DOCKERD(8)

NAME
dockerd - Enable daemon mode

SYNOPSIS
dockerd [--add-runtime[=[]]] [--authorization-plugin[=[]]] [-b|--bridge[=BRIDGE]] [--bip[=BIP]] [--bip6[=BIP]] [--bridge-accept-fwmark[=[]]] [--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]] [--firewall-backend[=BACKEND]] [--fixed-cidr[=FIXED-CIDR]] [--fixed-cidr-v6[=FIXED-CIDR-V6]] [-G|--group[=docker]] [--help] [-H|--host[=[]]] [--host-gateway-ip[=HOST-GATEWAY-IP]] [--http-proxy[""]] [--https-proxy[""]] [--icc[=true]] [--init[=false]] [--init-path[=""]] [--insecure-registry[=[]]] [--ip[=0.0.0.0]] [--ip-forward[=true]] [--ip-forward-no-drop[=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]

DESCRIPTION
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]

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.

--authorization-plugin=""
  Set authorization plugins to load

-b, --bridge=""
  Attach containers to a pre-existing network bridge, instead of docker0; use
  'none' to disable the default bridge network

--bip=""
  Use the provided CIDR notation IPv4 address for the default bridge network;
  Mutually exclusive of -b

--bip6=""
  Use the provided CIDR notation IPv6 address for the default bridge network;
  Mutually exclusive of -b

--bridge-accept-fwmark="" Bridge networks will accept packets with this firewall mark/mask.

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

--default-gateway-v6=""
  IPv6 default gateway for the default bridge network

--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.

--firewall-backend=""
  Firewall backend to use, iptables or nftables.

--fixed-cidr=""
  IPv4 subnet for the default bridge network (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 the default bridge network (e.g., 2001:db8::/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.

--help
  Print usage statement

-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.

--host-gateway-ip=[2001:db8::1234]
  Supply host addresses to substitute for the special string host-gateway in
  --add-host options. Addresses from the docker0 bridge are used by default.
  Two of these options are allowed, one IPv4 and one IPv6 address.

--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 communication in the default bridge
  network. 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 host IP address to use when publishing container ports from the
  default bridge network. 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 an IPv6 enabled bridge network. 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-forward-no-drop=true|false
  When false, the default, if Docker enables IP forwarding itself (see
  --ip-forward), and --iptables or --ip6tables are enabled, it
  also sets the default policy for the FORWARD chain in the iptables or
  ip6tables filter table to DROP.

When true, and when IP forwarding is already enabled, Docker does
  not modify the default policy of the FORWARD chain.

--ip-masq=true|false
  Enable IP masquerading for default 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 on the default bridge network. Default is false.
  By default, Docker will generate a ULA subnet, --default-addresss-pool
  or --fixed-cidr-v6 can be used to override the subnet. 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 network MTU for the default bridge network. 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.

--allow-direct-routing=true|false
  Allow remote access to published ports on container IP addresses.
  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.

STORAGE DRIVER OPTIONS
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..

ZFS options

  zfs.fsname
Set zfs filesystem under which docker will create its own datasets. By default docker will pick up the zfs filesystem where docker graph (/var/lib/docker) is located.

Example use: dockerd -s zfs --storage-opt zfs.fsname=zroot/docker

Btrfs options

  btrfs.min_space
Specifies the minimum size to use when creating the subvolume which is used for containers. If user uses disk quota for btrfs when creating or running a container with --storage-opt size option, docker should ensure the size cannot be smaller than btrfs.min_space.

Example use: docker daemon -s btrfs --storage-opt btrfs.min_space=10G

Access authorization
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.

RUNTIME EXECUTION OPTIONS
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.

HISTORY
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.