move databases files location

hello,

my postgresql installation from redhat package:
$ rpm -q postgresql
postgresql-7.4.17-1.RHEL4.1
 is located in /var partition, unfortunalty it is nearly full
$ df -H .
Filesystem             Size   Used  Avail Use% Mounted on
/dev/sda12              11G   8.2G   1.7G  84% /var

How can I tell postgresql to record databases in an other partition ?
For now they are in:
[root@metarisk1 /var/lib/pgsql/data/base]
$ ls
1      17142     18275591  26876456  537107  6123076  657110   802399
17141  17837306  18372925  533001    596944  61317    7321277  8500925

will it be simply a move of the files, or should I have to dump&restore
the databases ?

thanks.