Linux - 免密码登录
ssh-keygen -t rsa -P ''
cat ~/.ssh/id_rsa.pub | ssh email@example.com "cat >> ~/.ssh/authorized_keys"
SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. While a password can eventually be cracked with a brute force attack, SSH keys are nearly impossible to decipher by brute force alone. Generating a key pair provides you with two long string of characters: a public and a private key. You can place the public key on any server, and then unlock it by connecting to it with a client that already has the private key. When the two match up, the system unlocks without the need for a password. You can increase security even more by protecting the private key with a passphrase.
The first step is to create the key pair on the client machine (there is a good chance that this will just be your computer):
ssh-keygen -t rsa
Once you have entered the Gen Key command, you will get a few more questions:
Enter file in which to save the key (/home/demo/.ssh/id_rsa):
You can press enter here, saving the file to the user home (in this case, my example user is called demo).
Enter passphrase (empty for no passphrase):
It’s up to you whether you want to use a passphrase. Entering a passphrase does have its benefits: the security of a key, no matter how encrypted, still depends on the fact that it is not visible to anyone else. Should a passphrase-protected private key fall into an unauthorized users possession, they will be unable to log in to its associated accounts until they figure out the passphrase, buying the hacked user some extra time. The only downside, of course, to having a passphrase, is then having to type it in each time you use the Key Pair.
The entire key generation process looks like this:
ssh-keygen -t rsa
Once the key pair is generated, it’s time to place the public key on the virtual server that we want to use.
You can copy the public key into the new machine’s authorized_keys file with the ssh-copy-id command. Make sure to replace the example username and IP address below.
Alternatively, you can paste in the keys using SSH:
cat ~/.ssh/id_rsa.pub | ssh firstname.lastname@example.org "mkdir -p ~/.ssh && cat >> ~/.ssh/authorized_keys"
No matter which command you chose, you should see something like:
The authenticity of host '22.214.171.124 (126.96.36.199)' can't be established.
Now you can go ahead and log into email@example.com and you will not be prompted for a password. However, if you set a passphrase, you will be asked to enter the passphrase at that time (and whenever else you log in in the future).
Once you have copied your SSH keys unto your server and ensured that you can log in with the SSH keys alone, you can go ahead and restrict the root login to only be permitted via SSH keys.
In order to do this, open up the SSH config file:
sudo nano /etc/ssh/sshd_config
Within that file, find the line that includes PermitRootLogin and modify it to ensure that users can only connect with their SSH key:
Put the changes into effect:
The Digital Ocean control panel allows you to add public keys to your new droplets when they’re created. You can generate the SSH Key in a convenient location, such as the computer, and then upload the public key to the SSH key section.
Then, when you create a new VPS, you can choose to include that public key on the server. No root password will be emailed to you and you can log in to your new virtual private server from your chosen client. If you created a passphrase, you will be prompted to enter that upon login.
By Etel Sverdlov