This comprehensive tutorial provides a detailed exploration of Linux user and group management, equipping readers with the knowledge and skills to effectively manage user accounts and group memberships in their Linux systems. By understanding the concepts of users, groups, and their associated permissions, readers will be able to enhance the security, accessibility, and overall management of their Linux environments.
Linux user management is a critical aspect of system administration and security. In Linux, every process and file is associated with a user and group, which determines access rights and permissions.
Linux distinguishes between different user types:
| User Type | Description | Characteristics |
|---|---|---|
| Root User | System administrator | Full system access, UID 0 |
| System Users | Service-specific accounts | Limited permissions, no login shell |
| Regular Users | Normal human users | Limited system access |
## Create a new user
sudo adduser username
## View current user
whoami
## List all users
cat /etc/passwd
## Switch user
su - username
## Check user details
id usernameUser account information is stored in key system files:
/etc/passwd: User account details/etc/shadow: Encrypted password information/etc/group: Group membership detailsGroups in Linux provide a mechanism for organizing and controlling user access to files and system resources. Each user can belong to multiple groups, enabling flexible permission management.
| Group Type | Description | Characteristics |
|---|---|---|
| Primary Group | Default group for a user | Created automatically with user account |
| Secondary Groups | Additional group memberships | Allows extended access permissions |
## Create a new group
sudo groupadd developers
## Add user to a group
sudo usermod -aG developers username
## List user's groups
groups username
## View group information
cat /etc/group## Permission format: rwxrwxrwx
## r: read, w: write, x: execute
## First trio: Owner permissions
## Second trio: Group permissions
## Third trio: Other permissions
## Example
-rw-r--r-- file.txt## Create a shared directory
mkdir /project
sudo chgrp developers /project
sudo chmod 770 /project
## Verify permissions
ls -ld /projectUser administration in Linux involves creating, modifying, and managing user accounts with precise control over system access and permissions.
| Command | Function | Usage |
|---|---|---|
| adduser | Create new user | sudo adduser username |
| usermod | Modify user account | sudo usermod -options username |
| userdel | Delete user account | sudo userdel username |
| passwd | Change user password | sudo passwd username |
## Create a new user with specific configuration
sudo adduser --gecos "Developer,Office,Phone,Home" developer
sudo usermod -aG sudo developer
## Set account expiration
sudo chage -E 2024-12-31 developer
## Lock/Unlock user account
sudo passwd -l username ## Lock
sudo passwd -u username ## Unlock## Display user account details
sudo chage -l username
## Configure password aging
sudo chage -M 90 -m 7 -W 14 username## Restrict user login
sudo usermod -s /sbin/nologin username
## Monitor user activities
last
lastb## View user details
cat /etc/passwd
cat /etc/shadowIn this Linux tutorial, we have covered the essential aspects of user and group management, including understanding user accounts, listing and viewing users and groups, managing user membership in groups, and exploring practical use cases and troubleshooting techniques. By mastering these concepts, readers will be able to effectively control access to system resources, enforce security policies, and ensure that users have the necessary permissions to perform their tasks in a Linux environment.
