diff --git a/docs/reference/commandline/dockerd.md b/docs/reference/commandline/dockerd.md index 6c49514ec48c..ff40ddf2bad4 100644 --- a/docs/reference/commandline/dockerd.md +++ b/docs/reference/commandline/dockerd.md @@ -396,36 +396,197 @@ Defaults to 20G. C:\> dockerd --storage-opt size=40G ``` -### Docker runtime execution options +### Runtime options The Docker daemon relies on a [OCI](https://github.com/opencontainers/runtime-spec) compliant runtime (invoked via the `containerd` daemon) as its interface to the Linux kernel `namespaces`, `cgroups`, and `SELinux`. -By default, the Docker daemon automatically starts `containerd`. If you want to -control `containerd` startup, manually start `containerd` and pass the path to -the `containerd` socket using the `--containerd` flag. For example: +#### Configure container runtimes + +By default, the Docker daemon uses runc as a container runtime. +You can configure the daemon to add additional runtimes. + +containerd shims installed on `PATH` can be used directly, without the need +to edit the daemon's configuration. For example, if you install the Kata +Containers shim (`containerd-shim-kata-v2`) on `PATH`, then you can select that +runtime with `docker run` without having to edit the daemon's configuration: ```console -$ sudo dockerd --containerd /var/run/dev/docker-containerd.sock +$ docker run --runtime io.containerd.kata.v2 ``` -Runtimes can be registered with the daemon either via the -configuration file or using the `--add-runtime` command line argument. +Container runtimes that don't implement containerd shims, or containerd shims +installed outside of `PATH`, must be registered with the daemon, either via the +configuration file or using the `--add-runtime` command line flag. + +For examples on how to use other container runtimes, see +[Alternative container runtimes](https://docs.docker.com/engine/alternative-container-runtimes) + +##### Configure runtimes using `daemon.json` -The following is an example adding 2 runtimes via the configuration: +To register and configure container runtimes using the daemon's configuration +file, add the runtimes as entries under `runtimes`: ```json { - "default-runtime": "runc", "runtimes": { - "custom": { - "path": "/usr/local/bin/my-runc-replacement", - "runtimeArgs": [ - "--debug" - ] + "": {} + } +} +``` + +The key of the entry (`` in the previous example) represents the name +of the runtime. This is the name that you reference when you run a container, +using `docker run --runtime `. + +The runtime entry contains an object specifying the configuration for your +runtime. The properties of the object depends on what kind of runtime you're +looking to register: + +- If the runtime implements its own containerd shim, the object shall contain + a `runtimeType` field and an optional `options` field. + + ```json + { + "runtimes": { + "": { + "runtimeType": "", + "options": {} + } + } + } + ``` + + See [Configure shims](#configure-containerd-shims). + +- If the runtime is designed to be a drop-in replacement for runc, + the object contains a `path` field, and an optional `runtimeArgs` field. + + ```json + { + "runtimes": { + "": { + "path": "/path/to/bin", + "runtimeArgs": ["...args"] + } + } + } + ``` + + See [Configure runc drop-in replacements](#configure-runc-drop-in-replacements). + +After changing the runtimes configuration in the configuration file, +you must reload or restart the daemon for changes to take effect: + +```console +$ sudo systemctl reload dockerd +``` + +##### Configure containerd shims + +If the runtime that you want to register implements a containerd shim, +or if you want to register a runtime which uses the runc shim, +use the following format for the runtime entry: + +```json +{ + "runtimes": { + "": { + "runtimeType": "", + "options": {} + } + } +} +``` + +`runtimeType` refers to either: + +- A fully qualified name of a containerd shim. + + The fully qualified name of a shim is the same as the `runtime_type` used to + register the runtime in containerd's CRI configuration. + For example, `io.containerd.runsc.v1`. + +- The path of a containerd shim binary. + + This option is useful if you installed the containerd shim binary outside of + `PATH`. + +`options` is optional. It lets you specify the runtime configuration that you +want to use for the shim. The configuration parameters that you can specify in +`options` depends on the runtime you're registering. For most shims, +the supported configuration options are `TypeUrl` and `ConfigPath`. +For example: + +```json +{ + "runtimes": { + "gvisor": { + "runtimeType": "io.containerd.runsc.v1", + "options": { + "TypeUrl": "io.containerd.runsc.v1.options", + "ConfigPath": "/etc/containerd/runsc.toml", + } + } + } +} +``` + +You can configure multiple runtimes using the same runtimeType. For example: + +```json +{ + "runtimes": { + "gvisor-foo": { + "runtimeType": "io.containerd.runsc.v1", + "options": { + "TypeUrl": "io.containerd.runsc.v1.options", + "ConfigPath": "/etc/containerd/runsc-foo.toml" + } }, + "gvisor-bar": { + "runtimeType": "io.containerd.runsc.v1", + "options": { + "TypeUrl": "io.containerd.runsc.v1.options", + "ConfigPath": "/etc/containerd/runsc-bar.toml" + } + } + } +} +``` + +The `options` field takes a special set of configuration parameters when used +with `"runtimeType": "io.containerd.runc.v2"`. For more information about runc +parameters, refer to the runc configuration section in +[CRI Plugin Config Guide](https://github.com/containerd/containerd/blob/v1.7.2/docs/cri/config.md#full-configuration). + +##### Configure runc drop-in replacements + +If the runtime that you want to register can act as a drop-in replacement for +runc, you can register the runtime either using the daemon configuration file, +or using the `--add-runtime` flag for the `dockerd` cli. + +When you use the configuration file, the entry uses the following format: + +```json +{ + "runtimes": { + "": { + "path": "/path/to/binary", + "runtimeArgs": ["...args"] + } + } +} +``` + +Where `path` is either the absolute path to the runtime executable, or the name +of an executable installed on `PATH`: + +```json +{ + "runtimes": { "runc": { "path": "runc" } @@ -433,24 +594,58 @@ The following is an example adding 2 runtimes via the configuration: } ``` -This is the same example via the command line: +And `runtimeArgs` lets you optionally pass additional arguments to the runtime. +Entries with this format use the containerd runc shim to invoke a custom +runtime binary. + +When you use the `--add-runtime` CLI flag, use the following format: ```console -$ sudo dockerd --add-runtime runc=runc --add-runtime custom=/usr/local/bin/my-runc-replacement +$ sudo dockerd --add-runtime = ``` -> **Note** -> -> Defining runtime arguments via the command line is not supported. +Defining runtime arguments via the command line is not supported. + +For an example configuration for a runc drop-in replacment, see +[Alternative container runtimes > youki](https://docs.docker.com/engine/alternative-runtimes/#youki) + +##### Configure the default container runtime + +You can specify either the name of a fully qualified containerd runtime shim, +or the name of a registered runtime. You can specify the default runtime either +using the daemon configuration file, or using the `--default-runtime` flag for +the `dockerd` cli. -#### Options for the runtime +When you use the configuration file, the entry uses the following format: -You can configure the runtime using options specified -with the `--exec-opt` flag. All the flag's options have the `native` prefix. A -single `native.cgroupdriver` option is available. +```json +{ + "default-runtime": "io.containerd.runsc.v1" +} +``` -The `native.cgroupdriver` option specifies the management of the container's -cgroups. You can only specify `cgroupfs` or `systemd`. If you specify +When you use the `--default-runtime` CLI flag, use the following format: + +```console +$ dockerd --default-runtime io.containerd.runsc.v1 +``` + +#### Run containerd standalone + +By default, the Docker daemon automatically starts `containerd`. If you want to +control `containerd` startup, manually start `containerd` and pass the path to +the `containerd` socket using the `--containerd` flag. For example: + +```console +$ sudo dockerd --containerd /run/containerd/containerd.sock +``` + +#### Configure cgroup driver + +You can configure how the runtime should manage container cgroups, using the +`--exec-opt native.cgroupdriver` CLI flag. + +You can only specify `cgroupfs` or `systemd`. If you specify `systemd` and it is not available, the system errors out. If you omit the `native.cgroupdriver` option,` cgroupfs` is used on cgroup v1 hosts, `systemd` is used on cgroup v2 hosts with systemd available. @@ -463,16 +658,19 @@ $ sudo dockerd --exec-opt native.cgroupdriver=systemd Setting this option applies to all containers the daemon launches. -Also Windows Container makes use of `--exec-opt` for special purpose. Docker user -can specify default container isolation technology with this, for example: +#### Configure container isolation technology (Windows) + +For Windows containers, you can specify the default container isolation +technology to use, using the `--exec-opt isolation` flag. + +The following example makes `hyperv` the default isolation technology: ```console > dockerd --exec-opt isolation=hyperv ``` -Will make `hyperv` the default isolation technology on Windows. If no isolation -value is specified on daemon start, on Windows client, the default is -`hyperv`, and on Windows server, the default is `process`. +If no isolation value is specified on daemon start, on Windows client, +the default is `hyperv`, and on Windows server, the default is `process`. ### Daemon DNS options