Add ubuntu notes

UBUNTU-NOTES.md

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+# Ubuntu
+
+The [Cartesi](http://cartesi.io) team is interested in having python images built for `linux/riscv46` architecture, so it can be used as a base image for Cartesi DApps written in python.
+
+Debian and buildpack-deps debian images, which are the base for the python image, are still unstable for `linux/riscv64` platform.
+
+On the other hand Ubuntu and buildpack-deps ubuntu images already have official builds for `linux/riscv64`.
+
+So this branch adds Ubuntu based variants for the `python` image.
+A [PR was opened upstream](https://github.com/docker-library/python/pull/791), but its unlikely to be accepted.
+
+In the meantime the Cartesi team is building the image and publishing as `cartesi/python`.
+
+```shell
+docker pull cartesi/python
+```
+
+## Building locally
+
+The primary change introduced in this branch was to `versions.sh`, adding `jammy` and `kinetic` variants. The other changes are generated by executing the following command, which uses Docker so it works on any platform.
+
+```shell
+docker run -it --rm -v $(pwd):/app ubuntu
+apt-get update
+apt-get install -y curl gawk git jq wget
+/app/update.sh
+```
+
+After running the command above several Dockerfiles are created or updated. The commands below build the images locally, using `dockerx` multi platform build.
+
+```shell
+docker buildx bake
+```
+
+> TODO: create a script to generate the [docker-bake.hcl](docker-bake.hcl) file from the [versions.json](versions.json) files.
+
+Several tags are built, the main one is `docker.io/cartesi/python:jammy`.

docker-bake.hcl

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+
+group "default" {
+  targets = ["v3_11-jammy"]
+}
+
+target "riscv" {
+  platforms = ["linux/riscv64"]
+}
+
+target "v3_7-jammy" {
+  inherits = ["riscv"]
+  context  = "3.7/jammy/"
+  tags     = ["docker.io/cartesi/python:3.7.16-jammy", "docker.io/cartesi/python:3.7-jammy"]
+}
+
+target "v3_8-jammy" {
+  inherits = ["riscv"]
+  context  = "3.8/jammy/"
+  tags     = ["docker.io/cartesi/python:3.8.16-jammy", "docker.io/cartesi/python:3.8-jammy"]
+}
+
+target "v3_9-jammy" {
+  inherits = ["riscv"]
+  context  = "3.9/jammy/"
+  tags     = ["docker.io/cartesi/python:3.9.16-jammy", "docker.io/cartesi/python:3.9-jammy"]
+}
+
+target "v3_10-jammy" {
+  inherits = ["riscv"]
+  context  = "3.10/jammy/"
+  tags     = ["docker.io/cartesi/python:3.10.10-jammy", "docker.io/cartesi/python:3.10-jammy"]
+}
+
+target "v3_11-jammy" {
+  inherits = ["riscv"]
+  context  = "3.11/jammy/"
+  tags     = ["docker.io/cartesi/python:3.11.2-jammy", "docker.io/cartesi/python:3.11-jammy", "docker.io/cartesi/python:3-jammy", "docker.io/cartesi/python:jammy"]
+}
+
+target "v3_12-jammy" {
+  inherits = ["riscv"]
+  context  = "3.12-rc/jammy/"
+  tags     = ["docker.io/cartesi/python:3.12.0a5-jammy", "docker.io/cartesi/python:3.12-rc-jammy"]
+}
+
+target "v3_7-kinetic" {
+  inherits = ["riscv"]
+  context  = "3.7/kinetic/"
+  tags     = ["docker.io/cartesi/python:3.7.16-kinetic", "docker.io/cartesi/python:3.7-kinetic"]
+}
+
+target "v3_8-kinetic" {
+  inherits = ["riscv"]
+  context  = "3.8/kinetic/"
+  tags     = ["docker.io/cartesi/python:3.8.16-kinetic", "docker.io/cartesi/python:3.8-kinetic"]
+}
+
+target "v3_9-kinetic" {
+  inherits = ["riscv"]
+  context  = "3.9/kinetic/"
+  tags     = ["docker.io/cartesi/python:3.9.16-kinetic", "docker.io/cartesi/python:3.9-kinetic"]
+}
+
+target "v3_10-kinetic" {
+  inherits = ["riscv"]
+  context  = "3.10/kinetic/"
+  tags     = ["docker.io/cartesi/python:3.10.10-kinetic", "docker.io/cartesi/python:3.10-kinetic"]
+}
+
+target "v3_11-kinetic" {
+  inherits = ["riscv"]
+  context  = "3.11/kinetic/"
+  tags     = ["docker.io/cartesi/python:3.11.2-kinetic", "docker.io/cartesi/python:3.11-kinetic", "docker.io/cartesi/python:3-kinetic", "docker.io/cartesi/python:kinetic"]
+}
+
+target "v3_12-kinetic" {
+  inherits = ["riscv"]
+  context  = "3.12-rc/kinetic/"
+  tags     = ["docker.io/cartesi/python:3.12.0a5-kinetic", "docker.io/cartesi/python:3.12-rc-kinetic"]
+}