User Management

# Add new user
sudo adduser username

# Add user with home directory
sudo useradd -m username

# Set password
sudo passwd username

# Add user with specific shell
sudo useradd -m -s /bin/bash username

# List all users
cut -d: -f1 /etc/passwd

# Show user details
id username

# Display user info
finger username

# Last login information
lastlog

# Create new group
sudo groupadd groupname

# Add user to group
sudo usermod -aG groupname username

# Remove user from group
sudo gpasswd -d username groupname

# List user groups
groups username

# List all groups
cut -d: -f1 /etc/group

# Edit sudoers file
sudo visudo

# Add user to sudo group
sudo usermod -aG sudo username

# Check sudo access
sudo -l

# Run command as another user
sudo -u username command

# Example sudoers entries:
username ALL=(ALL:ALL) ALL
%group ALL=(ALL) NOPASSWD: /specific/command

# Sudo timeout configuration
Defaults timestamp_timeout=15

# Create user home directory
sudo mkhomedir_helper username

# Copy skeleton files
sudo cp -r /etc/skel/. /home/username/

# Set ownership
sudo chown -R username:username /home/username

# Bash profile files
~/.bashrc      # Interactive shell configuration
~/.profile     # Login shell configuration
~/.bash_logout # Logout actions

# Example .bashrc additions:
alias ll='ls -la'
export EDITOR=nano

# Install password quality tools
sudo apt install libpam-pwquality

# Configure password requirements
sudo nano /etc/security/pwquality.conf

# Example settings:
minlen = 12
minclass = 3
maxrepeat = 2

# Set password expiry
sudo chage -M 90 username

# View password aging info
sudo chage -l username

# Force password change
sudo chage -d 0 username

# Account expiry
sudo chage -E 2024-12-31 username

# Lock user account
sudo usermod -L username

# Unlock user account
sudo usermod -U username

# Disable account (no login)
sudo usermod -s /usr/sbin/nologin username

# Check account status
sudo passwd -S username

# Generate SSH key pair
ssh-keygen -t rsa -b 4096

# Copy public key to server
ssh-copy-id username@server

# Add key to authorized_keys
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

# Set proper permissions
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

# Change file ownership
sudo chown user:group filename

# Change permissions
chmod 755 filename
chmod u+x filename

# View permissions
ls -la filename

# Default permissions
umask 022

# Install ACL tools
sudo apt install acl

# Set ACL
setfacl -m u:username:rw filename

# View ACL
getfacl filename

# Remove ACL
setfacl -x u:username filename

# System-wide variables
sudo nano /etc/environment

# User-specific variables
nano ~/.bashrc

# Example variables:
export PATH=$PATH:/custom/path
export EDITOR=nano
export BROWSER=firefox

# Set default desktop
sudo update-alternatives --config x-session-manager

# User desktop configuration
~/.config/         # Modern applications
~/.local/share/    # User data

# GNOME settings
dconf dump / > settings-backup.dconf
dconf load / < settings-backup.dconf

# Backup user account
sudo tar -czf user-backup.tar.gz /home/username

# Backup user configuration
sudo tar -czf config-backup.tar.gz \
  /home/username/.bashrc \
  /home/username/.profile \
  /home/username/.config

# Export user info
getent passwd username > user-export.txt

# Create user on new system
sudo useradd -m -u $(id -u username) username

# Restore user data
sudo tar -xzf user-backup.tar.gz -C /

# Show logged in users
who
w

# Login history
last
last username

# Failed login attempts
sudo lastb

# Login logs
sudo tail -f /var/log/auth.log

# Disk usage by user
sudo du -sh /home/*

# Process by user
ps aux | grep username

# User limits
ulimit -a

# Set resource limits
sudo nano /etc/security/limits.conf

# Create multiple users from file
while read username; do
  sudo adduser $username
done < userlist.txt

# Mass password reset
while read username; do
  echo "$username:newpassword" | sudo chpasswd
done < userlist.txt

# Customize /etc/skel for new users
sudo nano /etc/skel/.bashrc
sudo cp custom-files /etc/skel/

# All new users will inherit these files

#!/bin/bash
# create-user.sh

read -p "Username: " username
read -s -p "Password: " password

sudo adduser --disabled-password --gecos "" $username
echo "$username:$password" | sudo chpasswd
sudo usermod -aG sudo,audio,video $username

echo "User $username created successfully"