Difference Between su and su – Command in Linux

As a new Linux user, you may always face confusion regarding the difference between `su` command and `su -` command. In Linux, the `su` command is used to switch to another user account. However, there are two variations of the `su` command: `su` and `su -` (su hyphen).

Linux User Environment: Linux’s systems are multi-user environments. Whenever the Linux operating system creates a new shell session (after a new terminal is started on Linux) it starts preparing an environment for itself. This environment basically holds the Environment variable (Environmental depends on shell type, Bash is generally used by most of the Linux distributions).

For example, pwd command is an environmental variable.

pwd

The key difference between `su` and `su -` Command in Linux

Difference	su	su –
Environment Variables	Retains the current user’s environment variables	Resets the environment variables to those of the target user
Working Directory	Keeps the current working directory.	Changes the working directory to the target user’s home directory.
Shell Settings	Retains the current user’s shell settings.	Resets the shell settings to those of the target user.
Path Variable	The target user’s PATH variable is not updated	The target user’s PATH variable is updated to include the user-specific directories.

The major difference between `su` & `su -` commands in Linux

su command is an abbreviation for “substitute user” because it is used for switching to another user during a normal login session, but it is often mistaken as an abbreviation for “super user” as mainly su command is used for getting “super user” privileges as when su command is run without a username, we automatically become the superuser after giving the correct root password and after that, we will enter root’s default environment, by only typing the following command:

su

give the root user password

Now logged in as root user/super user

root user/super user

Directory Differences between `su` & `su -` command in Linux

When we switch from one user to another user using the normal `su` command the current directory remains the same as of the previous user like this

su noobietechs

pwd

When we switch from one user to another user using su — command the current directory changes to the home directory of the target user like this:

Path Differences between `su` & `su -` commands in Linux

`su` command does not create a new User Environment (in the simple term they pretend to be the target user) but `su -` creates a totally new User Environment (in the simple term they are actually the target user) that we can check with environment variables like:

echo $PATH

For `su` command:

su

echo $PATH

For su – command

su –

echo $PATH

For more info check the `su` manual by using the following command

man su

man su

Frequently Asked Question

When to use which command in between `su` and `su -`?

`su` command is used when we need to switch to another user account temporarily and want to retain our current environment. For example, when we are executing specific commands as a different user.

`su -` command is used when we want to fully log in as another user and work within their environment. For example, as if we have logged in directly with their account.
It’s important to note that both commands require the appropriate user’s password to complete the switch.