bionic (8) dockerd.8.gz

Provided by: docker.io_20.10.21-0ubuntu1~18.04.3_amd64 bug

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 for each pull. Default is 3.

       --max-concurrent-uploads=5
         Set the max concurrent uploads for each push. 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

   dm.thinpooldev
       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

   dm.directlvm_device
       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

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

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

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

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

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

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

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

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

   dm.basesize
       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

   dm.fs
       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

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

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

   dm.mountopt
       Specifies extra mount options used when mounting the thin devices.

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

   dm.use_deferred_removal
       Enables use of deferred device removal if libdm and the kernel driver support the mechanism.

       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

   dm.use_deferred_deletion
       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 dm.use_deferred_removal=true

       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.

   dm.loopdatasize
       Note: This option configures devicemapper loopback, which should not be used in production.

       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

   dm.loopmetadatasize
       Note: This option configures devicemapper loopback, which should not be used in production.

       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

   dm.datadev
       (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 advantages.

   dm.metadatadev
       (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.

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

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

   dm.blkdiscard
       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 removal.

       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

   dm.override_udev_sync_check
       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, run:

                  $ 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 ⟨https://github.com/docker/docker/issues/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 happening.

       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 ⟨https://github.com/docker/docker/issues/4036⟩.
       Otherwise, set this flag for migrating existing Docker daemons to a daemon with a supported environment.

   dm.min_free_space
       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%

   dm.xfs_nospace_max_retries
       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

   dm.libdm_log_level
       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

   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

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.

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

   kv.certfile
       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.

   kv.keyfile
       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 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.commailto:shishir.mahajan@redhat.com⟩ based on docker.com source material and internal work.