file and directory operations

Question 1

Assuming you are currently in a directory containing a directory named templates. What is the command to delete templates?

Answer 1

rm -R templates

Question 2

What is the command to delete recursively a directory and all its content? Give an example for a directory named files.

Answer 2

rm -R files

Question 3

What is the command to list the last 250 lines from a file called myfile.txt ?
(assuming you are currently in the directory of the file)

Answer 3

tail -n myfile.txt

Question 4

What is the command to keep listing the last 250 lines from a file called myfile.txt as it changes?
(assuming you are currently in the directory of the file)

Answer 4

tail -f -n 250 myfile.txt

Question 5

What is the command to restart a Linux server immediately?

Answer 5

reboot now

Question 6

What is the command to get all the IP addresses associated with a Linux installation?

Answer 6

ip addr show

Question 7

What is the nginx command to tell nginx to reload its config?

Answer 7

nginx -s reload

Question 8

What is the command to remove the user deploy from the wheel group on rhel?

Answer 8

gpasswd -d deploy wheel

Question 9

What is the command to see all the groups a user called deploy belongs to?

Answer 9

groups deploy

Question 10

What is the command to tell Linux to start a service at boot time? Give an example for a service called HelloWorld.

Answer 10

sudo systemctl enable HelloWorld

Question 11

If you have a service with the logical name HelloWorld what is the command to get the log entries only for that service?

Answer 11

sudo journalctl -u HelloWorld

Question 12

What is the command to get the status of a service called HelloWorld?

Answer 12

sudo systemctl status HelloWorld

Question 13

What is the command to start a service called HelloWorld?

Answer 13

sudo systemctl start HelloWord

Question 14

Are directory and filename case sensitive in Linux?

Answer 14

yes

Question 15

How do you stop a service called HelloWorld?

Answer 15

sudo systemctl stop HelloWorld

Question 16

How do you reload the services config in linux?

Answer 16

sudo systemctl daemon-reload

Question 17

What is the command to set the timezone to EST?

Answer 17

sudo timedatectl set-timezone America/Toronto

Question 18

On a rhel linux system where are the .service files located?

Answer 18

/etc/systemd/system/
For example:
/etc/systemd/system/HelloWorld.service

Question 19

What is the command to ssh in a remote server at 146.190.242.245 with the root user if you are in your home directory and your key is at .ssh/id_rsa

Answer 19

ssh -i .ssh/id_rsa root@146.190.242.245

Question 20

to confirm: where are the nginx config files located on a rhel system?

Answer 20

/etc/nginx/conf.d/
For example:
/etc/nginx/conf.d/hello.conf

Question 21

What is the curl flag to ignore a self-signed certificate?

Answer 21

curl -k http://142.112.48.65:80

Question 22

Commands to shutdown a server

Answer 22

shutdown now
or
poweroff

Question 23

How can you check if 2 files have the same content?

Answer 23

cmp -s /tmp/file1 /tmp/file2

Question 24

What is the ls command flag to ignore directory?

Answer 24

ls -d

Question 25

What is the ls command to seach for files (not directories) that starts with a?

Answer 25

ls -d a*

Question 26

What is the ls command to seach for files (not directories) that starts with a or c?

Answer 26

ls -d [ac]*

Question 27

What is the command to install firewalld in rhel?

Answer 27

dnf install firewalld

Question 28

Once you install firewalld what do you need to do first?

Answer 28

To make sure it start at boot:
systemctl enable firewalld
To start it now without rebooting:
systemctl start firewalld

Question 29

In firewalld how do you authorize your IP for everything if your IP is 142.112.48.65?

Answer 29

firewall-cmd –permanent –add-rich-rule=’rule family=”ipv4” source address=”142.112.48.65” accept’

Question 30

How do you reload firewalld after you made changes?

Answer 30

firewall-cmd –reload

Question 31

How can you see the current rules in firewalld?

Answer 31

firewall-cmd –list-all

Question 32

How can you permanently remove a service called cockpit?

Answer 32

firewall-cmd –permanent –remove-service=cockpit

Question 33

To complete: How can you test a rule to let’s say remove ssh from firewalld?

Answer 33

firewall-cmd –remove-service=ssh
(We omit the firewalld –permanent flag

Question 34

How can we reload systemctl?

Answer 34

systemctl daemon-reload

Question 35

Where do you need to put your .service file when you deploy a .net app on a rhel server?

Answer 35

/etc/systemd/system/

Question 36

Where do you put the nginx config for a .net app you deploy? Let’s say for a project called hello ? Provide the full path including the name of the file.

Answer 36

/etc/nginx/conf.d/hello.conf

Question 37

For the following command:
firewall-cmd –remove-service=cockpit
What will be the lifetime of this command?

Answer 37

The rule will be in effect immediately and until your reboot the server or do:
firewall-cmd –reload

Question 38

or the following command:
firewall-cmd –permanent –remove-service=cockpit
What will be the lifetime of this command?

Answer 38

The rule won’t be in effect immediately. It will be in effect once you run:
firewall-cmd –reload
or:
reboot the server

Question 39

How can you get the status of selinux?

Answer 39

run:
sestatus

Question 40

How can you verify a certificate with curl?

Answer 40

curl –verbose https://www.google.com
If we see the line:
* SSL certificate verify ok.
It means it’s good.

Question 41

How can you check the time from the command line in linux?

Answer 41

type:
date

Question 42

How do you chain commands?

Answer 42

Using &&

Question 43

In a rhel system how can you get the list of the last updates installed?

Answer 43

sudo dnf history list last
or
sudo dnf history list

The last flag restrict the list to the most recent updates

Question 44

In a rhel system how can you check if updates are available without upgrading the system?

Answer 44

dnf check-upgrade

Question 45

In a rhel system how do you perform an update?

Answer 45

dng upgrade