NAME¶

dockerd - Enable daemon mode

SYNOPSIS¶

dockerd [--add-runtime[=[]]] [--allow-nondistributable-artifacts[=[]]] [--api-cors-header=[=API-CORS-HEADER]] [--authorization-plugin[=[]]] [-b|--bridge[=BRIDGE]] [--bip[=BIP]] [--cgroup-parent[=[]]] [--cluster-store[=[]]] [--cluster-advertise[=[]]] [--cluster-store-opt[=map[]]] [--config-file[=/etc/docker/daemon.json]] [--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-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]] [--fixed-cidr[=FIXED-CIDR]] [--fixed-cidr-v6[=FIXED-CIDR-V6]] [-G|--group[=docker]] [-H|--host[=[]]] [--help] [--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-opt[=map[]]] [--mtu[=0]] [--max-concurrent-downloads[=3]] [--max-concurrent-uploads[=5]] [--max-download-attempts[=5]] [--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]]

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.

--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.

--cluster-store=""
URL of the distributed storage backend

--cluster-advertise=""
Specifies the 'host:port' or interface:port combination that this
particular daemon instance should use when advertising itself to the cluster.
The daemon is reached through this value.

--cluster-store-opt=""
Specifies options for the Key/Value store.

--config-file="/etc/docker/daemon.json"
Specifies the JSON file path to load the configuration from.

--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, 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-runtime="runc"
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=64MiB
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.

--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

--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 --ip-forward=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, please 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 please 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-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.

--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 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=15
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.

STORAGE DRIVER OPTIONS¶

Docker uses storage backends (known as "graphdrivers" 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 devicemapper, zfs and btrfs. Options for devicemapper are prefixed with dm, options for zfs start with zfs and options for btrfs start with btrfs.

Specifically for devicemapper, the default is a "loopback" model which requires no pre-configuration, but is extremely inefficient. Do not use it in production.

To make the best use of Docker with the devicemapper backend, you must have a recent version of LVM. Use lvm to create a thin pool; for more information see man lvmthin. Then, use --storage-opt dm.thinpooldev to tell the Docker engine to use that pool for allocating images and container snapshots.

Devicemapper options¶

    $ sudo service docker stop


    $ sudo rm -rf /var/lib/docker


    $ sudo service docker start

    $ docker info


    [...]


     Udev Sync Supported: true


    [...]

    $ dockerd --storage-opt dm.override_udev_sync_check=true

$ sudo dockerd --storage-opt dm.xfs_nospace_max_retries=0

$ sudo dockerd \


      --log-level debug \


      --storage-opt dm.libdm_log_level=7

ZFS options¶

Btrfs options¶

CLUSTER STORE OPTIONS¶

The daemon uses libkv to advertise the node within the cluster. Some Key/Value backends support mutual TLS, and the client TLS settings used by the daemon can be configured using the --cluster-store-opt flag, specifying the paths to PEM encoded files.

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.