User Env

.profile

.profile is the first file it is loaded by the shell when a user opens one. If this is missing it might be .bash_profile. if you have a .bash_profile and you create a .profile then profile is loaded first

You can easily lock a user by adding a exit statement in the .profile file :)

PATH

The execution flow of a particular application is given by it’s location in the PATH env variable. Lets say i inherit a default PATH env from the default machine configuration that has some outdated binary and i want to use the new version. i can change this without the help of sysadmin by adding the location of the new binary in front of the old one in the PATH env var

packer@host01:~$ echo $PATH
/root/go/bin:/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
packer@host01:~$ PATH=/home/packer/bin/:$PATH
packer@host01:~$ echo $PATH
/home/packer/bin/:/root/go/bin:/usr/local/go/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin

LD_LIBRARY_PATH

Same as PATH but for libraries.