In order create user account linux server with ssh keypair for login server with putty tool.
Follow the below steps:
Step 1: Login to Linux server where you want to create user account.
Step 2: create user accouunt by using below command
useradd -m -s /bin/bash <user name>
Step 3: To check whether user account created
Step 4: Switch into created user
su - <user name>
Step 5: create .ssh directory under user's home folder
/home/<user name>/ mkdir .ssh
Step 6: change the .ssh directory permission and navigate to that directory
chmod 700 .ssh
step 7: under the user's home folder in .ssh directory. need to generate keypair
step 8: It will generate two files
id_rsa ----> this private key of user
id_rsa.pub ----> this is the public key user
step 9: create a file called authorized_keys and copy the content of from id_rsa to authorized_keys file
cp id_rsa.pub authorized_keys
step 10: change the permission of authorized_keys
chmod 600 authorized_keys
step 11: copy the id_rsa file content to vdc server and open and notepate paste the content and save the file with pem extentio "filename.pem"
step 12: open puttygen tool and load the pem file and save as the private key. it will prompting to save your file. now your pem file is converted into ppk file
step 13: try to login with this ppk file for specified linux server