How to Use SSH Commands wihout Enter Password

To copy files from local computer to a server with SSH,

scp test.txt testuser@remote.host.com:/tmp/

By this command I can copy test.txt file from current local directory to /tmp/ folder on remote host. 

Or to download some files from server to the local computer:

scp testuser@remote.host.com:/tmp/*.txt ~/Downloads

Or to create a directory on remote server:

ssh testuser@remote.host.com "mkdir /home/testuser/newdir"

On every command, when the connection was established, I am asked the password for testuser

It's a pitty that the password can't pass as a command parameter. So when executing more and more scp commands, each time password will asked.

This annoying problem also restrict me to automatize copy files between local computer and remote server.

So I searched to get over this problem. The solution is using public/private keys for authentication. Here are the steps.

Step 1. On the local computer, create a new private/public keys pair by following command:

$ ssh-keygen -t rsa

This will create two files in your (hidden) ~/.ssh directory.
Private key: id_rsa
Public key: id_rsa.pub

If you don't want to be asked for a password each time you connect, just press enter when asked for a password when creating the key pair.

Step 2. After generating private/public keys pair, now copy the public key id_rsa.pub to the server and rename it as authorized_keys and put it into ~/.ssh/ folder. 
So that the location of the public key should be  as ~/.ssh/authorized_keys 
(In this case the full path is /home/testuser/.ssh/authorized_keys)

To do this automatically:

ssh-copy-id user@server

If server port other than 22, it can be specified as follow:

ssh-copy-id "user@server -p 12345"

That's it. Now we should connect from local computer without asking for password.
Also we can transfer files between local-server without password.

For Better SSH Security

Disable root Login:

Edit /etc/ssh/sshd_config and set the following line

PermitRootLogin no

Allow Only Specified Users:

Open /etc/ssh/sshd_config with text editor and allow specific users to be able to login using SSH.

AllowUsers testuser user2 user3

After changes, restart the SSH service:

service ssh restart

Reference:

Share Share Editor: editor | Posted: 2012/12/18 | Views: 4368

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