> On Aug. 27, 2015, 10:42 p.m., Jie Yu wrote:
> > src/slave/containerizer/provisioners/backends/overlay.cpp, lines 101-103
> > <https://reviews.apache.org/r/37853/diff/1/?file=1056428#file1056428line101>
> >
> >     Hum, I'd like to understand why overlay backend cannot support 1 layer. 
> > Any reason?

The mount options for overlayfs either takes one lowerdir, one upperdir and one 
workdir, or at least 2 lowerdirs. It's just how the function works.


> On Aug. 27, 2015, 10:42 p.m., Jie Yu wrote:
> > src/slave/containerizer/provisioners/backends/overlay.cpp, line 111
> > <https://reviews.apache.org/r/37853/diff/1/?file=1056428#file1056428line111>
> >
> >     I think you should be able to use strings::join here:
> >     
> >     ```
> >     strings::join(":", layers);
> >     ```

The format would be dir1:dir2:dir3 etc. I'm just wondering is it possible to 
have the semi colon only appear between the directories? If I'm thinking about 
this correctly, strings::join will give me :dir1:dir2:dir3? Also since I'm 
stacking the layers in reverse from the comment above, does this still apply?


> On Aug. 27, 2015, 10:42 p.m., Jie Yu wrote:
> > src/slave/containerizer/provisioners/backends/overlay.cpp, lines 110-114
> > <https://reviews.apache.org/r/37853/diff/1/?file=1056428#file1056428line110>
> >
> >     Could you please add a comment about the ordering the layers will be 
> > stacked.
> >     
> >     I think we should add a document at the backend interface as well 
> > stating that layers are stacking in such a way that the front layer in the 
> > vector will be the bottom most layer (i.e., applied first).
> >     
> >     The lowerdir here should actually reverse the order of the layers 
> > vector.
> >     
> >     ```
> >     The specified lower directories will be stacked beginning from the 
> > rightmost one and going left.  In the above example lower1 will be the top, 
> > lower2 the middle and lower3 the bottom layer.
> >     ```

Where would I add this document? I could just add it to the flag?


> On Aug. 27, 2015, 10:42 p.m., Jie Yu wrote:
> > src/slave/containerizer/provisioners/backends/overlay.cpp, line 58
> > <https://reviews.apache.org/r/37853/diff/1/?file=1056428#file1056428line58>
> >
> >     You also want to check if overlay fs is supported or not. Not every 
> > linux kernel supports overlay fs.

How would I check this?


- Mei


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On Aug. 27, 2015, 9:11 p.m., Mei Wan wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/37853/
> -----------------------------------------------------------
> 
> (Updated Aug. 27, 2015, 9:11 p.m.)
> 
> 
> Review request for mesos, Ben Mahler, Chi Zhang, Ian Downes, and Jie Yu.
> 
> 
> Bugs: MESOS-2971
>     https://issues.apache.org/jira/browse/MESOS-2971
> 
> 
> Repository: mesos
> 
> 
> Description
> -------
> 
> Implemented the overlay filesystem backend by layering the images as a 
> read-only filesystem.
> 
> 
> Diffs
> -----
> 
>   src/Makefile.am 7b620ff 
>   src/slave/containerizer/provisioners/backend.cpp 2f7c335 
>   src/slave/containerizer/provisioners/backends/overlay.hpp PRE-CREATION 
>   src/slave/containerizer/provisioners/backends/overlay.cpp PRE-CREATION 
> 
> Diff: https://reviews.apache.org/r/37853/diff/
> 
> 
> Testing
> -------
> 
> I haven't done any official testing. When I was working off Ian's branch, I 
> tested it manually and the provisioning works.
> 
> 
> Thanks,
> 
> Mei Wan
> 
>

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