df (disk free space) in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the df command do in Linux?

The df command shows how much disk space is used and free on your file systems.

beginner

How do you display disk space in human-readable format using df?

Use df -h. It shows sizes in KB, MB, or GB for easier reading.

intermediate

What does the df -T option show?

It shows the type of each file system along with disk usage.

intermediate

If you want to check disk space for a specific directory, how do you use df?

Run df /path/to/directory. It shows disk usage for the file system containing that directory.

advanced

What does the df --total option do?

It adds a summary line showing total disk space used and available across all file systems.

Which command shows disk space in a human-readable format?

A df -T

B df -h

C df --total

D df -a

df -h shows disk space in KB, MB, or GB, making it easy to read.

What information does df primarily provide?

A Memory usage

B CPU usage

C Disk free and used space

D Network status

df reports disk space usage and availability on file systems.

How do you find the file system type with df?

A df -T

B df -i

C df --total

D df -h

df -T adds a column showing the file system type.

Which command shows total disk usage across all file systems?

A df -h

B df -a

C df -T

D df --total

df --total adds a summary line with total disk usage.

To check disk space for the directory /home/user, you run:

A All of the above

B df -h /home/user

C df /home/user

D df -T /home/user

All these commands show disk space info for the file system containing /home/user, with different details.

Explain how to use the df command to check disk space in a way that's easy to understand.

Think about how you would tell a friend to see free space on their computer.

Describe the difference between df and df -T.

What extra info does the -T option add?

Practice

1. What does the df command do in Linux?

easy

A. Shows disk free space on mounted filesystems

B. Displays running processes

C. Lists files in a directory

D. Shows network connections

Solution

1. Step 1: Understand the purpose of df

   The df command is used to report disk space usage on mounted filesystems.

2. Step 2: Compare with other commands

   Other options like listing processes or files are done by different commands like ps or ls.

3. Final Answer:

   Shows disk free space on mounted filesystems -> Option A

4. Quick Check:

   df = disk free space [OK]

Hint: Remember: df = disk free space quick check [OK]

Common Mistakes:

• Confusing df with ls or ps commands
• Thinking df shows network info
• Assuming df lists files

2. Which of these is the correct syntax to show disk space in human-readable format?

easy

A. df -r

B. df -h

C. df --list

D. df -x

Solution

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

   The -h option in df shows sizes in easy units like MB, GB.

2. Step 2: Check other options

   Options like -r, --list, or -x do not provide human-readable output.

3. Final Answer:

   df -h -> Option B

4. Quick Check:

   -h means human-readable [OK]

Hint: Use -h for human-readable sizes with df [OK]

Common Mistakes:

• Using -r or -x instead of -h
• Forgetting the dash before h
• Trying --list which is invalid

3. What will be the output of the command df -h /home?

medium

A. Shows disk usage of the /home filesystem in human-readable format

B. Shows disk usage of the root filesystem

C. Shows all mounted filesystems in bytes

D. Shows network disk usage

Solution

1. Step 1: Understand the command arguments

   The command df -h /home checks disk space for the /home directory only, with human-readable sizes.

2. Step 2: Eliminate other options

   It does not show root filesystem unless /home is on root, nor does it show all filesystems or network usage.

3. Final Answer:

   Shows disk usage of the /home filesystem in human-readable format -> Option A

4. Quick Check:

   df -h /home = /home usage human-readable [OK]

Hint: Add path after df -h to check specific folder space [OK]

Common Mistakes:

• Assuming it shows all filesystems
• Confusing /home with root filesystem
• Expecting output in bytes without -h

4. You run df -h /nonexistent and get an error. What is the likely cause?

medium

A. You need root permissions to run df

B. The df command does not support -h option

C. The path /nonexistent does not exist or is not mounted

D. The disk is full

Solution

1. Step 1: Analyze the error cause

   Running df on a path that does not exist or is not mounted causes an error.

2. Step 2: Check other options

   df supports -h, does not require root, and disk full does not cause this error.

3. Final Answer:

   The path /nonexistent does not exist or is not mounted -> Option C

4. Quick Check:

   Invalid path = error [OK]

Hint: Check if path exists before using df on it [OK]

Common Mistakes:

• Thinking -h is unsupported
• Assuming root needed for df
• Confusing disk full with path error

5. You want to check disk space for all mounted filesystems but exclude the tmpfs type. Which command will do this?

hard

A. df -h --exclude tmpfs

B. df -h --exclude=tmpfs

C. df -h --ignore-type tmpfs

D. df -h -x tmpfs

Solution

1. Step 1: Identify the correct option to exclude filesystem type

   The -x option excludes a filesystem type in df. So df -h -x tmpfs excludes tmpfs.

2. Step 2: Verify other options

   Options like --exclude-type, --exclude, or --ignore-type are invalid for df.

3. Final Answer:

   df -h -x tmpfs -> Option D

4. Quick Check:

   -x excludes filesystem type [OK]

Hint: Use -x to exclude filesystem types in df [OK]

Common Mistakes:

• Using invalid options like --exclude-type
• Confusing exclude with ignore
• Forgetting dash before x