Installing an overlay in the install space of the underlay

Question

Is it possible to install an overlay in the same install space as an underlay? For example, if I have a base install from source in /opt/ros/hydro, it might be convenient to extend it with additional packages in an overlayed workspace instead of augmenting the original workspace (which for the desktop-full install has about 250 packages on hydro). If those additional packages are merely dependencies (i.e. I don't intend to modify them) and not specific to one project, installing them on top of the underlay in /opt/ros/hydro would be convenient.

---

Originally posted by demmeln on ROS Answers with karma: 4306 on 2014-03-07

Post score: 0

Answer 1

Yes, that is no problem.

This is commonly used to install multiple packages / workspace to a single location. Basically /opt/ros/DISTRO can be considered as an example since every Debian package is its own little "workspace".

---

Originally posted by Dirk Thomas with karma: 16276 on 2014-03-07

This answer was ACCEPTED on the original site

Post score: 1

---

Original comments

Comment by demmeln on 2014-03-07:
I was woundering precicely if for debian packages there was something special going on to make it work. Thanks.

Comment by Dirk Thomas on 2014-03-07:
One thing is special for the Debian packages. Only the catkin package comes with the setup files. If you install workspace they will always overwrite the existing setup files. But that should not be an issue since the generated content should be identical.

Comment by demmeln on 2014-03-07:
Aha. Is this true for 'sibling overlays'? I.e. if I have two workspaces A and B both overlaying workspace C, they both install the same setup files, therefore I can install both A and B in the same install space, right?

Comment by Dirk Thomas on 2014-03-07:
Without thinking too much about that scenario I would say "yes, that should work".