how to get user id from auth_user table in django. Suppose the username is available to me.
auth_user
Assuming the user exists:
from django.contrib.auth.models import User User.objects.get(username=the_username).pk
The user does not have a backend, so you should use the UserManager (or BaseUserManager if you have a user class of the user)
BaseUserManager.get_by_natural_key(username)
https://docs.djangoproject.com/en/1.6/topics/auth/customizing/#django.contrib.auth.models.BaseUserManager