Lesson 5

Question 1

How are users and groups indentified?

Answer 1

UIDs and GIDs

Question 2

What is the length of modern UIDs?

Answer 2

64 bits

Question 3

Every user has a UID and a GID

Answer 3

True

Question 4

What is the UID of root?

Answer 4

0

Question 5

What unique characteristics do user account shave?

Answer 5

UID starting with 1000
A defined home directory
A defined login shell

Question 6

Name attributes of system accounts?

Answer 6

UID under 100 or 500-999
No home directory
No shell defined

Question 7

What is the primary difference between system and service accounts?

Answer 7

Not a huge difference but their UID/GID/s will be different, service account >1000

Question 8

What is the command to change the shell?

Answer 8

chsh

Question 9

What does the id command do?

Answer 9

Lists basic information about the current shell user

Question 10

what do the “who” and “w” commands do?

Answer 10

they list active logins to the system

Question 11

What’s the biggest issue with using su to switch to root?

Answer 11

If a regular user’s session is compromised, the root password could be captured

Question 12

Name the main configuration file locations for user accounts and access controls

Answer 12

/etc/passwd
/etc/group
/etc/shadow (passwords)
/etc/gshadow

Question 13

what does the /etc/sudoers file contain?

Answer 13

users who can use the sudo command

Question 14

What is the /etc/passwd file?

Answer 14

commonly referred to as the “password file”. each line contains multiple fields always delimited by a colon

Question 15

What is the GECOS field?

Answer 15

contains three or more fields delimited by a comma, normally NAME, LOCATION,CONTACT

Question 16

What does the chfn command do?

Answer 16

Changes information int he GECOS field

Question 17

what does /etc/group store?

Answer 17

colon delimited information about groups

NAME:PASSWORD:GID:MEMBERS

Question 18

In which files are UID and GID stored?

Answer 18

/etc/passwd

Question 19

In which file are Groups stored?

Answer 19

/etc/group

Question 20

In which file are passwords stored?

Answer 20

/etc/shadow

Question 21

How are passwords stored?

Answer 21

With a one way hash

Question 22

Which command to get all active logins on the system?

Answer 22

W command

Question 23

command to add a user?

Answer 23

useradd username

Question 24

command to set a users password?

Answer 24

passwd username

Question 25

which command to list a users information?

Answer 25

id username

Question 26

lists the groups that a user is part of

Answer 26

groups username

Question 27

how do delete a user?

Answer 27

userdel -r username

Question 28

what is the /etc/skel directory?

Answer 28

contains the skeleton structure files and directories to create for a users home directory when created

Question 29

how to add a new group

Answer 29

groupadd groupname

Question 30

how to delete a group

Answer 30

groupdel groupname

Question 31

how to lock a user account?

Answer 31

passwd -l username

Question 32

which file does this entry belong to? developer:x:1010:frank,grace,dave

Answer 32

/etc/group

Question 33

which file does this entry belong to? root:x:0:0:root:/root:/bin/bash

Answer 33

/etc/passwd

Question 34

which file does this entry belong to? henry:$1$.AbCdEfGh123456789A1b2C3d4.:18015:20:90:5:30::

Answer 34

/etc/shadow

Question 35

which file does this entry belong to? henry:x:1000:1000:User Henry:/home/henry:/bin/bash

Answer 35

/etc/passwd

Question 36

which file does this entry belong to? staff:!:dave:carol,emma

Answer 36

/etc/gshadow

Question 37

web_developer:!:kevin:grace,kevin,christian who is the administrator of this group?

Answer 37

Kevin

Question 38

Where you can you see a users password expiration?

Answer 38

in /etc/shadow in the third group

Question 39

Where can you see when a users password expires?

Answer 39

Second to last field in /etc/shadow

Question 40

Using symbolic mode, what are the symbols to add, remove or set a specific value?

Answer 40

+, -, =

Question 41

If you want to grant write permission to a file for members of a group what would the command be (symbolic mode)

Answer 41

chmod g+w file.type

Question 42

If you want to remove read permissions of a user from a file in symbolic mode?

Answer 42

chmod u-r filename

Question 43

In symbolic mode, set rw permissions for all on a file

Answer 43

chmod a=rw- filename

Question 44

In symbolic mode how can you edit permissions for file and group at the same time?

Answer 44

chmod u+rwx,g-x filename

Question 45

how can you modify permissions recursively?

Answer 45

chomd -R u+rwx directoryname/

Question 46

In numeric mode how could use set user and group to read write?

Answer 46

chomd 660 file

Question 47

In numeric mode describe the octet values

Answer 47

Read = 4 Write = 2 Execute = 1 So r/w would be 6 for each group

Question 48

When is symbolic mode better than numeric mode?

Answer 48

When you want to just change one specific permission without having to correctly write the others ex: chmod u+x filename

Question 49

what is chown?

Answer 49

Used to modify the ownership of a file or directory

Question 50

What is the chown syntax?

Answer 50

chown username:groupname filename

Question 51

Use chown to change ownership of a file to jane

Answer 51

chown jane filename

Question 52

how to query groups on your system with a command

Answer 52

groups

Question 53

command to show members of a group

Answer 53

groupmems

Question 54

What does the sticky bit do?

Answer 54

Applies only to directories and prevents users from removing or renaming a file in a directory unless they own that file or directory

Question 55

what does chgrp do?

Answer 55

changes the owning group of a file

Question 56

what does ls -ld do?

Answer 56

Lists the attributes of a directory instead of listing its contents

Question 57

What is the GID flag

Answer 57

Sets Group ID Bit, octal value of 2. Can be applied to executable files or directories. On an executable it will make the process executing it inherit the privileges of the group who owns the file

Question 58

what kind of file is this? brw-rw---- 1 root disk 8, 17 Dec 21 18:51 /dev/sdb1

Answer 58

a block device as annotated by the "b"

Question 59

What are temporary files?

Answer 59

Files used by programs to store data that is only needed for a short period of time

Question 60

Where are temp files normally stored?

Answer 60

/tmp /var/temp /run

Question 61

What does the sticky bit do?

Answer 61

it prevents users from removing or renaming a file within that directory unless they own the file

Question 62

What problem does the sticky bit solve?

Answer 62

For global areas like /tmp, it allows the prevention of users from deleting files that they do not own

Question 63

what does SUID do?

Answer 63

Applies to executables and enables the file to run with the permissions of the owner and not the person executing it

Question 64

What does SGID do?

Answer 64

Allows a file to be executed with the privileges of the group and not the user executing it

Question 65

what command would you use to create a hard link named hardlink in the directory /home/carol/Documents/ to a file named target.txt in the current directory?

Answer 65

ln target.txt /home/carol/Documents/hardlink

Question 66

how do you create a symbolic link named softlink in /home/carol/Documents/ pointing to a file target.txt in the current directory?

Answer 66

ln -s target.txt /home/carol/Documents/softlink

Question 67

what's the difference between a hard link and a symbolic (soft) link?

Answer 67

a hard link is another name for the same file (points to the same inode), while a symbolic link is a pointer to the path of the original file.

Question 68

what is the chmod symbolic mode parameter to enable the sticky bit on a directory?

Answer 68

chmod +t

Question 69

if you create a symbolic link without specifying the full path to the target, what might happen if you move the link?

Answer 69

the link might break because the system interprets the target's location as relative to the link's location.

Question 70

which temporary directory must be cleared during the boot process?

Answer 70

/tmp

Question 71

explain the difference between a hard link to a file and a copy of this file.

Answer 71

a hard link points to the same inode as the original file, so changes to one affect the other. a copy is a separate file with its own inode, so changes to one do not affect the other.

Question 72

what is an inode?

Answer 72

a data structure that stores attributes about the file including it's memory location etc