Hoofdstuk 7 meerkeuze

Question 1

Compression on a file works by:

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

Answer 1

Removing redundant information

Question 2

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

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

Answer 2

A log file

Question 3

Lossy compression:
(choose three)

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

Answer 3

Is often used with images
Usually results better compression than lossless
Sacrifices some quality

Question 4

You type gzip myfile.tar. What happens?
(choose two)

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

Answer 4

myfile. tar is removed

myfile. tar.gz holds a compressed version of myfile.tar

Question 5

How would you obtain output similar to the following?
compressed​​ ​​​uncompressed ratio uncompressed_name
278168 1016950 72.6% tags

gunzip –t tags
file tags
gzip –l tags

Answer 5

gzip –l tags

Question 6

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

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

Answer 6

tar –cjf documents.tbz Documents

Question 7

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

    –t
    -c
    –j
    -x
    –n

Answer 7

-c

Question 8

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

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

Answer 8

tar –tzf foo.tar.gz

Question 9

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

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

Answer 9

File names to be added to the archive

Question 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
Only files starting with /home will be extracted from the archive
The command will print out each filename as it is processed
Files that are present in the archive might overwrite files in /home
The output file will be compressed

Answer 10

The command will print out each filename as it is processed

The output file will be compressed

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

Answer 11

tar –xzf backup.tar.gz home/fred/

Question 12

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

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

Answer 12

zip -r mydocs.zip Documents

Question 13

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

    showzip documents.zip
    zip –lf documents.zip
    zip –l documents.zip
    unzip –list documents.zip
    unzip –l documents.zip

Answer 13

unzip –l documents.zip

Question 14

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

    zip –x documents.zip ProjectX
    unzip documents.zip | grep ProjectX
    unzip –t documents.zip ProjectX
    unzip documents.zip ProjectX
    unzip documents.zip ProjectX/*

Answer 14

unzip documents.zip ProjectX/*

Question 15

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

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

Answer 15

The file will not be compressed any further than it already was

Question 16

Which of the following commands can be used to compress a file?
(choose three)

    bunzip2
    bzip2
    gzip
    cat
    zip

Answer 16

bzip2
gzip
zip

Question 17

The three main modes of tar are:
(choose three)

    Copy
    List
    Compress
    Create
    Extract

Answer 17

List
Create
Extract

Question 18

In the command tar –czf foo.tar.gz bar, what is the purpose of the f 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
Tells tar to copy only files, and not directories
Specifies extra compression is to be used
Tells tar to write to the file that follows the flag

Answer 18

Tells tar to write to the file that follows the flag

Question 19

Which two commands do the same thing?
(choose two)

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

Answer 19

tar –czf foo.tar.gz foo

tar –c foo | gzip > foo.tar.gz

Question 20

The _____ command is normally executed daily to update the database of all files that are on the system.

updatedb
search
locate
find

Answer 20

updatedb