SSH from Windows to Linux without a password and without Putty

SSH into Linux from Windows is possible through the Cygwin SSH client, but logging in without a password can be a little tricky. It look me a little trial and error to get it working, so here are my steps:

Open a command prompt and login as root or another user with root privileges.

Create the user, if you haven't already and set the password (I'm using techn, change it to whatever username you want).

useradd techn
passwd techn

Give this user root privileges for now. You can take them away later, if needed.

usermod -G root techn

Create the .ssh directory for techn

mkdir /home/techn/.ssh

Give ownership of the .ssh directory to techn

 chown techn:root .ssh

Assign permissions for this directory to techn

chmod 700 /home/techn/.ssh

Exit the ssh session

exit

From the windows command prompt, run ssh-keygen

ssh-keygen

Choose the defaults, use a password if you want.

Now, the public key (id_rsa.pub) needs to be transferred to the linux server. If you were doing this from linux, you could use the ssh-copy-id script, but this doesn't work from the windows command prompt. So, we use this instead:

cat .ssh/id_rsa.pub | ssh techn@LINUX-HOST "cat >> ~/.ssh/authorized_keys"

It should ask you for techn's password. Supply it and if you receive no error messages, you've succeeded in sending the public key to your linux host. This only works if you have root privileges, sudo doesn't seem to work here. Now you should be able to login without a password:

ssh techn@LINUX-HOST

The following instructions only apply if you want to set up techn with sudo.

On the linux server, install sudo

apt-get install sudo

Log out and log back in as root and remove techn from the root group and put them in the the sudo group

usermod -G sudo techn

Create a text file called 'techn' in your home directory and paste this inside it:

techn ALL=(ALL) ALL

Set the right permissions for this file

chmod 440 techn

Move the file to sudoers.d directory

mv techn /etc/sudoers.d

Do NOT try create this file directly in the sudoers.d directory. You will run in to all kinds of trouble.