I tried to use m.rot90 to rotate a raster map and it tells that the raster
map I wanted to totate does not existed. Why does this happen?
m.rot90 does NOT operate on GRASS raster data. Instead, it expects data in
the format written by the m.* tape and file extraction programs. Also, the
full pathname must be used in specifying the name of an already existing
file; the current mapset search list is not considered, nor is it applicable.
Hope this clarifies your situation.