De acordo com Wiki do Ubuntu sobre Variáveis de Ambiente em ~/.pam_environment ou em /etc/environment , dependendo sobre o que você deseja para todos os usuários ou apenas o seu usuário.
Session-wide environment variables
Environment variable settings that should affect just a particular user (rather then the system as a whole) should be set into:
~/.pam_environment- This file is specifically meant for setting a user's environment. It is not a script file, but rather consists of assignment expressions, one per line.Note: Using
.pam_environmentrequires a re-login in order to initialize the variables. Restarting just the terminal is not sufficient to be able to use the variables.
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System-wide environment variables
Environment variable settings that affect the system as a whole (rather then just a particular user) should not be placed in any of the many system-level scripts that get executed when the system or the desktop session are loaded, but into
/etc/environment- This file is specifically meant for system-wide environment variable settings. It is not a script file, but rather consists of assignment expressions, one per line. Specifically, this file stores the system-wide locale and path settings.