File Permissions

Question 1

What is the syntax that constitutes a file permission?

Answer 1

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

Question 2

What is the syntax that constitutes a directory permission?

Answer 2

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

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

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

Question 5

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

Answer 5

• |rwx|r–|— = -|7|4|0

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

Question 6

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

Answer 6

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 7

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

Answer 7

chmod nnn file/folder

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

Question 8

What is a sticky bit?

Answer 8

In linux all users including other can delete a write protected file if they have permissions of the containing folder
Setting the sticky bit on folder allows only the deletion of things you own

Question 9

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

Answer 9

chmod o+t folder

*only applies to the permission of other

Question 10

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

Answer 10

chmod o-t folder

Question 11

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

Answer 11

chmod 1nnn folder

i.e chmod 1770 folder

Question 12

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

Answer 12

chmod 0nnn folder

i.e chmod 0770 folder

Question 13

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

Answer 13

chown user:group file

*leave either field blank to change only user/group

Question 14

How do you change the permissions of a folder recursively?

Answer 14

chmod -R >permission< directory

Question 15

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

Answer 15

chmod -R >permission< directory/*

Question 16

What is the permission hierachy for files and directories?

Answer 16

user
group
other

*first membership applies

Question 17

What is the command to create a symbolic link?

Answer 17

ln -s /path/to/file linkname

Question 18

What is the command to remove a symbolic link?

Answer 18

unlink

i.e unlink linkename

Question 19

What is denoted by file with c as the listing?

Answer 19

Character device

Question 20

What is denoted by file with b as the listing?

Answer 20

Block device

Question 21

What is denoted by file with l as the listing?

Answer 21

Symbolic Link