du (disk usage by directory) in Linux CLI - Mini Project: Build & Apply

Disk Usage Summary with du Command

📖 Scenario: You are managing files on your Linux system. You want to check how much disk space different directories use to keep your system organized and avoid running out of space.

🎯 Goal: Build a simple script that uses the du command to show disk usage of directories in a specified folder, filter results by a size threshold, and display the filtered output.

📋 What You'll Learn

Use the du command to get disk usage of directories

Create a variable to hold the target directory path

Create a variable to hold the minimum size threshold in kilobytes

Filter the du output to show only directories larger than the threshold

Print the filtered disk usage results

💡 Why This Matters

🌍 Real World

System administrators often need to monitor disk usage to prevent storage issues and optimize space.

💼 Career

Knowing how to use disk usage commands and filter their output is essential for Linux system management and troubleshooting.

1

Set the target directory

Create a variable called target_dir and set it to "/var/log" to specify the directory you want to check disk usage for.

Linux CLI

# Create a variable called target_dir and set it to "/var/log"
# Your code here

Hint

Use target_dir="/var/log" to set the directory path.

2

Set the minimum size threshold

Create a variable called min_size and set it to 1000 to represent the minimum directory size in kilobytes for filtering.

Linux CLI

target_dir="/var/log"
# Create a variable called min_size and set it to 1000
# Your code here

Hint

Use min_size=1000 to set the size threshold in KB.

3

Get and filter disk usage

Use the du -k --max-depth=1 "$target_dir" command to get disk usage in kilobytes for directories inside target_dir. Then use awk to filter and keep only lines where the size is greater than or equal to min_size. Store the filtered output in a variable called filtered_usage.

Linux CLI

target_dir="/var/log"
min_size=1000
# Use du and awk to filter directories by min_size and save to filtered_usage
# Your code here

Hint

Use du -k --max-depth=1 "$target_dir" piped to awk -v min="$min_size" '$1 >= min'.

4

Display the filtered disk usage

Print the contents of the filtered_usage variable to show the directories that meet the size threshold.

Linux CLI

target_dir="/var/log"
min_size=1000
filtered_usage=$(du -k --max-depth=1 "$target_dir" | awk -v min="$min_size" '$1 >= min')
# Print the filtered_usage variable
# Your code here

Hint

Use echo "$filtered_usage" to display the filtered results.

Practice

1. What does the du command primarily show in Linux?

easy

A. The disk space used by files and directories

B. The number of files in a directory

C. The current directory path

D. The list of running processes

Solution

1. Step 1: Understand the purpose of du

   The du command stands for disk usage and shows how much space files and directories use.

2. Step 2: Compare options

   Options B, C, and D relate to other commands like ls or ps, not du.

3. Final Answer:

   The disk space used by files and directories -> Option A

4. Quick Check:

   du = disk space used [OK]

Hint: Remember: du = disk usage, shows space used [OK]

Common Mistakes:

• Confusing du with ls or ps commands
• Thinking du shows file counts
• Assuming du shows current directory path

2. Which du command option shows sizes in a human-readable format?

easy

A. -s

B. -c

C. -a

D. -h

Solution

1. Step 1: Identify the option for human-readable sizes

   The -h option makes sizes easier to read by adding units like K, M, G.

2. Step 2: Understand other options

   -s summarizes, -a shows all files, -c adds a total line.

3. Final Answer:

   -h -> Option D

4. Quick Check:

   -h = human-readable sizes [OK]

Hint: Use -h for sizes like KB, MB, GB [OK]

Common Mistakes:

• Using -s expecting human-readable sizes
• Confusing -a or -c with size formatting
• Omitting the -h option for readability

3. What is the output of the command du -sh /var/log if the /var/log directory uses 120M of disk space?

medium

A. 120M

B. 120M /var/log

C. 120MB /var/log

D. 120 /var/log

Solution

1. Step 1: Understand the command options

   -s summarizes total size, -h shows human-readable format.

2. Step 2: Predict output format

   The output shows size with unit, a tab, then directory path: "120M\t/var/log".

3. Final Answer:

   120M /var/log -> Option B

4. Quick Check:

   du -sh output = size + tab + path [OK]

Hint: du -sh shows size and path separated by tab [OK]

Common Mistakes:

• Omitting the tab separator
• Writing size without unit
• Showing size without path

4. You run du -h /home/user but get an error: "du: invalid option -- 'h'". What is the likely cause?

medium

A. The directory /home/user does not exist

B. You need to run the command as root

C. The du command does not support the -h option on this system

D. You must use --human-readable instead of -h

Solution

1. Step 1: Analyze the error message

   The error says -h is invalid, meaning this du version lacks that option.

2. Step 2: Check other options

   Running as root or directory existence wouldn't cause invalid option error; -h is standard, no need for long form.

3. Final Answer:

   The du command does not support the -h option on this system -> Option C

4. Quick Check:

   Invalid option error means unsupported flag [OK]

Hint: Invalid option means your du version lacks that flag [OK]

Common Mistakes:

• Assuming permission or path errors cause invalid option
• Trying --human-readable instead of checking version
• Ignoring error message details

5. You want to find the total disk usage of all subdirectories inside /home/user but only see sizes for individual files. Which command correctly summarizes each subdirectory size in human-readable form?

hard

A. du -sh /home/user/*

B. du -ah /home/user

C. du -h /home/user

D. du -s /home/user

Solution

1. Step 1: Understand the goal

   You want sizes of each subdirectory summarized, not individual files.

2. Step 2: Analyze options

   du -ah shows all files and dirs, du -sh on directory alone summarizes total only, du -s no human-readable. du -sh /home/user/* summarizes each subdirectory separately in human-readable form.

3. Final Answer:

   du -sh /home/user/* -> Option A

4. Quick Check:

   Use du -sh with wildcard for each subdir [OK]

Hint: Use du -sh with * to summarize each subdirectory [OK]

Common Mistakes:

• Using -a to include files instead of just dirs
• Using -s alone for total only
• Not using wildcard to list subdirectories