linux

Question 1

command to list out all the files or directories available in a directory

Answer 1

ls

Question 2

This command lists the account name associated with the current login.

Answer 2

whoami

Question 3

Sometime you might be interested to know who is logged in to the computer at the same time.

There are three commands available to get you this information, based on how much you wish to know about the other users:

Answer 3

users, who, w

Question 4

command to get a count of the total number of lines, words, and characters contained in a file

Answer 4

wc

$ wc filename
2 19 103 filename
$

Question 5

display content of a file and the line numbers

Answer 5

cat -n

cat -b (this will not count numbers of empty lines)

$ cat -b filename
1 This is unix file….I created it for the first time…..
2 I’m going to save this content in this file.
$

Question 6

command to make a copy of a file

Answer 6

cp

$ cp source_file destination_file

Question 7

command to change the name of a file

Answer 7

mv

$ mv old_file new_file

Question 8

command to delete a file

Answer 8

rm

$ rm filename

Question 9

formatted directory listing with hidden files

Answer 9

ls -al or ls -la

Question 10

change to a directory

Answer 10

cd

Question 11

show current directory

Answer 11

pwd

Question 12

create a directory

Answer 12

mkdir

Question 13

output the contents of a file as it grows

Answer 13

tail -f file

Question 14

show kernal config

Answer 14

uname -a

Question 15

show this months calendar

Answer 15

cal

Question 16

show current date/time

Answer 16

date

Question 17

show uptime

Answer 17

uptime

Question 18

cpu info

Answer 18

cat /proc/cpuinfo

Question 19

memory info

Answer 19

cat /proc/meminfo

Question 20

show disk usage

Answer 20

df

Question 21

show directory space usage

Answer 21

du

and du -sh for human readable version

Question 22

show memory and swap usage

Answer 22

free

Question 23

show possible locations of app

Answer 23

whereis app

Question 24

search for a pattern in files

Answer 24

grep [pattern] files
grep -r pattern dir = search recursively for pattern in dir
command | grep pattern = search for the pattern in the output of the command

Question 25

find all instances of file

Answer 25

locate $locate file

Question 26

halts current command

Answer 26

ctrl + c

Question 27

stops current command

Answer 27

ctrl + z

Question 28

brings most recent job to foreground

Answer 28

fg

Question 29

lists stopped/bacgkround jobs, resume stopped job in the background

Answer 29

bg

Question 30

log out of current session

Answer 30

ctrl + d

Question 31

erases one word in current line

Answer 31

ctrl + w

Question 32

erases whole line

Answer 32

ctrl + u

Question 33

reverse lookup of previous commands

Answer 33

ctrl + r

Question 34

list of commands used

Answer 34

history

Question 35

repeat last command as root

Answer 35

!!

Question 36

log out of current session

Answer 36

exit

Question 37

brings job n to foreground

Answer 37

fg n

Question 38

displays the details of the active user e.g. uid, gid, and groups

Answer 38

id

Question 39

shows the last logins in the system

Answer 39

last

Question 40

adds the group 'admin'

Answer 40

groupadd "admin"

Question 41

adds the user sam

Answer 41

adduser "sam"

Question 42

delets user sam

Answer 42

userdel "sam"

Question 43

forcefully removes a file

Answer 43

rm -f filename

Question 44

removes a directory recursively

Answer 44

rm -r directory_name

Question 45

encripts a file

Answer 45

gpg -c file_name

Question 46

decrypts a file

Answer 46

gpg file_name.gpg

Question 47

executes commands from standard input

Answer 47

xargs

Question 48

lists files that are open by processes

Answer 48

lsof

Question 49

find firefox process ID

Answer 49

pgrep firefox

Question 50

visualizing processes in tree model

Answer 50

pstree

Question 51

kills/terminates all processes named proc

Answer 51

killall proc

Question 52

terminates process with a given pid

Answer 52

kill pid

Question 53

displays all running processes

Answer 53

top

Question 54

displays memory map of processes

Answer 54

pmap

Question 55

searches for the id of the process "telnet"

Answer 55

ps aux | grep "telnet"

Question 56

sts rwx for owner, rw for group and everyone

Answer 56

chmod 766

Question 57

sets rwx to owner and r_x to group and everyone

Answer 57

chmod 755

Question 58

sets rwx permissions to owner, group, and everyone (everyone else who has access to the server)

Answer 58

chmod 777

Question 59

change owner and group owner of the file

Answer 59

chown owner-user: owner-group file_name

Question 60

displays ip addresses and all the network interfaces

Answer 60

ip addr show

Question 61

displays ip addresses of all network interfaces

Answer 61

ifconfig

Question 62

retrieves DNS information about a domain

Answer 62

dig domain

Question 63

performs refverse lookup on a domain

Answer 63

dig -x host

Question 64

performs an ip lookup for the domain name

Answer 64

host google.com

Question 65

displays local ip address

Answer 65

hostname -i

Question 66

downloads a file from an online source

Answer 66

wget file_name

Question 67

displays all active listening ports

Answer 67

netstat -pnltu

Question 68

creates archive file called 'home.tar' from file 'home'

Answer 68

tar -cf home.tar home

Question 69

extract archive file 'files.tar'

Answer 69

tar -xf files.tar

Question 70

creates gzipped tar archive file from soruce folder

Answer 70

tar -zcvf home.tar.gz source-folder

Question 71

compression a file with .gz extension

Answer 71

gzip file

Question 72

install source (compliation)

Answer 72

./configure make make install

Question 73

search for a given pattern in files

Answer 73

grep 'pattern' files

Question 74

find file names that begin with 'index' in /home folder

Answer 74

find /home/ -name "index"

Question 75

find files greater than 10000k in the home folder

Answer 75

find /home -size +1000k

Question 76

securely connect to host as user

Answer 76

ssh user@host

Question 77

securely connect to host using a specified pert

Answer 77

ssh -p port user@host

Question 78

securely connect to the system via ssh default part 22

Answer 78

ssh host

Question 79

connect to host via telnet default port 23

Answer 79

telnet host

Question 80

securely copy file.txt to server2 in /tmp directory

Answer 80

scp file.txt server2/tmp

Question 81

synchronize contents in /home/apps directory with /backup directory

Answer 81

rsync -a /home/apps /backup/

Question 82

displays free space on mounted systems

Answer 82

df -h

Question 83

displays free inodes on filesystems

Answer 83

df -i

Question 84

shows disk partitions, sizes, and types

Answer 84

fdisk -l

Question 85

displays disk usage in the current directory in a human-readable format

Answer 85

du -sh

Question 86

displays target mount point for all filesystems

Answer 86

findmnt

Question 87

mount a device

Answer 87

mount device-path mount-point

Question 88

displays bootup messages

Answer 88

dmesg

Question 89

displays information about systems hardware configureation

Answer 89

lshw

Question 90

displays block devices related information

Answer 90

lsblk

Question 91

displays pci devices in a tree-like diagram

Answer 91

lspci -tv

Question 92

displays usb devices in a tree-like diagram

Answer 92

lsusb -tv

Question 93

displays hardware information from the BIOS

Answer 93

dmidecode

Question 94

displays information about disk data

Answer 94

hdparm -i /dev/xda

Question 95

conducts a read speed test on device xda

Answer 95

hdparm -tT /dev/xda

Question 96

tests for unreadable blocks on disk

Answer 96

badblocks -s /dev/xda

Question 97

displays information about the user

Answer 97

finger username

Question 98

query and change the system clock

Answer 98

timedatectl

Question 99

shows system reboot history

Answer 99

last reboot