ch3. Users And Groups

Question 1

usermod
usermod -l
usermod -c

Answer 1

Bash command to change a user account
-l change username
-c change comment field

Question 2

passwd -l
passwd -u

Answer 2

Bash command
-l lock an account
-u unlock an account

Question 3

userdel
userdel -r

Answer 3

Bash command to delete a user account. Without options, does not delete the home directory, or saved files.
-r deletes the account including the home directory and saved files

Question 4

/etc/group

Answer 4

stores all group information

Question 5

group fields

Answer 5

Group Name : Password : Group ID : Group List (list of members)

Question 6

groupadd
groupadd -g
.
groupadd -f
groupadd -o
groupadd -g
groupadd -n

Answer 6

Bash command to create a group (by default, no password, no members)
-g create group with name or ID
.
-f exit command with a success status if the group already exists
-o create a group with a non-unique group ID
-g change the ID of an existing group
-n change the name of an existing group

Question 7

groupdel

Answer 7

Bash command to delete a group, but does not delete members of the group

Question 8

usermod -a -G

Answer 8

Bash command to add a user to a group

Question 9

whoami

Answer 9

Bash command to display current username of currently logged-in account

Question 10

who
who -u

Answer 10

Bash command to print the details of of a user currently logged into a system, including: username, system name, and length of connection
-u prints user and idle time

Question 11

standard user prompt

Answer 11

$

Question 12

root user prompt

Answer 12

#

Question 13

w (command)

Answer 13

Bash command to print the status of the system + users logged in, + current activities of users

Question 14

last

Answer 14

Bash command to print information about connect times of users
useful for finding what commands were recently run

Question 15

Where does ‘last’ retrieve info from?

Answer 15

/var/log/wtmp

Question 16

.bashrc

Answer 16

file that allows customization of user’s own environment. In particular, enables command line alias that will only affect the .bashrc file’s user. Also creates an environment variable, set default directories, and file permissions for the default user. Also determines the default command prompt.

Question 17

.bash_profile

Answer 17

shell config for initial login environment. (only used for very first login.) Think of as a default config for new users.

Question 18

file to be edited to allocate system rights to other users on the system?

Answer 18

/etc/sudoers

Question 19

file would be modified when using the useradd, usermod, or userdel commands

Answer 19

/etc/passwd

Question 20

which file contains the hashed version of each user’s password?

Answer 20

/etc/shadow

Question 21

when a new user is created, what file is copied into the new users home directory, and can be used to configure new user’s default directory?

Answer 21

/etc/skel

Question 22

/etc/profile

Answer 22

system wide account settings for all users, not just new users. Is read before Bash configs, so any individual customizations take priority over what is established here

Question 23

/etc/profile.d

Answer 23

location for scripts that admin use for system-wide variables

Question 24

/etc/bashrc (repeat?)

Answer 24

system wide settings for the command line environment

Question 25

user accounts are referenced by:

Answer 25

UID or User ID

Question 26

the root account is used for:

Answer 26

for admin tasks, and to security guard applications/commands

Question 27

Principal of Least Privilege

Answer 27

to grant minimal access to a system while still meeting the needs of the user

Question 28

Service Account

Answer 28

an account disabled from a user logging into, used to grant permissions to services and applications

Question 29

When to log into root

Answer 29

never

Question 30

sudoedit

Answer 30

Bash command to allow a user to edit a file even if the file is only available to root and allows use of any file editor

Question 31

%editors ALL = sudoedit path/to/file

Answer 31

example of a group file edit that allows all users in the editor’s group to edit /path/to/file with sudoedit

Question 32

visudo
visudo -c
.
visudo -f
visudo -s
visudo -x

Answer 32

Bash command to edit the /etc/sudoers file in a safe manner by verifying the syntax of proposed edits before committing them.
-c check the file for errors
.
-f check/edit the file location
-s check file in strict mode
-x output the file in a json file format

Question 33

Wheel Group

Answer 33

Allows member users access to the sudo command

Question 34

id

Answer 34

prints the username of the currently logged in account

Question 35

useradd

Answer 35

creates a new user in /etc/passwd

Question 36

/etc/login.defs

Answer 36

file that configures new user accounts

Question 37

/home/username

Answer 37

location of a user’s home directory

Question 38

what does useradd not do?

Answer 38

It does not create a password for the new user account, and until one is created, the account cannot be signed into

Question 39

useradd -c
useradd -e
useradd -s
useradd -D

Answer 39

-c sets comment field of account (usually the full name of the user)
-e sets the expiration date
-s sets the default shell for the user
-D prints the default config for a new user

Question 40

passwd

Answer 40

Bash command to set or reset the password for a user account. Any user can use it to reset their own account.

Question 41

/etc/passwd

Answer 41

file that stores the: username, user id, group id, comment, home directory, and login shell for all users. It stored the passwords as well in legacy systems.

Question 42

‘sudo !!’ (command)

Answer 42

Bash command that executes the previously entered command as root

Question 43

/etc/shadow

Answer 43

file that stores: username, password (in a hashed format), and various values relating to password change and warnings

Question 44

chage
chage -E

chage -M
chage -W

Answer 44

command stands for ‘change age’
-E change the expiration date for a user account

-M change the number of days until a user needs to change their password
-W change the days ahead warning that a password needs to be changed