If you are bash user, you may know how to add and change system environment.

Modify current terminal system environment(it is contemporary)

Run $ export PATH="/usr/bin:$PATH" but when you startup a new terminal it is will invalid.

Edit ~/.profile and ~/.bashrc it impacts current user

Add $ export PATH="/usr/bin:$PATH" into ~/.profile and ~/.bashrc but when other user open a new terminal it is not effected.

Add into /root/.profile it is effected for all users

Add $ export PATH="/usr/bin:$PATH" into /root/.profile.

But if you are a fish shell user like me, something dislike above.

Add set --export PATH /usr/bin into ~/.config/fish/config.fish(if you do not have this file touch it).

Run $ help set to browse its official documents to get more information about set.