sshkey usage

A tutorial about how to add ssh key in server and how to use it connect to the server in client

1.Generate a pair of keys

ssh-keygen

Then,It will prompt you to write some information 1.where this pair of keys will be saved 2.Enter passphrase--empty for no passphrase.If you have written this,you need to fill in the password everytime when you connect to the server(Although you have the private key)

At this,you have 2 files(id_rsa.pub and id_rsa) in ~/.ssh/ diretory

⚠️ Set permission 0600 to file ~/.ssh/authorized_keys

2.Upload the public key to the server

You should know:In client,Its name is ssh;In Server,Its name is sshd!!!!!

You need to upload the id_rsa.pub and rename it to 'authorized_keys' That is means the content in id_rsa.pub should be in ~/.ssh/authorized_keys at last.

multi-authorized_keys

0.You could add many public keys in a server.

1.The file ~/.ssh/authorized_keys could include many keys.

method:everyline include the content of a public key,That is OK!(Warning:This method is not useful for private key file,such as id_rsa.You should use ssh/scp -i [file_name] to assign private key to connect when you have two or more private keys!)

Port setting difference between ssh and scp

ssh: use -p to assign port

scp: use -P to assign port

Use in Termux(Android for Linux emulator)

Permissions of the private key must be 400,either the ssh will ignore it for safe when you use ssh to servers

Use ~/.ssh/config to simplify your connection operation

Template:

	Host <shortAlias>
		HostName < IP | FQDN >
		Port <portNumber>
		User <loginUser>