mesos git commit: Added document for overlayfs backend.

[ji...@apache.org]

Repository: mesos
Updated Branches:
  refs/heads/master 7f2f1ab58 -> 5e50ad37a


Added document for overlayfs backend.

Review: https://reviews.apache.org/r/44391/


Project: http://git-wip-us.apache.org/repos/asf/mesos/repo
Commit: http://git-wip-us.apache.org/repos/asf/mesos/commit/5e50ad37
Tree: http://git-wip-us.apache.org/repos/asf/mesos/tree/5e50ad37
Diff: http://git-wip-us.apache.org/repos/asf/mesos/diff/5e50ad37

Branch: refs/heads/master
Commit: 5e50ad37abe474c2590c4cc9daeedb1d00ad7b6b
Parents: 7f2f1ab
Author: Guangya Liu <gy...@gmail.com>
Authored: Thu Mar 10 15:45:51 2016 -0800
Committer: Jie Yu <yu...@gmail.com>
Committed: Thu Mar 10 15:49:45 2016 -0800

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 docs/container-image.md | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)
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http://git-wip-us.apache.org/repos/asf/mesos/blob/5e50ad37/docs/container-image.md
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diff --git a/docs/container-image.md b/docs/container-image.md
index 0cab13a..db4b291 100644
--- a/docs/container-image.md
+++ b/docs/container-image.md
@@ -285,7 +285,28 @@ agent flag `--sandbox_directory` properly).
 
 ### Overlay
 
-TODO(jieyu): Add documentation for overlay here.
+The reson overlay backend was introduced is because the copy backend
+will waste IO and space while the bind backend can only deal with one
+layer. The overlay backend allows containizer to utilize the
+filesystem to merge multiple filesystems into one efficiently.
+
+As the overlay backend request multiple lower layers support, the
+version of linux kernel should be greater than 4.0, refer
+[here](https://github.com/manjaro/manjaro-tools-iso-profiles/issues/40)
+for more detail.
+
+For more information of overlayfs, please refer to
+[here](https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt).
+
+The overlay backend currently has these two limitations:
+
+1. The overlay backend only supports more than one single layer. One
+single layer images will fail to provision and the container will fail
+to launch! This limitation will be solved soon.
+
+2. Similar to the bind backend, the filesystem will be read-only.
+Please refer to the second limitation of the bind backend for more
+details. We will resolve this limitation soon.
 
 
 ## Executor Dependencies in a Container Image