You can double check this by running the following command. # echo "AllowGroups 2g-admin" > /etc/ssh/sshd_config In this example, we are going to disable ssh access for 2g-admin group. To do so, just append the following value in /etc/ssh/sshd_config file. If you would like to allow more than one group then you have to add the groups with space in the same line. We can allow/grant the ssh access for a particular group or list of groups using the following method. How to Allow user groups to Access SSH in Linux? Mar 29 01:53:48 CentOS7 sshd: Failed password for invalid user user1 from 192.168.1.6 port 42522 ssh2 Mar 29 01:53:46 CentOS7 sshd: pam_unix(sshd:auth): authentication failure logname= uid=0 euid=0 tty=ssh ruser= rhost=192.168.1.6 user=user1 Mar 29 01:53:46 CentOS7 unix_chkpwd: password check failed for user (user1) Mar 29 01:53:42 CentOS7 sshd: input_userauth_request: invalid user user1 Output: Mar 29 01:53:42 CentOS7 sshd: User user1 from 192.168.1.6 not allowed because listed in DenyUsers So, you will be getting an error message as shown below when you are try to login. Simply open a new terminal or session and try to access the Linux system with blocked user. Just bounce the ssh service and see the magic. # cat /etc/ssh/sshd_config | grep -i denyusers # echo "DenyUsers user1" > /etc/ssh/sshd_config In this example, we are going to disable ssh access for user1. If you would like to disable more than one user then you have to add the users with space in the same line. We can block/disable the ssh access for a particular user or list of the users using the following method. How To Block Users To Access SSH In Linux? Mar 29 02:01:13 CentOS7 sshd: pam_unix(sshd:session): session opened for user user3 by (uid=0) Mar 29 02:00:43 CentOS7 sshd: Failed password for invalid user user2 from 192.168.1.6 port 42568 ssh2Īt the same time user3 is allowed to login into the system because it’s in allowed users list. Mar 29 02:00:40 CentOS7 sshd: pam_unix(sshd:auth): authentication failure logname= uid=0 euid=0 tty=ssh ruser= rhost=192.168.1.6 user=user2 Mar 29 02:00:40 CentOS7 unix_chkpwd: password check failed for user (user2) Mar 29 02:00:35 CentOS7 sshd: input_userauth_request: invalid user user2 Output: Mar 29 02:00:35 CentOS7 sshd: User user2 from 192.168.1.6 not allowed because not listed in AllowUsers For example user2 is not allowed for SSH login and will be getting an error message as shown below. Simply open a new terminal or session and try to access the Linux system with different user. We can allow/enable the ssh access for a particular user or list of the users using the following method. How to Allow a User to access SSH in Linux? These can be accomplished via traditional tools such as telnet or rcp, these are insecure and use transfer password in cleartext format while performing any action. It handles user authentication, encryption, transferring files between computers and tunneling. Secure Shell (ssh) is a free open source networking tool which allow us to access remote system over an unsecured network using Secure Shell (SSH) protocol. Navigate to the following URL to know more about openSSH usage. Why are we doing this? due to security reason. In this article we will show you, how to perform this in details. It can be done by making the necessary changes in /etc/ssh/sshd_config file. There are many ways available to perform this.However, we need to go with simple and easy method. How to achieve this? Which is the simple and best way? Based on your organization standard policy, you may need to allow only the list of users or user groups who are allowed to access the Linux system.
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