📘Cisco DevNet Associate (200-901 DEVASC)
1. Introduction to Bash Script Automation
A Bash script is a text file that contains a series of commands written for the Bash shell (Bourne Again Shell). The Bash shell is the default command-line interpreter on many Linux and Unix systems.
A Bash script allows administrators and developers to automatically execute multiple commands in sequence instead of running them manually one by one.
In IT environments, Bash scripts are commonly used to automate tasks such as:
- Managing files
- Installing applications
- Managing users
- Navigating directories
- Running system maintenance tasks
- Configuring services
For the DEVASC exam, you should be able to identify what workflow is being automated when looking at a Bash script.
A workflow simply means:
A sequence of automated tasks that are executed to achieve a specific goal.
2. Basic Structure of a Bash Script
A Bash script usually starts with a shebang line.
#!/bin/bash
This line tells the system that the script should run using the Bash shell.
Example script structure:
#!/bin/bashecho "Starting automation task"# Commands go hereecho "Task completed"
Typical components of a script include:
- Commands
- Variables
- Conditions
- Loops
- Comments
3. Common Workflows Automated by Bash Scripts
For the DEVASC exam, the most common workflows you must recognize are:
- File management
- Application installation
- User management
- Directory navigation
Each workflow uses specific commands.
4. File Management Automation
Purpose
File management automation involves creating, copying, moving, deleting, or modifying files automatically.
In IT environments, this is commonly used for:
- Log file processing
- Configuration file backup
- File cleanup
- Automated report generation
Common Commands Used
| Command | Purpose |
|---|---|
ls | List files |
cp | Copy files |
mv | Move or rename files |
rm | Delete files |
touch | Create new file |
cat | Display file contents |
tar | Archive files |
Example Bash Script – File Backup
#!/bin/bashcp /etc/config/app.conf /backup/app.conf
echo "Configuration file backed up"
Workflow Being Automated
- Locate the configuration file.
- Copy the file to a backup directory.
- Display confirmation.
This script automates a file backup workflow.
Example – Cleaning Old Log Files
#!/bin/bashrm /var/log/old_logs/*.log
echo "Old logs removed"
Workflow
- Identify old log files
- Delete them automatically
This automates a log cleanup workflow.
5. Application Installation Automation
Purpose
Bash scripts can automate software installation and system setup.
This is common in:
- Server provisioning
- Development environments
- Infrastructure automation
- System deployment
Common Package Managers
Linux systems use package managers.
Examples:
| OS | Package Manager |
|---|---|
| Ubuntu / Debian | apt |
| RedHat / CentOS | yum or dnf |
Example Bash Script – Install Application
#!/bin/bashsudo apt update
sudo apt install nginx -y
echo "Nginx installed successfully"
Workflow Being Automated
- Update package repository
- Install application
- Confirm installation
This automates application deployment.
Example – Installing Multiple Tools
#!/bin/bashsudo apt install git -y
sudo apt install python3 -y
sudo apt install curl -yecho "Development tools installed"
Workflow
This script automates:
- Installation of development tools
- Preparing a system for development work
6. User Management Automation
Purpose
User management scripts automate creating, modifying, or deleting system users.
This is useful in:
- Enterprise server administration
- Lab environments
- Automated system provisioning
- DevOps infrastructure
Common User Management Commands
| Command | Purpose |
|---|---|
useradd | Create new user |
userdel | Delete user |
usermod | Modify user |
passwd | Set password |
groupadd | Create group |
Example Bash Script – Create User
#!/bin/bashsudo useradd devuser
sudo passwd devuserecho "User account created"
Workflow Being Automated
- Create new user account
- Assign password
- Confirm creation
This automates user provisioning.
Example – Create Multiple Users
#!/bin/bashuseradd user1
useradd user2
useradd user3echo "Multiple users created"
Workflow
This automates:
- Bulk user creation
Often used in lab environments or test systems.
7. Directory Navigation Automation
Purpose
Directory navigation scripts automate moving between directories and performing tasks in specific locations.
This is important when:
- Managing configuration files
- Running build scripts
- Processing logs
- Running automation pipelines
Common Directory Commands
| Command | Purpose |
|---|---|
pwd | Show current directory |
cd | Change directory |
mkdir | Create directory |
rmdir | Remove directory |
Example Bash Script – Create Project Structure
#!/bin/bashmkdir project
cd project
mkdir logs
mkdir configecho "Project directories created"
Workflow Being Automated
- Create project directory
- Navigate into directory
- Create subdirectories
This automates project environment setup.
Example – Log Processing Workflow
#!/bin/bashcd /var/log
ls
Workflow
- Move to log directory
- List available log files
This automates log directory inspection.
8. Combined Workflow Automation
In real IT environments, Bash scripts often combine multiple workflows.
Example:
#!/bin/bashmkdir /backup
cp /etc/nginx/nginx.conf /backup/
apt install nginx -y
systemctl start nginxecho "Server configured"
Workflow Steps
- Create backup directory
- Backup configuration file
- Install application
- Start service
This automates system provisioning and configuration.
9. Recognizing a Workflow in a Bash Script (Important for the Exam)
When analyzing a Bash script, look at the commands used.
Example
useradd testuser
passwd testuser
Workflow: User creation
apt install python3
apt install pip
Workflow: Application installation
cp config.txt /backup/
Workflow: File backup
mkdir logs
cd logs
Workflow: Directory setup
10. Benefits of Bash Script Automation
Automation using Bash scripts provides several benefits in IT environments.
1. Time Efficiency
Tasks run automatically without manual input.
2. Consistency
Scripts execute the same steps every time.
3. Reduced Human Errors
Automation minimizes mistakes in repetitive tasks.
4. Scalability
Scripts can configure many systems quickly.
5. Integration with DevOps Tools
Bash scripts are often used in:
- CI/CD pipelines
- Infrastructure automation
- System provisioning
11. Role of Bash Scripts in Infrastructure Automation
In modern IT environments, Bash scripts help automate:
- Server initialization
- Application deployment
- Configuration backup
- Log monitoring
- Network configuration scripts
They often work together with tools like:
- configuration management platforms
- container environments
- CI/CD pipelines
12. Key Exam Points to Remember
For the Cisco DEVASC exam, remember these important concepts:
1. Bash Script
A text file containing Linux shell commands executed automatically.
2. Workflow
A sequence of automated tasks performed by a script.
3. Common Automated Workflows
You should recognize scripts related to:
- File management
- Application installation
- User management
- Directory navigation
4. Identify Workflow by Commands
| Command | Workflow |
|---|---|
cp, mv, rm | File management |
apt, yum, dnf | Application installation |
useradd, passwd | User management |
cd, mkdir | Directory navigation |
13. Quick Exam Summary
A Bash script automates command-line tasks in Linux systems.
In the DEVASC exam, you may be given a script and asked to identify what workflow it automates.
Typical workflows include:
- File operations (copy, delete, backup)
- Software installation
- System user creation
- Directory creation and navigation
To identify the workflow, analyze the commands used inside the script.
