SSH

Question 1

What is the purpose of SSH (Secure Shell)?

Answer 1

used to connect the remote server and execute commands remotely on a remote server. remote connection and remote execution.

Question 2

Which package is required for SSH installation?

Answer 2

rpm -qa | grep openssh* will give
openssh-clients and openssh-server

Question 3

How can you verify whether the necessary package for SSH is installed on your machine or not?

Answer 3

yum list installed | grep openssh* or rpm -qa | grep openssh*

Question 4

What is the configuration file for the SSH server?

Answer 4

/etc/ssh/sshd_config

Question 5

Which configuration file is associated with the SSH client?

Answer 5

/etc/ssh/ssh_config is the
configuration file for the client.

Question 6

What steps can you take to ensure SSH remains persistent, active, and running?

Answer 6

systemctl enable sshd –now will start and enable sshd service

Question 7

How would you confirm whether the SSH server's port (sshd) is actively listening or not?

Answer 7

netstat -tunap | grep 22 or netstat -tunap | grep sshd will show listen. lsof -i :22

Question 8

What method would you use to display a list of all ESTABLISHED connections?

Answer 8

netstat -tunap | grep -i establish

Question 9

How can you retrieve a list of security logs relevant to SSH?

Answer 9

grep -i sshd
/var/log/secure

Question 10

How would you list all system logs pertaining to SSH?

Answer 10

grep -i sshd /var/log/messages

Question 11

Which hidden directory contains files related to SSH authentication for a particular
user?

Answer 11

users home directory has a directory called .ssh

Question 12

Name the file created during SSH authentication for any server containing fingerprints.

Answer 12

.ssh/known_hosts has the hostname, ip address and fingerprints. Fingerprints are recognition, unique.

Question 13

How can you establish an SSH connection from server A to server B?

Answer 13

ssh
root@ipaddress or ssh user@ipaddress.

Question 14

How can you execute a command from server A on server B without switching to
server B?

Answer 14

ssh user@ipaddress “command syntax” for example ssh user@ipaddress “touch file1”

Question 15

How can we secure the system by disabling direct root logins through SSH?

Answer 15

vi into
/etc/ssh/sshd_config and edit PermitRootLogin from “yes” to “no”.

Question 16

What are the various tools you have utilized for remote access and data transfer?

Answer 16

scp,
ssh, rsync, ftp/vsftp.

Question 17

You have received a support ticket indicating that a client is experiencing
unresponsiveness from the server and is unable to establish an SSH connection. How would
you approach troubleshooting this issue?

Answer 17

a. check ssh package – rpm -qa |grep openssh* or yum list installed | grep openssh*.
b. Check service status with systemctl status sshd.
c. Check if port is listening netstat -tunap | grep ssh.
d. Check TCP wrapper in /etc/hosts.deny.

Question 18

In a scenario with two hosts, A and B, a user requests assistance in setting up
passwordless SSH authentication. Where would the associated keys be stored?

Answer 18

in the users
home directory under .ssh

Question 19

If an attempt to SSH as the root user with the correct password proves unsuccessful, how would you go about diagnosing and resolving the problem?

Answer 19

check the /etc/ssh/sshd_config file for PermitRootLogin settings and permission.

Question 20

What is the significance of utilizing SSH key-based authentication?

Answer 20

we can access without password. we can execute commands without password, secure access, do not need to share root password

Question 21

Could you explain the process of modifying the SSHD port, and outline the steps to
allow this new port through the firewalld?

Answer 21

a. vi and change port in /etc/ssh/sshd_config.
b. Add port number to the firewall, firewall-cmd –add-port=1234/tcp –permanent.
c. firewall-cmd –reload.
d. setenforce 0.
e. systemctl reload/restart service.

Question 22

In the event that a service (specifically SSHD) fails to initiate, could you enumerate
some of the preliminary troubleshooting measures you might implement?

Answer 22

package, service,
port, tcp wrapper. check credentials for specific user. keys may be expired.

Question 23

What type of information is typically stored within the known_hosts file?

Answer 23

hostname, ip
address and fingerprints