Why disk management prevents outages in Linux CLI - Challenge Your Understanding

Challenge - 5 Problems

💻 Command Output

intermediate

Disk usage monitoring command output

You run the command df -h / on a Linux server to check disk usage of the root partition. What is the expected output format?

Linux CLI

df -h /

A

Filesystem Size Used Avail Use% Mounted on
/dev/sda1 50G 30G 20G 150% /

B

Filesystem Size Used Avail Use% Mounted on
/dev/sda1 50G 60G 20G 120% /

C

Filesystem Size Used Avail Use% Mounted on
/dev/sda1 50G 30G 20G 60% /

D

Filesystem Size Used Avail Use% Mounted on
/dev/sda1 50G 30G 20G 0% /

💡 Hint

Disk usage percentages cannot exceed 100%.

The df -h command shows disk usage with human-readable sizes. The Use% column shows the percentage of used space, which cannot be more than 100%.

🧠 Conceptual

intermediate

Why monitoring disk space prevents outages

Why does monitoring disk space usage help prevent system outages?

A Because it allows administrators to free up space before the disk is full, avoiding system crashes.

B Because it automatically deletes files when disk space is low.

C Because it increases the disk size without manual intervention.

D Because it disables all running services when disk space is low.

💡 Hint

Think about what happens when a disk is completely full.

Monitoring disk space helps admins act before the disk fills up, preventing crashes or service failures caused by no available space.

🔧 Debug

advanced

Identify the error in disk space alert script

This script is intended to alert when disk usage exceeds 90%. What error causes it to never alert?

usage=$(df / | tail -1 | awk '{print $5}' | sed 's/%//')
if [ $usage -gt 90 ]
then
  echo "Disk usage critical: $usage%"
fi

Linux CLI

usage=$(df / | tail -1 | awk '{print $5}' | sed 's/%//')
if [ $usage -gt 90 ]
then
  echo "Disk usage critical: $usage%"
fi

A The variable $usage is treated as a string, causing the numeric comparison to fail.

B The sed command removes the percent sign incorrectly, leaving a non-numeric value.

C The if statement syntax is incorrect; it needs double brackets [[ ]] for numeric comparison.

D The script works correctly and will alert when usage is above 90%.

💡 Hint

Check how shell compares numbers inside single brackets.

The script correctly extracts the numeric disk usage and compares it with 90 using -gt inside single brackets, which works in POSIX shell.

🚀 Application

advanced

Automate disk cleanup to prevent outages

Which script snippet safely deletes only log files older than 30 days in /var/log to free disk space?

A rm /var/log/*.log -mtime +30

B find /var/log -type f -name '*.log' -mtime +30 -exec rm {} \;

C find /var/log -name '*.log' -delete

D find /var/log -type f -name '*.log' -mtime -30 -exec rm {} \;

💡 Hint

Use find with -mtime to select files older than 30 days.

Option B uses find to locate files ending with .log older than 30 days and deletes them safely. Other options either misuse rm or delete all logs regardless of age.

🧠 Conceptual

expert

How disk management strategies prevent outages in production

Which of the following best explains how disk management strategies prevent outages in production systems?

A By proactively monitoring disk usage, automating cleanup, and alerting admins, systems avoid crashes caused by full disks.

B By disabling all write operations when disk usage reaches 80%, preventing data loss.

C By automatically increasing disk size without human intervention to handle any load.

D By moving all data to RAM to avoid disk usage entirely.

💡 Hint

Think about practical, reliable ways to keep systems running smoothly.

Effective disk management includes monitoring, cleanup automation, and alerting to prevent full disks that cause outages. Other options are impractical or impossible.

Practice

1. Why is regular disk management important to prevent system outages?

easy

A. It helps avoid running out of disk space and system crashes.

B. It makes the computer run faster by increasing CPU speed.

C. It changes the screen resolution automatically.

D. It updates the operating system without user permission.

Solution

1. Step 1: Understand disk space impact

   Running out of disk space can cause programs to fail and the system to crash.

2. Step 2: Recognize disk management role

   Disk management monitors and frees space to keep the system stable.

3. Final Answer:

   It helps avoid running out of disk space and system crashes. -> Option A

4. Quick Check:

   Disk space management prevents crashes = B [OK]

Hint: Disk space full? System crashes. Manage disks to prevent that. [OK]

Common Mistakes:

• Confusing disk management with CPU or display settings
• Thinking disk management updates software automatically
• Ignoring disk space as a cause of outages

2. Which Linux command correctly shows disk usage of all mounted filesystems?

easy

A. top

B. ls -l

C. df -h

D. ps aux

Solution

1. Step 1: Identify command purpose

   The df command reports disk space usage; -h makes it human-readable.

2. Step 2: Compare other commands

   ls -l lists files, top shows processes, ps aux lists running processes.

3. Final Answer:

   df -h -> Option C

4. Quick Check:

   Disk usage command = df -h [OK]

Hint: Use df -h to check disk space in human-friendly format. [OK]

Common Mistakes:

• Using ls or ps commands to check disk space
• Forgetting the -h option for readable sizes
• Confusing process commands with disk commands

3. What is the output of the command lsblk on a Linux system?

medium

A. Prints the contents of the current directory.

B. Shows current CPU usage statistics.

C. Displays network interface details.

D. Lists all block devices like disks and partitions.

Solution

1. Step 1: Understand lsblk command

   lsblk lists block devices such as hard drives and their partitions.

2. Step 2: Eliminate unrelated outputs

   CPU stats, network info, and directory contents are shown by other commands like top, ifconfig, and ls.

3. Final Answer:

   Lists all block devices like disks and partitions. -> Option D

4. Quick Check:

   lsblk shows disks and partitions = A [OK]

Hint: lsblk lists disks and partitions clearly. [OK]

Common Mistakes:

• Confusing lsblk with commands showing CPU or network info
• Expecting file listings instead of device info
• Assuming lsblk modifies disks instead of listing

4. You run df -h and see 100% usage on /dev/sda1. What is the best immediate action to prevent outages?

medium

A. Change the screen resolution to reduce load.

B. Delete unnecessary files or move data to free space.

C. Run top to kill CPU-heavy processes.

D. Restart the computer immediately without checking disk.

Solution

1. Step 1: Analyze disk full problem

   100% disk usage means no free space, risking crashes and data loss.

2. Step 2: Choose proper action

   Deleting or moving files frees space immediately; restarting or changing screen resolution won't fix disk space.

3. Final Answer:

   Delete unnecessary files or move data to free space. -> Option B

4. Quick Check:

   Free disk space to prevent outages = D [OK]

Hint: Free disk space first to avoid crashes. [OK]

Common Mistakes:

• Restarting without fixing disk space
• Confusing CPU load with disk space issues
• Trying unrelated fixes like screen changes

5. You want to automate disk checks to prevent outages. Which script snippet correctly checks disk usage and warns if usage exceeds 90% on /dev/sda1?

hard

A. usage=$(df /dev/sda1 | tail -1 | awk '{print $5}' | sed 's/%//'); if [ "$usage" -gt 90 ]; then echo "Warning: Disk usage above 90%"; fi

B. usage=$(top -b | grep sda1); if [ "$usage" -gt 90 ]; then echo "Warning"; fi

C. usage=$(lsblk /dev/sda1); if [ "$usage" -gt 90 ]; then echo "Warning"; fi

D. usage=$(ps aux | grep sda1); if [ "$usage" -gt 90 ]; then echo "Warning"; fi

Solution

1. Step 1: Extract disk usage percentage correctly

   The command df /dev/sda1 shows disk usage; awk '{print $5}' gets the percent; sed 's/%//' removes the percent sign.

2. Step 2: Use conditional to warn if usage > 90%

   The if statement compares usage as a number and prints a warning if above 90.

3. Final Answer:

   usage=$(df /dev/sda1 | tail -1 | awk '{print $5}' | sed 's/%//'); if [ "$usage" -gt 90 ]; then echo "Warning: Disk usage above 90%"; fi -> Option A

4. Quick Check:

   Correct disk usage check and warning = A [OK]

Hint: Use df and awk to get usage, then compare with if. [OK]

Common Mistakes:

• Using unrelated commands like top or ps for disk usage
• Not removing % sign before numeric comparison
• Incorrect syntax in if statement