Linux Maintenance

Question 1

Search system for root SUID bit set

Answer 1

find / -user root -perm 4000
Or -perm -u+s

Question 2

How to view all processes Inc background

Answer 2

ps aux

Question 3

Which command lets you view process by most resources used with updates every 3 seconds

Answer 3

top

NB press ‘H’ while running for interactive commands

Question 4

3 ways to change priority of process

Answer 4

nice -n <-20..19> PSPATH

renice <-20..19> PSID

Press ‘R’ while running ‘top’

Question 5

What is the absolute kill signal

Answer 5

kill -9 PID

Question 6

What is the kill hang up signal

Answer 6

kill -1 PID

Question 7

What is the kill interrupt signal

Answer 7

kill -2 PID

Question 8

What is the kill termination (and default) signal

Answer 8

kill -15 PID

Question 9

What is the kill with core dump signal saved to working directory and called core)

Answer 9

kill -3 PID

Question 10

How to start a task/process and have it run in the background

Answer 10

PS/CMD &

Question 11

How do you bring a process back to the foreground

Answer 11

fg PSID

Question 12

How do you schedule a process

Answer 12

at <7.20pm> <08/08/1888>
at NOW + <5 minutes/hours>

Question 13

How do you view default environment variables

Answer 13

env

Question 14

How do you view ALL variables (env,shell,usr,aliases)

Answer 14

set (| more)

Question 15

How do you make a variable change permanent

Answer 15

export VARIABLE

(after changing the VARIABLE)

Question 16

How do you view your PATH

Answer 16

echo $PATH

Question 17

How do you view the content of a variable

Answer 17

Use a $
Eg echo $VARIABLE

Question 18

How do you add to the PATH

Answer 18

PATH=$PATH:/DIR

Question 19

How do you archive a group of similar files

Answer 19

tar -cvf OUTPUT.tar FILE FILE

Question 20

How do you view contents of a .tar

Answer 20

tar -tvf FILE

Question 21

How do you extract a .tar

Answer 21

tar -xvf FILE

Question 22

How do you use gzip

Answer 22

gzip FILE.*

Creates a .gz extension

gunzip FILE.*

Question 23

How do you use ‘compress’

Answer 23

compress FILE.*

Creates a .Z extension

uncompress FILE.*

Question 24

How do you make an exact copy of a file/dir

Answer 24

dd if=<file/dir> of=<file/dir >

Question 25

What are two common options for dd

Answer 25

bs=BLOCK IN BYTES

conv=noerror

Question 26

How do you produce a list of ‘block’ devices

Answer 26

lsblk

Question 27

How do you view a full list of (drive) devices?

Answer 27

sudo fdisk -l

Question 28

How would you mount a second hard drive

Answer 28

mount /dev/sdb1 /mnt

Question 29

How would you mount a flash drive

Answer 29

mount /dev/sdc1 /media

Question 30

Where are files systems that are mounted at boot time stored?

Answer 30

/etc/fstab

(Short for filesystem table)

Question 31

How would you unmount a hard drive

Answer 31

umount /dev/sdb1

Question 32

What command to view basic information and free space on mounted discs/devices

Answer 32

df /PATH

Or no path needed to view all

Question 33

How would you check for errors in the filesystem?

Answer 33

fsck

unmount first
-p automatically repairs

Question 34

How do you see all the WAPs in range?

Answer 34

iwlist INTERFACE scan

eg iwlist wlan0 scan

Question 35

How would you connect to an WAP

Answer 35

nmcli device wifi connect SSID password PASSWORD

Question 36

What command do you use to ‘tune’ kernel options

Answer 36

sysctl

Question 37

How do you make sysctl changes (carefully) permanent

Answer 37

Edit /etc/sysctl.conf

Question 38

How do you find out more information about your OS

Answer 38

uname -a

Question 39

ps options

Answer 39

-a of all users
-e all processes running on sys
-t all processes run by terminal
-u username and start time
-x run by current user