How to Use SSH Remote Connection to Server?

Recently saw the relevant commands for remote connection to the server, let's summarize the relevant content of SSH first

SSH connection process
Open SSH service
SSH commands
Server public key record file
Make an ssh user who can log in immediately without a password
SSH connection process

Step 1: The server opens the SSH service for the first time, and <br> will automatically create the /etc/ssh/ssh_host* public key file and private key file
<br>The second step: the client actively links to the SSH server
<br>Step 3: The server transmits its public key file to the client (clear text)
<br>Step 4: If the client connects to the server for the first time

The difference will be compared if it has been recorded. Reject if different.
If you accept this public key, then calculate your own public and private keys for this link

Step 5: The client sends its public key to the server

Step 6: Start two-way encryption and decryption

Open SSH service
`/etc/init.d/ssh restart`

SSH commands
`ssh [-f] [-o] [-p] account@IP [command]`
|Parameter|Meaning|
|:||
|-f|Do not log in, execute the "back command" directly on the remote server|
|-o|Additional parameters|
|-p|Use other port, default 22|
Examples:
A: Log in to the account msdoge of the remote host 192.168.0.115
`1, ssh msdoge@192.168.0.155
2. Enter the password`

B: Turn off 192.168.0.115 without logging in
`1, ssh -f msdoge@192.168.0.115 shutdown -h now
 2. Enter the password`

Server public key record file
When ssh connects to the fourth step, the client compares the data of the server's public key in the local ~/.ssh/known_hosts file with the server's public key for this connection. If there is a difference, it will refuse the connection to prevent connecting to the disguised server.

If SSH is reinstalled on the server and the /etc/ssh/ssh_host* public key file is recalculated in the first step, the public key may be different from the previous one, but the IP is the same. At this time, the client will avoid connecting Go to the disguised server and refuse the connection.

At this time, the client can delete the corresponding server public key data by vim to ~/.ssh/knoen_hosts

Make an ssh user who can log in immediately without a password
Step 1: Use the ssh-keygen command to make a public key private key file

ssh-keygen [-t rsa|dsa]
-t: select the password algorithm, default rsa

Step 2: Upload the generated public key file to the server

scp ~/.ssh/id_rsa.pub msdoge@192.168.0.115:~

Step 3: Configure on the server

#Log in to the remote host and enter the password
ssh msdoge@192.168.0.115

#According to the configuration file /etc/ssh/sshd_config
#AuthorizedKeysFile settings
#Place the public key file in ~/.ssh/authorized_keys

#If the server is not used for the first time, you need to build it yourself
#Permission must be 700!
mkdir ~/.ssh
chmod 700 ~/.ssh

cat ~/id_rsa.pub >> ~/.ssh/authorized_keys
#authorized_keys permissions must be 644!
chmod 644 ~/.ssh/authorized_keys