User and permission management is one of the most important aspects of Linux system administration. Whether you are a DevOps engineer, system administrator, or Linux beginner, understanding how users, groups, and file permissions work is essential for maintaining system security and stability.
This is Part 2 of our Linux command series. In this guide, you’ll learn how to create and manage users, work with groups, and control file access using permissions. Each command is explained with clear examples so you can practice confidently.
Linux User, Group, and Permission Commands – Overview
| Command | Description |
|---|---|
useradd | Create a new user account |
passwd | Set or change a user password |
id | Display user UID, GID, and groups |
groupadd | Create a new group |
usermod | Modify user accounts |
chown | Change file owner |
chgrp | Change group ownership |
chmod | Change file permissions |
User Management Commands
Create a New User
sudo useradd john sudo useradd -m -s /bin/bash john
The useradd command creates a new user account. The -m option creates a home directory, and -s defines the default shell.
Set or Change User Password
sudo passwd john
This command assigns or updates a password for a user. Only root or sudo users can change other users’ passwords.
View User Details
id john
Displays the user ID (UID), group ID (GID), and all groups the user belongs to.
Switch Users
su - john
Switches to another user and loads their environment variables.
Run Commands as Root
sudo apt update
The sudo command allows permitted users to run commands with administrative privileges.
Delete a User
sudo userdel john
Removes a user account from the system. Use with caution.
Group Management Commands
Create a Group
sudo groupadd developers
Creates a new group that can be used to manage permissions for multiple users.
View All Groups
getent group
Displays all system groups from the group database.
Add User to a Group
sudo usermod -aG developers john
Adds a user to a supplementary group without removing existing group memberships.
Delete a Group
sudo groupdel developers
Deletes a group from the system if it’s no longer required.
File Ownership Commands
Change File Owner
sudo chown john file.txt
Changes the ownership of a file to the specified user.
Change Group Ownership
sudo chgrp developers file.txt
Assigns a file to a specific group.
Change Owner and Group
sudo chown john:developers file.txt
Updates both the user and group ownership in a single command.
Recursive Ownership Change
sudo chown -R john:developers myfolder
Recursively changes ownership for a directory and all its contents.
File Permission Commands
Full Permissions (Not Recommended)
chmod 777 file.txt
Grants read, write, and execute permissions to everyone. This is insecure and should be avoided in production.
Set Specific Permissions
chmod 751 file.txt
Permission breakdown:
- Owner: Read, Write, Execute
- Group: Read, Execute
- Others: Execute only
Recursive Permission Change
chmod -R 777 myfolder
Applies permissions to all files and subdirectories. Use carefully to avoid security risks.
You’ve now learned how to manage users, groups, ownership, and permissions in Linux. In the next part of this series, we’ll cover process management, networking, and package commands.
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