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Add documentation for using overlay2

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Add mention in dockerd command line and storage driver selection documentation.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
This commit is contained in:
Derek McGowan 2016-06-13 11:06:47 -07:00
parent 23e5c94cfb
commit a546042b91
3 changed files with 44 additions and 20 deletions
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11
docs/reference/commandline/dockerd.md
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@ -142,7 +142,7 @@ precedence over `HTTP_PROXY`.
### Daemon storage-driver option
The Docker daemon has support for several different image layer storage
drivers: `aufs`, `devicemapper`, `btrfs`, `zfs` and `overlay`.
drivers: `aufs`, `devicemapper`, `btrfs`, `zfs`, `overlay` and `overlay2`.
The `aufs` driver is the oldest, but is based on a Linux kernel patch-set that
is unlikely to be merged into the main kernel. These are also known to cause
@ -180,9 +180,14 @@ Linux kernel as of [3.18.0](https://lkml.org/lkml/2014/10/26/137). Call
> inode consumption (especially as the number of images grows), as well as
> being incompatible with the use of RPMs.
The `overlay2` uses the same fast union filesystem but takes advantage of
[additional features](https://lkml.org/lkml/2015/2/11/106) added in Linux
kernel 4.0 to avoid excessive inode consumption. Call `dockerd -s overlay2`
to use it.
> **Note:**
> It is currently unsupported on `btrfs` or any Copy on Write filesystem
> and should only be used over `ext4` partitions.
> Both `overlay` and `overlay2` are currently unsupported on `btrfs` or any
> Copy on Write filesystem and should only be used over `ext4` partitions.
### Storage driver options

51
docs/userguide/storagedriver/selectadriver.md
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@ -34,14 +34,14 @@ and all containers created by that daemon instance use the same storage driver.
The table below shows the supported storage driver technologies and their
driver names:
|Technology |Storage driver name |
|--------------|---------------------|
|OverlayFS |`overlay` |
|AUFS |`aufs` |
|Btrfs |`btrfs` |
|Device Mapper |`devicemapper` |
|VFS |`vfs` |
|ZFS |`zfs` |
|Technology |Storage driver name |
|--------------|-----------------------|
|OverlayFS |`overlay` or `overlay2`|
|AUFS |`aufs` |
|Btrfs |`btrfs` |
|Device Mapper |`devicemapper` |
|VFS |`vfs` |
|ZFS |`zfs` |
To find out which storage driver is set on the daemon, you use the
`docker info` command:
@ -71,14 +71,15 @@ For example, the `btrfs` storage driver on a Btrfs backing filesystem. The
following table lists each storage driver and whether it must match the host's
backing file system:
|Storage driver |Commonly used on |Disabled on |
|---------------|-----------------|-----------------------------------------|
|`overlay` |`ext4` `xfs` |`btrfs` `aufs` `overlay` `zfs` `eCryptfs`|
|`aufs` |`ext4` `xfs` |`btrfs` `aufs` `eCryptfs` |
|`btrfs` |`btrfs` _only_ | N/A |
|`devicemapper` |`direct-lvm` | N/A |
|`vfs` |debugging only | N/A |
|`zfs` |`zfs` _only_ | N/A |
|Storage driver |Commonly used on |Disabled on |
|---------------|-----------------|----------------------------------------------------|
|`overlay` |`ext4` `xfs` |`btrfs` `aufs` `overlay` `overlay2` `zfs` `eCryptfs`|
|`overlay2` |`ext4` `xfs` |`btrfs` `aufs` `overlay` `overlay2` `zfs` `eCryptfs`|
|`aufs` |`ext4` `xfs` |`btrfs` `aufs` `eCryptfs` |
|`btrfs` |`btrfs` _only_ | N/A |
|`devicemapper` |`direct-lvm` | N/A |
|`vfs` |debugging only | N/A |
|`zfs` |`zfs` _only_ | N/A |
> **Note**
@ -198,6 +199,24 @@ the guidance offered by the table below along with the points mentioned above.
![](images/driver-pros-cons.png)
### Overlay vs Overlay2
OverlayFS has 2 storage drivers which both make use of the same OverlayFS
technology but with different implementations and incompatible on disk
storage. Since the storage is incompatible, switching between the two
will require re-creating all image content. The `overlay` driver is the
original implementation and the only option in Docker 1.11 and before.
The `overlay` driver has known limitations with inode exhaustion and
commit performance. The `overlay2` driver addresses this limitation, but
is only compatible with Linux kernel 4.0 and later. For users on a pre-4.0
kernel or with an existing `overlay` graph, it is recommended to stay
on `overlay`. For users with at least a 4.0 kernel and no existing or required
`overlay` graph data, then `overlay2` may be used.
> **Note**
> `overlay2` graph data will not interfere with `overlay` graph data. However
> when switching to `overlay2`, the user is responsible for removing
> `overlay` graph data to avoid storage duplication.
## Related information

2
man/dockerd.8.md
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@ -226,7 +226,7 @@ output otherwise.
Force the Docker runtime to use a specific storage driver.
**--selinux-enabled**=*true*|*false*
Enable selinux support. Default is false. SELinux does not presently support the overlay storage driver.
Enable selinux support. Default is false. SELinux does not presently support either of the overlay storage drivers.
**--storage-opt**=[]
Set storage driver options. See STORAGE DRIVER OPTIONS.