Files: / etc / profile ~ / .bashrc and ~ / .bash_profile using differences:
/ Etc / profile: global environment variables, execute reboot your machine once for setting environment variables, change some parameters such as the kernel command.
/ Etc / bashrc: global variables landing, such as alias.
bashrc and bash_profile: Login Actions performed mainly used to set aliases and other little tricks.
bash_profile each landing will be performed during the execution of the call bashrc, bashrc not always landing will be executed.
alias and unalias, alias write in .bashrc, .bash_profilc every time you login into effect, the difference is positive for all user settings or individual user.
alias, cd, pwd called internal variables, no configuration file, use enable queries.