ask...!!!

["ria ulfa" <riakdr@xxxxxxxxx>]

i use linux fedora 7 and database PostgreSQL 8.
i want to copy table in postgre to a file.
i used code : simps=# COPY log TO '/root/documents/log.sql';
      note= simps: name of database
but there is error:  could not open file "/root/documents/log.sql" for writing: Permission denied
what can i do for repair this error??