Release Process

The following documents the release process used with mcuboot.

Version numbering

MCUboot uses semantic versioning, where version numbers follow a MAJOR.MINOR.PATCH format with the following guidelines on incremeting the numbers:

  1. MAJOR version when you make incompatible API changes,

  2. MINOR version when you add functionality in a backwards-compatible manner, and

  3. PATCH version when you make backwards-compatible bug fixes.

We add pre-release tags of the format MAJOR.MINOR.PATCH-rc1.

We mark in documentation an MCUBoot development version using the format MAJOR.MINOR.PATCH-dev.

Release Notes

Before making a release, be sure to update the docs/ to describe the release. This should be a high-level description of the changes, not a list of the git commits.

Release Candidates

Prior to each release, tags are made (see below) for at least one release candidate (a.b.c-rc1, followed by a.b.c-rc2, etc, followed by the official a.b.c release). The intent is to freeze the code for a time, and allow testing to happen.

During the time between rc1 and the final release, the only changes that should be merged into main are those to fix bugs found in the rc and Mynewt metadata as described in the next section.

imgtool release

imgtool is released through (The Python package index) and requires that its version to be updated by editing scripts/imgtool/ and modifying the exported version:

imgtool_version = "A.B.CrcN"

This version should match the current release number of MCUboot; rcN (with no dash!) is accepted for pre-release version under test, and numbers only for final releases. For more info see:

Mynewt release information

On Mynewt, newt always fetches a versioned MCUBoot release, so after the rc step is finished, the release needs to be exported by modifying repository.yml in the root directory; it must be updated with the new release version, including updates to the pseudo keys (*-(latest|dev)).

Tagging and Release

To make a release, make sure your local repo is on the tip version by fetching from origin. Typically, the releaser should create a branch named after the particular release.

Create a commit on top of the branch that modifies the version number in the top-level, and create a commit, with just this change, with a commit text similar to “Bump to version a.b.c”. Having the version bump helps to make the releases easier to find, as each release has a commit associated with it, and not just a tag pointing to another commit.

Once this is done, the release should create a signed tag:

git tag -s va.b.c-rcn

with the appropriate tag name. The releaser will need to make sure that git is configured to use the proper signing key, and that the public key is signed by enough parties to be trusted.

At this point, the tag can be pushed to github to make the actual release happen:

git push origin HEAD:refs/heads/main
git push origin va.b.c-rcn

Branching after a Release

After the final (non-rc) a.b.0 release is made, a new branch must be created and pushed:

git checkout va.b.c
git checkout -b va.b-branch
git push origin va.b-branch

This branch will be used to generate new incremental PATCH releases for bug fixes or required minor updates (eg, new imgtool features).

Post release actions

Mark the MCUBoot version as a development version. The version number used should be specified for the next expected release. It should be larger than the last release version by incrementing the MAJOR or the MINOR number. It is not necessary to define the next version precisely as the next release version might still be different as it might be needed to do:

  • a patch release

  • a MINOR release while a MAJOR release was expected

  • a MAJOR release while a MINOR release was expected