Restore data from tar file
You will need a locally installed PostgreSQL of the same major as the data directory archive. For example, if the archive came from 9.1.5 you would need some 9.1.x on the local machine, it doesn't matter if it's 9.1.0 or 9.1.9, but it must be 9.1 not 9.2 or 9.0.

If you don't have 9.1, you can install it from packages or just download the source and compile it locally.

Then, if you just want to dump the data to reload into an existing local PostgreSQL install:


Unpack the archive
If necessary set your PATH so that PostgreSQL 9.1's bin directory is first on the PATH
PGPORT=5435 pg_ctl -D /path/to/unpacked/archive start
PGPORT=5435 pg_dumpall --globals-only
Dump each database with pg_dump


If you instead want to restore the database so it runs instead of whatever's locally running, you must:


Ensure the current install is of the same major version
Stop the current PostgreSQL: service postgresql stop
Rename the data directory. On CentOS it'll be in /var/lib/pgsql/9.1/data/, so something like sudo mv /var/lib/pgsql/9.1/data /var/lib/pgsql/9.1/data.old. Do not delete it; if it turns out there is data in there you forgot you needed, this way you can still get it back.
Move the unpacked archive to the old data directory location, e.g sudo mv /path/to/unpacked/archive/folder /var/lib/pgsql/9.1/data
Set the permissions: sudo chown postgres:postgres /var/lib/pgsql/9.1/data; sudo chmod 700 /var/lib/pgsql/9.1/data
Edit postgresql.conf to reflect any required changes for the local install
Start PostgreSQL: service postgresql start


Some details like service name, path, etc will vary depending on whether you're running the original Red Hat packages of PostgreSQL, or whether you installed from http://yum.postgresql.org/ .