mirror of
https://github.com/moby/moby.git
synced 2022-11-09 12:21:53 -05:00
Closes #13323 and carries
Entering comments Signed-off-by: Mary Anthony <mary@docker.com>
This commit is contained in:
Mary Anthony
parent
40a41ffdf0
commit
078b23a37d
3 changed files with 211 additions and 259 deletions
|
|
@ -71,204 +71,14 @@ status information about the driver.
|
|||
* `Metadata loop file` file attached to `Metadata file`, if loopback device is used
|
||||
* `Library Version` from the libdevmapper used
|
||||
|
||||
### options
|
||||
### About the devicemapper options
|
||||
|
||||
The devicemapper backend supports some options that you can specify
|
||||
when starting the docker daemon using the `--storage-opt` flags.
|
||||
This uses the `dm` prefix and would be used something like `docker -d --storage-opt dm.foo=bar`.
|
||||
|
||||
Here is the list of supported options:
|
||||
|
||||
* `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 the empty
|
||||
case the larger the device is. **Warning**: 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 will require additional steps to take effect: 1)
|
||||
stop `docker -d`, 2) `rm -rf /var/lib/docker`, 3) start `docker -d`.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.basesize=20G``
|
||||
|
||||
* `dm.loopdatasize`
|
||||
|
||||
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. Note that the file is sparse, so it will not initially take
|
||||
up this much space.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.loopdatasize=200G``
|
||||
|
||||
* `dm.loopmetadatasize`
|
||||
|
||||
Specifies the size to use when creating the loopback file for the
|
||||
"metadadata" device which is used for the thin pool. The default size is
|
||||
2G. Note that the file is sparse, so it will not initially take
|
||||
up this much space.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.loopmetadatasize=4G``
|
||||
|
||||
* `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:
|
||||
|
||||
``docker -d --storage-opt dm.fs=xfs``
|
||||
|
||||
* `dm.mkfsarg`
|
||||
|
||||
Specifies extra mkfs arguments to be used when creating the base device.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt "dm.mkfsarg=-O ^has_journal"``
|
||||
|
||||
* `dm.mountopt`
|
||||
|
||||
Specifies extra mount options used when mounting the thin devices.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.mountopt=nodiscard``
|
||||
|
||||
* `dm.thinpooldev`
|
||||
|
||||
Specifies a custom blockdevice to use for the thin pool.
|
||||
|
||||
If using a block device for device mapper storage, ideally lvm2
|
||||
would be used to create/manage the thin-pool volume that is then
|
||||
handed to docker to exclusively create/manage the thin and thin
|
||||
snapshot volumes needed for its containers. Managing the thin-pool
|
||||
outside of docker makes for the most feature-rich method of having
|
||||
docker utilize device mapper thin provisioning as the backing
|
||||
storage for docker's containers. lvm2-based thin-pool management
|
||||
feature highlights include: automatic or interactive thin-pool
|
||||
resize support, dynamically change thin-pool features, automatic
|
||||
thinp metadata checking when lvm2 activates the thin-pool, etc.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.thinpooldev=/dev/mapper/thin-pool``
|
||||
|
||||
* `dm.datadev`
|
||||
|
||||
Specifies a custom blockdevice to use for data for the thin pool.
|
||||
|
||||
If using a block device for device mapper storage, ideally both
|
||||
datadev and metadatadev should be specified to completely avoid
|
||||
using the loopback device.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.datadev=/dev/sdb1 --storage-opt dm.metadatadev=/dev/sdc1``
|
||||
|
||||
* `dm.metadatadev`
|
||||
|
||||
Specifies a custom blockdevice to use for metadata for the thin
|
||||
pool.
|
||||
|
||||
For best performance the metadata should be on a different spindle
|
||||
than the data, or even better on an SSD.
|
||||
|
||||
If setting up a new metadata pool it is required to be valid. This
|
||||
can be achieved by zeroing the first 4k to indicate empty
|
||||
metadata, like this:
|
||||
|
||||
``dd if=/dev/zero of=$metadata_dev bs=4096 count=1``
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.datadev=/dev/sdb1 --storage-opt dm.metadatadev=/dev/sdc1``
|
||||
|
||||
* `dm.blocksize`
|
||||
|
||||
Specifies a custom blocksize to use for the thin pool. The default
|
||||
blocksize is 64K.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.blocksize=512K``
|
||||
|
||||
* `dm.blkdiscard`
|
||||
|
||||
Enables or disables the use of blkdiscard when removing
|
||||
devicemapper devices. This is enabled by default (only) if using
|
||||
loopback devices and is required to resparsify the loopback file
|
||||
on image/container removal.
|
||||
|
||||
Disabling this on loopback can lead to *much* faster container
|
||||
removal times, but will make the space used in /var/lib/docker
|
||||
directory not be returned to the system for other use when
|
||||
containers are removed.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.blkdiscard=false``
|
||||
|
||||
* `dm.override_udev_sync_check`
|
||||
|
||||
Overrides the `udev` synchronization checks between `devicemapper` and `udev`.
|
||||
`udev` is the device manager for the Linux kernel.
|
||||
|
||||
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 `udev` sync not being
|
||||
supported, set `dm.override_udev_sync_check` to true:
|
||||
|
||||
$ docker -d --storage-opt dm.override_udev_sync_check=true
|
||||
|
||||
When this value is `true`, the `devicemapper` 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.use_deferred_removal`
|
||||
|
||||
Enables use of deferred device removal if libdm and kernel driver
|
||||
support the mechanism.
|
||||
|
||||
Deferred device removal means that if device is busy when devices is
|
||||
being removed/deactivated, then a deferred removal is scheduled on
|
||||
device. And devices automatically goes away when last user of device
|
||||
exits.
|
||||
|
||||
For example, when container exits, its associated thin device is
|
||||
removed. If that devices has leaked into some other mount namespace
|
||||
can can't be removed now, container exit will still be successful
|
||||
and this option will just schedule device for deferred removal and
|
||||
will not wait in a loop trying to remove a busy device.
|
||||
|
||||
Example use:
|
||||
|
||||
``docker -d --storage-opt dm.use_deferred_removal=true``
|
||||
|
||||
These options are currently documented both in [the man
|
||||
page](../../../man/docker.1.md) and in [the online
|
||||
documentation](https://docs.docker.com/reference/commandline/daemon/#docker-
|
||||
execdriver-option). If you add an options, update both the `man` page and the
|
||||
documentation.
|
||||
|
|
|
|||
|
|
@ -178,7 +178,24 @@ Particular storage-driver can be configured with options specified with
|
|||
`--storage-opt` flags. Options for `devicemapper` are prefixed with `dm` and
|
||||
options for `zfs` start with `zfs`.
|
||||
|
||||
Currently supported options of `devicemapper`:
|
||||
* `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 Docker makes for the most feature-rich
|
||||
method of having Docker utilize device mapper thin provisioning as the
|
||||
backing storage for Docker's 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.
|
||||
|
||||
Example use:
|
||||
|
||||
docker -d --storage-opt dm.thinpooldev=/dev/mapper/thin-pool
|
||||
|
||||
* `dm.basesize`
|
||||
|
||||
|
|
@ -188,9 +205,9 @@ Currently supported options of `devicemapper`:
|
|||
10 GB of space on the pool. However, the filesystem will use more space for
|
||||
the empty case the larger the device is.
|
||||
|
||||
**Warning:** 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 will require additional steps to take effect:
|
||||
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
|
||||
|
|
@ -202,9 +219,12 @@ Currently supported options of `devicemapper`:
|
|||
|
||||
* `dm.loopdatasize`
|
||||
|
||||
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. Note that
|
||||
the file is sparse, so it will not initially take up this much space.
|
||||
>**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:
|
||||
|
||||
|
|
@ -212,10 +232,12 @@ Currently supported options of `devicemapper`:
|
|||
|
||||
* `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.
|
||||
Note that the file is sparse, so it will not initially take up this much
|
||||
space.
|
||||
"metadadata" 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:
|
||||
|
||||
|
|
@ -248,6 +270,8 @@ Currently supported options of `devicemapper`:
|
|||
|
||||
* `dm.datadev`
|
||||
|
||||
(Deprecated, use `dm.thinpooldev`)
|
||||
|
||||
Specifies a custom blockdevice to use for data for the thin pool.
|
||||
|
||||
If using a block device for device mapper storage, ideally both datadev and
|
||||
|
|
@ -256,12 +280,12 @@ Currently supported options of `devicemapper`:
|
|||
|
||||
Example use:
|
||||
|
||||
$ docker -d \
|
||||
--storage-opt dm.datadev=/dev/sdb1 \
|
||||
--storage-opt dm.metadatadev=/dev/sdc1
|
||||
$ docker -d --storage-opt dm.datadev=/dev/sdb1 --storage-opt dm.metadatadev=/dev/sdc1
|
||||
|
||||
* `dm.metadatadev`
|
||||
|
||||
(Deprecated, use `dm.thinpooldev`)
|
||||
|
||||
Specifies a custom blockdevice to use for metadata for the thin pool.
|
||||
|
||||
For best performance the metadata should be on a different spindle than the
|
||||
|
|
@ -270,13 +294,11 @@ Currently supported options of `devicemapper`:
|
|||
If setting up a new metadata pool it is required to be valid. This can be
|
||||
achieved by zeroing the first 4k to indicate empty metadata, like this:
|
||||
|
||||
$ dd if=/dev/zero of=$metadata_dev bs=4096 count=1
|
||||
$ dd if=/dev/zero of=$metadata_dev bs=4096 count=1
|
||||
|
||||
Example use:
|
||||
|
||||
$ docker -d \
|
||||
--storage-opt dm.datadev=/dev/sdb1 \
|
||||
--storage-opt dm.metadatadev=/dev/sdc1
|
||||
$ docker -d --storage-opt dm.datadev=/dev/sdb1 --storage-opt dm.metadatadev=/dev/sdc1
|
||||
|
||||
* `dm.blocksize`
|
||||
|
||||
|
|
@ -325,7 +347,7 @@ Currently supported options of `devicemapper`:
|
|||
To allow the `docker` daemon to start, regardless of `udev` sync not being
|
||||
supported, set `dm.override_udev_sync_check` to true:
|
||||
|
||||
$ docker -d --storage-opt dm.override_udev_sync_check=true
|
||||
$ docker -d --storage-opt dm.override_udev_sync_check=true
|
||||
|
||||
When this value is `true`, the `devicemapper` continues and simply warns
|
||||
you the errors are happening.
|
||||
|
|
@ -337,6 +359,7 @@ Currently supported options of `devicemapper`:
|
|||
> Otherwise, set this flag for migrating existing Docker daemons to
|
||||
> a daemon with a supported environment.
|
||||
|
||||
|
||||
## Docker execdriver option
|
||||
|
||||
Currently supported options of `zfs`:
|
||||
|
|
|
|||
209
man/docker.1.md
209
man/docker.1.md
|
|
@ -297,79 +297,198 @@ inside it)
|
|||
|
||||
# STORAGE DRIVER OPTIONS
|
||||
|
||||
Options to storage backend can be specified with **--storage-opt** flags. The
|
||||
only backend which currently takes options is *devicemapper*. Therefore use these
|
||||
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 only
|
||||
backend that currently takes options is *devicemapper*. Therefore use these
|
||||
flags with **-s=**devicemapper.
|
||||
|
||||
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.
|
||||
|
||||
Here is the list of *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 create snapshot volumes needed for images and
|
||||
containers.
|
||||
|
||||
Managing the thin-pool outside of Docker makes for the most feature-rich method
|
||||
of having Docker utilize device mapper thin provisioning as the backing storage
|
||||
for Docker's 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.
|
||||
|
||||
Example use: `docker -d --storage-opt dm.thinpooldev=/dev/mapper/thin-pool`
|
||||
|
||||
#### 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 the empty
|
||||
case the larger the device is. **Warning**: This value affects the system-wide
|
||||
"base" empty filesystem that may already be initialized and inherited by pulled
|
||||
images.
|
||||
|
||||
#### dm.loopdatasize
|
||||
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. Note that the
|
||||
file is sparse, so it will not initially take up this much space.
|
||||
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.
|
||||
|
||||
#### dm.loopmetadatasize
|
||||
Specifies the size to use when creating the loopback file for the "metadadata"
|
||||
device which is used for the thin pool. The default size is 2G. Note that the
|
||||
file is sparse, so it will not initially take up this much space.
|
||||
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: `docker -d --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"
|
||||
|
||||
Specifies the filesystem type to use for the base device. The
|
||||
supported options are `ext4` and `xfs`. The default is `ext4`.
|
||||
|
||||
Example use: `docker -d --storage-opt dm.fs=xfs`
|
||||
|
||||
#### dm.mkfsarg
|
||||
|
||||
Specifies extra mkfs arguments to be used when creating the base device.
|
||||
|
||||
Example use: `docker -d --storage-opt "dm.mkfsarg=-O ^has_journal"`
|
||||
|
||||
#### dm.mountopt
|
||||
|
||||
Specifies extra mount options used when mounting the thin devices.
|
||||
|
||||
#### dm.datadev
|
||||
Specifies a custom blockdevice to use for data for the thin pool.
|
||||
Example use: `docker -d --storage-opt dm.mountopt=nodiscard`
|
||||
|
||||
If using a block device for device mapper storage, ideally both datadev and
|
||||
metadatadev should be specified to completely avoid using the loopback device.
|
||||
#### 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: `docker -d --storage-opt dm.use_deferred_removal=true`
|
||||
|
||||
#### 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: `docker -d --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
|
||||
"metadadata" 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: `docker -d --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
|
||||
Specifies a custom blockdevice to use for metadata for the thin pool.
|
||||
|
||||
For best performance the metadata should be on a different spindle than the
|
||||
data, or even better on an SSD.
|
||||
(Deprecated, use `dm.thinpooldev`)
|
||||
|
||||
If setting up a new metadata pool it is required to be valid. This can be
|
||||
achieved by zeroing the first 4k to indicate empty metadata, like this:
|
||||
|
||||
dd if=/dev/zero of=/dev/metadata_dev bs=4096 count=1
|
||||
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.
|
||||
|
||||
Specifies a custom blocksize to use for the thin pool. The default
|
||||
blocksize is 64K.
|
||||
|
||||
Example use: `docker -d --storage-opt dm.blocksize=512K`
|
||||
|
||||
#### dm.blkdiscard
|
||||
Enables or disables the use of blkdiscard when removing devicemapper devices.
|
||||
This is enabled by default (only) if using loopback devices and is required to
|
||||
resparsify the loopback file on image/container removal.
|
||||
|
||||
Disabling this on loopback can lead to *much* faster container removal times,
|
||||
but will prevent the space used in `/var/lib/docker` directory from being returned to
|
||||
the system for other use when containers are removed.
|
||||
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.
|
||||
|
||||
# EXAMPLES
|
||||
Launching docker daemon with *devicemapper* backend with particular block devices
|
||||
for data and metadata:
|
||||
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.
|
||||
|
||||
docker -d -s=devicemapper \
|
||||
--storage-opt dm.datadev=/dev/vdb \
|
||||
--storage-opt dm.metadatadev=/dev/vdc \
|
||||
--storage-opt dm.basesize=20G
|
||||
Example use: `docker -d --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:
|
||||
|
||||
$ docker -d --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.
|
||||
|
||||
# EXEC DRIVER OPTIONS
|
||||
|
||||
|
|
|
|||
Loading…
Reference in a new issue