CS199_Week_3

Question 1

At a low level, users are represented by an integer called…?

Answer 1

a User ID (uid).

Question 2

Every process that runs on the system runs a …?

Answer 2

given uid.

Question 3

Every file in the file system is owned by a …?

Answer 3

uid

Question 4

The /etc/passwd file maps uids to…?

Answer 4

user accounts.

Question 5

User accounts map uids to a…?

Answer 5

username, password, Group Id(s), a home directory, and a login shell.

Question 6

Passwords are changed with…?

Answer 6

passwd command.

Question 7

Passwords now store in…?

Answer 7

/etc/shadow

safer to do this, only user root can view file, change password using passwd

Question 8

Three types of users…?

Answer 8

Normal, root and system.

Question 9

Normal users…?

Answer 9

• Real people
• Login shell is /bin/bash
• Home directory inside /home
• UID over 500

Question 10

The root User…?

Answer 10

• UID 0

- Free rein on system: she may modify or remove any file; she may run any command; she may kill any process.

Question 11

System users…?

Answer 11

• Components of system, not real people
• UID in range 1 -499
• Example : Processes that handle email often run as the username mail

Question 12

Fundamentally, a group is just…?

Answer 12

an integer group id (gid)

Question 13

Every process that runs on the system runs…?

Answer 13

under a collection of groups (gids)

Question 14

The /etc/group file maps gids to…?

Answer 14

group names and group memberships

Question 15

Every file in the file system is owned by …?

Answer 15

a single gid

Question 16

Users have a single primary group defined in…?

Answer 16

the /etc/passwd file.

Question 17

Users may be members of multiple secondary groups, defined in the…?

Answer 17

/etc/groups file.

Question 18

Every file must have a group owner, there must be a…?

Answer 18

default group associated with each user.
(This default group becomes the group owner of newly created files. This group is known as a user’s primary group. A user’s primary group is defined in the fourth field of a user’s /etc/passwd entry.)

Question 19

In addition to a primary group, users may optionally belong to…?

Answer 19

other groups as well.

These groups are termed secondary groups, and are defined (coincidentally) in the fourth field of the /etc/group file.

Question 20

Use usermod and groupmod commands to…?

Answer 20

modify group membership.

Question 21

The id command displays..?

Answer 21

user and group information.

Question 22

The whoami command reports…?

Answer 22

the current username

Question 23

The who, users, and w commands…?

Answer 23

report users with active sessions.

Question 24

The finger command reports when users were last…?

Answer 24

logged onto the system, and other user information. (A .plain file can be placed in the user’s home directory with more information)

Question 25

The su command allows a user to…?

Answer 25

switch user id

Question 26

The su command is usually called with a ..?

Answer 26

hyphen, such as su -, to specify that the user should effectively log in as the new user.

Question 27

The newgrp command, also called sg, allows a user to…?

Answer 27

switch primary group id.