Part 1 : SSH key without a password
To set up a passwordless SSH connection for the root user you need to have root access on the server. Easiest method is to temporarily allow root to log in over ssh via password. One way or another you need root access on the server to do this. If you do not have root access on the server, contact the server administrator for help.
On the client (where you ssh FROM)
First make a ssh key with no password. I highly suggest you give it a name rather then using the default
ssh-keygen -f foo
The -f option specifies a file name, foo is an example, use whatever name you wish.
When you are prompted for a password, just hit the enter key and you will generate a key with no password.
Next you need to transfer the key to the server. Easiest method is to use ssh-copy-id
. To do this you must temporarily allow root to ssh into the server.
On the server (where you ssh TO)
edit /etc/ssh/sshd_config
sudo nano /etc/ssh/sshd_config
Make sure you allow root to log in with the following syntax
PasswordAuthentication yes
PermitRootLogin yes
Restart the server
sudo service ssh restart
Set a root password, use a strong one
sudo passwd
On the client :
From the client, Transfer the key to the server
ssh-copy-id -i ~/.ssh/foo root@server
change "foo" the the name of your key and enter your server root password when asked.
Test the key
ssh -i ~/.ssh/foo root@server
Assuming it works, unset a root password and disable password login.
On the server :
sudo passwd -l root
Edit /etc/ssh/sshd_config
sudo nano `/etc/ssh/sshd_config`
Change the following :
PasswordAuthentication no
PermitRootLogin without-password
Restart the server
sudo service ssh restart
On the client (Test):
You should now be able to ssh in with your key without a password and you should not be able to ssh in as any user without a key.
ssh -i ~/.ssh/foo root@server
Part 2 : Running commands via sudo without entering a password
You configure sudo to allow you to run commands without a password.
This is answered here in two places:
Of the two, I suggest allowing as few commands as possible (first answer) rather then all commands (second answer).