Postgresql: Can't access to file « $libdir/postgis-2.1 » no such file or directory

Finally "solve" the issue compiling from source postgis 2.2.2 (that also requires gdal, proj4 and geos) and then issuing

CREATE EXTENSION postgis;
CREATE EXTENSION postgis_topology;

since DROP EXTENSION postgis; tells me postgis wasn't present anymore.

And finally:

ALTER EXTENSION postgis UPDATE TO '2.2.2';
ALTER EXTENSION postgis_topology UPDATE TO '2.2.2';

Got access again to my geom data and functions from PostgreSQL 9.4. It seems that compiling from source updated correctly the variable path for postgresql and installed /usr/lib/postgresql/9.4/lib/postgis-2.2.so that wasn't present anymore (for postgis-2.1.so as well), even with (re)installing from apt-get.

Hope this will help.

First run (as postgres administrator)

ALTER EXTENSION postgis UPDATE;

If this returns successfully, then check what version you have

SELECT PostGIS_Full_Version();

If however, the server returns that it cannot find the extension postgis, then run

CREATE EXTENSION postgis;
CREATE EXTENSION postgis_topology;
ALTER EXTENSION postgis UPDATE;

and again check by running

SELECT PostGIS_Full_Version();