For this purpose, you can set up OS X to automatically log in a user on startup. Follow the steps given below to enable automatic login for a user:
Open up “System Preferences” from the Apple Menu.
Select “Users & Groups.”
Click on the Lock icon in the lower-left corner. Enter your password when prompted.
Click on “Login Options.”
From the Automatic Login drop-down menu, you can select the user you want to log in automatically when you boot up the system. If you have a system set up for presentation or media center services, you may want the same app to start up when you fire up your Mac. If that’s the case, follow the steps below:
Navigate to “System Preferences -> Users & Groups”. Click the Lock icon to make changes.
Select the user account which you’ve set up to log in automatically.
In the “Login Items” tab, select the app(s) you want to start automatically when the system is turned on.
Remember to use Automatic Login responsibly, as it will give anyone who has physical access to the system entry to the machine’s contents. Passwords will still be required to log in to the system through network services like file-sharing and remote log-in through SSH and other Terminal services. You can also disable Automatic Login by simply navigating to “System Preferences -> Users & Groups -> Login Options” and select “Off” from the Automatic Login drop-down list.
