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# Runtime

This repository contains the runtime for the
[Kata Containers](https://github.com/kata-containers) project.

For details of the other Kata Containers repositories, see the
[repository summary](https://github.com/kata-containers/kata-containers).

* [Introduction](#introduction)
* [License](#license)
* [Platform support](#platform-support)
    * [Hardware requirements](#hardware-requirements)
* [Quick start for users](#quick-start-for-users)
* [Quick start for developers](#quick-start-for-developers)
* [Architecture overview](#architecture-overview)
* [Configuration](#configuration)
* [Logging](#logging)
* [Debugging](#debugging)
* [Limitations](#limitations)
* [Community](#community)
    * [Contact](#contact)
* [Further information](#further-information)

## Introduction

`kata-runtime`, referred to as "the runtime", is the Command-Line Interface
(CLI) part of the Kata Containers runtime component. It leverages the
[virtcontainers](https://github.com/kata-containers/runtime/tree/master/virtcontainers)
package to provide a high-performance standards-compliant runtime that creates
hardware-virtualized containers.

The runtime is
[OCI](https://github.com/opencontainers/runtime-spec)-compatible,
[CRI-O](https://github.com/kubernetes-incubator/cri-o)-compatible, and
[Containerd](https://github.com/containerd/containerd)-compatible,
 allowing it
to work seamlessly with both Docker and Kubernetes respectively.

## License

The code is licensed under an Apache 2.0 license.

See [the license file](LICENSE) for further details.

## Platform support

Kata Containers currently works on systems supporting the following
technologies:

- [Intel](https://www.intel.com) VT-x technology.
- [ARM](https://www.arm.com) Hyp mode (virtualization extension).
- [IBM](https://www.ibm.com) Power Systems.
- [IBM](https://www.ibm.com) Z mainframes.
### Hardware requirements

The runtime has a built-in command to determine if your host system is capable
of running a Kata Container:

```bash
$ kata-runtime kata-check
```

> **Note:**
>
> If you run the previous command as the `root` user, further checks will be
> performed (e.g. it will check if another incompatible hypervisor is running):
>
> ```bash
> $ sudo kata-runtime kata-check
> ```

## Quick start for users

See the [installation guides](https://github.com/kata-containers/documentation/tree/master/install/README.md)
available for various operating systems.

## Quick start for developers

See the
[developer guide](https://github.com/kata-containers/documentation/blob/master/Developer-Guide.md).

## Architecture overview

See the [architecture overview](https://github.com/kata-containers/documentation/blob/master/architecture.md)
for details on the Kata Containers design.

## Configuration

The runtime uses a TOML format configuration file called `configuration.toml`.
The file contains comments explaining all options.

> **Note:**
>
> The initial values in the configuration file provide a good default configuration.
> You might need to modify this file if you have specialist needs.

Since the runtime supports a
[stateless system](https://clearlinux.org/features/stateless),
it checks for this configuration file in multiple locations, two of which are
built in to the runtime. The default location is
`/usr/share/defaults/kata-containers/configuration.toml` for a standard
system. However, if `/etc/kata-containers/configuration.toml` exists, this
takes priority.

The command below lists the full paths to the configuration files that the
runtime attempts to load. The first path that exists is used:

```bash
$ kata-runtime --kata-show-default-config-paths
```

Aside from the built-in locations, it is possible to specify the path to a
custom configuration file using the `--kata-config` option:

```bash
$ kata-runtime --kata-config=/some/where/configuration.toml ...
```

The runtime will log the full path to the configuration file it is using. See
the [logging](#Logging) section for further details.

To see details of your systems runtime environment (including the location of
the configuration file being used), run:

```bash
$ kata-runtime kata-env
```

## Logging

The runtime provides `--log=` and `--log-format=` options. However, the
runtime always logs to the system log (`syslog` or `journald`).

To view runtime log output:

```bash
$ sudo journalctl -t kata-runtime
```

For detailed information and analysis on obtaining logs for other system
components, see the documentation for the
[kata-log-parser](https://github.com/kata-containers/tests/tree/master/cmd/log-parser)
tool.

## Debugging

See the
[debugging section of the developer guide](https://github.com/kata-containers/documentation/blob/master/Developer-Guide.md#troubleshoot-kata-containers).

## Limitations

See the
[limitations file](https://github.com/kata-containers/documentation/blob/master/Limitations.md)
for further details.

## Community

See [the community repository](https://github.com/kata-containers/community).

### Contact

See [how to reach the community](https://github.com/kata-containers/community/blob/master/CONTRIBUTING.md#contact).

## Further information

See the
[project table of contents](https://github.com/kata-containers/kata-containers)
and the
[documentation repository](https://github.com/kata-containers/documentation).