Change Ambari default admin password

1. Stop Ambari server
2. Log on to ambari server host shell
3. Run 'psql -U ambari-server ambari'
4. Enter password ****  (this password is stored in
/etc/ambari-server/conf/password.dat)
5. In psql:
update ambari.users set
user_password='538916f8943ec225d97a9a86a2c6ec0818c1cd400e09e03b660fdaaec4af29ddbb6f2b1033b81b00'
where user_name='admin'
6. Quit psql
7. Run 'ambari-server restart'

Note: The password used in step 5 is the encrypted form of 'admin'.
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To change passdword after installation :
 ambari_password='zaidololo'
curl  -u admin:admin -H "X-Requested-By: Goll" -X PUT -d "{ \"Users\": { \"user_name\": \"admin\", \"old_password\": \"admin\", \"password\": \"${ambari_password}\" }}" ambari.realtime002.test.goll.com:8080/api/v1/users/admin

One can simply use "ambari-admin-password-reset"
This is the easiest way. You don't need to do anything else.

ambari-admin-password-reset is only available with the Sandbox which I don't use.
But thanks for the tip :)

works