yoctoproject.org/cgit/cgit.cgi/yocto-autobuilder-helper/, then
   create config-local.json by copying config.json (and removing sections that
   aren't required). Since the contents of config-local.json are an overlay for
   those in config.json, this will preserve as much of the initial configuration
   as possible.
5. Change the BB_HASHSERVE value in config-local.json to point to the IP and
   port you specified in step 3
6. Commit the changes in the local yocto-autobuilder-helper repository
7. In <autobuilderpath>/yocto-controller/yoctoabb/config.py, change the entry
   for "yocto-autobuilder-helper" under "repos" to point at your local copy of
   the yocto-autobuilder-helper repository.

After these steps have been taken, the workers that you start should attach to
your local hash equivalency server and be able to complete a target build.

### 1.6) Special Notes for the Worker Environment

The QEMU tap interfaces also need to be generated and owned by the worker's user
(created above).  One way to this is to compile the
`meta/recipes-devtools/qemu/qemu-helper/tunctl.c` file and run it _N_ times on
the worker's host.  See the related `qemu-helper-native` recipe for
instructions.  The resulting executable would be run _N_ times (e.g., 8), so for
example: `sudo tunctl -u $(id -u pokybuild) -g $(id -g pokybuild) -t tun0`.

Another way to create these interface is to let the build fail once, then issue
a command like this from a user with sudo permissions on the worker:

```
sudo /home/pokybuild/yocto-worker/qemuarm/build/scripts/runqemu-gen-tapdevs \
    $(id -u pokybuild) $(id -g pokybuild) \
    8 \
    /home/pokybuild/yocto-worker/qemuarm/build/build/tmp/sysroots-components/x86_64/qemu-helper-native/usr/bin
```

In the above command, we assume the a build named qemuarm failed.  The value of
8 is the number of tap interfaces to create on the worker.

### 1.3) Adding Dedicated Worker Nodes

Running both the controller and the worker together on a single machine
can quickly result in long build times and an unresponsive web UI,
especially if you plan on running any of the more comprehensive builders
(e.g. a-full). Additional workers can be added to the cluster by
following the steps in Section 1, except that the yocto-controller steps
do not need to be repeated. For example, to add a new worker
"ala-blade51" to an Autobuilder cluster with a yocto-controller at the
IP address 147.11.105.72:

1. On the yocto-controller host, add the name of the new worker to a worker
list (or create a new one) e.g. 'workers_wrlx = ["ala-blade51"]' and
make sure that it is added to the "workers" list.

2. On the new worker node:

```
useradd -m --system pokybuild
cd /home/pokybuild
mkdir -p git/trash
buildbot-worker create-worker -r --umask=0o22 yocto-worker 147.11.105.72 ala-blade51 pass
chown -R pokybuild:pokybuild /home/pokybuild
```

 > Note 1: The URL/IP given to the create-worker command must match the
host running the yocto-controller.

 > Note 2: The "pass" argument given to the create-worker command must
match the common "worker_pass" variable set in yocto-controller/yoctoabb/config.py.

3. Once you have finished with configuration, you can run the following
and the worker should successfully join the cluster and become available
to use with the builders, where "yocto-worker/" is the directory created
in step 2:

```
buildbot-worker start yocto-worker/
```



### 1.4) Configuring NFS for the Autobuilder Cluster

The Yocto Autobuilder relies on NFS to distribute a common sstate cache
and other outputs between nodes. A similar configuration can be
deployed by performing the steps given below, which were written for
Ubuntu 18.04.In order for both the controller and worker nodes to be able
to access the NFS share without issue, the "pokybuild" user on all
systems must have the same UID/GID, or sufficient permissions must be
granted on the /srv/autobuilder path (or wherever you modified the config
files to point to). The following instructions assume a controller node
at 147.11.105.72 and a single worker node at 147.11.105.71, but
additional worker nodes can be added as needed (see the previous
section).

1. On the NFS host:

```
sudo apt install -y nfs-kernel-server
sudo mkdir -p /srv/autobuilder/autobuilder.yoctoproject.org/
sudo chown -R pokybuild:pokybuild /srv/autobuilder/autobuilder.yoctoproject.org
```
2. Add the following to /etc/exports, replacing the path and IP fields
   as necessary for each client node:
```
/srv/autobuilder/autobuilder.yoctoproject.org/ 147.11.105.71(rw,sync,no_subtree_check)
```

3. Run
```
sudo systemctl restart nfs-kernel-server
```

4. Adjust the firewall (if required). Example:
```
sudo ufw allow from 147.11.105.71 to any port nfs
```

5. On the client node(s):
```
sudo apt-get install nfs-common
sudo mount 147.11.105.72:/srv/autobuilder/autobuilder.yoctoproject.org/ /srv/autobuilder/autobuilder.yoctoproject.org/
```

## 2) Basics

This section is an overview of operation and a few basic configuration file
relationships.  See Section 3 for more detailed instructions.

### 2.1) Start / Stop the Master and Worker Services

Per the installation in Section 1, both the Master and Worker are running on
the same host and the service files (Appendix A) maintain that assumption.
To start all services:

```
sudo systemctl start yocto-controller yocto-worker yocto-janitor
```

Depending on your web front-end setup (reverse proxy, etc.), you should now
be able to access the BuildBot web UI at the address you specified in 
`yoctoabb/master.cfg` during the installation (e.g., https://localhost:8010).

### 2.2) Build Schedule Types

The `yoctoabb/schedulers.py` defines three main types of build schedules:
triggerable, force, and nightly.  The `wait-quick` and `wait-full` schedules
are triggerable, and each has a specific list of builders that are defined
in the `yoctoabb/config.py` variables: `trigger_builders_wait_quick` and 
`trigger_builders_wait_full`, respectively.  Each of the builders in those
lists also have a force schedule for manual runs.  To run all of them, the 
`a-quick` and `a-full` schedules exist; those names are also the names of
the builders.  Finally, there is one nightly build defined which runs the 
a-quick builder against the `HEAD` of the various master branches to help
maintain freshness of the shared state and downloads caches.

### 2.3) Running a Triggered Build Manually

Assuming you have the controller and worker running, log into the BuildBot
web server on port 8010.  Click on the Builds, Builders left menu.  It should
populate the main panel (right) with a table showing all builders defined
between the `yoctoabb/config.py` and the combination of any config JSON
files loaded for `yocto-autobuilder-helper` (e.g., `config.json`).  The
status of associated workers is shown with a bubble graph on the far
right of this panel.  One should be green,  yours, because it's
associated in `yoctoabb/config.py`, `builder_to_workers` map to that
build by being one of the default builders.

Select one of the builders, for example `beaglebone`.  At the top right,
you will see _Force Build_ (this is a force because all builders in the
`yoctoabb/config.py` `subbuilders` list get a _Force Scheduler_, per 
`yoctoabb/schedulers.py`).  Click that button and fill in your name
(as _you <your@email.com>_) and a reason for forcing a build.  Scroll
to the bottom, setting branches and revisions you want along the way,
and press _Start Build_.

Your browser will automatically navigate to the builder's status as the
worker begins executing the build.

### 2.4) Shared State and Downloads Mirrors

One of the main useful features of having this build server is to speed
up builds at development workstations.  Both of these are defined by the 
`yocto-autobuilder-json/config.json` (or your extra configuration if
following the standalone installation instructions above).  The main
variables are `BASE_SHAREDIR` and `BASE_PUBLISHDIR`.  These two are re-used
in the bitbake configuration variables DLDIR and SSTATEDIR to help individual
builds re-use prior work.  The default is to append `BASE_SHAREDDIR` with 
`current_sources` and `pub/sstate`, respectively.  These paths can be shared
by NFS, HTTPS, etc.  In the example below, we're using https and assuming
that a static file server has been configured to share the former under
`yocto_downloads` and the latter as `yocto_sstate`.  To use these at a
developer's station, set the following in the `build/conf/local.conf`:

```
SSTATE_MIRRORS ?= "file://.* http://your.site.com/yocto_sstate/PATH;downloadfilename=PATH \n"
PREMIRRORS_prepend = "\
    git://.*/.* http://your.site.com/yocto_downloads/ \n \
    ftp://.*/.* http://your.site.com/yocto_downloads/ \n \
   http://.*/.* http://your.site.com/yocto_downloads/ \n \
   https://.*/.* http://your.site.com/yocto_downloads/ \n \
"
```

The developers have stated that this single shared state and downloads cache can
be shared across multiple tagged versions of Poky, so there is no need to
maintain separate paths for different releases.

 > Full Disclosure: In practice, the author has not seen a single successful
 > cache query from the shared state mirror, as seen through the web server
 > logs, despite using the same revision of branches at the server and desktop.
 > YMMV.  The downloads mirror however worked as expected.

### 2.5) Clearing Build History, Old Workers

 > _TODO:_ This is really heavy-handed; it removes all history.  You could try
 > your luck at directly editing the state.sqlite file.

All of the build history and worker related information is stored in a
database, `yocto-controller/state.sqlite`.  From the `yocto-controller`
directory, while it isn't runnign, delete the database and recreate
it: `buildbot upgrade-master`.  Then restart the controller.

# 3) Configuration

As mentioned before, BuildBot is the underlying tool that Autobuilder2 uses. 
It's a python3-based framework that consists of a master and multiple workers
that may be remotely connected.  Per this guide, both are installed on the same
host under `/home/pokybuild`.

The configuration for the controller is in `/home/pokybuild/yocto-controller`. 
This directory also contains the Yocto Project's Autobuilder source code
(in `yoctoabb`) and master configuration file, `master.cfg`.  The `master.cfg`
is a python file that pulls in other configuration data from the Autobuilder
source code directory.  Based on comments in the `yoctoabb/master.cfg`,
provisions have been made so that you can run `buildbot sighup` from this
directory, which would cause the configuration to reload without taking down the
controller.  This configuration data file primarily controls the web server and
what port(s) are open for workers.  It also controls authentication and
notification services (by way of importing `services.py` and `www.py`,
see BuildBot's own documentation for answers).

The main `yoctoabb/config.py` pairs up with
the `yocto-autobuilder-helper/config.json` to define the relationship between
what builds exist and what those builds _do_ in terms of steps to run.  There is
a lot of duplication between these two scripts that must be managed manually,
especially as it pertains to builders, the layer repositories each needs, and
the locations of those layer repositories.

Another interesting thing about this configuration is that only one branch of
the `yocto-autobuilder-helper` is ever pulled even if you manually specify a
different branch for a non-triggered build.  For example, manually Force
Building `beaglebone` does not give you a chance to change
yocto-autobuilder-helper branches but doing the same for `a-quick` would.  So if
you have a repository that contains multiple layers and for `rocko` you need one
of them, but for `thud` you need 2, your builder will fail if you run the build
on `rocko` because the worker will try to use the `thud` build
instructions...the only ones it knows unless you are using multiple branches of
`yocto-autobuilder-helper` (`thud`, `warrior`, etc.) and running `a-quick`
forced builds or configured additional `nightly` builds for different branchs.
There is also no way, from a single configuration JSON stack, to specify a
builder being only compatible with a specific layer branch other than having
multiple branches and omitting that builder from the incompatible branches, then
forcing a trigger build.  This is controlled by `schedulers.py`, so it's not a
limitation; instead consider this a _flag_ of something you probably want to
change if you have to maintain multiple branches in regression.

The remaining portion of this section will focus on the changes required to the
various configuration files to accomplish specific tasks, which will hopefully
provide some guardrails and sign posts along the way for when you do something
wrong.

## 3.1) Repositories

There are two main areas where repositories are defined.  The first is
in `yoctoabb/config.py`, which provides builders with a default set of
repositories stored locally at the worker.  The second place is more nuanced, in
your `config.json` stack of the `yocto-autobuilder-helper` under
the `repo-defaults`.  This map defines a duplicate of that information, which is
consumed by the layer-config and run-config scripts by way of the `NEEDREPOS`
and `ADDLAYER` lists on a given template or override.

The `NEEDREPOS` behavior ensures that the copies of your meta layers are
organized in the `BUILDDIR/../` correctly, and then if `no-layer-add` is set
to `false` (or omitted), will automatically call `bitbake-layers add-layer...`
to update your build's `bblayers.conf` file.  This process goes in order of
build dependencies.  The content of `NEEDREPOS` can be either a repo that is a
layer, or a repo that contains multiple layers.  In the latter case,
specifying `meta-openembedded/meta-oe` will copy the whole
repo `meta-openembedded` and then call `bitbake-layers add-layer...` for only
the sub-layer, `meta-oe` (assuming you've set `no-layer-add` to `false` for that
repo; the default is `true`).

The `ADDLAYER` behavior is similar but is processed during the `run-config` step
that executes all of your steps.  You can add this variable at the _step_ level
(it does not work at the builder level; `run-config` doesn't pick it up).  Each
list item in this variable takes the form: `${BUILDDIR}/../path/to/layer`.

 > **IMPORTANT:** The order of these two lists matter!  If you add a layer that
 > has unmet dependencies on other layers (i.e., they're not in `bblayers.conf`
 > yet), the next repo/layer in the list will fail to add because you've
 > technically broken your layer configuration (bitbake cannot parse it because
 > dependencies are missing).

 > **IMPORTANT:** If you allowed `NEEDREPOS` to update your `bblayers.conf`
 > file, then you do not need to use `ADDLAYER` as it'll be redundant.

## 3.2) Workers

As stated previously, this is exclusively defined by the `yoctoabb/config.py`
file.  In it, there is a section of workers that culminate into a final map that
defines build names vs. compatible workers, with default carrying the generic
meaning that it should be applicable to any build.  Ultimately the list of
workers defined in this configuration can be also thought of as _users_ of the
system because a worker will fail to join the master if it's not in this list or
provides an incorrect password (variable: `worker_password`).

You will also notice in the standard configuration file that there are workers
in the cluster for CentOS and Ubuntu, etc. since they're testing build host OS
-specific things.

If you would like to trim this list down to just the workers you have at your
site:

 1. You can safely remove any of the `workers_*` lists since they're only used
    locally to the `config.py`.
 2. Retain the following related
    variables: `workers`, `all_workers`, `builder_to_workers`.  They're used
    elsewhere.

## 3.3) Builds and Builders

This section details how to configure new builds, and thus, new builders.  There
are two main files involved in this relationship: `yoctoabb/config.py` and the
configuration JSON files you specified for `yocto-autobuilder-helper`.  Only
builds that exist in both places will actually be visible and usable at the UI. 
The remaining subsections below are general guidelines for how these various
files interact.

**Removing Builders:**

 1. You must keep the `buildertorepos` and `repos` maps.  The former provides a
    top-level set of builders and must include a key for default.  This map
    indicates which source code repositories to install for a given builder by
    way of a repository name.  The compliment to this map is `repos`, the list
    of repository locations and revisions. 
 2. You must keep the `subbuilders` list because it is used
    by `yoctoabb/builders.py` and `yoctoabb/schedulers.py`.
 3. You must keep the `a-quick` and `a-full` builds unless you are also
    modifying `yoctoabb/builders.py`, `generate-test-result-index.py`, and
    `schedulers.py` to remove those references as well.
 4. For any build you remove from `yoctoabb/config.py`, you should also remove
    in your `yocto-autobuilder-helper/config.json` file (if not purely for the
    sake of being tidy).

**Adding Builders:**

 1. If the build will only be manually run: add it to the
    `yoctoabb/config.py` subbuilders list.
 2. If the build will be run by either of the default `a-quick` or `a-full`
    builds, add the name instead to the `trigger_builders_wait_[quick|full]`
    list of your choice.  If you want both, add it to
    `the trigger_builders_wait_shared` list.
 3. If you have added a build that has requirements differing from
    the `yocto-autobuilder-helper/config.json` `defaults` map, create an entry
    for the builder in `the overrides` map fill in the details (see below for
    more suggestions).
 4. If the build has a set of layer repositories that differs from the `default`
    list in the `yoctoabb/config.py` `buildertorepos` map, you need to add a
    reference to its needs in that map.
 5. If the the repositories the builder requires are not listed in
    the `yoctoabb/config.py` `repos` map, add it under the same name with its
    default branch.
 6. If you have added repositories, you should also add it to
    the `yocto-autobuilder-helper/config.json` `repo-defaults` map.
 7. You should create `an overrides` for the builder that specifies `NEEDSREPOS`
    to identify those layers and `ADDLAYER` for any layers that have
    the `no-layer-add` flag set to `false` in the `repo-defaults` map.
 8. If these needs are shared among multiple builders, consider adding these
    changes instead to a new, named template in the `templates` map and then for
    each affected builder, set the value of its `overrides` `TEMPLATE` to that
    named template.

**Anatomy: _overrides_ and _templates_**

All of these guidelines pertain to the `yocto-autobuilder-helper/config.json`
file (and any overlay configurations you have).  The main difference between
these two items is that an `overrides` entry can specify the `TEMPLATE`
variable, the value of which must exist in the `templates` map.  There is no
provision for template stacking (i.e., adding `TEMPLATE` to a template has no
effect).  Otherwise as the names imply the `overrides` values will take
precedence over any named template and the `defaults`.

 > NOTE: This is not a comprehensive list.

 1. Top-level variables:
   1. `BUILDINFO` – boolean – If enabled, the values of `BUILDINFOVARS` are
      added to the list of variables in the build environment.
   2. `BUILDHISTORY` – boolean – Enables `INHERIT += 'buildhistory'` BitBake
      behavior.
   3. `BUILDINFOVARS` – list – For inheriting from `image-buildinfo` to save off
      additional build variables.
   4. `DISTRO` – string – Distro conf to use from the layer in the build.
   5. `DLDIR` – string – Set the bitbake `DL_DIR` to where downloads should be
      stored (e.g., `"DL_DIR = 'some_path'"`).
   6. `PACKAGE_CLASSES` – string – Set to the value of the Yocto
      `PACKAGE_CLASSES` variable
   7. `SDKEXTRAS` – list – Unknown.  To some end, the example appends
      `SSTATE_MIRRORS` with the Yocto Project's shared state release mirror.
   8. `SDKMACHINE` – string – Examples are `x86_64`, `i686`, etc.
   9. `SENDERRORS` – boolean – Executes the `upload-error-reports` script which
      ultimately runs the `send-error-report` script (from `poky/scripts`) to
      upload the results to a log server.
   10. `SSTATEDIR` – list – Presumably a list of additions to the `SSTATE_DIR`
       variable where each item in the list appends or removes that variable.
   11. `SSTATEDIR_RELEASE` – list – Presumably a list of additions to the
       `SSTATE_DIR` variable during release builds
   12. `WRITECONFIG` – boolean – If enabled, the `setup-config` script is
       run.  **Required** if specifying `extravars`.
   13. `extravars` – list – Contains additional BitBake varaibles that will be
       added to the tail of `build/conf/auto.conf`.
 2. _stepN_ -level variables:
   1. `ADDLAYER` – list – These named layers will be added to the
      `bblayers.conf` file.  At the end of the step, the layers will be removed
      in reverse order.  This is useful if your `repo-defaults` -defined
      repository has `no-layer-add` set to `true`.  This will log
      as _stepN**a**_.
   2. `BBTARGETS` – string – BitBake arguments passed to the bitbake, e.g.,
      core-image-minimal.  These will be appended with -k (continue) so that all
      targets will be attempted rather than stopping at the first error.  This
      will log as _stepN**b**_.
   3. `SANITYTARGETS` – string – BitBake targets that will be run in an emulated
      environment for testing.  This will log as _stepN**c**_.
   4. `EXTRACMDS` – list – List of commands to run within the BitBake
      environment (e.g., wic).  This will log as _stepN**d**_.
   5. `EXTRAPLAINCMDS` – list – List of commands to run without sourcing
      the oe-init-build-env script.  This will log as _stepN**d**_.

## Appendix A - Systemd Services

### yocto-controller.service

```
[Unit]
Description=Yocto Autobuilder2 Master
Documentation=man:buildbot(1) https://docs.buildbot.net/
Wants=yocto-janitor.service

[Service]
PIDFile=/home/pokybuild/yocto-controller/twistd.pid
Type=forking
WorkingDirectory=/home/pokybuild/yocto-controller
User=pokybuild
Group=nogroup
TimeoutStartSec=15
Environment=ABHELPER_JSON="config.json config-local.json"
ExecStart=/usr/bin/env buildbot start
ExecStop=/usr/bin/env buildbot stop
ExecReload=/usr/bin/env buildbot reconfig

[Install]
WantedBy=multi-user.target
```

### yocto-worker.service

```
[Unit]
Description=Buildbot Worker
Wants=network.target
After=network.target
Wants=yocto-controller.service

[Service]
Type=forking
PIDFile=/home/pokybuild/yocto-worker/twistd.pid
WorkingDirectory=/home/pokybuild
ExecStart=/usr/bin/env buildbot-worker start yocto-worker
ExecReload=/usr/bin/env buildbot-worker restart yocto-worker
ExecStop=/usr/bin/env buildbot-worker stop yocto-worker
Restart=always
User=pokybuild
Group=nogroup

[Install]
WantedBy=multi-user.target
```

### yocto-janitor.service

```
[Unit]
Description=Buildbot Janitor
Wants=network.target
After=network.target

[Service]
Type=simple
PIDFile=/home/pokybuild/yocto-autobuilder-helper/janitor.pid
WorkingDirectory=/home/pokybuild/yocto-autobuilder-helper
Environment=ABHELPER_JSON="config.json config-local.json"
ExecStart=/home/pokybuild/yocto-autobuilder-helper/janitor/ab-janitor
User=pokybuild
Group=nogroup

[Install]
WantedBy=multi-user.target
```