zrepl

zrepl is a one-stop ZFS backup & replication solution.

User Documentation

User Documentation can be found at zrepl.github.io.

Bug Reports

1. If the issue is reproducible, enable debug logging, reproduce and capture the log.
2. Open an issue on GitHub, with logs pasted as GitHub gists / inline.

Feature Requests

1. Does your feature request require default values / some kind of configuration? If so, think of an expressive configuration example.
2. Think of at least one use case that generalizes from your concrete application.
3. Open an issue on GitHub with example conf & use case attached.
4. Optional: Contact Christian Schwarz for contract work.

The above does not apply if you already implemented everything. Check out the Coding Workflow section below for details.

Development

zrepl is written in Go and uses Go modules to manage dependencies. The documentation is written in ReStructured Text using the Sphinx framework.

Building

Go Code

Dependencies:

• Go
• GNU Make
• Git
• wget (make generate)
• unzip (make generate)

Some Go code is generated, and generated code is committed to the source tree. Therefore, building does not require having code generation tools set up. When making changes that require code to be (re-)generated, run make generate. I downloads and installs pinned versions of the code generation tools into ./build/install. There is a CI check that ensures Git state is clean, i.e., code generation has been done by a PR and is deterministic.

Docs

Install uv, then run make docs. uv automatically manages Python and dependencies.

Testing

The test suite is split into pure Go tests (make test-go) and platform tests that interact with ZFS and thus generally require root privileges (sudo make test-platform). Platform tests run on their own pool with the name zreplplatformtest, which is created using the file vdev in /tmp.

For a full code coverage profile, run make test-go COVER=1 && sudo make test-platform && make cover-merge. An HTML report can be generated using make cover-html.

Circle CI

We use CircleCI for automated build & test pre- and post-merge.

There are two workflows:

• ci runs for every commit / branch / tag pushed to GitHub. It is supposed to run very fast (<5min and provides quick feedback to developers). It runs formatting checks, lints and tests on the most important OSes / architectures.

• release runs

  • on manual triggers through the CircleCI API (in order to produce a release)
  • periodically on master

Artifacts are stored in CircleCI.

Releasing

All zrepl releases are git-tagged and then published as a GitHub Release. There is a git tag for each zrepl release, usually vMAJOR.MINOR.0. We don't move git tags once the release has been published.

The procedure to issue a release is as follows:

• Prepare the release (as a PR to master):
  • Finalize docs/changelog.rst for the release.
  • Update the supporters list based on contributors for this release:

    claude --permission-mode default '/update-supporters v0.6.1..v0.7.0'
    

    Replace version tags with the appropriate range for your release.
  • Merge the PR. Docs are auto-published to zrepl.github.io on merge.
• Tag the release:
  • Git tag the release on the master branch (e.g., vMAJOR.MINOR.0).

    make tag-release ZREPL_TAG_VERSION=v0.7.0
    

  • Push the tag.
• Build and publish:

  • Run the release pipeline against the master branch (trigger via CircleCI UI). This URL: https://app.circleci.com/pipelines/github/zrepl/zrepl?branch=master. Example pipeline: https://app.circleci.com/pipelines/github/zrepl/zrepl/8547

  • Download artifacts using this handy makefile target. Note: JOB_NUM must be the job number from the release-upload job, not the pipeline number. Find it via: pipeline → release workflow → release-upload job number. Example URL: https://app.circleci.com/pipelines/github/zrepl/zrepl/8547/workflows/65feb2c9-15d7-46ab-a551-46d62a5769b0/jobs/66079/steps

    make download-circleci-release JOB_NUM=66079
    

  • Verify checksums and sign the checksums file:

    make verify-and-sign
    

  • Create GitHub draft release and upload artifacts:

    claude --permission-mode default '/draft-release v0.7.0'
    

    This command will verify that artifacts are ready, create the draft release, and upload all artifacts.

  • Review the draft release on GitHub, then publish, with the box checked to create a GitHub "Discussion" for the release.

• Immediately after hitting publish.
  • Update the release on GitHub to link to the discussion.
  • Update docs/changelog.rst to link to the GitHub release.
  • Update docs/_templates/versions.html to link to the GitHub release.
  • Announce release in the zrepl Matrix channel & other socials as applicable. Link to the GitHub release as the entrypoint.
• After a couple of days
  • Add the .rpm and .deb files to the official zrepl repos.
    • Code for management of these repos: https://github.com/zrepl/package-repo-ops (private repo at this time)

Patch releases, Go toolchain updates, APT/RPM Package rebuilds

vMAJOR.MINOR.0 is typically a tagged commit on master, because development velocity isn't high and thus release branches for stabilization aren't necessary.

Occasionally though there is a need for patch changes to a release, e.g.

• security issue in a dependency
• Go toolchain update (e.g. security issue in standard library)

The procedure for this is the following

• create a branch off the release tag we need to patch, named releases/MAJOR.MINOR.X
• that branch will never be merged into master, it'll be a dead-end for this specific patch
• make changes in that branch
• make the final commit that bumps version numbers
• create the git tag
• follow general procedure for publishing the release (previous sectino

For Go toolchain updates and package rebuilds with no source code changes, leverage the APT/RPM package revision field. Control via the ZREPL_PACKAGE_RELEASE Makefile variable, see origin/releases/0.6.1-2 for an example.

Updating Dependencies

• Update the go directive and toolchain directive in go.mod
  • go is the minimum supported version
  • toolchain is the preferred toolchain version if GOTOOLCHAIN is not specified

Run go mod tidy to ensure consistency.

Update Go module dependencies:

# Update all other dependencies
go get -u -t ./...
go mod tidy

# Above might fail if there are version selection conflicts.
# Figure out what's going on by updating packages from error messages first.
# Example:
go get -u google.golang.org/genproto google.golang.org/grpc google.golang.org/protobuf

Update codegen & lint tools

• protoc => build/get_protoc.bash
  • GH releases publish sha256 sums
• golangci-lint => build/get_golangci_lint.bash
• bump versions in build/tools.go
  • we use the tools.go trick:
  • go get -tags tools -u example.com/tool ; go mod tidy
  • review whether we're ready to switch to go tool: https://github.com/zrepl/zrepl/pull/909

Now run make generate.

Run make lint and make vet.

Update the CI configuration .circleci/config.yml:

• Update Go version references (we reference the minimum and max supported version)
• Set Makefile RELEASE_GOVERSION to the new Go version
• Update the pinned ZFS release tags in the platformtest matrix (zfs_release parameter) to the latest patch releases of each OpenZFS branch (currently 2.2, 2.3, 2.4)
• Update the pinned Ubuntu machine image for platformtest (e.g. ubuntu-2404:2025.09.1) — this is pinned rather than current so the ZFS build cache stays valid across runs

Update docs build tooling:

• Update uv version in .circleci/config.yml (search for astral.sh/uv/ and cache keys containing the version)
• Check if there's now a CircleCI orb for uv that we could use
• Update Python version in docs/.python-version

Update docs dependencies (Sphinx, sphinx-rtd-theme):

• Check current versions in docs/pyproject.toml
• Review upstream changelogs for breaking changes
• Update version constraints in pyproject.toml and the uv lockfile (see uv docs on dependencies):
• Test locally with make docs

Kick a full CI pipeline run (do_ci=true and do_release=true).

Merge PR with merge commit.

Notes to Distro Package Maintainers

• The Makefile in this project is not suitable for builds in distros.
• Run the platform tests (Docs -> Usage -> Platform Tests) on a test system to validate that zrepl's abstractions on top of ZFS work with the system ZFS.
• Ship a default config that adheres to your distro's hier and logging system.
• Ship a service manager file and please try to upstream it to this repository.
  • dist/systemd contains a Systemd unit template.
• Ship other material provided in ./dist, e.g. in /usr/share/zrepl/.
• Have a look at the Makefile's ZREPL_VERSION variable and how it passed to Go's ldFlags. This is how zrepl version knows what version number to show. Your build system should set the ldFlags flags appropriately and add a prefix or suffix that indicates that the given zrepl binary is a distro build, not an official one.
• Make sure you are informed about new zrepl versions, e.g. by subscribing to GitHub's release RSS feed.