Manipulating files and directories

Question 1

What is the command to create a directory?

Answer 1

mkdir

Question 2

What is the command to remove an empty directory?

Answer 2

rmdir

Question 3

What is the command to remove a directory with contents

Answer 3

rm -r

Question 4

What is the command to create a parent directory and subdirectory?

Answer 4

mkdir -p

i.e mkdir -p parent/child

Question 5

What is the command to create a non existing file/ update the timestamp of an existing file/directory?

Answer 5

touch

i.e touch file

Question 6

What is the command to rename a file/directory?

Answer 6

mv

i.e mv oldname newname

Question 7

What is the command to copy a directory and its contents?

Answer 7

cp -r

-R –recursive

Question 8

What is the command to create a symbolic link?

Answer 8

ln -s >pathtoreference< >link<

i.e ln -s /var/spool/mail mail

Question 9

When creating a symlink, what are the permissions?

Answer 9

Full permissions to view where the link points to, however it does not reflect the permissions of the file it is linking to.

Question 10

How do you create a hard link?

Answer 10

ln >pathtorefrence< >link

Question 11

How does a hard link work?

Answer 11

Links directly to an inode on the file system, inode location will exist until all referring links are removed. Permissions/time stamp are identical across links. Unlike symbolic links hard links cannot link across file systems (inc. partitions)

Question 12

How do you view the inode for a file/directory?

Answer 12

ls -i

Question 13

How many links will a symbolic link have vs a hard link?

Answer 13

Symbolic link will have 1 link to the location

Hard link will have 2 links because each links to an inode location

Question 14

What is the syntax that constitutes a file permission?

Answer 14

• |rwx|rwx|rwx (read write execute)
  type|user|group|other
  no access means -
  i.e -|r-x|-w-|rw-

Question 15

What is the syntax that constitutes a directory permission?

Answer 15

d|rwx|rwx|rwx (read write cdinto)
type|user|group|other
no access means -
i.e d|r-x|-w-|—

Question 16

What is the octal notation associated with a file/folder permission?

Answer 16

d|421|421|421
d|rwx|rwx|rwx
-|421|421|421
-|rwx|rwx|rwx

Question 17

What would the octal notation equivalent be for d|r-x|r-x|rwx?

Answer 17

d|r-x|r-x|rwx = d|5|5|7

d|4+0+1|4+0+1|4+2+1

Question 18

What would the octal notation equivalent be for -|rwx|r–|—?

Answer 18

• |rwx|r–|— = -|7|4|0

- |4+2+1|4+0+0|0+0+0

Question 19

How would you change the permissions of a file/folder without octal notation?

Answer 19

chmod u/g/o +/- r/w/x file/folder

i. e chmod ug+x file/folder
* have to repeat for giving unique permissions (appending and omitting)

Question 20

How could you change the permissions of a file/folder using octal notation

Answer 20

chmod nnn file/folder

i. e chmod 750 file/folder
* efficient in giving unique permissions in one command (arbitrarily set)

Question 21

What is a sticky bit?

Answer 21

In linux all users including other can delete a write protected file if they have permissions (wx) of the containing folder
Setting the sticky bit on folder allows deletion only with elevated privileges, essentially write privileges for creation but not deletion. i.e. /tmp

Question 22

How do you set the sticky bit for a folder without octal notation?

Answer 22

chmod o+t folder

*only applies to the permission of other

Question 23

How do you remove the sticky bit for a folder without using octal notation?

Answer 23

chmod o-t folder

Question 24

How do you set the sticky bit for a file using octal notation?

Answer 24

chmod 1nnn folder

i.e chmod 1770 folder

Question 25

How do you remove the sticky bit for a folder using octal notation?

Answer 25

chmod 0nnn folder

i.e chmod 0770 folder

Question 26

What is the command to change the owner of a file or directory?

Answer 26

chown user:group file

*leave either field blank to change only user/group

Question 27

How do you change the permissions of a folder recursively?

Answer 27

chmod -R >permission< directory

Question 28

How would you change the permissions of the contents of a directory excluding the folder itself?

Answer 28

chmod -R >permission< directory/*

Question 29

What is the permission hierachy for files and directories?

Answer 29

user
group
other

*first membership applies

Question 30

What is the command to remove a symbolic link?

Answer 30

unlink

i.e unlink linkename

Question 31

What is denoted by file with c as the listing?

Answer 31

Character device

Question 32

What is denoted by file with b as the listing?

Answer 32

Block device

Question 33

What is denoted by file with l as the listing?

Answer 33

Symbolic Link

Question 34

What defines default permissions for a file/directory?

Answer 34

umask

Question 35

How do you apply permissions recursively to a folder?

Answer 35

chmod -R

Question 36

What is the command to log into a group and create a file/directory with the specified group instead of the user?

Answer 36

newgrp

i. e newgrp wheel
* newgrp to logout

Question 37

When applying execute permissions to a directory recursively, how do you exclude files within the directory

Answer 37

chmod u/g/o+X

*capital symbols, only works with execute permission

Question 38

What are setuid and setgid?

Answer 38

setuid enables a file to be ran with the exact permissions as the owner of the file *i.e /usr/bin/passwd
setgid enables a file to be ran with the exact permissions as the group of the file *i.e /usr/bin/wall

Question 39

How do you modify a file to setuid and setgid with octal notation?

Answer 39

setuid - chmod 4nnn
setgid - chmod 2nnn
i.e chmod 6754 would setuid and setgid for file

Question 40

How do you modify a file to setuid and setgid with symbolic notation?

Answer 40

setuid - chmod u+s

setgid - chmod g+s

Question 41

When creating a file/directory, what will the group owner be?

Answer 41

The primary group of the user the file/directory was created with

Question 42

How do you use object notation to set unique permissions?

Answer 42

chmod u=,g=,o=

i.e chmod u=rwx,g=rwx,o=rx

Question 43

To delete a file, what permissions are required?

Answer 43

Write and execute permissions to the containing directory

*file permissions are not relevant

Question 44

How would you make the the contents of a directory always have the same group owner as the directory itself?

Answer 44

use SETGID
chmod g+s {directory}
Any new files/directories within the folder will have the same group owner