Sharing a GRASS database
Here are some suggestions on how multiple people at a site can collaborate on one GRASS database, sharing data.
Using the same mapset, sequentially
GRASS does not allow two users to run in the same mapset at the same time. It is possible for two different users to take turns using a mapset at different times. This is complicated by the fact that GRASS will not allow itself to be run in a mapset owned by a different operating-system user. If you try to do this, you will get a "permission denied" error, which is entirely independent of the permission checking of your operating system. The solution is either to change the ownership of the mapset (the directory and all files and subdirectories contained therein) prior to a different user running GRASS in that mapset, or to have a separate mapset for each username.
Limitations: possibly inefficient use of users' time because people must take turns.
Using per-user mapsets
If you use a separate mapset for each operating-system username, you can use g.mapsets to add additional mapsets to the search path,
which will allow you to access files from either mapset by name without having to use the map@mapset syntax.
Limitations: you still can only use g.remove, g.rename, and g.copy on maps in your current mapset.
If you try to replace a map that exists under the the same name in one of the other mapsets, the old map will continue to exist but will be masked for you (but not for other users) by your new map. This behavior may not be what you expect.
References
Thread on GRASS-user mailing list on "shared access to mapsets" (source of the information in this article)
Sharing GRASS maps
To give data to someone else in the native GRASS GIS formats (no data loss due to exporting!), use: