👉🏻Linux provides powerful command-line tools for managing users and groups. In this post, you'll learn how to use essential commands like useradd, usermod, userdel, and passwd, as well as how to manage groups and understand the important files involved in user and group management.
👤 User Management Commands
➕ useradd
Used to add a new user.
# Create a new user
sudo useradd username
# Create user with home directory and default shell
sudo useradd -m -s /bin/bash username
Options:
-d _path_: specify custom path of home directory.
-u _uid_: set custom UID.
-g _group_ : set primary group for user
-G _group_ : add user to supplementary groups.
-c "comment" : add comment to GECOS field.
-e "YYYY-MM-DD" : set account expiration date.
🛠️ usermod
Modify an existing user.
Syntax:
usermod [OPTIONS] user
# Change a user's login name
sudo usermod -l newname oldname
# Change the user's home directory
sudo usermod -d /new/home username
# Add user to a group
sudo usermod -aG groupname username
Options:
-l _newusername_: change login name
-d _path_ : change user's home directory.
-m: move content of current directory to new directory. Used with -d option while changing directory.
-s _path_: change user's default shell.
-u _new_uid : change uid of user.
-g _new_group_ : change primary group.
-G _new_group_ : add or replace supplementary group.
❌ userdel
Delete a user.
# Delete a user
sudo userdel username
# Delete a user and their home directory
sudo userdel -r username
🔑 passwd
Set or change user passwords.
# Set password for a user
sudo passwd username
# Lock a user account
sudo passwd -l username
# Unlock a user account
sudo passwd -u username
📂 Important Files in User and Group Management
/etc/passwd
Contains basic user account information.
👉🏻Format:
username:x:UID:GID:comment:home_directory:shell
/etc/shadow
Contains encrypted user passwords and password-related info.
/etc/group
Stores group information.
👉🏻Format:
groupname:x:GID:members
/etc/gshadow
Secure group account information including group passwords.
🧠 Summary
Mastering user and group management is essential for any Linux administrator. Make sure you understand how these commands and files work together to control access, enhance security, and structure your system efficiently.
Happy Learning! 🚀
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