Mastering sudo: 4 Essential Commands for Root Access and User Switching

Introduction

When using Linux, switching privileges is commonly done with sudo or su root . Beyond these basic usages, sudo offers several advanced operations that many users overlook. This article walks through the most useful sudo commands.

1. sudo su -

This command logs in to a new root shell using the current user's password. It reloads system configuration files such as /etc/profile and /etc/bashrc , and also reloads the root user's $SHELL configuration (e.g., /root/.bashrc for Bash or /root/.zshrc for Zsh), providing a full root environment.

<code>$ sudo su -
# env | grep -E '(HOME|SHELL|USER|LOGNAME|^PATH|PWD|TEST_ETC|TEST_ZSH|TEST_PRO|TEST_BASH|TEST_HOME|SUDO)'
</code>

2. sudo -i

This command behaves similarly to sudo su - , giving you a root environment while preserving some information about the invoking user.

<code>$ sudo -i
# env | grep -E '(HOME|SHELL|USER|LOGNAME|^PATH|PWD|TEST_ETC|TEST_ZSH|TEST_PRO|TEST_BASH|TEST_HOME|SUDO)'
</code>

3. sudo -s

This starts a non‑login root shell using the current user's $SHELL . It does not load /etc/profile or other system-wide files, so variables defined there (e.g., TEST_ETC ) are absent, but it does load the root user's shell configuration (e.g., /root/.zshrc if $SHELL is Zsh). The working directory remains unchanged.

<code>$ sudo -s
# env | grep -E '(HOME|SHELL|USER|LOGNAME|^PATH|PWD|TEST_ETC|TEST_ZSH|TEST_PRO|TEST_BASH|TEST_HOME|SUDO)' --color
</code>

4. sudo "command"

Prefix any command with sudo to execute it with root privileges, e.g., sudo git --version . When run, sudo resets the environment to a secure set of variables and does not load the user's shell configuration, so custom variables like TEST_ETC or TEST_PRO are missing. The secure path is defined in /etc/sudoers under the secure_path setting.

<code>$ sudo env | grep -E '(HOME|SHELL|USER|LOGNAME|^PATH|PWD|TEST_ETC|TEST_ZSH|TEST_PRO|TEST_BASH|TEST_HOME|SUDO)' --color
</code>

Note that sudo echo $PATH and sudo env | grep PATH may show different values because the former expands $PATH before sudo runs.

The sudo capabilities, especially those defined in /etc/sudoers , are powerful and worth further exploration.