Command Line Basics

Question 1

How to get help in Linux

Answer 1

-?, -h or -help

grep –help

Question 2

General syntax for a command Linux ?

Answer 2

command -[switch] parameter

Question 3

Linux Control Function Keys

Answer 3

Ctrl+c : interrupts a process
Ctrl+z: Pauses a process
fg: Resumes a pauses process

Question 4

How to graphically display folder and file structures

Answer 4

Use the tree command

Question 5

command helps us find file in the linux file system.

It is very efficient and fast as it uses indexing databases.

Answer 5

locate

Question 6

How to update the indexed database manually?

Answer 6

sudo updatedb

Question 7

What are the Linux file permissions?

Answer 7

■ R for read
■ W for write
■ X for executable

Question 8

What is chmod used for?

Answer 8

To change file permission
Syntax: chmod [permissions] [file]
use either the alphabets or bits to assign permissions

Question 9

What command is used to change the ownership of a file?

Answer 9

chown

Syntax : chown root [file] . Use chown root:group [file]

Question 10

What does the find command do ?

Answer 10

used to find files and doesn’t use indexed database.
take longer but gives but gives real-time outputs of the file locations. It is more robust and reliable.
ex: find path –name ″filename″

Question 11

grep

Answer 11

It uses pattern based searching.
grep [search] [directory]
grep -a : searches binary files

Question 12

What’s the linux boot process?

Answer 12

BIOS -> Boot loader (GRUB) -> initrd -> /boot

Question 13

What is stored in /boot?

Answer 13

Kernel, initial ram disk, other files needed to boot the OS

Question 14

What is is vmlinux or vmlinuz(compressed) ?

Answer 14

The linux kernel

Question 15

How to view the kernel boot messages?

Answer 15

dmesg OR /var/log/dmesg

Question 16

What are the linux runlevels?

Answer 16

0: power off
1: single user mode
2-5: normal system operations
6: reboot

Runlevels are replaced by systemd.
use systemctl command to change targets.

Question 17

What does linux use for logging?

Answer 17

syslog

Question 18

How does syslog categorizes messages?

Answer 18

By the use of:

• Facilities (the source of the message)
• Severities (Urgency categorization)

Question 19

What are the Severity types in syslog?

Answer 19

• emergency
• alert
• critical
• error
• warning
• notice
• info

Question 20

How does a syslog server process messages?

Answer 20

• syslogd
  or rsyslog
  or syslog-ng

Question 21

How to generate your own log messages?

Answer 21

Use the logger utility.

Question 22

How to automatically prune logfiles and keep your disk from filling with old messages?

Answer 22

Use the logrotate utility

Question 23

What are the two types of disk partitions?

Answer 23

MBR - Master Boot Record (Max 2TB)

GPT - GUID Partition Table

Question 24

What are the three disk partition utilities ?

Answer 24

fdisk: Create and modify partitions
gdisk
parted

Question 25

What tool is used to create file systems?

Answer 25

mkfs | ex: mkfs -t ext4 /dev/sdb2

Question 26

What is the df command for ?

Answer 26

To show how much disk is in use?

Question 27

What is the umount command for?

Answer 27

To disconnect a disk from the linux system. | ex: umount /dev/sdb2

Question 28

What is /etc/fstab used for?

Answer 28

To control what file system gets mounted where and in what order.

Question 29

How to view the labels and UUIDs of storage devices attached to the system?

Answer 29

Use: lsblk -f blkid

Question 30

How to create disk lables?

Answer 30

e2lable

Question 31

Where are account information stored?

Answer 31

/etc/passwd and /etc/shadow

Question 32

What attributes accounts have?

Answer 32

``` username UID GID Comment home directory shell ```

Question 33

How to Create, Delete, Modify accounts?

Answer 33

useradd userdel usermod

Question 34

Where is the group information stored?

Answer 34

/etc/group

Question 35

How to create, delete, modify a group?

Answer 35

groupadd groupdel groupmod

Question 36

How to view group memberships for accounts?

Answer 36

groups {account} groups ex: groups bob

Question 37

Class A first octet?

Answer 37

1 .0 > 127.0

Question 38

Class B

Answer 38

128.0 > 191.255 | Hosts: 65, 536

Question 39

Class C

Answer 39

192.0.0 > 233..255.255 | Hosts: 255

Question 40

What is the Private Address Space?

Answer 40

10. 0.0.0 - 10.255.255.255 172. 16.0.0 - 172.31.255.255 192. 168.0.0 - 192.168.255.255

Question 41

How to display the FQDN?

Answer 41

hostname -f

Question 42

How to display the hostname?

Answer 42

hostname or uname -n

Question 43

To lookup or resolve an IP or a DNS name?

Answer 43

Use : host or dig

Question 44

What does the /etc/hosts file contain?

Answer 44

A list of IP addresses and host names

Question 45

what does /etc/nsswitch.conf file do?

Answer 45

Controls the order in which lookups are performed. | ex: DNS or hosts file first.

Question 46

How to define if network interfaces use DHCP or Static?

Answer 46

Red Hat: /etc/sysconfig/network-scripts/ifcfg-Device Ubuntu: /etc/network/interfaces

Question 47

Shell environment configuration is located?

Answer 47

/etc/profile

Question 48

How to manually assign IP addresses?

Answer 48

Use ip or ifconfig | ifup/ifdown : to bring up or down an interface

Question 49

How to see the process running on a system?

Answer 49

ps

Question 50

How to display a list of jobs?

Answer 50

jobs

Question 51

How to kill a process or job?

Answer 51

kill PID/job ID

Question 52

Schedule a task?

Answer 52

cron

Question 53

How to ■ Make changes to stream of texts? ■ Search and replace text?

Answer 53

sed Ex: s/old/new/g interpret as string///replace all strings found.

Question 54

What is sort used for ?

Answer 54

To organize that we get for an output

Question 55

What is uniq used for?

Answer 55

To remove redundant results Usually used with The -c switch is used to count the words

Question 56

What is used for? | ListOpenFiles

Answer 56

Shows files that are currently being accessed Display a lot of system usage Can be used to find files that shouldn't be open

Question 57

How to create hidden files in linux?

Answer 57

start the file name with a ( . )

Question 58

How to create a batch of new users?

Answer 58

Use the command A batch mode for creating new users.