# libostree

This project is now known as "libostree", though it is still appropriate to use

the previous name: "OSTree" (or "ostree"). The focus is on projects which use

libostree's shared library, rather than users directly invoking the command line

tools (except for build systems). However, in most of the rest of the

documentation, we will use the term "OSTree", since it's slightly shorter, and

changing all documentation at once is impractical. We expect to transition to

the new name over time.

As implied above, libostree is both a shared library and suite of command line

tools that combines a "git-like" model for committing and downloading bootable

filesystem trees, along with a layer for deploying them and managing the

bootloader configuration.

The core OSTree model is like git in that it checksums individual files and has

a content-addressed-object store. It's unlike git in that it "checks out" the

files via hardlinks, and they thus need to be immutable to prevent corruption.

Therefore, another way to think of OSTree is that it's just a more polished

version of

[Linux VServer hardlinks](http://linux-vserver.org/index.php?title=util-vserver:Vhashify&oldid=2285).

**Features:**

 - Transactional upgrades and rollback for the system

 - Replicating content incrementally over HTTP via GPG signatures and "pinned TLS" support

 - Support for parallel installing more than just 2 bootable roots

 - Binary history on the server side (and client)

 - Introspectable shared library API for build and deployment systems

 - Flexible support for multiple branches and repositories, supporting

   projects like [flatpak](https://github.com/flatpak/flatpak) which

   use libostree for applications, rather than hosts.

## Documentation

For more information, see the [project documentation](docs/index.md) or the

[project documentation website](https://ostreedev.github.io/ostree).

## Operating systems and distributions using OSTree

[Endless OS](https://endlessos.com/) uses libostree for their host system as

well as flatpak. See

their [eos-updater](https://github.com/endlessm/eos-updater)

and [deb-ostree-builder](https://github.com/dbnicholson/deb-ostree-builder)

projects.

Fedora derivatives use rpm-ostree (noted below); there are 3 variants using OSTree:

 - [Fedora CoreOS](https://getfedora.org/en/coreos/)

 - [Fedora Silverblue](https://silverblue.fedoraproject.org/)

 - [Fedora IoT](https://iot.fedoraproject.org/)

Red Hat Enterprise Linux CoreOS is a derivative of Fedora CoreOS, used in [OpenShift 4](https://try.openshift.com/).

The [machine-config-operator](https://github.com/openshift/machine-config-operator/blob/master/docs/OSUpgrades.md)

manages upgrades.  RHEL CoreOS is also the successor to RHEL Atomic Host, which

uses rpm-ostree as well.

[GNOME Continuous](https://wiki.gnome.org/Projects/GnomeContinuous) is

where OSTree was born - as a high performance continuous delivery/testing

system for GNOME.

[Liri OS](https://liri.io/download/silverblue/) has the option to install

their distribution using ostree.

## Distribution build tools

[meta-updater](https://github.com/advancedtelematic/meta-updater) is

a layer available for [OpenEmbedded](http://www.openembedded.org/wiki/Main_Page)

systems.

[QtOTA](http://doc.qt.io/QtOTA/) is Qt's over-the-air update framework

which uses libostree.

The [BuildStream](https://gitlab.com/BuildStream/buildstream) build and

integration tool supports importing and exporting from libostree repos.

Fedora [coreos-assembler](https://github.com/coreos/coreos-assembler) is

the build tool used to generate Fedora CoreOS derivatives.

## Projects linking to libostree

[rpm-ostree](https://github.com/projectatomic/rpm-ostree) is used by the

Fedora-derived operating systems listed above.  It is a full hybrid

image/package system.  By default it uses libostree to atomically replicate a base OS

(all dependency resolution is done on the server), but it supports "package layering", where

additional RPMs can be layered on top of the base.  This brings a "best of both worlds""

model for image and package systems.

[eos-updater](https://github.com/endlessm/eos-updater) is a daemon that implements updates

on EndlessOS.

[flatpak](https://github.com/flatpak/flatpak) uses libostree for desktop

application containers. Unlike most of the other systems here, flatpak does not

use the "libostree host system" aspects (e.g. bootloader management), just the

"git-like hardlink dedup". For example, flatpak supports a per-user OSTree

repository.

## Language bindings

libostree is accessible via [GObject Introspection](https://gi.readthedocs.io/en/latest/);

any language which has implemented the GI binding model should work.

For example, Both [pygobject](https://pygobject.readthedocs.io/en/latest/)

and [gjs](https://gitlab.gnome.org/GNOME/gjs) are known to work

and further are actually used in libostree's test suite today.

Some bindings take the approach of using GI as a lower level and

write higher level manual bindings on top; this is more common

for statically compiled languages.  Here's a list of such bindings:

 - [ostree-go](https://github.com/ostreedev/ostree-go/)

 - [ostree-rs](https://gitlab.com/fkrull/ostree-rs/)

## Building

Releases are available as GPG signed git tags, and most recent

versions support extended validation using

[git-evtag](https://github.com/cgwalters/git-evtag).

However, in order to build from a git clone, you must update the

submodules.  If you're packaging OSTree and want a tarball, I

recommend using a "recursive git archive" script.  There are several

available online;

[this code](https://github.com/ostreedev/ostree/blob/master/packaging/Makefile.dist-packaging#L11)

in OSTree is an example.

Once you have a git clone or recursive archive, building is the

same as almost every autotools project:

```

git submodule update --init

env NOCONFIGURE=1 ./autogen.sh

./configure --prefix=...

make

make install DESTDIR=/path/to/dest

```

## Contributing

See [Contributing](docs/CONTRIBUTING.md).

## Licensing

The licensing for the *code* of libostree can be canonically found in the individual files;

and the overall status in the [COPYING](https://github.com/ostreedev/ostree/blob/master/COPYING)

file in the source.  Currently, that's LGPLv2+.  This also covers the man pages and API docs.

The license for the manual documentation in the `doc/` directory is:

`SPDX-License-Identifier: (CC-BY-SA-3.0 OR GFDL-1.3-or-later)`

This is intended to allow use by Wikipedia and other projects.

In general, files should have a `SPDX-License-Identifier` and that is canonical.