I forgot the password I entered during postgres installation

1. find the file pg_hba.conf – it may be located, for example in /etc/postgresql-9.1/pg_hba.conf.

   cd /etc/postgresql-9.1/

2. Back it up

   cp pg_hba.conf pg_hba.conf-backup

3. place the following line (as either the first un-commented line, or as the only one):

For all occurrence of below (local and host) , except replication
section if you don’t have any it has to be changed as follow ,no MD5
or Peer authentication should be present.

local  all   all   trust

4. restart your PostgreSQL server (e.g., on Linux:)

   sudo /etc/init.d/postgresql restart

   If the service (daemon) doesn’t start reporting in log file:

   local connections are not supported by this build

   you should change

   local all all trust

   to

   host all all 127.0.0.1/32 trust

5. you can now connect as any user. Connect as the superuser postgres (note, the superuser name may be different in your installation. In some systems it is called pgsql, for example.)

   psql -U postgres

   or

   psql -h 127.0.0.1 -U postgres

   (note that with the first command you will not always be connected with local host)

6. Reset password (‘replace my_user_name with postgres since you are resetting postgres user)

   ALTER USER my_user_name with password 'my_secure_password';

7. Restore the old pg_hba.conf as it is very dangerous to keep around

   cp pg_hba.conf-backup pg_hba.conf

8. restart the server, in order to run with the safe pg_hba.conf

   sudo /etc/init.d/postgresql restart

Further Reading about that pg_hba file: http://www.postgresql.org/docs/9.1/static/auth-pg-hba-conf.html