The cloud images bundled by various Linux distributions have password authentication disabled by default for security reasons. The only possible way to login to an instance launched using one of these images is by specifying a security key during boot and using the key to ssh. Often you would want to enable password authentication like say to login through VNC console for debugging. This post will take you through the steps involved for enabling password authentication.
login using the pem key
ssh -i key_pair-name.pem user@floatingip
Create and attach a key-pair before you launch any instance.
On an OpenStack setup you can create key-pairs under:
Project-> Compute-> Key Pairs.
As soon as you create one you would be prompted to download and save it to your disk. Later you can use the
key-pair-name.pem file to ssh into your instance. Depending on the distribution of your image you have a default user to login as. For example on an Ubuntu image the default user is
ubuntu. For Centos, the default user is
centos. You can replace the floatingip with the FloatingIP address of your instance.
Elevate your privileges
sudo su -
Create a new user
useradd -G sudo -U -m username
username with the name of your choice. The above command adds the newly created user to the ‘sudo’ group. This is necessary because in most cloud images all members of ‘sudo’ group have password-less ‘sudo’ access. Without this you might not be able to elevate your privileges after login. On certain systems that do not have ‘sudo’ group ‘admin’ group will have ‘sudo’ access and you can replace ‘sudo’ with ‘admin’ in the above command.
Set the password for the new user
Enter the new password for the user and confirm the same.
/etc/ssh/sshd_config and set the following parameters:
ChallengeResponseAuthentication yes PasswordAuthentication yes
Additionally if you want to enable root login you can set the below param too:
Exit and save the file.
Then set a password for root user too:
And enter the new password for root user and confirm the same.
Restart SSH Service
For Ubuntu Servers:
service ssh restart
For Centos Servers:
service sshd restart