SSH

Question 1

Where you will look into if user can’t SSH and can’t log into the system?

Answer 1

/var/log/secure

Question 2

Why do you need an ssh-key based entry?

Answer 2

Key-based authentication provides two primary benefits:
*helps mitigate brute-force password attacks against SSH.
*prevents administrators from being required to manually type password in automated process such as scripts or sensible.

Question 3

How to ensure SSH is persistent, and running/active , how do you check if SHHD is listening or not?

Answer 3

• systemctl enable sshd for persistent
  *systemctl is-enabled sshd
  *systemctl is-active
  *Systemctl status sshd
• netstat -tunap | grep sshd of is listing or not

Question 4

How do you change the port for sshd, and how would you allow the port in firewalld?

Answer 4

• vi/etc/ssh/ssh_config
  *firewall-cmd –add-port=3456/tcp –permanent
  *firewall-cmd –add-service=ssh/tcp –permanent

Question 5

What command you use to list all the security/system logs that pertain to ssh?

Answer 5

For security
/var/log/secure
For system logs
var/log/messages | grep ssh

Question 6

How can we disabled direct root login on to the system by using SSH?

Answer 6

*vi /etc/ssh/sshd_config
*permitroot login on
Systemctl restart sshd

Question 7

Trying to ssh as root and put in correct root password and it’s not working; how would you troubleshoot that?

Answer 7

Check if the root login is enabled
Grep permit /etc/ssh/sshd_config

Question 8

A client’s is asking server is responding. He can’t ssh, what you will do to fix it?

Answer 8

First thing is to identify where the problem lies . If it’s the client or the host.
Taking in consideration that both of us we are connected.
*check if sshd service is running
*check systemctl sshd status
*port is listening
*firewalld is permitting

Question 9

A service sshd fails to start. What are some of the troubleshooting steps you’d take?

Answer 9

Systemctl status sshd
Jounalctl -u sshd
Grep sshd /var/log/messages
Check the configuration file
/etc/ssh/sshd_config for any errors
Check if fiwerewall permits
Port is allow
Host ip address is allowed

Question 10

How will you list all the ESTABLISHED connections?

Answer 10

netstat -tunap | grep ESTABLISHED

Question 11

How do you change the port for sshd, and how would you allow that port in firewalld?

Answer 11

firewall-cmd –add-port=80/tcp –permanent
firewall-cmd –reload

Question 12

how do you list kernel logs /boot up logs?

Answer 12

cat /var/log/dmesg