bzip2 and xz compression in Linux CLI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of bzip2 and xz commands in Linux?

They are used to compress and decompress files to save disk space and reduce transfer time.

beginner

How do you compress a file named file.txt using bzip2?

Run the command bzip2 file.txt. It creates file.txt.bz2 and removes the original file.

beginner

How do you decompress a .xz file named archive.xz?

Use the command unxz archive.xz or xz -d archive.xz. It restores the original file and removes the compressed one.

intermediate

Which compression tool generally provides better compression ratio: bzip2 or xz?

xz usually compresses files smaller than bzip2, but it may take more time to compress.

intermediate

How can you keep the original file after compressing with bzip2?

Use the -k option: bzip2 -k file.txt keeps file.txt and creates file.txt.bz2.

What file extension does bzip2 compression create?

A .gz

B .xz

C .bz2

D .zip

bzip2 creates files ending with .bz2.

Which command decompresses an .xz file?

A unxz file.xz

B bzip2 -d file.xz

C gzip -d file.xz

D xz -c file.xz

unxz or xz -d decompress .xz files.

How to compress a file with xz and keep the original file?

A xz file.txt

B xz -k file.txt

C xz -d file.txt

D xz --remove file.txt

The -k option keeps the original file after compression.

Which tool is usually faster at compressing files?

A xz

B Neither compresses files

C Both are equally fast

D bzip2

bzip2 is generally faster but compresses less tightly than xz.

What happens to the original file after running bzip2 file.txt without options?

A It is deleted

B It is renamed

C It stays unchanged

D It is copied

By default, bzip2 deletes the original file after compression.

Explain how to compress and decompress files using both bzip2 and xz commands.

Think about the commands and file extensions for both tools.

Compare bzip2 and xz in terms of compression ratio and speed.

Focus on size and speed differences.

Practice

1. What does the bzip2 command do in Linux?

easy

A. Deletes files permanently

B. Compresses files to make them smaller

C. Changes file permissions

D. Lists files in a directory

Solution

1. Step 1: Understand the purpose of bzip2

   The bzip2 command is used to compress files, reducing their size.

2. Step 2: Compare with other options

   Options B, C, and D describe unrelated file operations, not compression.

3. Final Answer:

   Compresses files to make them smaller -> Option B

4. Quick Check:

   bzip2 compresses files = A [OK]

Hint: bzip2 always compresses files to save space [OK]

Common Mistakes:

• Confusing compression with deletion
• Thinking bzip2 changes file permissions
• Assuming bzip2 lists files

2. Which command correctly compresses a file named data.txt using xz and keeps the original file?

easy

A. xz data.txt

B. xz -d data.txt

C. xz --delete data.txt

D. xz -k data.txt

Solution

1. Step 1: Identify the option to keep original files

   The -k option tells xz to keep the original file after compression.

2. Step 2: Check other options

   xz data.txt compresses but deletes original; B decompresses; D is invalid for keeping files.

3. Final Answer:

   xz -k data.txt -> Option D

4. Quick Check:

   Use -k to keep original = C [OK]

Hint: Use -k with xz to keep original file after compression [OK]

Common Mistakes:

• Forgetting -k deletes original file
• Using -d which decompresses instead
• Assuming --delete keeps original

3. What is the output of the command sequence?

echo "Hello" > file.txt
bzip2 -k file.txt
ls file.txt file.txt.bz2

medium

A. file.txt.bz2

B. file.txt

C. file.txt file.txt.bz2

D. No files listed

Solution

1. Step 1: Understand bzip2 -k effect

   The -k option keeps the original file file.txt and creates compressed file.txt.bz2.

2. Step 2: List files after compression

   Both file.txt and file.txt.bz2 exist, so ls shows both.

3. Final Answer:

   file.txt file.txt.bz2 -> Option C

4. Quick Check:

   -k keeps original and compressed files = B [OK]

Hint: bzip2 -k keeps original and compressed files both [OK]

Common Mistakes:

• Assuming original file is deleted
• Expecting only compressed file
• Thinking no files remain

4. You run xz -d file.xz but get an error saying "file.xz: No such file or directory". What is the likely problem?

medium

A. The file file.xz does not exist in the current directory

B. The -d option is invalid for decompression

C. You need to use -k to decompress

D. The file is already decompressed

Solution

1. Step 1: Understand the error message

   The error "No such file or directory" means the file file.xz is missing in the current folder.

2. Step 2: Check command options

   -d is correct for decompression; -k is unrelated to decompression; file must exist to decompress.

3. Final Answer:

   The file file.xz does not exist in the current directory -> Option A

4. Quick Check:

   File missing causes No such file error = A [OK]

Hint: Check file exists before decompressing with -d [OK]

Common Mistakes:

• Thinking -d is wrong option
• Using -k to decompress
• Ignoring file location

5. You have a large log file server.log. You want to compress it using bzip2 but keep the original file and later decompress it. Which sequence of commands is correct?

hard

A. bzip2 -k server.log
bzip2 -d server.log.bz2

B. bzip2 server.log
bzip2 -k -d server.log.bz2

C. bzip2 -d server.log
bzip2 -k server.log.bz2

D. bzip2 -k -d server.log
bzip2 server.log.bz2

Solution

1. Step 1: Compress with original kept

   Use bzip2 -k server.log to compress and keep the original file.

2. Step 2: Decompress the compressed file

   Use bzip2 -d server.log.bz2 to decompress back to original format.

3. Final Answer:

   bzip2 -k server.log bzip2 -d server.log.bz2 -> Option A

4. Quick Check:

   Use -k to keep original, -d to decompress = D [OK]

Hint: Compress with -k, decompress with -d for safe file handling [OK]

Common Mistakes:

• Using -d to compress
• Not keeping original file
• Mixing options order incorrectly