dockerd - Man Page

• Run Docker daemon: dockerd
• Run Docker daemon and configure it to listen to specific sockets (UNIX and TCP): dockerd --host unix://path/to/tmp.sock --host tcp://ip
• Run with specific daemon PID file: dockerd --pidfile path/to/pid_file
• Run in debug mode: dockerd --debug
• Run and set a specific log level: dockerd --log-level debug|info|warn|error|fatal

tldr.sh

dockerd [--add-runtime[=[]]] [--allow-nondistributable-artifacts[=[]]] [--api-cors-header=[=API-CORS-HEADER]] [--authorization-plugin[=[]]] [-b|--bridge[=BRIDGE]] [--bip[=BIP]] [--cgroup-parent[=[]]] [--config-file[=path]] [--containerd[=SOCKET-PATH]] [--data-root[=/var/lib/docker]] [-D|--debug] [--default-cgroupns-mode[=host]] [--default-gateway[=DEFAULT-GATEWAY]] [--default-gateway-v6[=DEFAULT-GATEWAY-V6]] [--default-address-pool[=DEFAULT-ADDRESS-POOL]] [--default-network-opt[=DRIVER=OPT=VALUE]] [--default-runtime[=runc]] [--default-ipc-mode=MODE] [--default-shm-size[=64MiB]] [--default-ulimit[=[]]] [--dns[=[]]] [--dns-opt[=[]]] [--dns-search[=[]]] [--exec-opt[=[]]] [--exec-root[=/var/run/docker]] [--experimental[=false]] [--feature[=NAME[=true|false]] [--fixed-cidr[=FIXED-CIDR]] [--fixed-cidr-v6[=FIXED-CIDR-V6]] [-G|--group[=docker]] [-H|--host[=[]]] [--help] [--http-proxy[""]] [--https-proxy[""]] [--icc[=true]] [--init[=false]] [--init-path[=""]] [--insecure-registry[=[]]] [--ip[=0.0.0.0]] [--ip-forward[=true]] [--ip-masq[=true]] [--iptables[=true]] [--ipv6] [--isolation[=default]] [-l|--log-level[=info]] [--label[=[]]] [--live-restore[=false]] [--log-driver[=json-file]] [--log-format="text|json"] [--log-opt[=map[]]] [--mtu[=0]] [--max-concurrent-downloads[=3]] [--max-concurrent-uploads[=5]] [--max-download-attempts[=5]] [--no-proxy[""]] [--node-generic-resources[=[]]] [-p|--pidfile[=/var/run/docker.pid]] [--raw-logs] [--registry-mirror[=[]]] [-s|--storage-driver[=STORAGE-DRIVER]] [--seccomp-profile[=SECCOMP-PROFILE-PATH]] [--selinux-enabled] [--shutdown-timeout[=15]] [--storage-opt[=[]]] [--swarm-default-advertise-addr[=IP|INTERFACE]] [--tls] [--tlscacert[=~/.docker/ca.pem]] [--tlscert[=~/.docker/cert.pem]] [--tlskey[=~/.docker/key.pem]] [--tlsverify] [--userland-proxy[=true]] [--userland-proxy-path[=""]] [--userns-remap[=default]] [--validate]

dockerd is used for starting the Docker daemon (i.e., to command the daemon to manage images, containers etc).  So dockerd is a server, as a daemon.

To run the Docker daemon you can specify dockerd. You can check the daemon options using dockerd --help. Daemon options should be specified after the dockerd keyword in the following format.

dockerd [Options]

--add-runtime=[]

Runtimes can be registered with the daemon either via the configuration file or using the --add-runtime command line argument.

The following is an example adding 2 runtimes via the configuration:

{
	"default-runtime": "runc",
	"runtimes": {
		"runc": {
			"path": "runc"
		},
		"custom": {
			"path": "/usr/local/bin/my-runc-replacement",
			"runtimeArgs": [
				"--debug"
			]
		}
	}
}

This is the same example via the command line:

$ sudo dockerd --add-runtime runc=runc --add-runtime custom=/usr/local/bin/my-runc-replacement

Note: defining runtime arguments via the command line is not supported.

--allow-nondistributable-artifacts=[]

Push nondistributable artifacts to the specified registries.

List can contain elements with CIDR notation to specify a whole subnet.

This option is useful when pushing images containing nondistributable
 artifacts to a registry on an air-gapped network so hosts on that network can
 pull the images without connecting to another server.

Warning: Nondistributable artifacts typically have restrictions on how
 and where they can be distributed and shared. Only use this feature to push
 artifacts to private registries and ensure that you are in compliance with
 any terms that cover redistributing nondistributable artifacts.

--api-cors-header=""

Set CORS headers in the Engine API. Default is cors disabled. Give urls like
 "http://foo, http://bar, ...". Give "*" to allow all.

--authorization-plugin=""

Set authorization plugins to load

-b,  --bridge=""

Attach containers to a pre-existing network bridge; use 'none' to disable
 container networking

--bip=""

Use the provided CIDR notation address for the dynamically created bridge
 (docker0); Mutually exclusive of -b

--cgroup-parent=""

Set parent cgroup for all containers. Default is "/docker" for fs cgroup
 driver and "system.slice" for systemd cgroup driver.

--config-file="/etc/docker/daemon.json"

 Specifies the JSON file path to load the configuration from. Default is
 /etc/docker/daemon.json.

--containerd=""

Path to containerd socket.

--data-root=""

Path to the directory used to store persisted Docker data such as
 configuration for resources, swarm cluster state, and filesystem data for
 images, containers, and local volumes. Default is /var/lib/docker.

-D,  --debug=true|false

Enable debug mode. Default is false.

--default-cgroupns-mode="host|private"

Set the default cgroup namespace mode for newly created containers. The argument
 can either be host or private. If unset, this defaults to host on cgroup v1,
 or private on cgroup v2.

--default-gateway=""

IPv4 address of the container default gateway; this address must be part of
 the bridge subnet (which is defined by -b or --bip)

--default-gateway-v6=""

IPv6 address of the container default gateway

--default-address-pool=""

Default address pool from which IPAM driver selects a subnet for the networks.
 Example: base=172.30.0.0/16,size=24 will set the default
 address pools for the selected scope networks to {172.30.[0-255].0/24}

--default-network-opt=DRIVER=OPT=VALUE

Default network driver options

--default-runtime="runtime"

Set default runtime if there're more than one specified by --add-runtime.

--default-ipc-mode="private|shareable"

Set the default IPC mode for newly created containers. The argument
 can either be private or shareable.

--default-shm-size=size

Set the daemon-wide default shm size for containers. Default is 64MiB.

--default-ulimit=[]

Default ulimits for containers.

--dns=""

Force Docker to use specific DNS servers.

--dns-opt=""

DNS options to use.

--dns-search=[]

DNS search domains to use.

--exec-opt=[]

Set runtime execution options. See Runtime Execution Options.

--exec-root=""

 Path to use as the root of the Docker execution state files. Default is
 /var/run/docker.

--experimental=""

Enable the daemon experimental features.

--feature=NAME[=true|false]

Enable or disable a feature in the daemon. This option corresponds
 with the "features" field in the daemon.json configuration file. Using
 both the command-line option and the "features" field in the configuration
 file produces an error. The feature option can be specified multiple times
 to configure multiple features.
 Usage example: --feature containerd-snapshotter or --feature containerd-snapshotter=true.

--fixed-cidr=""

IPv4 subnet for fixed IPs (e.g., 10.20.0.0/16); this subnet must be nested in
 the bridge subnet (which is defined by -b or --bip).

--fixed-cidr-v6=""

IPv6 subnet for global IPv6 addresses (e.g., 2a00:1450::/64)

-G,  --group=""

Group to assign the unix socket specified by -H when running in daemon mode.
 use '' (the empty string) to disable setting of a group. Default is docker.

-H,  --host=[unix:///var/run/docker.sock]: tcp://[host:port] to bind or unix://[/path/to/socket] to use.

The socket(s) to bind to in daemon mode specified using one or more
 tcp://host:port, unix:///path/to/socket, fd://* or fd://socketfd.

--help

Print usage statement

--http-proxy""

Proxy URL for HTTP requests unless overridden by NoProxy.

--https-proxy""

Proxy URL for HTTPS requests unless overridden by NoProxy.

--icc=true|false

Allow unrestricted inter-container and Docker daemon host communication. If
 disabled, containers can still be linked together using the --link option
 (see docker-run(1)). Default is true.

--init

Run an init process inside containers for signal forwarding and process
 reaping.

--init-path

Path to the docker-init binary.

--insecure-registry=[]

Enable insecure registry communication, i.e., enable un-encrypted and/or
 untrusted communication.

List of insecure registries can contain an element with CIDR notation to
 specify a whole subnet. Insecure registries accept HTTP and/or accept HTTPS
 with certificates from unknown CAs.

Enabling --insecure-registry is useful when running a local registry.
 However, because its use creates security vulnerabilities it should ONLY be
 enabled for testing purposes.  For increased security, users should add their
 CA to their system's list of trusted CAs instead of using
 --insecure-registry.

--ip=""

Default IP address to use when binding container ports. Default is 0.0.0.0.

--ip-forward=true|false

Enables IP forwarding on the Docker host. The default is true. This flag
 interacts with the IP forwarding setting on your host system's kernel. If
 your system has IP forwarding disabled, this setting enables it. If your
 system has IP forwarding enabled, setting this flag to false
 has no effect.

This setting will also enable IPv6 forwarding if you have both
 --ip-forward=true and --fixed-cidr-v6 set. Note that this may reject
 Router Advertisements and interfere with the host's existing IPv6
 configuration. For more information, consult the documentation about
 "Advanced Networking - IPv6".

--ip-masq=true|false

Enable IP masquerading for bridge's IP range. Default is true.

--iptables=true|false

Enable Docker's addition of iptables rules. Default is true.

--ipv6=true|false

Enable IPv6 support. Default is false. Docker will create an IPv6-enabled
 bridge with address fe80::1 which will allow you to create IPv6-enabled
 containers. Use together with --fixed-cidr-v6 to provide globally routable
 IPv6 addresses. IPv6 forwarding will be enabled if not used with
 --ip-forward=false. This may collide with your host's current IPv6
 settings. For more information consult the documentation about
 "Advanced Networking - IPv6".

--isolation="default"

Isolation specifies the type of isolation technology used by containers.
  Note that the default on Windows server is process, and the default on
  Windows client is hyperv. Linux only supports default.

-l,  --log-level="debug|info|warn|error|fatal"

Set the logging level. Default is info.

--label="[]"

Set key=value labels to the daemon (displayed in docker info)

--live-restore=false

Enable live restore of running containers when the daemon starts so that they
 are not restarted. This option is applicable only for docker daemon running
 on Linux host.

--log-driver="json-file|syslog|journald|gelf|fluentd|awslogs|splunk|etwlogs|gcplogs|none

"
 Default driver for container logs. Default is json-file.
 Warning: docker logs command works only for json-file logging driver.

--log-format="text|json"

Set the format for logs produced by the daemon. Default is "text".

--log-opt=[]

Logging driver specific options.

--mtu=0

Set the containers network mtu. Default is 0.

--max-concurrent-downloads=3

Set the max concurrent downloads. Default is 3.

--max-concurrent-uploads=5

Set the max concurrent uploads. Default is 5.

--max-download-attempts=5

Set the max download attempts for each pull. Default is 5.

--no-proxy="""

Comma-separated values specifying hosts that should be excluded from proxying.

--node-generic-resources=[]

Advertise user-defined resource. Default is [].
 Use this if your swarm cluster has some nodes with custom
 resources (e.g: NVIDIA GPU, SSD, ...) and you need your services to land on
 nodes advertising these resources.
 Usage example: --node-generic-resources "NVIDIA-GPU=UUID1"
 --node-generic-resources "NVIDIA-GPU=UUID2"

-p,  --pidfile="path"

Path to use for daemon PID file. Default is /var/run/docker.pid.

--raw-logs

Output daemon logs in full timestamp format without ANSI coloring. If this
 flag is not set, the daemon outputs condensed, colorized logs if a terminal
 is detected, or full ("raw") output otherwise.

--registry-mirror=://

Prepend a registry mirror to be used for image pulls. May be specified
 multiple times.

-s,  --storage-driver=""

Force the Docker runtime to use a specific storage driver.

--seccomp-profile=""

Path to seccomp profile.

--selinux-enabled=true|false

Enable selinux support. Default is false.

--shutdown-timeout=seconds

Set the shutdown timeout value in seconds. Default is 15.

--storage-opt=[]

Set storage driver options. See Storage Driver Options.

--swarm-default-advertise-addr=IP|INTERFACE

Set default address or interface for swarm to advertise as its
 externally-reachable address to other cluster members. This can be a
 hostname, an IP address, or an interface such as eth0. A port cannot be
 specified with this option.

--tls=true|false

Use TLS; implied by --tlsverify. Default is false.

--tlscacert=~/.docker/ca.pem

Trust certs signed only by this CA.

--tlscert=~/.docker/cert.pem

Path to TLS certificate file.

--tlskey=~/.docker/key.pem

Path to TLS key file.

--tlsverify=true|false

Use TLS and verify the remote (daemon: verify client, client: verify daemon).
 Default is false.

--userland-proxy=true|false

Rely on a userland proxy implementation for inter-container and
 outside-to-container loopback communications. Default is true.

--userland-proxy-path=""

Path to the userland proxy binary.

--userns-remap=default|uid:gid|user:group|user|uid

Enable user namespaces for containers on the daemon. Specifying "default"
 will cause a new user and group to be created to handle UID and GID range
 remapping for the user namespace mappings used for contained processes.
 Specifying a user (or uid) and optionally a group (or gid) will cause the
 daemon to lookup the user and group's subordinate ID ranges for use as the
 user namespace mappings for contained processes.

--validate

Validate daemon configuration and exit.

Docker uses storage backends (known as "storage drivers" in the Docker internals) to create writable containers from images.  Many of these backends use operating system level technologies and can be configured.

Specify options to the storage backend with --storage-opt flags. The backends that currently take options are zfs and btrfs. Options for zfs start with zfs., and options for btrfs start with btrfs..

Docker's access authorization can be extended by authorization plugins that your organization can purchase or build themselves. You can install one or more authorization plugins when you start the Docker daemon using the --authorization-plugin=PLUGIN_ID option.

dockerd --authorization-plugin=plugin1 --authorization-plugin=plugin2,...

The PLUGIN_ID value is either the plugin's name or a path to its specification file. The plugin's implementation determines whether you can specify a name or path. Consult with your Docker administrator to get information about the plugins available to you.

Once a plugin is installed, requests made to the daemon through the command line or Docker's Engine API are allowed or denied by the plugin. If you have multiple plugins installed, each plugin, in order, must allow the request for it to complete.

For information about how to create an authorization plugin, see access authorization plugin ⟨https://docs.docker.com/engine/extend/plugins_authorization/⟩ section in the Docker extend section of this documentation.

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.

The native.cgroupdriver option specifies the management of the container's cgroups. 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.

This example sets the cgroupdriver to systemd:

$ sudo dockerd --exec-opt native.cgroupdriver=systemd

Setting this option applies to all containers the daemon launches.

Sept 2015, Originally compiled by Shishir Mahajan shishir.mahajan@redhat.com ⟨mailto:shishir.mahajan@redhat.com⟩ based on docker.com source material and internal work.