Create a “Hello World” rock¶
Prerequisites¶
snap enabled system (https://snapcraft.io)
LXD installed (https://linuxcontainers.org/lxd/getting-started-cli/)
skopeo installed (https://github.com/containers/skopeo)
Docker installed (https://snapcraft.io/docker)
a text editor
Install Rockcraft¶
Install Rockcraft on your host:
sudo snap install rockcraft --classic
Project Setup¶
Create a new directory and write the following into a text editor and
save it as rockcraft.yaml
:
# Metadata section
name: hello
summary: Hello World
description: The most basic example of a rock.
version: "latest"
license: Apache-2.0
base: bare
build-base: [email protected]
platforms:
amd64: # Make sure this value matches your computer's architecture
# Parts section
parts:
hello:
plugin: nil
stage-packages:
- hello
This file instructs Rockcraft to build a rock that only has the hello
package (and its dependencies) inside. For more information about the parts
section, check Part properties. The remaining YAML fields correspond to
metadata that help define and describe the rock. For more information about all
available fields check rockcraft.yaml.
Pack the rock with Rockcraft¶
To build the rock, run:
rockcraft pack
The output should look as follows:
Launching instance...
Retrieved base bare for amd64
Extracted bare:latest
Executed: pull hello
Executed: pull pebble
Executed: overlay hello
Executed: overlay pebble
Executed: build hello
Executed: build pebble
Executed: stage hello
Executed: stage pebble
Executed: prime hello
Executed: prime pebble
Executed parts lifecycle
Exported to OCI archive 'hello_latest_amd64.rock'
At the end of the process, a file named hello_latest_amd64.rock
should be
present in the current directory. That’s your rock, in oci-archive format
(a tarball).
Run the rock in Docker¶
First, import the recently created rock into Docker:
sudo /snap/rockcraft/current/bin/skopeo --insecure-policy copy oci-archive:hello_latest_amd64.rock docker-daemon:hello:latest
Now run the hello
command from the rock:
docker run --rm hello:latest exec hello -t
Which should print:
hello, world