Build your first Ubuntu Core image

[degville]

This tutorial will guide you through the steps required to create your own Ubuntu Core image, with your own selection of snaps, and install it on a Raspberry Pi.

The same process can be used to build Ubuntu Core images for various hardware and devices.

Here’s what you’ll need for the tutorial

• a basic understanding of Linux and the command line
• a Raspberry Pi 4 Model B, or later
  • 4GB+ microSD card
  • keyboard and display (for setup only)
  • Ethernet or wireless network connectivity
• host system running Ubuntu 22.04 LTS or later
• 10GB of free storage space
• a microSD card reader
• a wireless network and access to the internet

The above requirements are specific to this tutorial. Other host distributions can be used, and other target platforms are supported.

Step-by-step guide

Here’s an overview of the steps required with links to our separate tutorials that deal with each individual step:

• 1. Create an Ubuntu One account
  • 1. Create the account online
  • 2. Retrieve your developer account id
• 2. Create the model assertion
  • 1. Download a model assertion
  • 2. Edit the model assertion
  • 2.1 authority-id and brand-id
  • 2.2 timestamp
  • 2.3 snaps
  • 2.4 my-model.json
  • 3. A complete model assertion
• 3. Sign the model assertion
  • 1. Create a key
  • 2. Register the key
  • 3. Sign the model
• 4. Build and write the image
  • 1. Compile the image
  • 2. Write the image
• 5. Boot the image
  • 1. Boot Ubuntu Core
  • 1.1 Configure a network connection
  • 2. Connect to the device

[rpjday1]

What’s with the timestamp example in section 4.2 ending in “0Z”? Is this some weird but valid variation?

[degville]

I think it’s the UTC offset from the timestamp in the model. Not sure how that’s been generated, but it’s accepted.

[rpjday1]

I’m not sure this page qualifies as a “Quick Start” guide … it jumps right into creating model assertions and building your own image. A quick start might be just downloading a ready-to-go image and booting your Raspberry Pi, or maybe even downloading a QEMU image and booting that.

[ogra]

That wouldn’t fit very well with the title, would it?

[degville]

I think @rpjday1 is referring to the title in the navigation which is indeed Quickstart guide (for consistency with other docs). But I think he’s right. It’s a tough place to start and not quick. I’ll shuffle this - put the install guides first and then this second with a new name.

[rpjday1]

At the very least, those first two tabs could be reversed … start with “Install Ubuntu Core” after which rename the other tab to “Build your own image”. That would flow more smoothly. Ah, as was just done.

[rpjday1]

I would put, as a first tutorial, downloading and running a QEMU image, so people don’t even need to invest in hardware. I think we have such a tutorial kicking around somewhere, so just add that as a TO-DO item.