I first came across the HNG Internship in 2020, a few months after I had gotten started in tech, and I ended up joining their cohort that was running that year for the frontend track. It was a great experience, and I learned a lot about projects, collaborations, and the pressure of limited timelines. HNG Internship supports various technical and non-technical tracks, i.e., Backend (C#, Golang, PHP, Python, Node.js), DevOps, Frontend, Mobile, Product Design, Digital Marketing, product testing, data analysis, and product management. If you’re interested in getting experience alongside several people in a gamified manner, you can sign up for HNG, and they also have an HNG Premium version of the program, which includes BootCamp training, one-on-one calls with mentors, assistance in job search, and more.
In this article I’m going to talk about the DevOps I’m taking up at HNG which requires writing a bash script that allows a user to input a text file with new employees who are developers and they’re to be assigned into groups, user passwords are to be saved into a file that can only be accessed by the owner and the logs of the script are also saved into a file
Requirements
The bash script should be able to take up a text file with employees’ names and be able to add and assign them to Linux groups and users. Users will have the same group name as their username, and the group name won't be written in the text file, e.g., bash create_user.sh, file_with_employee_names.txt (added to groups & assigned)
The user can have multiple groups, and each group is delimited or separated by a comma but the usernames and groups are separated by semicolons
the script should be able to set up home directories with permission and ownership
the script should generate random passwords for all users and the passwords will be securely stored on /var/secure/user_passwords.txt. This script should also check if the user already exists in this file - return an error message or so.
The script should log all actions to /var/log/user_management.log (it creates and contains all actions performed by the script)
The script should store the list of all users and their passwords, separated by commas, on /var/secure/user.password.cvs. The file owner should be the only one to read it
We start by creating a folder locally:
$ vagrant up
$ mkdir employeebashscript
$ cd employeebashscript
$ touch create_user.sh
$ touch README.md
We initialize our bash script with the bash bang, which consists of the directory bash shell program to be used for script execution. The hash exclamation mark #! character sequence is referred to as the Shebang. It’s used to set the path of the bash program.
#!/bin/bash
Next, we will write a function and call that will be used to install some packages we might need in case they're not locally installed once the script is executed
install_packages() {
if command -v apt-get &>/dev/null; then
sudo apt-get update
sudo apt-get install -y passwd openssl || echo "Failed to install packages"
elif command -v yum &>/dev/null; then
sudo yum install -y passwd openssl || echo "Failed to install packages"
fi
}
install_packages
When the script is executed, we will pass a text file that has a list of employees so that the bash script will add and assign them to groups. This part will ensure that we execute the script with a file with employees’ names
if [ -z "$1" ]; then
echo "Usage: $0 file_with_employee_names.txt"
exit 1
fi
input_file=$1
if [ ! -f $input_file ]; then
echo "File $input_file does not exist"
exit 1
fi
While the script is executed, we will need a secure folder that will have a user_passwords.txt file that will store the passwords generated for users, as well as a user_management.log that will keep all logs and a user_passwords.csvfile that will have a list of users and their passwords, which will be accessed only by the file owner
sudo mkdir -p /var/secure
sudo touch /var/secure/user_passwords.txt /var/secure/user_passwords.csv
sudo touch /var/log/user_management.log
We will now create a while loop that ensures that the script checks all conditions and gets executed:
It will read through the files to check whether a username already exists before it gets created
It creates users and groups together with additional groups
Ensuring the home directory permissions are set correctly
Generating a random password for the user, checking if the user exists in the password file before storing their password
Check the username if it exists in the file with the list of passwords and usernames before adding it
while IFS= read -r line; do
username=$(echo $line | cut -d';' -f1)
groups=$(echo $line | cut -d';' -f2 | tr ',' ' ')
if id $username &>/dev/null; then
echo "User $username already exists" | tee -a /var/log/user_management.log
continue
fi
sudo useradd -m -s /bin/bash $username
sudo groupadd $username
sudo usermod -a -G $username $username
for group in $groups; do
sudo groupadd $group
sudo usermod -a -G $group $username
done
echo "User $username has been created and assigned to groups: $groups" | tee -a /var/log/user_management.log
home_dir="/home/$username"
sudo chmod 700 $home_dir
sudo chown $username:$username $home_dir
echo "Home directory permissions for $username have been set" | sudo tee -a /var/log/user_management.log
password=$(openssl rand -base64 12)
echo "$username:$password" | sudo chpasswd
if grep -q "^$username" /var/secure/user_passwords.txt; then
echo "User $username already exists in the password file" | tee -a /var/log/user_management.log
else
echo "$username:$password" | sudo tee -a /var/secure/user_passwords.txt
echo "User $username has been added to the password file" | tee -a /var/log/user_management.log
fi
if grep -q "^$username," /var/secure/user_password.csv; then
echo "User $username already exists in the password file" | tee -a /var/log/user_management.log
else
echo "$username,$password" | sudo tee -a /var/secure/user_passwords.csv
echo "User $username has been added to the password file" | tee -a /var/log/user_management.log
fi
done < $input_file
Lastly, we have to secure our password files
sudo chown root:root /var/secure/user_passwords.txt /var/secure/user_passwords.csv
sudo chmod 600 /var/secure/user_passwords.txt /var/secure/user_passwords.csv
Complete Script
#!/bin/bash
install_packages() {
if command -v apt-get &>/dev/null; then
sudo apt-get update
sudo apt-get install -y passwd openssl || echo "Failed to install packages"
elif command -v yum &>/dev/null; then
sudo yum install -y passwd openssl || echo "Failed to install packages"
fi
}
install_packages
if [ -z "$1" ]; then
echo "Usage: $0 file_with_employee_names.txt"
exit 1
fi
input_file=$1
if [ ! -f $input_file ]; then
echo "File $input_file does not exist"
exit 1
fi
sudo mkdir -p /var/secure
sudo touch /var/secure/user_passwords.txt /var/secure/user_passwords.csv
sudo touch /var/log/user_management.log
while IFS= read -r line; do
username=$(echo $line | cut -d';' -f1)
groups=$(echo $line | cut -d';' -f2 | tr ',' ' ')
if id $username &>/dev/null; then
echo "User $username already exists" | tee -a /var/log/user_management.log
continue
fi
sudo useradd -m -s /bin/bash $username
sudo groupadd $username
sudo usermod -a -G $username $username
for group in $groups; do
sudo groupadd $group
sudo usermod -a -G $group $username
done
echo "User $username has been created and assigned to groups: $groups" | tee -a /var/log/user_management.log
home_dir="/home/$username"
sudo chmod 700 $home_dir
sudo chown $username:$username $home_dir
echo "Home directory permissions for $username have been set" | sudo tee -a /var/log/user_management.log
password=$(openssl rand -base64 12)
echo "$username:$password" | sudo chpasswd
if grep -q "^$username" /var/secure/user_passwords.txt; then
echo "User $username already exists in the password file" | tee -a /var/log/user_management.log
else
echo "$username:$password" | sudo tee -a /var/secure/user_passwords.txt
echo "User $username has been added to the password file" | tee -a /var/log/user_management.log
fi
if grep -q "^$username," /var/secure/user_password.csv; then
echo "User $username already exists in the password file" | tee -a /var/log/user_management.log
else
echo "$username,$password" | sudo tee -a /var/secure/user_passwords.csv
echo "User $username has been added to the password file" | tee -a /var/log/user_management.log
fi
done < $input_file
sudo chown root:root /var/secure/user_passwords.txt /var/secure/user_passwords.csv
sudo chmod 600 /var/secure/user_passwords.txt /var/secure/user_passwords.csv
echo "User creation process has been completed successfully"
Making the Script Executable and Executing
$ chmod +x create_user.sh
We will need a sample text file with the employees to test the bash script file_with_employee_names.txt
$ touch file_with_employee_names.txt
$ nano file_with_employee_names.txt
$ cat file_with_employee_names.txt
alice;dev,admin
bob;dev
charlie;admin
dave;dev,qa,admin
eve;qa
$ ./create_user.sh file_with_employee_names.txt
Thanks for reading through the article. It has been an interesting experience getting started with DevOps, learning how to write Bash scripts, and understanding how they help ease the deployment process. You can leave a comment regarding the article and what I can improve on.
