Why sysadmin scripts automate operations in Bash Scripting - See It in Action

Why sysadmin scripts automate operations

📖 Scenario: You are a system administrator who wants to save time and avoid mistakes by automating repetitive tasks on your server.

🎯 Goal: Build a simple bash script that automates checking disk space and alerts if usage is above a set limit.

📋 What You'll Learn

Create a variable with disk usage data

Set a threshold value for disk usage

Use a conditional statement to check if disk usage exceeds the threshold

Print an alert message if the threshold is exceeded

💡 Why This Matters

🌍 Real World

Sysadmins use scripts like this to monitor servers and avoid downtime by catching problems early.

💼 Career

Knowing how to write simple automation scripts helps sysadmins save time and reduce errors in daily tasks.

1

Set up disk usage data

Create a variable called disk_usage and set it to the value 85 to represent disk usage percentage.

Bash Scripting

# Create a variable called disk_usage and set it to 85
# Your code here

Hint

Use disk_usage=85 to assign the value.

2

Set the usage threshold

Create a variable called threshold and set it to 80 to represent the disk usage limit.

Bash Scripting

disk_usage=85
# Create a variable called threshold and set it to 80
# Your code here

Hint

Use threshold=80 to assign the value.

3

Check if disk usage exceeds threshold

Use an if statement to check if disk_usage is greater than threshold. Inside the if, write a command to print "Disk usage is above threshold!".

Bash Scripting

disk_usage=85
threshold=80
# Use if statement to check if disk_usage > threshold
# Print alert message inside if
# Your code here

Hint

Use if [ "$disk_usage" -gt "$threshold" ] and echo inside.

4

Display the alert message

Run the script to print the alert message if disk usage is above the threshold.

Bash Scripting

disk_usage=85
threshold=80
if [ "$disk_usage" -gt "$threshold" ]; then
    echo "Disk usage is above threshold!"
fi
# Run the script to display the message
# Your code here

Hint

Run the script and check the output.

Practice

1. Why do sysadmins use scripts to automate operations?

easy

A. To save time by automating repetitive tasks

B. To make the system slower

C. To increase manual work

D. To avoid using computers

Solution

1. Step 1: Understand the purpose of automation

   Automation helps reduce repetitive manual work by letting scripts do the tasks.

2. Step 2: Identify the benefit for sysadmins

   Saving time and effort is the main reason sysadmins automate operations.

3. Final Answer:

   To save time by automating repetitive tasks -> Option A

4. Quick Check:

   Automation saves time = C [OK]

Hint: Automation means less manual work, more saved time [OK]

Common Mistakes:

• Thinking automation slows systems
• Believing automation increases manual work
• Confusing automation with avoiding computers

2. Which of these is the correct way to start a bash script for automation?

easy

A. function main() {}

B. print('Hello World')

C. #!/bin/bash

D.

Solution

1. Step 1: Identify the bash script shebang

   The line #!/bin/bash tells the system to use bash to run the script.

2. Step 2: Check other options for language mismatch

   Options A, B, and C are for other languages, not bash.

3. Final Answer:

   #!/bin/bash -> Option C

4. Quick Check:

   Shebang for bash = D [OK]

Hint: Bash scripts start with #!/bin/bash line [OK]

Common Mistakes:

• Using Python or JavaScript syntax in bash scripts
• Omitting the shebang line
• Confusing script languages

3. What will this script output?

#!/bin/bash
count=0
for file in /tmp/*; do
  if [ -f "$file" ]; then
    ((count++))
  fi
done
echo $count

medium

A. Number of files in /tmp directory

B. List of all files in /tmp

C. Error message about syntax

D. Zero always

Solution

1. Step 1: Understand the loop and condition

   The script loops over all items in /tmp, checks if each is a file, and counts them.

2. Step 2: Determine the output

   It prints the total count of files found in /tmp, not the list or zero.

3. Final Answer:

   Number of files in /tmp directory -> Option A

4. Quick Check:

   Count files in /tmp = A [OK]

Hint: Count files by looping and incrementing count [OK]

Common Mistakes:

• Thinking it lists files instead of counting
• Assuming syntax error due to ((count++))
• Believing output is always zero

4. Find the error in this script snippet that aims to backup a file:

#!/bin/bash
file="/etc/passwd"
cp $file /backup/
if [ $? -eq 0 ]; then
  echo "Backup successful"
else
  echo "Backup failed"
fi

medium

A. The variable file is not defined correctly

B. The /backup directory may not exist, causing cp to fail

C. The if condition syntax is wrong

D. The echo commands are missing quotes

Solution

1. Step 1: Check the copy command and target directory

   The script copies /etc/passwd to /backup/. If /backup/ does not exist, cp will fail.

2. Step 2: Verify other parts for correctness

   Variable is defined correctly, if syntax is valid, and echo quotes are optional but fine.

3. Final Answer:

   The /backup directory may not exist, causing cp to fail -> Option B

4. Quick Check:

   Missing target directory causes failure = B [OK]

Hint: Ensure target directories exist before copying files [OK]

Common Mistakes:

• Assuming variable is wrong
• Thinking if syntax is incorrect
• Believing echo needs quotes always

5. A sysadmin wants to automate checking disk space and send an alert if usage exceeds 80%. Which script snippet correctly automates this?

hard

A. usage=$(df / | tail -1 | awk '{print $5}')
if [ $usage -eq 80 ]; then
echo "Disk usage is exactly 80%"
fi

B. usage=$(df / | head -1 | awk '{print $5}')
if [ $usage -lt 80 ]; then
echo "Disk usage is low"
fi

C. usage=$(df / | tail -1 | awk '{print $4}')
if [ $usage -gt 80 ]; then
echo "Alert: Disk usage high"
fi

D. usage=$(df / | tail -1 | awk '{print $5}' | sed 's/%//')
if [ $usage -gt 80 ]; then
echo "Alert: Disk usage is above 80%"
fi

Solution

1. Step 1: Extract disk usage percentage correctly

   The command extracts the 5th column from df output (like '85%'), then removes the '%' sign to get a number.

2. Step 2: Check the condition for usage above 80%

   The script compares usage number to 80 and alerts if greater, matching the requirement.

3. Final Answer:

   usage=$(df / | tail -1 | awk '{print $5}' | sed 's/%//') if [ $usage -gt 80 ]; then echo "Alert: Disk usage is above 80%" fi -> Option D

4. Quick Check:

   Extract usage and alert if >80% = A [OK]

Hint: Remove % sign before numeric comparison [OK]

Common Mistakes:

• Comparing strings with % sign included
• Using wrong df column for usage
• Checking for exact 80% instead of greater