backup:/var/backups# su - postgres
postgres@backup:~$ ps
ps             psfaddtable    psfstriptable  pstree         pstruct
psed           psfgettable    psql           pstree.x11
postgres@backup:~$ psql noc
psql (8.4.8)
Type "help" for help.

noc=#
noc=# ^D\q
postgres@backup:~$ psql noc -W
Password:
psql (8.4.8)
Type "help" for help.

noc=# ^D\q
postgres@backup:~$ logout
backup:/var/backups#
backup:/var/backups#
backup:/var/backups#
backup:/var/backups#

backup:/var/backups/noc_install/mapnik# OS
bash: OS: command not found