[Trac #1155] use CLONE_NEWNS and bind mounts to give activities fixed-location bundle directories

[Zarro Boogs per Child]

#1155: use CLONE_NEWNS and bind mounts to give activities fixed-location bundle
directories
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 Reporter:  AlbertCahalan  |       Owner:  krstic   
     Type:  defect         |      Status:  new      
 Priority:  normal         |   Milestone:  Untriaged
Component:  security       |    Keywords:           
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 Currently an activity needs to support being relocated to an arbitrary
 directory so that name conflicts can be resolved.

 Since Bitfrost will be using namespace tricks to jail things anyway, that
 problem can be eliminated. Every activity can have the same directory.
 Using the root directory would make sense.

 So /usr/share/activities/foo/bar becomes /bar when foo runs, and
 /usr/share/activities/foo~1/bar becomes /bar when foo~1 runs. Because of
 CLONE_NEWNS, both foo and foo~1 can run simultaneously without conflict.

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Ticket URL: <http://dev.laptop.org/ticket/1155>
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