NDG Linux Essentials 2.21 | Archiving and Compression Module 9 | Chapter 09 Exam Answers

NDG Linux Essentials 2.21 | Archiving and Compression Module 9 | Chapter 09 Exam Answers Full 100% 2023

These are questions of Cisco NDG Linux Essentials 2.21 Archiving and Compression Chapter 09 Exam Answers full 100% with the latest version and updated in 2023. All answers are verified by experts with explanations.

1. Compression of a file works by:

   • Storing most of the data on removable media and just leaving a pointer
   • Consolidating multiple files into one
   • Eliminating gaps within the file
   • Removing the high order bit from each byte
   • Removing redundant information

   • Answers Explanation & Hint: File compression techniques aim to reduce the file size by identifying and eliminating redundant or repetitive data in the file. Redundant information is data that appears more than once within the file or can be predicted or represented more efficiently using fewer bits or symbols. There are different compression algorithms and methods that achieve this goal. The result is a smaller compressed file that can be stored or transmitted more efficiently, taking up less storage space or requiring less bandwidth. When you decompress or uncompress the file, it can be restored to its original form, retaining its original content and structure.

2. In general, for which of the following would you want to use lossless compression?

   • An mp3 audio file
   • A log file
   • A movie
   • A JPEG image
   • An encrypted email

   • Answers Explanation & Hint: In general, you would want to use lossless compression for the following: A log file: Log files typically contain important records and data entries that need to be preserved accurately for analysis and debugging. Lossless compression ensures that no information is lost during compression and decompression, maintaining the integrity of the log data. An encrypted email: Encrypted emails are important for secure communication, and any loss of data in the encrypted message could compromise its confidentiality and integrity. Lossless compression ensures that the encrypted content remains intact and can be decrypted correctly. Lossless compression algorithms guarantee that the original data can be perfectly reconstructed after compression and decompression, without any loss of information. This is in contrast to lossy compression, which sacrifices some data to achieve higher compression ratios, making it suitable for scenarios where some loss of quality is acceptable, such as multimedia files like MP3 audio, movies, and JPEG images.

3. Lossy compression:

   (choose three)

   • Is often used with documents
   • Usually results better compression than lossless
   • Is often used with images
   • Sacrifices some quality
   • Decompresses to an identical version as the original

   • Answers Explanation & Hint: Usually results in better compression than lossless: Lossy compression generally achieves higher compression ratios than lossless compression. By sacrificing some quality and discarding non-essential data, lossy compression can significantly reduce file sizes. Is often used with images: Lossy compression is commonly used for image files, such as JPEG format, in applications where some loss of image quality is acceptable to achieve smaller file sizes. Sacrifices some quality: As mentioned, lossy compression intentionally discards certain data to achieve higher compression, resulting in a loss of quality compared to the original data. Lossy compression is well-suited for scenarios where some loss of quality is acceptable, such as in multimedia applications like images, videos, and audio files. It is often used to achieve higher levels of compression compared to lossless compression, which can lead to significant reductions in file size. However, it is not appropriate for documents or data where preserving every detail is essential.

4. You type gzip myfile.tar. What happens?

   (choose two)

   • myfile.tar is unarchived into the current directory
   • myfile.tar is removed
   • myfile.tar.gz holds a compressed version of myfile.tar
   • An error; you forgot to specify the file with -f
   • An error; you forgot to pass the name of the output file

   • Answers Explanation & Hint: myfile.tar is removed: When you use the gzip command to compress a file, it replaces the original file (myfile.tar in this case) with the compressed version (myfile.tar.gz). The original file is removed, and only the compressed file remains. myfile.tar.gz holds a compressed version of myfile.tar: The gzip command compresses the file myfile.tar and creates a new file named myfile.tar.gz, which holds the compressed version of the original file.

5. How would you obtain output similar to the following?
   compressed uncompressed ratio uncompressed_nam

   278168  1016950  72.6%  tags

   • gunzip –t tags
   • file tags
   • >gzip –l tags

   • Answers Explanation & Hint: The command gzip -l tags provides the output similar to the format you mentioned: compressed uncompressed ratio uncompressed_name 278168 1016950 72.6% tags The gzip -l command provides a listing of compression details for the file “tags.” It displays the compressed and uncompressed sizes and calculates the compression ratio, providing the output in the specified format. Thank you for providing the correct command, and I apologize for any confusion caused by my earlier responses.

6. Which command would you use to archive the Documents directory and compress it with bzip2 compression?

   • tar –cjf Documents
   • tar –fzc Documents documents.tbz
   • tar –czf documents.tbz
   • tar –cf Documents documents.tbz
   • tar –cjf documents.tbz Documents

   • Answers Explanation & Hint: The correct command to archive the “Documents” directory and compress it with bzip2 compression is tar -cjf documents.tbz Documents Explanation: tar: The tar command is used for archiving files and directories. -c: This option tells tar to create a new archive. -j: This option specifies bzip2 compression. -f: This option allows you to specify the filename of the archive. documents.tbz: This is the name of the compressed archive that will be created. Documents: This is the name of the directory to be archived and compressed. The command will create a new archive named “documents.tbz” that contains the “Documents” directory, compressed using bzip2 compression.

7. Which flag would you pass to tar in order to have it make a new archive?

   • -n
   • -t
   • -x
   • -j
   • -c

8. Which command will show what is inside the compressed tarball with a name of foo.tar.gz?

   • tar –tzf foo.tar.gz
   • tar –tf foo.tar.gz
   • tar –tjf foo.tar.gz
   • tar –lf foo.tar.gz
   • tar –xf foo.tar.gz

9. In the command tar-cvjf foo.tbz a b c, what are a, b, and c?

   • Matching operators; anything starting with a, b, or c will be added
   • Nothing; –cvjf only expects one parameter
   • Extra flags passed to tar
   • File names to be added to the archive
   • a is the directory that will be prepended to files; b and c are files inside it

10. Given the command tar –cvjf homedirs.tbz /home, which of the following are true?

    (choose two)

    • The /home directory will be restored with the contents of homedirs.tbz
    • The output file will be compressed
    • Only files starting with /home will be extracted from the archive
    • Files that are present in the archive might overwrite files in /home
    • The command will print out each filename as it is processed

11. You archived your users’ directories into a file called backup.tar.gz. You then view the archive and see the filenames follow this convention:

    home/username/somefile

    How will you extract just the files for the user called fred?

    •  tar –tjf backup.tar.gz /home/fred
    • tar –xjf backup.tar.gz home/fred/
    • tar –tzf /home/fred < backup.tar.gz
    • tar –xzf backup.tar.gz fred
    •  tar –xzf backup.tar.gz home/fred/

12. Which of the following commands will create a zipfile with the contents of your Documents directory?

    • zip –c mydocs.zip Documents
    • zip mydocs.zip Documents
    • zip –f mydocs.zip Documents
    • zip -cf mydocs.zip Documents
    • zip -r mydocs.zip Documents

13. Given a file called documents.zip, how can you see what’s in it without extracting the files?

    • unzip -l documents.zip
    • zip -lf documents.zip
    • showzip documents.zip
    • unzip --list documents.zip
    • zip -l documents.zip

14. Given a file called documents.zip, how can you extract just the files under ProjectX?

    • unzip documents.zip Project
    • unzip documents.zip ProjectX/*
    • zip -x documents.zip ProjectX
    • unzip documents.zip | grep ProjectX
    • unzip -t documents.zip ProjectX

15. You try to compress a file that is already compressed. Which of the following statements is true?

    • The file will actually be uncompressed
    • The compression algorithm needs to be set to the “currently compressed” mode for it to be compressed further
    • The file will not be compressed any further than it already was
    • The file changed while you were compressing it
    • The file will be deleted

16. Which of the following commands can be used to compress a file?

    (choose three)

    • cat
    • zip
    • bunzip2
    • gzip
    • bzip2

17. The three main modes of tar are:

    (choose three)

    • Create
    • Copy
    • Extract
    • Compress
    • List

18. In the command tar -czf foo.tar.gz bar, what is the purpose of the f flag?

    • Tells tar to copy only files, and not directories
    • Tells tar to write to the file that follows the flag
    • Tells tar to read from the file that follows the flag
    • Tells tar to print the name of each file as it is processed
    • Specifies extra compression is to be used

19. Which two commands do the same thing?

    (choose two)

    • tar -czf foo.tar.gz foo
    • tar -c foo | gzip > foo.tar.gz
    • tar -x foo | gzip
    • tar -tzf foo.tar.gz
    • tar -xzf foo.tar.gz

20. Which two programs use the Lempel-Ziv-Markov chain algorithm?

    (choose two)

    • bzip
    • lossless
    • gzip
    • lossy
    • xz

21. By default, the zip command replaces uncompressed files with compressed files.

    True or False?

    • True
    • False