Edit your config file sudo nano /etc/ssh/sshd_config
(or use vim, kwrite, whatever editor instead of nano)
Add this line AllowUsers otheruser
and possibly DenyUsers myuser
Save and close sshd_config file
Reboot your machine or restart SSH service sudo systemctl restart sshd
AllowUsers
This keyword can be followed by a list of user name patterns, separated by spaces.If specified, login is allowed only for user names that match one of the patterns.*' and
?' can be used as wildcards in the patterns.Only user names are valid; a numerical user ID is not recognized.By default, login is allowed for all users.If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts.
DenyUsers
This keyword can be followed by a list of user name patterns, separated by spaces.Login is disallowed for user names that match one of the patterns.*' and
?' can be used as wildcards in the patterns.Only user names are valid; a numerical user ID is not recognized.By default, login is allowed for all users. If the pattern takes the form USER@HOST then USER and HOST are separately checked, restricting logins to particular users from particular hosts.