pg_upgrade invalid option

I've tried following the instructions on this page:
http://www.postgresql.org/files/documentation/books/aw_pgsql/node267.html

This mentions a -f option but my version of pg_upgrade doesn't appear
to support this:

/usr/lib64/postgresql-9.0/bin/pg_upgrade: invalid option -- 'f'

The only options available are:

Options:
 -b, --old-bindir=old_bindir      old cluster executable directory
 -B, --new-bindir=new_bindir      new cluster executable directory
 -c, --check                      check clusters only, don't change any data
 -d, --old-datadir=old_datadir    old cluster data directory
 -D, --new-datadir=new_datadir    new cluster data directory
 -g, --debug                      enable debugging
 -G, --debugfile=debug_filename   output debugging activity to file
 -k, --link                       link instead of copying files to new cluster
 -l, --logfile=log_filename       log session activity to file
 -p, --old-port=old_portnum       old cluster port number (default 5432)
 -P, --new-port=new_portnum       new cluster port number (default 5432)
 -u, --user=username              clusters superuser (default "postgres")
 -v, --verbose                    enable verbose output
 -V, --version                    display version information, then exit
 -h, --help                       show this help, then exit

Are those instructions for an older version?

Thanks

Thom