How to stop postgres from autostarting during start up

On Ubuntu 16.04 or later (which use systemd) you'd use this command

sudo systemctl disable postgresql

If you want to re-enable, you'd do

sudo systemctl enable postgresql

On Ubuntu 15.10 and older, you can use update-rc.d:

janus@Zeus:~$ sudo update-rc.d -f postgresql remove
 Removing any system startup links for /etc/init.d/postgresql ...
   /etc/rc0.d/K21postgresql
   /etc/rc1.d/K21postgresql
   /etc/rc2.d/S19postgresql
   /etc/rc3.d/S19postgresql
   /etc/rc4.d/S19postgresql
   /etc/rc5.d/S19postgresql
   /etc/rc6.d/K21postgresql
janus@Zeus:~$

Using update-rc.d is better but you can do it with chkconfig:

sudo apt-get install chkconfig
sudo chkconfig -s  postgresql off

In Ubuntu 12.04, you also need to create a symlink to insserv's location:

sudo ln -s /usr/lib/insserv/insserv /sbin/insserv

This can help you: http://www.linuxquestions.org/questions/linux-general-1/how-to-remove-postgresql-from-startup-481963/#post2417585

But install chkconfig first:

sudo apt-get install chkconfig

and then use it

chkconfig