You can change it from the configuration file.

In the configuration file, you can set admin_passwd and restart your ODOO server.

in /etc/odoo.conf set:

[options]
admin_passwd = mysupersecretpassword
db_host = 192.168.1.2
db_port = 5432
db_user = odoo
db_password = pwd
dbfilter = ^mycompany.*$

If the database-management screen should be left accessible, the admin_passwd setting must be changed from its admin default: this password is checked before allowing database-alteration operations.

The database management screens are protected by the admin_passwd setting. This setting can only be set using configuration files, and is simply checked before performing database alterations. 
It should be set to a randomly generated value to ensure third parties can not use this interface.