Allow option to override kernel check in overlay2
Add option to skip kernel check for older kernels which have been patched to support multiple lower directories in overlayfs.
Fixes
@@ -566,6 +566,17 @@ options for `zfs` start with `zfs` and options for `btrfs` start with `btrfs`.
Example use:
$ docker daemon -s btrfs --storage-opt btrfs.min_space=10G
+#### Overlay2 options
+
+* `overlay2.override_kernel_check`
+
+ Overrides the Linux kernel version check allowing overlay2. Support for
+ specifying multiple lower directories needed by overlay2 was added to the
+ Linux kernel in 4.0.0. However some older kernel versions may be patched
+ to add multiple lower directory support for OverlayFS. This option should
+ only be used after verifying this support exists in the kernel. Applying
+ this option on a kernel without this support will cause failures on mount.
+
## Docker runtime execution options
The Docker daemon relies on a
