Chapter 7

Question 1

How does Linux represent users and groups internally?

Answer 1

With numbers.

Question 2

Where will you find the group file?

Answer 2

/etc/group

Question 3

What file defines user accounts?

Answer 3

/etc/passwd

Question 4

What do we call user numbers and group numbers, respectively?

Answer 4

UID User IDs and GID Group IDs.

Question 5

What are the first 100 user and group ids and what are they for?

Answer 5

0-99, they are reserved for system use, things like accounts associated with utilities and functions

Question 6

What is the root GID and UID>

Answer 6

0

Question 7

What command adds users.

Answer 7

useradd (sometimes adduser)

Question 8

How do you change user passwords?

Answer 8

passwd [username]

To change your own password omit the username.

Question 9

Why use usermod?

Answer 9

It allows you to modify current accounts. It supports -m which moves files to the user’s new directory, also -l which changes the username if need be. Also -L and -U to lock and unlock a user’s password.

Question 10

When you change a username, how do you help the user keep permissions?

Answer 10

chown -R sally /home/sally

This gives her permissions of all files in her home directory

Question 11

Why use chage?

Answer 11

It allows you to modify accounts to expire if the password hasn’t been changed often enough or a specific time has expired.

Question 12

Name a way to alter accounts without using commands.

Answer 12

Directly edit /etc/passwd (Where user info is stored) or

/etc/shadow (Where the shadow password is stored.

Question 13

How should you remove users?

Answer 13

Change ownership or backup their files.
userdel -r [username]
-r removes their files
-f or –force forces deletion even if they are logged in.

Question 14

How do you add a group?

Answer 14

groupadd

Question 15

How do you hunt down stray user files after the user has been deleted?

Answer 15

Use find and their former user id.

Question 16

How do you edit an existing groups settings?

Answer 16

groupmod

Question 17

How do you add a user to a new group?

Answer 17

usermod G [list all groups separated by commas including old and new groups.]

Question 18

How do you hunt down stray user files after the user has been deleted?

Answer 18

Use find and their former user id.

Question 19

How do you edit an existing groups settings?

Answer 19

gpasswd

Question 20

How do you modify a group’s settings without using commands?

Answer 20

Modify the /etc/group file or

/etc/gshadow file

Question 21

How do you delete groups?

Answer 21

groupdel [groupname]

don’t forget to find and delete orphan files.

Question 22

What is syslogd and how is it configured?

Answer 22

It is the system log daemon and is configured through the /etc/syslog.conf file

Question 23

How do you manually create log entries?

Answer 23

logger with it’s options

Often used in scripts to log details of what the script does

Question 24

How do you alter log rotation?

Answer 24

edit /etc/logrotate.conf

refers to /etc/logrote.d

Question 25

How do you set the software clock?

Answer 25

date [MMDDhhmmYEAR] it assumes local | use -u for UTC

Question 26

How do you sync the hardware and software clocks?

Answer 26

hwclock and use its options

Question 27

What do you call the levels of NTP hierarchy?

Answer 27

Stratum

Question 28

How do you do a one time NPT sync

Answer 28

ntpdate [ip address of NTP server]

Question 29

What is the order of the 5 cron fields?

Answer 29

Minute, Hour, Day of Month, Month, Day of Week.

Question 30

What are the cron number rules

Answer 30

24 hour clock. separated by commas are match any. separated by - means all in the range. means wildcard, / means skip /10 means run every ten minutes

Question 31

How do you make a user cron job?

Answer 31

crontab | crontab -u makes it for another user

Question 32

Why use anacron?

Answer 32

It performs cron jobs for computers that are regularly turned off. Usually from a startup script.

Question 33

Why use at?

Answer 33

It schedules a command for one time in the future.

Question 34

Name the logging codes in order of priority.

Answer 34

From highest to lowest. | emerg, crit, warning, debug

Question 35

Summarize methods of creating and modifying user accounts?

Answer 35

Accounts can be created or modified with the help of tools designed for this purpose, such as useradd and usermod. Alternatively, you can directly edit the /etc/passwd and /etc/shadows files which hold the account information.

Question 36

Describe the function of groups in Linux

Answer 36

Linux Groups enable security features to be applied to arbitrary groups of users. Each group holds an arbitrary collection of users, and group permissions can be set on files, giving all group members the same access rights to files.

Question 37

explain the purpose of the skeleton files

Answer 37

Skeleton files provide a core set of configuration files that should be present in users' home directories when those directories are created. They provide a starting point for users to modify their important shell and other configuration files.

Question 38

Describe how log rotation is managed?

Answer 38

Log rotation is controlled via the /etc/logro-tate.conf file(which typically refers to files in the /etc/logrotate.d/) Entries in these files tell the system whether to rotate logs at fixed intervals or when they reach particular sizes. When a log rotates, its renamed (and possibly compressed) a new log file is created and the oldest archived log files may be deleted.

Question 39

Summarize how to review journal data?

Answer 39

The systemd-journald service is responsible for journal message data. The daemon is controlled via the /etc/systemd/journal.conf config file. This journal message data can only be viewed using the journal journalctl utility. To View systems journal data, you must either use superuser privileges or be a member of the systemd-journal group. Users can view their own user journal data files. To View the entire current file, simply use the journalctl command with no parameter. to parse out journal data, use the various filters available with the journalctl utility via parametrs

Question 40

explain the two types of clocks in x86 and x86-64 hardware?

Answer 40

The hardware clocks keeps time when the computer is powered down, but most programs don't use it while the computer is running.Such programs refer to the software clock, which is set from the hardware clock when the computer boots.

Question 41

Network Time Protocol

Answer 41

is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in current use.

Question 42

Describe how to configure anacron jobs?

Answer 42

anacron jobs are controlled from the /etc/anacron tab file. The file is checked to see when each listed job was last executed, and it ensures that the designated time period between executions is followed. Time periods are listed in number of days. No time period can be less than one day and therefore jobs needing to be run more than one time per day should not use anacron. Often anacron itself is run from a system start script from a cron job.