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Thierry Lam
Asked: 2010-02-06 20:54:20 +0800 CST

What's the default superuser username/password for postgres after a new install?

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I have just installed postgres 8.4 on Ubuntu 9.10 and it has never asked me to create a superuser. Is there a default superuser and its password? If not, how do I create a new one?

user-management postgresql

5 Answers

  1. Best Answer

    CAUTION The answer about changing the UNIX password for "postgres" through "$ sudo passwd postgres" is not preferred, and can even be DANGEROUS!

    This is why: By default, the UNIX account "postgres" is locked, which means it cannot be logged in using a password. If you use "sudo passwd postgres", the account is immediately unlocked. Worse, if you set the password to something weak, like "postgres", then you are exposed to a great security danger. For example, there are a number of bots out there trying the username/password combo "postgres/postgres" to log into your UNIX system.

    What you should do is follow Chris James's answer:

    sudo -u postgres psql postgres

# \password postgres

Enter new password:

    To explain it a little bit. There are usually two default ways to login to PostgreSQL server:

    1. By running the "psql" command as a UNIX user (so-called IDENT/PEER authentication), e.g.: sudo -u postgres psql. Note that sudo -u does NOT unlock the UNIX user.

    2. by TCP/IP connection using PostgreSQL's own managed username/password (so-called TCP authentication) (i.e., NOT the UNIX password).

    So you never want to set the password for UNIX account "postgres". Leave it locked as it is by default.

    Of course things can change if you configure it differently from the default setting. For example, one could sync the PostgreSQL password with UNIX password and only allow local logins. That would be beyond the scope of this question.

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  2. Enter on the command line:

    $ sudo -u postgres psql postgres
postgres=# \password postgres

    You'll see:

    Enter new password: 
Enter it again:
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  3. You manipulate postgres through the user postgres, as so:

    # su - postgres
$ createdb mydb
$ psql -s mydb
# create user someuser password 'somepassword';
# GRANT ALL PRIVILEGES ON DATABASE mydb TO someuser;
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  4. In Windows, do the following (IMPORTANT: Use a Windows administrator account):

    1. After installation, open <PostgreSQL PATH>\data\pg_hba.conf.

    2. Modify these two lines, and change "md5" to "trust":

      host all all 127.0.0.1/32 md5

      host all all ::1/128 md5

    3. Restart the PostgreSQL service (might not be necessary).

    4. (Optional) Open a command prompt, and change code page to 1252:

      cmd.exe /c chcp 1252

    5. Log in to PostgreSQL. Non password will be needed (notice the uppercase -U parameter):

      psql -U postgres

    6. (Optional, recommended for security reasons) Change the postgres user's password:

      \password postgres

      and change "trust" back to "md5" in pg_hba.conf.

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  5. If you are trying to access the PostgreSQL shell, you can type:

    psql -U postgres my_database

    Where my_database is your database name.

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