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@@ -69,7 +69,7 @@ expect an integer, and they can only be specified once.
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use '' (the empty string) to disable setting of a group
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-g, --graph="/var/lib/docker" Path to use as the root of the Docker runtime
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-H, --host=[] The socket(s) to bind to in daemon mode or connect to in client mode, specified using one or more tcp://host:port, unix:///path/to/socket, fd://* or fd://socketfd.
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- --icc=true Enable inter-container communication
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+ --icc=true Allow unrestricted inter-container and Docker daemon host communication
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--insecure-registry=[] Enable insecure communication with specified registries (disables certificate verification for HTTPS and enables HTTP fallback) (e.g., localhost:5000 or 10.20.0.0/16)
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--ip=0.0.0.0 Default IP address to use when binding container ports
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--ip-forward=true Enable net.ipv4.ip_forward
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@@ -164,13 +164,16 @@ serious kernel crashes. However, `aufs` is also the only storage driver that all
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containers to share executable and shared library memory, so is a useful choice
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when running thousands of containers with the same program or libraries.
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-The `devicemapper` driver uses thin provisioning and Copy on Write (CoW) snapshots.
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-This driver will create a 100GB sparse file containing all your images and
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-containers. Each container will be limited to a 10 GB thin volume, and either of
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-these will require tuning - see [~jpetazzo/Resizing Docker containers with the
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-Device Mapper plugin]( http://jpetazzo.github.io/2014/01/29/docker-device-mapper-resize/)
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-To tell the Docker daemon to use `devicemapper`, use
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-`docker -d -s devicemapper`.
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+The `devicemapper` driver uses thin provisioning and Copy on Write (CoW)
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+snapshots. For each devicemapper graph location – typically
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+`/var/lib/docker/devicemapper` – a thin pool is created based on two block
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+devices, one for data and one for metadata. By default, these block devices
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+are created automatically by using loopback mounts of automatically created
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+sparse files. Refer to [Storage driver options](#storage-driver-options) below
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+for a way how to customize this setup.
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+[~jpetazzo/Resizing Docker containers with the Device Mapper plugin](
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+http://jpetazzo.github.io/2014/01/29/docker-device-mapper-resize/) article
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+explains how to tune your existing setup without the use of options.
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The `btrfs` driver is very fast for `docker build` - but like `devicemapper` does not
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share executable memory between devices. Use `docker -d -s btrfs -g /mnt/btrfs_partition`.
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@@ -179,6 +182,135 @@ The `overlay` is a very fast union filesystem. It is now merged in the main
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Linux kernel as of [3.18.0](https://lkml.org/lkml/2014/10/26/137).
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Call `docker -d -s overlay` to use it.
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+#### Storage driver options
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+
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+Particular storage-driver can be configured with options specified with
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+`--storage-opt` flags. The only driver accepting options is `devicemapper` as
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+of now. All its options are prefixed with `dm`.
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+
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+Currently supported options are:
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+
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+ * `dm.basesize`
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+
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+ Specifies the size to use when creating the base device, which limits the
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+ size of images and containers. The default value is 10G. Note, thin devices
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+ are inherently "sparse", so a 10G device which is mostly empty doesn't use
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+ 10 GB of space on the pool. However, the filesystem will use more space for
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+ the empty case the larger the device is.
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+
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+ **Warning**: This value affects the system-wide "base" empty filesystem
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+ that may already be initialized and inherited by pulled images. Typically,
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+ a change to this value will require additional steps to take effect:
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+
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+ $ sudo service docker stop
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+ $ sudo rm -rf /var/lib/docker
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+ $ sudo service docker start
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.basesize=20G
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+
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+ * `dm.loopdatasize`
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+
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+ Specifies the size to use when creating the loopback file for the "data"
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+ device which is used for the thin pool. The default size is 100G. Note that
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+ the file is sparse, so it will not initially take up this much space.
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.loopdatasize=200G
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+
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+ * `dm.loopmetadatasize`
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+
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+ Specifies the size to use when creating the loopback file for the
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+ "metadata" device which is used for the thin pool. The default size is 2G.
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+ Note that the file is sparse, so it will not initially take up this much
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+ space.
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.loopmetadatasize=4G
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+
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+ * `dm.fs`
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+
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+ Specifies the filesystem type to use for the base device. The supported
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+ options are "ext4" and "xfs". The default is "ext4"
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.fs=xfs
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+
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+ * `dm.mkfsarg`
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+
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+ Specifies extra mkfs arguments to be used when creating the base device.
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt "dm.mkfsarg=-O ^has_journal"
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+
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+ * `dm.mountopt`
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+
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+ Specifies extra mount options used when mounting the thin devices.
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.mountopt=nodiscard
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+
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+ * `dm.datadev`
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+
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+ Specifies a custom blockdevice to use for data for the thin pool.
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+
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+ If using a block device for device mapper storage, ideally both datadev and
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+ metadatadev should be specified to completely avoid using the loopback
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+ device.
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+
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+ Example use:
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+
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+ $ sudo docker -d \
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+ --storage-opt dm.datadev=/dev/sdb1 \
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+ --storage-opt dm.metadatadev=/dev/sdc1
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+
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+ * `dm.metadatadev`
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+
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+ Specifies a custom blockdevice to use for metadata for the thin pool.
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+
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+ For best performance the metadata should be on a different spindle than the
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+ data, or even better on an SSD.
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+
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+ If setting up a new metadata pool it is required to be valid. This can be
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+ achieved by zeroing the first 4k to indicate empty metadata, like this:
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+
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+ $ dd if=/dev/zero of=$metadata_dev bs=4096 count=1
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+
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+ Example use:
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+
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+ $ sudo docker -d \
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+ --storage-opt dm.datadev=/dev/sdb1 \
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+ --storage-opt dm.metadatadev=/dev/sdc1
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+
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+ * `dm.blocksize`
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+
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+ Specifies a custom blocksize to use for the thin pool. The default
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+ blocksize is 64K.
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.blocksize=512K
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+
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+ * `dm.blkdiscard`
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+
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+ Enables or disables the use of blkdiscard when removing devicemapper
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+ devices. This is enabled by default (only) if using loopback devices and is
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+ required to res-parsify the loopback file on image/container removal.
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+
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+ Disabling this on loopback can lead to *much* faster container removal
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+ times, but will make the space used in `/var/lib/docker` directory not be
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+ returned to the system for other use when containers are removed.
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+
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+ Example use:
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+
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+ $ sudo docker -d --storage-opt dm.blkdiscard=false
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+
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### Docker exec-driver option
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The Docker daemon uses a specifically built `libcontainer` execution driver as its
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Sven Dowideit