Building a bootable target

In order to build a raptor target that can be turned into a bootable iso, there are a few requirements we need to consider:

• The distribution must be Debian-based (or, preferably, Debian)
• The package live-boot must be installed, since it contains the necessary tools and scripts
• A linux kernel package must be installed (e.g. linux-image-amd64).

Here is an example of a fairly minimal base layer, which can be turned into an iso:

# Start from a docker iso
FROM docker://debian:trixie

# Set root password to "raptor"
RUN usermod -p "$1$GQf2tS9s$vu72NbrDtUcvvqnyAogrH0" root

# Update package sources, and install packages
RUN apt-get update
RUN apt-get install -qy systemd-sysv live-boot linux-image-amd64

The kernel package can take a bit of time to install, so let’s start a new layer for further customization. This way, we don’t need to rebuild the base layer with every change we make to the upper layer:

# Start from previous layer
FROM base

# Update package sources, and install ssh server
RUN apt-get update
RUN apt-get install -qy openssh-server

Of course, these layers could easily be combined, but it is good to get in a habit of separating things into reasonable layers. This improves caching and makes builds faster, since more can be reused between builds.

Now we are ready to build the layers. Since ssh derives from base (which derives from a docker layer), we just have to request raptor to build ssh. Raptor automatically determines dependencies, and builds them as needed.

sudo raptor build ssh

You should now see raptor build the ssh layer, with all command output from the apt-get commands being shown in the terminal.

Once complete, you can quickly verify that the layer is complete, by running the same command again. This time it should very quickly display a message, indicating that each layer is complete:

$ sudo raptor build ssh
[*] Completed [675DE2C3A4D8CD82] index.docker.io-library-debian-trixie
[*] Completed [AB1DD71BFD07718B] base
[*] Completed [80E4F4E5B0E2F6BA] ssh

In the next chapter we will see how we can turn these layers into a bootable iso file.