Since we know where the startup files are and what they contain, we can modify them to customize our environment.
As a general rule, to add directories to your
PATH or define additional environment variables, place those changes in .bash_profile (or equivalent, according to your distribution—for example, Ubuntu uses .profile). For everything else, place the changes in .bashrc. Unless you are the system administrator and need to change the defaults for all users of the system, restrict your modifications to the files in your home directory. It is certainly possible to change the files in /etc such as profile, and in many cases it would be sensible to do so, but for now let’s play it safe.