Complete view of where the PATH variable is set in bash

environment-variablespath

I've read in a couple of places that the PATH is set in /etc/profile or the .profile file that's in the home dir.

Are these the only places that the path is set in? I want a better understanding of it.

In the /etc/profile file, as the following comment says "system-wide .profile file for the Bourne shell". Does that mean that profile files are the main configuration files for bash?

In that file I don't see the PATH var being set at all. In the .profile file in the home directory there's this line:

PATH="$HOME/bin:$PATH"

That's resetting PATH by the looks because it's concatenating the already set $PATH string with $HOME/bin: right? But if etc/profile and ~/.profile are the only files setting PATH where is $PATH coming from in that line of code if it's not defined in /etc/profile?

Can someone experienced please give a broad and detailed explanation of the PATH variable? Thanks!

Best Answer

There are many places where PATH can be set.

The login program sets it to a default value. How this default value is configured is system-dependent. On most non-embedded Linux systems, it's taken from /etc/login.defs, with different values for root and for other users. Consult the login(1) manual on your system to find out what it does.

On systems using PAM, specifically the pam_env module, environment variables can be set in the system-wide file /etc/environment and the per-user file ~/.pam_environment.

Then most ways to log in (but not cron jobs) execute a login shell which reads system-wide and per-user configuration files. These files can modify the value of PATH, typically to add entries but sometimes in other ways. Which files are read depend on what the login shell is. Bourne/POSIX-style shells read /etc/profile and ~/.profile. Bash reads /etc/profile, but for the per-user file it only reads the first existing file among ~/.bash_profile, ~/.bash_login and ~/.profile. Zsh reads /etc/zshenv, ~/.zshenv, /etc/zprofile, ~/.zprofile, /etc/zlogin and ~/.zlogin. Many GUI sessions arrange to load /etc/profile and ~/.profile, but this depends on the display manager, on the desktop environment or other session startup script, and how each distribution has set these up.

Related Solutions

Add Multiple Subdirectories to PATH Under Same Parent Directory

Adding a directory to PATH only makes the executables in this directory available as bare command names. This does not extend to subdirectories.

You can put a loop in your .profile (not .bashrc) to add multiple directories, for example:

for d in ~/tools/*/bin; do
  PATH="$PATH:$d"
done

(You don't need to repeat export: when a variable is exported, it stays exported, and modifications are reflected in the environment).

If you create new directories under tools, this will not be reflected in your ongoing session, only the next time .profile is read. If this is not satisfactory, you can use a different approach: put a single directory such as ~/bin in your PATH, and when you install software, create symbolic links in ~/bin. Stow (or its alternative XStow) is a good way of doing this; see Keeping track of programs for an overview of how this works.

Linux – where is the PATH for users set in linux, before any shell, or sudo, pam.d changes it

It's hard-coded in the sshd binary.

$ strings /usr/sbin/sshd |grep /usr/local/bin
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11
/usr/local/bin:/usr/bin:/bin:/usr/bin/X11:/usr/games

In the OpenSSH portable code, that's _PATH_STDPATH which defaults to /usr/bin:/bin:/usr/sbin:/sbin for both root and non-root. The Debian build rules set this to /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin for root, /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games for non-root on Ubuntu, /usr/local/bin:/usr/bin:/bin on installation live media (udeb), and /usr/local/bin:/usr/bin:/bin:/usr/games for non-root otherwise.

Best Answer

Related Solutions

Add Multiple Subdirectories to PATH Under Same Parent Directory

Linux – where is the PATH for users set in linux, before any shell, or sudo, pam.d changes it

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