SSH

Question 1

SSH config file

Answer 1

~/.ssh/config

Question 2

~/.ssh/config

Answer 2

Must be readable and writable only by the user

Question 3

Make ~/.ssh/config readable and writeable

Answer 3

chmod 600 ~/.ssh/config

Question 4

SSH client reads its configuration in the following precedence order:

Answer 4

Options specified from the command line.
Options defined in the ~/.ssh/config
Options defined in the /etc/ssh/ssh_config

Question 5

SSH config files: /etc/ssh/ssh_config

Answer 5

/etc/ssh/ssh_config

~/.ssh/config

Question 6

ssh port:

Answer 6

Port 22

Question 7

Change ssh default port:

Answer 7

1. # sudo vim /etc/ssh/sshd_config
2. Search for line with Port 22, remove the hash # and enter the new SSH port number.
   Port 5522
3. # sudo systemctl restart sshd
4. # ss -an | grep 5522

Question 8

Update ssh allowing login without password /passphrase

Answer 8

# ssh-agent bash 
# ssh-add ~/.ssh/id_rsa

Question 9

Add keygen at 4096

Answer 9

ssh-keygen -t rsa -b 4096

Question 10

Create ssh rsa key

Answer 10

ssh-keygen -t rsa

Question 11

Create and copy ssh key

Answer 11

1. ssh-keygen -t rsa -b 4096
2. ssh-copy-id user@172.980.34.200
3. ssh user@IP

Question 12

Disable rootlogin

Answer 12

Step 1: # vi sshd_config

Step 2: Find: PermitRootLogin yes
change to: # PermitRootLogin

Step 3# systemctl restart sshd