The Bash script presented here automates the process of user creation on a Linux system. By prompting the administrator for a username and password, it checks for empty inputs and pre-existing users, then securely creates a new user account.
Script to add a user with password
Let me first show what the output of the script looks like:
$ ./add_user_script.sh Enter the username: myuser Enter the password: 'myuser' added successfully$ ./add_user_script.sh Enter the username: myuser Enter the password: 'myuser' already exists. please use different user
The above output shows the script prompted for username and password and successfully created the user account. When you run the script a second time, it detects that myuser already exists and hence informs you to use a different username.
Script
#!/bin/bash
#
# Script to add a user
# Function to read password securely
read_password()
{
# Disable echo.
stty -echo
# Set up trap to ensure echo is enabled before exiting if the script
# is terminated while echo is disabled.
trap 'stty echo' EXIT
# Read password.
read "$@"
# Enable echo.
stty echo
trap - EXIT
# Print a newline because the newline entered by the user after
# entering the passcode is not echoed. This ensures that the
# next line of output begins at a new line.
echo
}
echo -n "Enter the username: "
read username
STATUS=0
if [ -z "${username}" ] ; then
echo "Username is not entered"
STATUS=1
exit $STATUS
fi
# Check if username already exists
getent passwd "${username}" > /dev/null
STATUS=$?
if [ "${STATUS}" == "0" ] ; then
echo "$username already exists. Please use a different user"
exit 1
fi
echo -n "Enter the password: "
read_password password
# Validate password input
if [ -z "${password}" ] ; then
echo "Password is not entered"
STATUS=1
exit $STATUS
else
# Create user with encrypted password
useradd $username -p "$(openssl passwd -6 $password)"
STATUS=$?
if [ "${STATUS}" == "0" ] ; then
echo "'$username' added successfully"
else
echo "Failed to create user '$username'"
STATUS=1
fi
fi
# Exit from script
exit $STATUS
In the script:
The script reads the username and password from the user. It defines a function called read_password which reads a password from the user while disabling the terminal echo to keep the password hidden.
echo -n "Enter the username: "
read username
echo -n "Enter the password: "
read_password password
It uses the getent command to check if the username already exists. If it does, the script prints an error message and exits with a status of 1.
if [ -z "${username}" ] ; then
echo "Username is not entered" >&2
STATUS=1
exit $STATUS
fi
getent passwd "${username}" > /dev/null
STATUS=$?
if [ "${STATUS}" -eq 0 ] ; then
echo "$username already exists. Please use a different user" >&2
exit 1
fi
The script uses openssl to encrypt the password and useradd to create the user with the encrypted password.
useradd "$username" -p "$(openssl passwd -6 "$password")"
Bypass password prompts
To ensure that commands run without interactive password prompts, you can use the following:
Using chpasswd:
$ useradd -m "<username>"
$ echo "<username>:<password>" | chpasswdUsing echo and passwd:
$ useradd -m “<username>”
$ echo “<password>\n<password>” | passwd <username>Remember here we are actually placing the password in the script, which is viable for security risk.
This script allows add a user without interactive password prompts with a default password.
#!/bin/bash
# Script to add user
# Default password for new users
default_password="mypasswd@123"
# Prompt for username
echo -n "Enter the username: "
read username
STATUS=0
# Check if username is empty
if [ -z "${username}" ] ; then
echo "Username is not entered" >&2
STATUS=1
exit $STATUS
fi
# Check if user already exists
getent passwd "${username}" > /dev/null
STATUS=$?
if [ "${STATUS}" -eq 0 ] ; then
echo "$username already exists. Please use a different user" >&2
exit 1
fi
# Create user
useradd -m "${username}" > /dev/null
STATUS=$?
if [ "${STATUS}" -eq 0 ] ; then
# Set the default password for the user
echo "${username}:${default_password}" | chpasswd &> /dev/null
echo "'$username' added successfully"
else
echo "Failed to create user '$username'" >&2
STATUS=1
fi
# Exit from script
exit $STATUS
Running the script:
$ ./add_user_bypass_script.sh
Enter the username: testuser
'testuser' added successfully
About The Author
Bobbin Zachariah
Bobbin Zachariah is an experienced Linux engineer who has been supporting infrastructure for many companies. He specializes in Shell scripting, AWS Cloud, JavaScript, and Nodejs. He has qualified Master’s degree in computer science. He holds Red Hat Certified Engineer (RHCE) certification and RedHat Enable Sysadmin.
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