df (disk free space) in Linux CLI - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Understanding the output of df -h

What is the output of the command df -h on a typical Linux system?

Linux CLI

df -h

A Shows disk usage in human-readable format with sizes like 1K, 234M, 2G

B Shows only the total disk size without usage details

C Shows network usage statistics

D Shows a list of running processes and their disk usage

💡 Hint

The -h option means human-readable sizes.

The df -h command displays disk space usage with sizes in easy-to-read units like KB, MB, or GB.

💻 Command Output

intermediate

Output of df --total

What does the df --total command add to the usual df output?

Linux CLI

df --total

A Shows only the total size of the root filesystem

B Displays disk usage for network filesystems only

C Adds a summary line showing total disk usage across all filesystems

D Shows disk usage sorted by mount point name

💡 Hint

Look for a line labeled 'total' at the end.

The --total option adds a summary line that sums up all disk usage values from the listed filesystems.

📝 Syntax

advanced

Correct usage of df to show inode usage

Which command correctly shows inode usage with df?

A df -i

B df --inodes

C df -h -i

D df --inode-usage

💡 Hint

The option for inode info is a short flag.

The -i option shows inode usage. --inodes and --inode-usage are invalid options.

🔧 Debug

advanced

Why does df /nonexistent fail?

What error does the command df /nonexistent produce and why?

Linux CLI

df /nonexistent

A df: Invalid argument - because the path is not a mount point

B df: Permission denied - because the user lacks rights

C df: Device busy - because the path is in use

D df: /nonexistent: No such file or directory - because the path does not exist

💡 Hint

Check if the path exists before running df.

If the path does not exist, df cannot find the filesystem and returns a 'No such file or directory' error.

🚀 Application

expert

Automate disk usage alert with df

You want to write a script that alerts you if any mounted filesystem is more than 90% full. Which command pipeline correctly extracts the usage percentage and filters filesystems over 90%?

A df -h | grep -v Filesystem | awk '{if ($5 > 90) print $1, $5}'

B df -h | awk 'NR>1 {sub(/%/, "", $5); if ($5 > 90) print $1, $5"%"}'

C df | awk '{if ($5 > 90) print $1, $5}'

D df -h | awk '{if ($5+0 > 90) print $1, $5}'

💡 Hint

You need to remove the % sign before comparing numbers.

Option B removes the % sign from the 5th column and compares the numeric value correctly. Others either miss removing % or skip header properly.