Path Environment Variable in Linux

How to permanently set $PATH on Linux/Unix

There are multiple ways to do it. The actual solution depends on the purpose.

The variable values are usually stored in either a list of assignments or a shell script that is run at the start of the system or user session. In case of the shell script you must use a specific shell syntax and export or set commands.

System wide

1. /etc/environment List of unique assignments. Allows references. Perfect for adding system-wide directories like /usr/local/something/bin to PATH variable or defining JAVA_HOME. Used by PAM and systemd.

2. /etc/environment.d/*.conf List of unique assignments. Allows references. Perfect for adding system-wide directories like /usr/local/something/bin to PATH variable or defining JAVA_HOME. The configuration can be split into multiple files, usually one per each tool (Java, Go, and Node.js). Used by systemd that by design do not pass those values to user login shells.

3. /etc/xprofile Shell script executed while starting X Window System session. This is run for every user that logs into X Window System. It is a good choice for PATH entries that are valid for every user like /usr/local/something/bin. The file is included by other script so use POSIX shell syntax not the syntax of your user shell.

4. /etc/profile and /etc/profile.d/* Shell script. This is a good choice for shell-only systems. Those files are read only by shells in login mode.

5. /etc/<shell>.<shell>rc. Shell script. This is a poor choice because it is single shell specific. Used in non-login mode.

User session

1. ~/.pam_environment. List of unique assignments, no references allowed. Loaded by PAM at the start of every user session irrelevant if it is an X Window System session or shell. You cannot reference other variables including HOME or PATH so it has limited use. Used by PAM.

2. ~/.xprofile Shell script. This is executed when the user logs into X Window System system. The variables defined here are visible to every X application. Perfect choice for extending PATH with values such as ~/bin or ~/go/bin or defining user specific GOPATH or NPM_HOME. The file is included by other script so use POSIX shell syntax not the syntax of your user shell. Your graphical text editor or IDE started by shortcut will see those values.

3. ~/.profile, ~/.<shell>_profile, ~/.<shell>_login Shell script. It will be visible only for programs started from terminal or terminal emulator. It is a good choice for shell-only systems. Used by shells in login mode.

4. ~/.<shell>rc. Shell script. This is a poor choice because it is single shell specific. Used by shells in non-login mode.

Notes

GNOME on Wayland starts a user login shell to get the environment. It effectively uses the login shell configurations ~/.profile, ~/.<shell>_profile, ~/.<shell>_login files.

Man pages

• environment
• environment.d https://linux.die.net/man/1/environment.d
• bash
• dash

Distribution-specific documentation

• Ubuntu
• Arch Linux

Related

Difference between Login Shell and Non-Login Shell?

How to set an environment variable to point to a location and how to set path of an environment variable in UBUNTU?

Yes, the above command sets variable when executing together with other commands like so:

$ VAR1=/home/folder1/lib123.so MY_AWESOME_COMMAND

Or you can use export so that you won't have to include the variable in each command.

$ export VAR1=/home/folder1/lib123.so

Test it below:

$ echo $VAR1
$ /home/folder1/lib123.so

Environment variable PATH on linux

I would setup a new alias in my .bashrc or .profile, which should be located under your home directory. Add the following to the end of the file:

alias firefox="/home/debian/firefox/firefox"

Save the file and reload it using:

source ~/.bashrc

Since you added the alias to your .bashrc this alias will be created everytime you open a new instance of a shell.

You could use nohup to keep the command running after the shell session ends:

alias firefox="nohup /home/debian/firefox/firefox &"

Notice the trailing & character, which will run the command in the background so you can keep using your terminal.

PATH environment variable in Linux

I would like to add a few more details to what @cnicutar has already mentioned.

Environment variables including PATH can be:

• System wide - The values of the environment variables last till the system is up
• Session wide - Lasts till a session lasts (till user logs out)

/etc/profile is meant for system settings for Bourne & Bourne compatible shells. The behavior of /etc/profile may vary across distributions.

For the latest Ubuntu distributions, it is recommended to use /etc/environment for system-wide settings. It is not recommended to use /etc/profile or /etc/bash.bashrc as noted the Ubuntu help.

On Ubuntu machines, /etc/profile is a shell script which sources the scripts in /etc/profile.d and the system-wide bashrc file in /etc/bash.bashrc, whereas /etc/environment is a text file consisting of variable assignments per line which are set into the system-wide environment.

For each user the values of environment variables including PATH (for the shell) can also be manipulated through ~/.profile, ~/.bash_profile, ~./bash_login, and ~/.bashrc where ~ means the user's home directory, like /home/alex/.

To see your current environment variables and their values, you can use printenv.

You can refer to the following link for more details on environment variables on Ubuntu systems: https://help.ubuntu.com/community/EnvironmentVariables

Error in setting the path variable in Linux

If you want to set the path environment variable, you need to use:
export PATH=/some/path:$PATH.

In your case, it would look like:
export PATH=$HOME/Toolchains/gcc-arm-none-eabi-9-2020-q2-update/bin:$PATH
The only downside to setting the path manually is that it will not persist across bash sessions. If you want this change to be permanent, then I would suggest adding that line to your .bashrc or .profile file in the home directory.

Where default PATH environment variable is defined

Where default PATH environment variable is defined

It depends. On the distribution, on the shell, on the environment, on OS, on configuration files.

I have some systems at hand, I see:

• ArchLinux adds to PATH in /etc/profile.
• OpenSuSE has yet a different code that adds to PATH from /etc/profile
• CentOS7 has has yet a different code in /etc/profile

I suspect that each distribution places files in slightly different places, they will ship with slightly different configuration.

how the environment is populated?

Bash has DEFAULT_PATH_VALUE that is used when PATH is not set. But don't look at the default value too much - package distrbutors overwrite it.

There is /etc/environment (and pam_env.conf) that are read by PAM on login. So when you login. But not when you chroot.

The is /etc/profile and ~/.profile files read by the shell. These scripts may read other files. So usually there is drop-in dir /etc/profile.d/*.

In bash there is /etc/bashrc or /etc/bash.bashrc /etc/bash.login /etc/bash.logout or similar and user configuration files ``~/.bashrcetc. In bash also/etc/bash_completion.dand all scripts in/usr/share/bash_completionare also sourced, when completion is enabled. BUT these files are for Bourne shell - there are also other shells, notablyzshandcsh`, and people use them and they have different syntax and different set of startup files.

Each of these scripts can manipulate PATH, it can reset it, append to it, do whatever it wants to it.

And there are also different set of files read on login/non-login + interactive/non-interactive shells, and these files can include each other (it's common to have .bash_profile or other files that just source .bashrc or similar).

What are defaults

The /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin looks like a good default that should be safe on any linux.

by the way, is surprisingly empty. Why?

My /etc/environment file is just empty and has only the default comment in linux-pam package. /etc/environment has a very simple syntax and is read by pam (there may be no pam on your system...). To modify shell environment, one would prefer shell files - so /etc/profile is the place to keep system modifications. Also /etc/environment has simple key=value syntax, wherea's in /etc/profile you have, well, shell. And /etc/environment is read on login by PAM - so putting PATH just there would break I think for example docker, it just runs a shell in chroot, there is login.

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