Master automation in Linux with Bash scripts! Discover how to create and debug scripts for user setup, including creating new users, setting passwords, adding them to groups, configuring SSH key-based login, and setting password expiry. We’ll also cover testing and verification.

Script:

#!/bin/bash
#Variables
USERNAME="Jason" # User account name
PASSWORD="P@ssw0rd" # User password
GROUP="developers" # Custom group name
SSH_DIR="/home/$USERNAME/.ssh"
PUB_KEY="ssh-rsa AAAAB3...your-public-key... user@kali" # Replace with your actual public key

#Step 1: Check if user already exists
if id "$USERNAME" &>/dev/null; then
  echo "Error: User '$USERNAME' already exists!"
  exit 1
fi

#Step 2: Create user and set password
echo "Creating user '$USERNAME'..."
useradd -m -s /bin/bash "$USERNAME"
if [ $? -ne 0 ]; then
  echo "Error: Failed to create user '$USERNAME'"
  exit 1
fi
echo "$USERNAME:$PASSWORD" | chpasswd
echo "Password set for user '$USERNAME'."

#Step 3: Add user to sudoers
echo "Granting sudo access to '$USERNAME'..."
usermod -aG sudo "$USERNAME"
if [ $? -ne 0 ]; then
  echo "Error: Failed to add '$USERNAME' to sudoers"
  exit 1
fi

#Step 4: Create custom group and add user
echo "Creating group '$GROUP' and adding user..."
groupadd "$GROUP" 2>/dev/null
usermod -aG "$GROUP" "$USERNAME"
if [ $? -ne 0 ]; then
  echo "Error: Failed to add '$USERNAME' to group '$GROUP'"
  exit 1
fi

#Step 5: Setup SSH key-based authentication
echo "Setting up SSH key-based authentication..."
mkdir -p "$SSH_DIR"
echo "$PUB_KEY" > "$SSH_DIR/authorized_keys"
chmod 600 "$SSH_DIR/authorized_keys"
chmod 700 "$SSH_DIR"
chown -R "$USERNAME:$USERNAME" "$SSH_DIR"
if [ $? -ne 0 ]; then
  echo "Error: Failed to set up SSH keys"
  exit 1
fi
echo "SSH keys configured for '$USERNAME'."

#Step 6: Set password expiry to 30 days
echo "Setting password expiry policy for '$USERNAME'..."
chage -M 30 "$USERNAME"
if [ $? -ne 0 ]; then
  echo "Error: Failed to set password expiry"
  exit 1
fi

#Step 7: Log activity to /var/log/user_setup.log
LOG_FILE="/var/log/user_setup.log"
echo "$(date) - User '$USERNAME' created and configured" >> "$LOG_FILE"
if [ $? -ne 0 ]; then
  echo "Error: Failed to write log to $LOG_FILE"
  exit 1
fi

#Step 8: Confirmation Message
echo "User '$USERNAME' created and configured successfully!"