document dirperm1 fix for in known issues
Since `dirperm1` requires a more recent aufs patch than many current OS release,
we cant remove completely. This documents that docker will apply `dirperm1`
automatically for systems that support it
@@ -280,8 +280,14 @@ The cache for `RUN` instructions can be invalidated by `ADD` instructions. See
- [Issue 783](https://github.com/docker/docker/issues/783) is about file
permissions problems that can occur when using the AUFS file system. You
- might notice it during an attempt to `rm` a file, for example. The issue
- describes a workaround.
+ might notice it during an attempt to `rm` a file, for example.
+
+ For systems that have recent aufs version (i.e., `dirperm1` mount option can
+ be set), docker will attempt to fix the issue automatically by mounting
+ the layers with `dirperm1` option. More details on `dirperm1` option can be
+ found at [`aufs` man page](http://aufs.sourceforge.net/aufs3/man.html)
+
+ If your system doesnt have support for `dirperm1`, the issue describes a workaround.
## CMD
