Made with ❤ by openSUSE.

umoci is a free software tool for manipulating and interacting with container images in the standardised Open Container Initiative’s image format. It provides one of the most flexible image management toolsets, requiring neither a daemon nor any particular filesystem setup. It is already used in a variety of different projects and by several companies.


umoci’s feature set is intentionally restricted, as it has well-defined goals.

  • Extraction of images produces a standardised OCI runtime bundle, which is immediately usable by runc or any other OCI-compliant runtime. However, these bundles are also usable without the need for containers (which means that builders can mutate the root filesystem in whatever fashion they choose).
  • Generates delta layers without requiring filesystem-specific features. Rather, it makes use of existing mtree manifest tooling to compute the deltas of paths in the root filesystem.
  • Supports rootless containers natively, both by allowing for extraction of layers that would normally require privileges and by generating runtime configurations that runc can use as an unprivileged user.
  • Internal libraries are entirely built around a generic content addressable store interface, allowing for code reuse by other projects and the possibility for new backends.


Pre-built binaries can be downloaded from umoci’s releases page. As umoci’s builds are reproducible, a cryptographic checksum file is included in the release assets. All of the assets are also signed with a release key.

pub   rsa4096 2016-06-21 [SC] [expires: 2031-06-18]
uid           [ultimate] Aleksa Sarai <>
uid           [ultimate] Aleksa Sarai <>
sub   rsa4096 2016-06-21 [E] [expires: 2031-06-18]

umoci is also available from several distribution’s repositories:

To build umoci from the source code, a simple make && make install should work on most machines. The changelog is also available.


umoci is licensed under the terms of the Apache 2.0 license.

umoci: Umoci Modifies Open Containers' Images
Copyright (C) 2016, 2017, 2018 SUSE LLC.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
See the License for the specific language governing permissions and
limitations under the License.