Balena CLI Masterclass
- Masterclass Type: Core
- Maximum Expected Time To Complete: 60 minutes
Introduction
The balena Command Line Interface (balena CLI) utility consists of a number of commands that allow a user to develop, deploy and manage balena fleets, as well as manage configuration & variables of the fleet and balenaOS images.
Almost everything that can be achieved via the balenaCloud dashboard can also be achieved via the balena CLI.
In this masterclass, you will learn how to:
- Login to your account
- Push your first release to a balena fleet
- Deploy locally built code to a balena fleet
- SSH into a balena device
- Push and build a release on the device over local network for fast development and prototyping
- Use private Docker registries for base images and services
- Create secret files and build arguments for building service images
If you have any questions about this masterclass as you proceed through it, or would like clarifications on any of the topics raised here, please do raise an issue as on the repository this file is contained in, or contact us on the balena forums where we'll be delighted to answer your questions.
The location of the repository that contains this masterclass and all associated code is https://github.com/balena-io/balena-cli-masterclass.
Hardware and Software Requirements
It is assumed that the reader has access to the following:
- A locally cloned copy of this repository
Balena CLI Masterclass.
Either:
git clone https://github.com/balena-io/balena-cli-masterclass.git- Download ZIP file (from 'Clone or download'->'Download ZIP') and then unzip it to a suitable directory
- A balena supported device, such as a balenaFin 1.1, Raspberry Pi 3 or Intel NUC. If you don't have a device, you can emulate an Intel NUC by installing VirtualBox and following this guide
- A suitable text editor for developing code on your development platform (eg. Visual Code)
- A suitable shell environment for command execution (such as
bash) - A balenaCloud account
- A local installation of Docker as well as a familiarity with Dockerfiles
- Should you wish to install via
npm, a NodeJS installation, including NPM is required. The use ofnvmis recommended, which allows you to alter the version of Node/NPM being used per-user, and also removes the need to install global dependencies usingsudo
Exercises
All of the following exercises assume that you are running the balena CLI from
a suitable Unix-based shell. The exercises include commands which can be run
in such a shell and are represented by a line prefixed with $. Information
returned from the execution of a command may be appended under the line to show
what might be returned. For example:
$ balena version
11.9.31. Installation and Authentication
1.1 Installation
First, we need to install balena CLI. The easiest way to achieve this is to use the installers for your OS from the balena CLI releases page. Choose the installer for your OS, download it, and follow the instructions. Note that there is not currently an installer for Linux, but you can download the standalone binary and then move it to a relevant location.
The alternative way to install it is via npm on a system running NodeJS.
Open a terminal on your development machine and run the following command:
$ npm --global install balena-cliThis will install the balena CLI globally and allow you to run it in a terminal
via balena <command>. Note that, depending on how you've installed NodeJS
and NPM, you may need to prefix this command with sudo. Also, if you get an
error such as EACCES: permission denied, add param --unsafe-perm right
after --global
1.2 Authentication
To use balena CLI, you need to log into a balenaCloud account. If you don't
have one, you can use the dashboard
here or sign up with the
login command by selecting I don't have a balena account!. Either way,
login via the terminal:
$ balena login
_ _
| |__ __ _ | | ____ _ __ __ _
| '_ \ / _` || | / __ \| '_ \ / _` |
| |_) | (_) || || ___/| | | || (_) |
|_.__/ \__,_||_| \____/|_| |_| \__,_|
Logging in to balena-cloud.com
? How would you like to login? (Use arrow keys)
❯ Web authorization (recommended)
Credentials
Authentication token
I don't have a balena account!You will be asked how you wish to authenticate with balenaCloud. The easiest method is that of 'Web authorization' which will bring up a browser window (and ask you to first login to balenaCloud if you have not) and ask you to confirm you wish to login.
Other authentication methods include using your username and password credentials or authentication token. Authentication tokens come in two types, API tokens and JSON Web Token (JWT) session tokens. Whilst API tokens do not expire, JWT session tokens do after 7 days.
Once logged in, a JWT session token will be saved in your
home directory (~/.balena/token). Be aware that the lifetime of a balena
JWT is limited to seven days, after which time reauthentication will be
required.
2. Creating a Fleet and Provisioning a Device
2.1 Creating a Fleet
Fleets can be created via the dashboard or via the balena CLI. We're going
to create a new fleet via balena CLI called cliFleet. Run the following
command:
$ balena fleet create cliFleetThis will ask you which device type you wish to create the fleet for.
You can scroll up and down this list using the arrow keys. For now, exit
the command by hitting Ctrl-C, as there's another, non-interactive way to
do this which we'll use instead. Type:
$ balena devices supportedto see a list of all supported device types by balenaCloud. For the rest of
this masterclass we're going to assume you're using a balenaFin, but you can
just as easily use any supported balena device.
We'll pass the balenaFin device type (fincm3) to the fleet creation
command directly:
$ balena fleet create cliFleet --type fincm3
Fleet created: slug "admin/clifleet", device type "fincm3"As can be seen, this will return the fleet's slug and device type.
If you're using a different device type, pass the appropriate device type
to the balena fleet create command instead.
Non-interactive commands are useful when you need to script actions via balena CLI for a shell script (although balena also includes HTTPS endpoints and SDKs which can be used for this purpose).
You can list the fleets currently owned by (or shared with) your account by typing:
$ balena fleets
ID NAME SLUG DEVICE TYPE ONLINE DEVICES DEVICE COUNT
1234567 cliFleet admin/clifleet fincm3 0 02.2 Provisioning a Device
You can now provision your balenaFin by downloading a provisioning image from the balenaCloud dashboard. Be sure to download a development image, as we'll be utilizing its features later.
Once the provisioning image is downloaded, connect your balenaFin to your development machine and run Etcher to flash it.
Once the image has been flashed to the balenaFin it will register itself and connect to the balenaCloud VPN, showing up in the dashboard and being viewable using balena CLI:
$ balena devices
ID UUID DEVICE NAME DEVICE TYPE FLEET NAME STATUS IS ONLINE SUPERVISOR VERSION OS VERSION DASHBOARD URL
7654321 1234567 restless-glade fincm3 cliFleet true https://dashboard.balena-cloud.com/devices/12345678901234567890123456789012/summaryYou can get detailed information on a device by using its Universally Unique Identifier (UUID), for example:
$ balena device 1234567
== RESTLESS GLADE
ID: 7654321
DEVICE TYPE: fincm3
STATUS: idle
IS ONLINE: true
IP ADDRESS: 192.168.1.173
FLEET NAME: cliFleet
UUID: 12345678901234567890123456789012
SUPERVISOR VERSION: 9.15.7
IS WEB ACCESSIBLE: false
OS VERSION: balenaOS 2.38.0+rev1
DASHBOARD URL: https://dashboard.balena-cloud.com/devices/12345678901234567890123456789012/summaryUUIDs can either be used in their shortened version (as above) or in their
long version (for example, the DASHBOARD URL field in the output above
shows the entire UUID for the device).
Be aware that there are ways to download, configure and provision a fleet image via balena CLI, but as some extra work is required to create a provisioning image (to allow greater flexibility) we'll go into that in the advanced masterclass.
3. Pushing Code to a Device
Once a fleet has been created, we want to be able to push a release to it.
There are a couple of ways to do this, but the most common is that of using
balena push. See the balena push docs to learn more about the command.
Alternatively, you can use legacy method of pushing code via git push. You
can learn about how to do so by going to the git push docs. Before moving
on to the next step, make sure you know how to push code to a device.
4. SSHing into a Device
Once a device has been provisioned, it can be accessed by SSHing into it via the
balenaCloud VPN. To do this, you need to add your public SSH key to your BalenaCloud
account. When added, specify the UUID of the device you want to SSH into
(remember you can see all your devices by running balena devices).
$ balena ssh 1234567
=============================================================
Welcome to balenaOS
=============================================================
root@827b231:~#By default, SSH access is routed into the host balenaOS shell. However, you can SSH into a service by specifying its name as part of the command:
$ balena ssh 1234567 main
root@827b231:/usr/src/app#This also works in multi-container fleets, simply pass the name of the
appropriate service as defined in docker-compose.yml you'd like to access
the shell for.
When using device UUIDs, balena ssh uses the balena VPN to create a secure
tunnel to the device and then forward SSH traffic between it and your
development machine (for production devices, this is the only available method).
For devices running development images on your local network, you can also
use SSH by specifying the hostname or IP address of that device (development
images have SSH enabled by default). Using balena ssh in this way doesn't use
the balena VPN and instead makes a direct SSH connection to the device.
For example:
$ balena ssh 192.168.1.2To find the hostname of a local development device, you can use balena scan:
$ sudo balena scan
Reporting scan results
-
host: 827b231.local
address: 192.168.1.173
dockerInfo:
Containers: 1
ContainersRunning: 1
ContainersPaused: 0
ContainersStopped: 0
Images: 2
Driver: aufs
SystemTime: 2019-09-05T13:31:34.910619617Z
KernelVersion: 4.14.98
OperatingSystem: balenaOS 2.38.0+rev1
Architecture: armv7l
dockerVersion:
Version: 18.09.6-dev
ApiVersion: 1.39In this instance 827b231.local is the hostname, so the device can be SSHd
into using balena ssh 827b231.local. Note that by default, the hostname
of a device is always its short UUID, so if you already know the UUID for the
device, you can balena ssh <uuid>.local without having to perform a
balena scan.
5. Building and Deploying a release without the Builder
5.1 Building an Image on a Development Machine
Whilst you can build the release image using the balenaCloud builder, it's also possible to build and generate the release's Docker images locally on your development machine.
There are several reasons why you want might to do this. For example, should your development machine exist on an air-gapped network (with no Internet connection), but the base images for a build as well as all the other package requirements your build will need, also exist on the local network, this allows builds for balena devices to still be carried out.
Another good example is if you have your own CI/CD pipeline with dedicated machines that cache specific package/build data that you use frequently. In these cases, a build on a local machine may be significantly quicker than using balena generic builders.
Before we try building locally, it's worth a note on an extra switch that can be
used with balena build. --emulated tells balena CLI that the target
architecture environment should be emulated, if it differs from that of the
native architecture on which balena CLI is being run. For example, most
development machines tend to use an x64 architecture, whereas a large number of
devices are based around Armv6 or v7 (and more lately v8) architectures. To
correctly build images for Arm targets, an x64 builder must emulate the target
architecture whilst running the Docker commands. Because we're assuming the use
of a balenaFin here, we'll run all local builds using the --emulated switch.
Should you be building for an Intel NUC, or other AMD64 based device, you do not
need to pass this switch in the following examples.
To carry out a local build requires more information than a balena push,
because balena CLI needs to know the CPU architecture and device type to produce
a Docker image that will work on the specified target. The easiest way to do
this is to specify a fleet, which will allow balena CLI to determine this
information itself by querying the balenaCloud API. In the
balena-cli-masterclass repository, execute this command:
$ balena build --fleet cliFleet --emulated
[Info] Creating default composition with source: /Work/Support/MasterClasses/repos/balena-cli-masterclass
[Info] Building for armv7hf/fincm3
[Info] Emulation is enabled
[Build] Built 1 service in 1:32
[Build] main Image size: 208.45 MBA call to docker images will show the newly built image:
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
balena-cli-masterclass_main latest 321025486d49 About a minute ago 219MBAs mentioned, there are instances where the ability to use balenaCloud is not
possible (for example an air-gapped network), or is not desirable. In these
situations, balena build can be notified of the device type and architecture
to build on the command line. To get the architecture of each supported device,
execute this command:
balena devices supported -vOnce you know the architecture and device type of the device you want to emulate, execute this command to start building:
$ balena build --arch armv7hf --deviceType fincm3 --emulated
[Info] Creating default composition with source: /Work/Support/MasterClasses/repos/balena-cli-masterclass
[Info] Building for armv7hf/fincm3
[Info] Emulation is enabled
[Build] Built 1 service in 1:41
[Build] main Image size: 219.15 MB
[Success] Build succeeded!There are a few caveats to building images locally, however. Emulated builds will always be slower than native builds due to having to mimic a different architecture. Coupled with other factors, such as potentially lower network bandwidth than that enjoyed by the balenaCloud builders, this can mean a far slower build than would occur than pushing to our native builders (which use both dedicated 64bit AMD64 and Arm servers).
5.2 Deploying an Image from a Development Machine
An image from a development machine can be deployed as a fleet release to balenaCloud from balena CLI. This allows any pre-built image to be uploaded directly to balena's registry without the requirement of the builder to generate it first. Assuming you've followed exercise 5.1, run the following:
$ balena deploy cliFleet balena-cli-masterclass_main:latest
[Info] Creating default composition with image: balena-cli-masterclass_main:latest
[Info] Everything is up to date (use --build to force a rebuild)
[Info] Creating release...
[Info] Pushing images to registry...
[Info] Saving release...
[Success] Deploy succeeded!
[Success] Release: b9e5ec4b309f91281ecb592028dcea0c
\
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/ / |
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,.-' >.'
<.'_.''
<'This will create a new release (visible via the dashboard), and push the image directly to the balena Docker registry. Your balenaFin should then download the new release and run it. This is useful if you already have an image pre-built and just need to upload it.
However, balena deploy also allows you to complete the build step as well
implicitly by not specifying an image to upload. Run the following command in
the balena-cli-masterclass repository:
$ balena deploy cliFleet --build --emulated
[Info] Creating default composition with source: /Work/Support/MasterClasses/repos/balena-cli-masterclass
[Info] Building for armv7hf/fincm3
[Build] Built 1 service in 0:58
[Build] main Image size: 213.80 MB
[Info] Creating release...
[Info] Pushing images to registry...
[Info] Saving release...
[Success] Deploy succeeded!
[Success] Release: 13f39923c2ddf95fa35a129d8efb5b53
\
\
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_.-(6' \
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<.'_.''
<'This forces the deploy command to first build (or rebuild if the image already
exists) the project before pushing it to the Docker registries.
6. Using Local Mode to Develop your Application
So far, you've seen how to push code to the balena builders or to build and push images on a development machine. Whilst practical solutions for pre-tested code, or for a CI pipeline, this is not a fast workflow for active development of an app by an engineer as it involves rebuilding an image and then delivering it to the target device.
To make active development of app easier for an engineer, balena devices provisioned with a development image include a device mechanism called 'Local Mode'. This can be activated easily from the dashboard. Go to your device's dashboard page, select 'Settings' from the lefthand toolbar, and then select 'Local mode'. Local mode does a couple of important things:
- Stops running the services currently associated with the device
- Exposes a Docker socket on the local network
Once activated, balena CLI can push code directly to the local device instead
of going via the balena builders. Code is built on the device and then executed,
which can significantly speed up development when requiring frequent changes.
As mentioned previously, you can find local devices on your network in
development mode by using balena scan.
balena push includes optional switches which allow you to specify that you
want to push code to a local device using the results from balena scan.
To see this working in practice, carry out a balena scan, and then pass either
the host or IP address to balena push whilst in the balena-cli-masterclass
repository:
$ balena push 827b231.local
[Info] Starting build on device 827b231.local
[Info] Creating default composition with source: .
[Build] [main] Step 1/8 : FROM balenalib/fincm3-node:8
[Build] [main] ---> 392c3f6339f7
[Build] [main] Step 2/8 : WORKDIR /usr/src/app
[Build] [main] ---> Running in 446517b1afdb
[Build] [main] Removing intermediate container 446517b1afdb
[Build] [main] ---> c27a2f22ba27
[Build] [main] Step 3/8 : COPY package.json package-lock.json ./
[Build] [main] ---> fc79948ab18b
[Build] [main] Step 4/8 : RUN npm install --ci --production && npm cache clean --force && rm -f /tmp/*
[Build] [main] ---> Running in 59c1b1cbe571
[Build] [main] added 50 packages from 37 contributors and audited 126 packages in 9.178s
[Build] [main] found 0 vulnerabilities
[Build] [main] npm
[Build] [main]
[Build] [main] WARN
[Build] [main]
[Build] [main] using --force
[Build] [main] I sure hope you know what you are doing.
[Build]
[Build] [main] Removing intermediate container 59c1b1cbe571
[Build] [main] ---> 0cdc6d1d7af9
[Build] [main] Step 5/8 : COPY src/ ./src/
[Build] [main] ---> 23e41b46ee6f
[Build] [main] Step 6/8 : CMD ["npm", "start"]
[Build] [main] ---> Running in c62943c5e22f
[Build] [main] Removing intermediate container c62943c5e22f
[Build] [main] ---> 9434eb22cc67
[Build] [main] Step 7/8 : LABEL io.resin.local.image=1
[Build] [main] ---> Running in 9023bae27f0f
[Build] [main] Removing intermediate container 9023bae27f0f
[Build] [main] ---> 7e2603a523f2
[Build] [main] Step 8/8 : LABEL io.resin.local.service=main
[Build] [main] ---> Running in 05feac72072e
[Build] [main] Removing intermediate container 05feac72072e
[Build] [main] ---> 9ef9a4510175
[Build] [main] Successfully built 9ef9a4510175
[Build] [main] Successfully tagged local_image_main:latest
[Info] Streaming device logs...
[Live] Watching for file changes...
[Live] Waiting for device state to settle...
[Logs] [9/5/2019, 2:34:37 PM] Creating network 'default'
[Logs] [9/5/2019, 2:34:37 PM] Creating volume 'resin-data'
[Logs] [9/5/2019, 2:34:37 PM] Installing service 'main sha256:9ef9a45101757ee81aa26d5ca43713289b2e99401d1b13e32842523876fde664'
[Logs] [9/5/2019, 2:34:38 PM] Installed service 'main sha256:9ef9a45101757ee81aa26d5ca43713289b2e99401d1b13e32842523876fde664'
[Logs] [9/5/2019, 2:34:38 PM] Starting service 'main sha256:9ef9a45101757ee81aa26d5ca43713289b2e99401d1b13e32842523876fde664'
[Logs] [9/5/2019, 2:34:39 PM] Started service 'main sha256:9ef9a45101757ee81aa26d5ca43713289b2e99401d1b13e32842523876fde664'
[Live] Device state settled
[Logs] [9/5/2019, 2:34:41 PM] [main]
[Logs] [9/5/2019, 2:34:41 PM] [main] > balena-cli-masterclass@1.0.0 start /usr/src/app
[Logs] [9/5/2019, 2:34:41 PM] [main] > node src/helloworld.js; sleep infinity
[Logs] [9/5/2019, 2:34:41 PM] [main]
[Logs] [9/5/2019, 2:34:41 PM] [main] Hello world!Once the code has been built on the device, it immediately starts executing
and logs are output to the console. You can halt the connection to the local
device by using Ctrl-C. Note that after disconnection, the service containers
on the device will continue to run.
In a multi-container environment, it may quickly become difficult for an engineer
to determine whether their code is working, especially if many services are
all outputting log information. In these cases, filtering log output via
service is possible, by using the --service switch (we've also used the
--nocache option here to force a rebuild and restart, else we wouldn't see any
other logs as the service wouldn't have changed):
$ balena push 827b231.local --service main --nocache
[Info] Starting build on device 827b231.local
[Info] Creating default composition with source: .
[Build] [main] Step 1/8 : FROM balenalib/fincm3-node:8
[Build] [main] ---> 392c3f6339f7
[Build] [main] Step 2/8 : WORKDIR /usr/src/app
[Build] [main] ---> Using cache
[Build] [main] ---> c27a2f22ba27
[Build] [main] Step 3/8 : COPY package.json package-lock.json ./
[Build] [main] ---> Using cache
[Build] [main] ---> fc79948ab18b
[Build] [main] Step 4/8 : RUN npm install --ci --production && npm cache clean --force && rm -f /tmp/*
[Build] [main] ---> Using cache
[Build] [main] ---> 0cdc6d1d7af9
[Build] [main] Step 5/8 : COPY src/ ./src/
[Build] [main] ---> 5adcd43b12c6
[Build] [main] Step 6/8 : CMD ["npm", "start"]
[Build] [main] ---> Running in a415b6e7f0af
[Build] [main] Removing intermediate container a415b6e7f0af
[Build] [main] ---> 1a1ff3926d42
[Build] [main] Step 7/8 : LABEL io.resin.local.image=1
[Build] [main] ---> Running in 7390bcd46425
[Build] [main] Removing intermediate container 7390bcd46425
[Build] [main] ---> ebf9fc9c43ed
[Build] [main] Step 8/8 : LABEL io.resin.local.service=main
[Build] [main] ---> Running in 52ab62708a46
[Build] [main] Removing intermediate container 52ab62708a46
[Build] [main] ---> 60f2a99b07c8
[Build] [main] Successfully built 60f2a99b07c8
[Build] [main] Successfully tagged local_image_main:latest
[Live] Waiting for device state to settle...
[Info] Streaming device logs...
[Live] Watching for file changes...
[Logs] [9/5/2019, 2:46:54 PM] [main]
[Logs] [9/5/2019, 2:46:54 PM] [main] > balena-cli-masterclass@1.0.0 start /usr/src/app
[Logs] [9/5/2019, 2:46:54 PM] [main] > node src/helloworld.js; sleep infinity
[Logs] [9/5/2019, 2:46:54 PM] [main]
[Logs] [9/5/2019, 2:46:54 PM] [main] Hello world!As you can see, none of the Supervisor logs were printed. Note that there is
also a balena logs command that is dedicated to just showing logs. This
command includes both the --system and --service switches to filter
output to just that of system messages or particular service messages (these
switches can be combined in a single balena logs call). This allows the
setup of multiple terminals to act as loggers whilst another is used to
carry out balena push executions. A few examples of logging are shown below:
balena logs 827b231.local --system --service main- Will output all system messages and those from themainservicebalena logs 827b231.local --service mainwill only output messages from themainservicebalena logs 827b231.local --service main --service secondarywill only output messages from themainandsecondaryservices
Local Mode also has another huge benefit, known as Livepush. Livepush makes intelligent decisions on how, or even if, to rebuild an image when changes are made. It does this by examining the source directory of an image being built on your local development machine (via balena CLI) and then deciding how to deal with changes.
In some cases, Livepush rebuilds relevant parts of the image before starting the
new image as the service. As an example of this, ensure you've executed
balena push in Local Mode:
$ balena push 827b231.local --service mainNow modify Dockerfile.template in the balena-cli-masterclass repository in a
text editor, inserting a new line between the COPY src/ ./src/ command and
CMD ["npm", "start"]:
...
COPY src/ ./src/
RUN echo "Rebuild the image"
CMD ["npm", "start"]Finally, save the changes to the file in your text editor. The Supervisor will immediately detect that the Dockerfile has changed and will start a rebuild of the service:
[Live] Detected Dockerfile change, performing full rebuild of service main
[Build] [main] Step 1/9 : FROM balenalib/fincm3-node:8
[Build] [main] ---> 392c3f6339f7
[Build] [main] Step 2/9 : WORKDIR /usr/src/app
[Build] [main] ---> Using cache
[Build] [main] ---> c27a2f22ba27
[Build] [main] Step 3/9 : COPY package.json package-lock.json ./
[Build] [main] ---> Using cache
[Build] [main] ---> fc79948ab18b
[Build] [main] Step 4/9 : RUN npm install --ci --production && npm cache clean --force && rm -f /tmp/*
[Build] [main] ---> Using cache
[Build] [main] ---> 0cdc6d1d7af9
[Build] [main] Step 5/9 : COPY src/ ./src/
[Build] [main] ---> fec02483c800
[Build] [main] Step 6/9 : RUN echo "Rebuild the image"
[Build] [main] ---> Running in 0c1f2cbca19f
[Build] [main] Rebuild the image
[Build] [main] Removing intermediate container 0c1f2cbca19f
[Build] [main] ---> aec92835242c
[Build] [main] Step 7/9 : CMD ["npm", "start"]
[Build] [main] ---> Running in 824e56df2920
[Build] [main] Removing intermediate container 824e56df2920
[Build] [main] ---> c49d013039de
[Build] [main] Step 8/9 : LABEL io.resin.local.image=1
[Build] [main] ---> Running in e9158ba83571
[Build] [main] Removing intermediate container e9158ba83571
[Build] [main] ---> 2317085d9161
[Build] [main] Step 9/9 : LABEL io.resin.local.service=main
[Build] [main] ---> Running in ebcaf1a3351d
[Build] [main] Removing intermediate container ebcaf1a3351d
[Build] [main] ---> fc5e4459c406
[Build] [main] Successfully built fc5e4459c406
[Build] [main] Successfully tagged local_image_main:latest
[Logs] [9/5/2019, 3:58:56 PM] [main]
[Logs] [9/5/2019, 3:58:56 PM] [main] > balena-cli-masterclass@1.0.0 start /usr/src/app
[Logs] [9/5/2019, 3:58:56 PM] [main] > node src/helloworld.js; sleep infinity
[Logs] [9/5/2019, 3:58:56 PM] [main]
[Logs] [9/5/2019, 3:58:56 PM] [main] Hello world!Once rebuilt, it will restart the service. Notice that the Rebuild the image
echoed line is now in the build log.
Livepush goes way further than this, however. Only files that affect the
building of the service force a rebuild. For other files, for example source
files that run in-service, the Supervisor replaces the files in-situ in the
relevant container layer.
To show this, continue to run the balena push command and then alter the
src/helloworld.js in a text editor and change:
console.log('Hello world!');to
console.log('Hello moon!');On saving the file, you'll see the following output:
[Live] Detected changes for container main, updating...
[Live] [main] Restarting service...
[Logs] [9/5/2019, 4:02:27 PM] [main]
[Logs] [9/5/2019, 4:02:27 PM] [main] > balena-cli-masterclass@1.0.0 start /usr/src/app
[Logs] [9/5/2019, 4:02:27 PM] [main] > node src/helloworld.js; sleep infinity
[Logs] [9/5/2019, 4:02:27 PM] [main]
[Logs] [9/5/2019, 4:02:28 PM] [main] Hello moon!Instead of rebuilding the image, which takes time, the file is injected directly into the container's file system and then it is restarted. This happens in a few seconds and makes the process of developing much faster and more convenient.
Sometimes an engineer may not want to rebuild code 'on the fly'. For this reason
balena push in Local Mode also has a --nolive option which can be passed
to it. When using this switch, engineers need to repush when they want to
rebuild code.
Livepush also supports balena logs, and can be used in the same way as
described earlier.
7. Using Private Registries
As well as using public Docker registries it's possible to instruct builders,
either balena-based or using Local Mode, to pull images from private Docker
registries. This is achieved by using the --registry-secrets switch when
calling balena push passing a filename containing the secret information.
This information can be in either YAML or JSON. For example, a relevant
JSON object containing this information follows:
{
"https://index.docker.io/v1/": {
"username": "myUser",
"password": "myPassword"
}
}If saved as a JSON file, for example secrets.json, it will then be used when
a base image or image for a service is pulled which requires credentials:
$ balena push --registry-secrets secrets.jsonYou can also save a file with secrets in JSON or YAML format in your home
directory, under ~/.balena/secrets.<yml|json>, which will automatically be
used for the secrets if it exists and the --registry-secrets switch has not
been passed to balena push.
8. Building with Secrets and Variables
Building images occasionally requires the use of credentials (such as those for private repositories), or environment variables that may change depending on circumstances such as architecture (for example package versioning).
The following exercise sections show you how to use build-time secrets and variable substitution.
8.1 Build Time Secrets
Sometimes it is necessary to build images using secret information, commonly to login to source repositories or fetch data that is required for the building of an image, but which should not exist in that image when run as a service container.
Our builders allow you to do this by adding such secrets in files in a
.balena directory in the root of the build directory. This allows them to
be passed to builders, which will use (and then discard) them for generating
images.
We'll make a few changes to the example project to show this in operation.
First, create a .balena directory in the root of the balena-cli-masterclass
directory, and then create an empty balena.yml file and create another
directory called secrets in the .balena directory. You should now have a
file tree that looks like this:
$ tree -a -I .git
.
├── .balena
│ ├── balena.yml
│ └── secrets
├── Dockerfile.template
├── README.md
├── package-lock.json
├── package.json
└── src
└── helloworld.jsYou can now add secrets to the build by adding a section to the balena.yml
file and then creating appropriate secret files in the .balena/secrets
directory. We'll add some now, open a text editor and fill the balena.yml
file with the following:
build-secrets:
global:
- source: my-build-secrets
dest: my-secretsNote that the source file should exist in the .balena/secrets directory, and
that it is mapped into the my-secrets file when the image is built.
Save the file, and create a new one called .balena/secrets/my-build-secrets
and copy the following into it:
This file has build-time secrets!Finally, we'll add a line into our Dockerfile that uses the secrets file, which
is mapped into the /run/secrets/ directory during build time:
COPY src/ ./src/
RUN cat /run/secrets/my-secrets
CMD ["npm", "start"]Now, push the project to the builders:
$ balena push cliFleet
[Info] Starting build for cliFleet, user heds
[Info] Dashboard link: https://dashboard.balena-cloud.com/apps/1505952/devices
[Info] Building on arm03
[Info] Pulling previous images for caching purposes...
[Success] Successfully pulled cache images
[main] Step 1/7 : FROM balenalib/fincm3-node:8
[main] ---> 392c3f6339f7
[main] Step 2/7 : WORKDIR /usr/src/app
[main] ---> f9c421b7aa77
[main] Removing intermediate container df598a62ef2c
[main] Step 3/7 : COPY package.json package-lock.json ./
[main] ---> 6af34973ecb0
[main] Removing intermediate container d7b84160d116
[main] Step 4/7 : RUN npm install --ci --production && npm cache clean --force && rm -f /tmp/*
[main] ---> Running in e0a52c6e7d2e
[main] added 50 packages from 37 contributors and audited 126 packages in 2.53s
[main] found 0 vulnerabilities
[main] npm
[main] WARN using --force
[main] I sure hope you know what you are doing.
[main]
[main] ---> 9ff0e005febd
[main] Removing intermediate container e0a52c6e7d2e
[main] Step 5/7 : COPY src/ ./src/
[main] ---> 211ef0e15576
[main] Removing intermediate container 75e2127552bf
[main] Step 6/7 : RUN cat /run/secrets/my-secrets
[main] ---> Running in 949098cba8b6
[main] This file has build-time secrets!
[main] ---> 6da25ec8f94f
[main] Removing intermediate container 949098cba8b6
[main] Step 7/7 : CMD npm start
[main] ---> Running in 1ae564a36e44
[main] ---> e590faac0013
[main] Removing intermediate container 1ae564a36e44
[main] Successfully built e590faac0013
[Info] Uploading images
[Success] Successfully uploaded images
[Info] Built on arm03
[Success] Release successfully created!
[Info] Release: cedeff39dc537c9cd4c1df3b97ffcbc7 (id: 1055448)
[Info] ┌─────────┬────────────┬────────────┐
[Info] │ Service │ Image Size │ Build Time │
[Info] ├─────────┼────────────┼────────────┤
[Info] │ main │ 208.47 MB │ 11 seconds │
[Info] └─────────┴────────────┴────────────┘
[Info] Build finished in 46 seconds
\
\
\\
\\
>\/7
_.-(6' \
(=___._/` \
) \ |
/ / |
/ > /
j < _\
_.-' : ``.
\ r=._\ `.
<`\\_ \ .`-.
\ r-7 `-. ._ ' . `\
\`, `-.`7 7) )
\/ \| \' / `-._
|| .'
\\ (
>\ >
,.-' >.'
<.'_.''
<'As you can see, step 6 output:
[main] Step 6/7 : RUN cat /run/secrets/my-secrets
[main] ---> Running in 949098cba8b6
[main] This file has build-time secrets!which is the contents of the secrets file. This file could obviously contain
a raft of different functions, including a script that gets executed, text
for filling in files, etc. As well as defining globally accessible secrets
(which are shared to all services being built), there is also the option to
define secrets that are only accessible to particular services, or to map them
to different paths. This becomes useful in multi-container build scenarios. This
can be achieved by appending a services section to build-secrets on the
balena.yml file. For example:
build-secrets:
services:
main:
- source: main-only-secrets
dest: my-main-secretsThis change would map the .balena/secrets/main-only-secrets file into the
/run/secrets/my-main-secrets runtime path at build-time but only for the
main service.
8.2 Build Time Variables
Another frequent build-time use is that of environment variables that may alter between builds but still use the same flow of a Dockerfile. Allowing these to be defined dynamically means that no changes to a Dockerfile are required as long as the variables are referenced within them.
Much in a similar way to secrets files, these are defined in the
.balena/balena.yml file. Add two new build-time arguments to your
balena.yml file:
build-variables:
global:
- BUILD_TIME_ARG_1=This is the first arg
- BUILD_TIME_ARG_2=This is the second argNow alter the Dockerfile to use them:
RUN cat /run/secrets/my-secrets
ARG BUILD_TIME_ARG_1
ARG BUILD_TIME_ARG_2
RUN echo "${BUILD_TIME_ARG_1}" && \
echo "${BUILD_TIME_ARG_2}"
CMD ["npm", "start"]Note that you need to ensure that both arguments are declared using the ARG
Docker command. Save the file and push to the builders:
$ balena push cliFleet --nocache
[Info] Starting build for cliFleet, user heds
[Info] Dashboard link: https://dashboard.balena-cloud.com/apps/1505952/devices
[Info] Building on arm01
[Info] Pulling previous images for caching purposes...
[Success] Successfully pulled cache images
[main] Step 1/10 : FROM balenalib/fincm3-node:8
[main] ---> 392c3f6339f7
[main] Step 2/10 : WORKDIR /usr/src/app
[main] ---> 0d930a93f967
[main] Removing intermediate container 37dcff73ed1b
[main] Step 3/10 : COPY package.json package-lock.json ./
[main] ---> 036c9574af90
[main] Removing intermediate container 19b7f4d28593
[main] Step 4/10 : RUN npm install --ci --production && npm cache clean --force && rm -f /tmp/*
[main] ---> Running in fa65ea126c2d
[main] added 50 packages from 37 contributors and audited 126 packages in 2.436s
[main] found 0 vulnerabilities
[main] npm
[main] WARN using --force I sure hope you know what you are doing.
[main]
[main] ---> 6369ab6a6802
[main] Removing intermediate container fa65ea126c2d
[main] Step 5/10 : COPY src/ ./src/
[main] ---> a7103d76c564
[main] Removing intermediate container ae6e3614de1d
[main] Step 6/10 : RUN cat /run/secrets/my-secrets
[main] ---> Running in 3bc6e36ce8d1
[main] This file has build-time secrets!
[main] ---> 6ee5058cc5f3
[main] Removing intermediate container 3bc6e36ce8d1
[main] Step 7/10 : ARG BUILD_TIME_ARG_1
[main] ---> Running in a42ba6af90d6
[main] ---> 06bd854b2e68
[main] Removing intermediate container a42ba6af90d6
[main] Step 8/10 : ARG BUILD_TIME_ARG_2
[main] ---> Running in dcc256fdc0a6
[main] ---> e283099d8adc
[main] Removing intermediate container dcc256fdc0a6
[main] Step 9/10 : RUN echo "${BUILD_TIME_ARG_1}" && echo "${BUILD_TIME_ARG_2}"
[main] ---> Running in 1c572bc0e7c0
[main] This is the first arg
[main] This is the second arg
[main] ---> 81c8da87d775
[main] Removing intermediate container 1c572bc0e7c0
[main] Step 10/10 : CMD npm start
[main] ---> Running in 81dd184fc8ee
[main] ---> d494a4090d2d
[main] Removing intermediate container 81dd184fc8ee
[main] Successfully built d494a4090d2d
[Info] Uploading images
[Success] Successfully uploaded images
[Info] Built on arm01
[Success] Release successfully created!
[Info] Release: 7efbc95825641b6482742a54c8e74010 (id: 1056307)
[Info] ┌─────────┬────────────┬────────────┐
[Info] │ Service │ Image Size │ Build Time │
[Info] ├─────────┼────────────┼────────────┤
[Info] │ main │ 208.48 MB │ 9 seconds │
[Info] └─────────┴────────────┴────────────┘
[Info] Build finished in 28 seconds
\
\
\\
\\
>\/7
_.-(6' \
(=___._/` \
) \ |
/ / |
/ > /
j < _\
_.-' : ``.
\ r=._\ `.
<`\\_ \ .`-.
\ r-7 `-. ._ ' . `\
\`, `-.`7 7) )
\/ \| \' / `-._
|| .'
\\ (
>\ >
,.-' >.'
<.'_.''
<'As can be seen, both build arguments were available in the log output:
[main] This is the first arg
[main] This is the second argIn the same way that build secrets can be made service specific, so may secret
build arguments, by specifying them directly in the .balena/balena.yml file:
build-variables:
services:
main:
- MAIN_ONLY_BUILD_ARG=This is only available when building 'main'An important note for build variables is that, unlike secrets, they will be defined and available as part of the final image. If you need variables to be secret, they should be defined specifically as secrets.
Conclusion
In this masterclass, you've learned how to use the most commonly used balena CLI commands, as well as how to start development using it. You should now be familiar and confident enough to:
- Create fleets for specific device types
- Provision devices as well as SSH into balenaOS and any running service container
- Push a release to fleets, either via
balena pushorgit push - Locally build service images on a development machine, as well as deploying those images to balenaCloud
- Switch a development device into Local Mode, push code locally to a device to build, and debug the app faster.
- Use Livepush to dynamically alter the app code on the fly and immediately see results on a device in Local Mode, as well as filter log output for specific services in the app.
- Use build secret files and arguments to generate images which should not include those secrets, as well as build variables
References
None