SSH passwordless login and sudo user

Password less SSH login to another server can be very useful when you want to configure a remote backup server or when migrating servers. For enabling this you need to have openSSH installed on the server. Here is a tutorial on how to configure password less SSH login to server ‘mars’ from server ‘earth’

1. Login to earth as root.

2. Run the command ssh-keygen -t rsa
If the key already exists you can either go to step 3 or you can generate a new key by overwriting existing key (see image). It would be better to overwrite the existing key if you did not generate it.

3. Change directory to /root/.ssh/

root@earth:~# cd /root/.ssh/
root@earth:~/.ssh#

4. Copy the contents of the file id_rsa.pub to the directory /root/.ssh/authorized_keys
scp -P id_rsa.pub root@mars_server_IP:/root/.ssh/authorized_keys

5. You will be able to login to the remote server ‘mars’ by typing ssh root@mars_server_IP -p without password now

Creating Sudo user to login as root:

1. Login to server as root

2. Create a new user by using the command

root@server:~# useradd user

3. Assign a password for the user by using the command
root@server:~# passwd user

4. Add the user to the admin group in /etc/groups

root@server:~# vi /etc/groups
admin:x:121:user1,user2

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