Provided by: docker.io_18.09.5-0ubuntu1_amd64 bug


       dockerd - Enable daemon mode


       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-gateway[=DEFAULT-GATEWAY]]
       [--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[=]] [--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]]
       [--node-generic-resources[=[]]] [-p|--pidfile[=/var/run/]] [--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]]


       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]


         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": [

       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.

         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.

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

         Set authorization plugins to load

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

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

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

         URL of the distributed storage backend

         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.

         Specifies options for the Key/Value store.

         Specifies the JSON file path to load the configuration from.

         Path to containerd socket.

         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.

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

         IPv6 address of the container default gateway

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

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

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

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

         Default ulimits for containers.

         Force Docker to use specific DNS servers

         DNS options to use.

         DNS search domains to use.

         Set runtime execution options. See RUNTIME EXECUTION OPTIONS.

         Path to use as the root of the Docker execution state files. Default is

         Enable the daemon experimental features.

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

         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.

         Print usage statement

         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.

         Run an init process inside containers for signal forwarding and process

         Path to the docker-init binary.

         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

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

         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".

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

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

         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 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.

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

         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.

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

         Logging driver specific options.

         Set the containers network mtu. Default is 0.

         Set the max concurrent downloads for each pull. Default is 3.

         Set the max concurrent uploads for each push. Default is 5.

         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/

         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.

         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.

         Path to seccomp profile.

         Enable selinux support. Default is false.

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

         Set storage driver options. See STORAGE DRIVER OPTIONS.

         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.

         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.

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

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

         Path to the userland proxy binary.

         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.


       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

       Specifies a custom block storage device to use for the thin pool.

       If using a block device for device mapper storage, it is best to use lvm to create and
       manage the thin-pool volume. This volume is then handed to Docker to exclusively create
       snapshot volumes needed for images and containers.

       Managing the thin-pool outside of Engine makes for the most feature-rich method of having
       Docker utilize device mapper thin provisioning as the backing storage for Docker
       containers. The highlights of the lvm-based thin-pool management feature include:
       automatic or interactive thin-pool resize support, dynamically changing thin-pool
       features, automatic thinp metadata checking when lvm activates the thin-pool, etc.

       As a fallback if no thin pool is provided, loopback files are created. Loopback is very
       slow, but can be used without any pre-configuration of storage. It is strongly recommended
       that you do not use loopback in production. Ensure your Engine daemon has a --storage-opt
       dm.thinpooldev argument provided.

       Example use:

       $ dockerd \
                --storage-opt dm.thinpooldev=/dev/mapper/thin-pool

       As an alternative to manually creating a thin pool as above, Docker can automatically
       configure a block device for you.

       Example use:

       $ dockerd \
                --storage-opt dm.directlvm_device=/dev/xvdf

       Sets the percentage of passed in block device to use for storage.

       $ sudo dockerd \
               --storage-opt dm.thinp_percent=95

       Sets the percentage of the passed in block device to use for metadata storage.

       $ sudo dockerd \
                --storage-opt dm.thinp_metapercent=1

       Sets the value of the percentage of space used before lvm attempts to autoextend the
       available space [100 = disabled]

       $ sudo dockerd \
                --storage-opt dm.thinp_autoextend_threshold=80

       Sets the value percentage value to increase the thin pool by when lvm attempts to
       autoextend the available space [100 = disabled]

       $ sudo dockerd \
                --storage-opt dm.thinp_autoextend_percent=20

       Specifies the size to use when creating the base device, which limits the size of images
       and containers. The default value is 10G. Note, thin devices are inherently "sparse", so a
       10G device which is mostly empty doesn't use 10 GB of space on the pool. However, the
       filesystem will use more space for base images the larger the device is.

       The base device size can be increased at daemon restart which will allow all future images
       and containers (based on those new images) to be of the new base device size.

       Example use: dockerd --storage-opt dm.basesize=50G

       This will increase the base device size to 50G. The Docker daemon will throw an error if
       existing base device size is larger than 50G. A user can use this option to expand the
       base device size however shrinking is not permitted.

       This value affects the system-wide "base" empty filesystem that may already be initialized
       and inherited by pulled images. Typically, a change to this value requires additional
       steps to take effect:

                  $ sudo service docker stop
                  $ sudo rm -rf /var/lib/docker
                  $ sudo service docker start

       Example use: dockerd --storage-opt dm.basesize=20G

       Specifies the filesystem type to use for the base device. The supported options are ext4
       and xfs. The default is ext4.

       Example use: dockerd --storage-opt dm.fs=xfs

       Specifies extra mkfs arguments to be used when creating the base device.

       Example use: dockerd --storage-opt "dm.mkfsarg=-O ^has_journal"

       Specifies extra mount options used when mounting the thin devices.

       Example use: dockerd --storage-opt dm.mountopt=nodiscard

       Enables use of deferred device removal if libdm and the kernel driver support the

       Deferred device removal means that if device is busy when devices are being
       removed/deactivated, then a deferred removal is scheduled on device. And devices
       automatically go away when last user of the device exits.

       For example, when a container exits, its associated thin device is removed. If that device
       has leaked into some other mount namespace and can't be removed, the container exit still
       succeeds and this option causes the system to schedule the device for deferred removal. It
       does not wait in a loop trying to remove a busy device.

       Example use: dockerd --storage-opt dm.use_deferred_removal=true

       Enables use of deferred device deletion for thin pool devices. By default, thin pool
       device deletion is synchronous. Before a container is deleted, the Docker daemon removes
       any associated devices. If the storage driver can not remove a device, the container
       deletion fails and daemon returns.

       Error deleting container: Error response from daemon: Cannot destroy container

       To avoid this failure, enable both deferred device deletion and deferred device removal on
       the daemon.

       dockerd --storage-opt dm.use_deferred_deletion=true --storage-opt

       With these two options enabled, if a device is busy when the driver is deleting a
       container, the driver marks the device as deleted. Later, when the device isn't in use,
       the driver deletes it.

       In general it should be safe to enable this option by default. It will help when
       unintentional leaking of mount point happens across multiple mount namespaces.

       Note: This option configures devicemapper loopback, which should not be used in

       Specifies the size to use when creating the loopback file for the "data" device which is
       used for the thin pool. The default size is 100G. The file is sparse, so it will not
       initially take up this much space.

       Example use: dockerd --storage-opt dm.loopdatasize=200G

       Note: This option configures devicemapper loopback, which should not be used in

       Specifies the size to use when creating the loopback file for the "metadata" device which
       is used for the thin pool. The default size is 2G. The file is sparse, so it will not
       initially take up this much space.

       Example use: dockerd --storage-opt dm.loopmetadatasize=4G

       (Deprecated, use dm.thinpooldev)

       Specifies a custom blockdevice to use for data for a Docker-managed thin pool.  It is
       better to use dm.thinpooldev - see the documentation for it above for discussion of the

       (Deprecated, use dm.thinpooldev)

       Specifies a custom blockdevice to use for metadata for a Docker-managed thin pool.  See
       dm.datadev for why this is deprecated.

       Specifies a custom blocksize to use for the thin pool.  The default blocksize is 64K.

       Example use: dockerd --storage-opt dm.blocksize=512K

       Enables or disables the use of blkdiscard when removing devicemapper devices.  This is
       disabled by default due to the additional latency, but as a special case with loopback
       devices it will be enabled, in order to re-sparsify the loopback file on image/container

       Disabling this on loopback can lead to much faster container removal times, but it also
       prevents the space used in /var/lib/docker directory from being returned to the system for
       other use when containers are removed.

       Example use: dockerd --storage-opt dm.blkdiscard=false

       By default, the devicemapper backend attempts to synchronize with the udev device manager
       for the Linux kernel.  This option allows disabling that synchronization, to continue even
       though the configuration may be buggy.

       To view the udev sync support of a Docker daemon that is using the devicemapper driver,

                  $ docker info
                   Udev Sync Supported: true

       When udev sync support is true, then devicemapper and udev can coordinate the activation
       and deactivation of devices for containers.

       When udev sync support is false, a race condition occurs between the devicemapper and udev
       during create and cleanup. The race condition results in errors and failures. (For
       information on these failures, see docker#4036

       To allow the docker daemon to start, regardless of whether udev sync is false, set
       dm.override_udev_sync_check to true:

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

       When this value is true, the driver continues and simply warns you the errors are

       Note: The ideal is to pursue a docker daemon and environment that does support
       synchronizing with udev. For further discussion on this topic, see docker#4036
       ⟨⟩.  Otherwise, set this flag for migrating
       existing Docker daemons to a daemon with a supported environment.

       Specifies the min free space percent in a thin pool require for new device creation to
       succeed. This check applies to both free data space as well as free metadata space. Valid
       values are from 0% - 99%. Value 0% disables free space checking logic. If user does not
       specify a value for this option, the Engine uses a default value of 10%.

       Whenever a new a thin pool device is created (during docker pull or during container
       creation), the Engine checks if the minimum free space is available.  If the space is
       unavailable, then device creation fails and any relevant docker operation fails.

       To recover from this error, you must create more free space in the thin pool to recover
       from the error. You can create free space by deleting some images and containers from tge
       thin pool. You can also add more storage to the thin pool.

       To add more space to an LVM (logical volume management) thin pool, just add more storage
       to the  group container thin pool; this should automatically resolve any errors. If your
       configuration uses loop devices, then stop the Engine daemon, grow the size of loop files
       and restart the daemon to resolve the issue.

       Example use:: dockerd --storage-opt dm.min_free_space=10%

       Specifies the maximum number of retries XFS should attempt to complete IO when ENOSPC (no
       space) error is returned by underlying storage device.

       By default XFS retries infinitely for IO to finish and this can result in unkillable
       process. To change this behavior one can set xfs_nospace_max_retries to say 0 and XFS will
       not retry IO after getting ENOSPC and will shutdown filesystem.

       Example use:

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

       Specifies the maxmimum libdm log level that will be forwarded to the dockerd log (as
       specified by --log-level). This option is primarily intended for debugging problems
       involving libdm. Using values other than the defaults may cause false-positive warnings to
       be logged.

       Values specified must fall within the range of valid libdm log levels. At the time of
       writing, the following is the list of libdm log levels as well as their corresponding
       levels when output by dockerd.

       │libdm LevelValue--log-level │
       │_LOG_FATAL  │ 2     │ error       │
       │_LOG_ERR    │ 3     │ error       │
       │_LOG_WARN   │ 4     │ warn        │
       │_LOG_NOTICE │ 5     │ info        │
       │_LOG_INFO   │ 6     │ info        │
       │_LOG_DEBUG  │ 7     │ debug       │

       Example use:

              $ sudo dockerd \
                    --log-level debug \
                    --storage-opt dm.libdm_log_level=7

ZFS options

       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

       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

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


       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.

       Specifies the path to a local file with PEM encoded CA certificates to trust

       Specifies the path to a local file with a PEM encoded certificate.  This certificate is
       used as the client cert for communication with the Key/Value store.

       Specifies the path to a local file with a PEM encoded private key.  This private key is
       used as the client key for communication with the Key/Value store.

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

              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 ⟨⟩ 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.

       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 ⟨⟩ based on source material and internal work.