The system default "profile" is /etc/profile.
Thse are called dot files "."extention to see them from the shell login in use
ls -la. Not all distro's create a .profile or .bash_profile in users home directory.
Any changes you want every user to have should be make in /etc/profile.
the genearl syntax is:
If you are new to Unix/Linux I would suggest that you read this Howto
before you go much furthure:
As well as the howto and guides on: