Brain's Workbench
Installing and configuring required packages
Start a terminal session and type:
sudo apt install libpam-google-authenticator
Configuring SSH
To make SSH use the Google Authenticator PAM module, add the following line to the /etc/pam.d/sshd file:
If you want to use a password to access the SSH server, a solution for fixing the Permission denied error is to enable password login in the sshd_config file.
To do this, open the file in a text editor. This example uses the nano editor:
sudo nano /etc/ssh/sshd_config
In the file, find the PasswordAuthentication line and make sure it ends with yes.
Find the ChallengeResponseAuthentication option and disable it by adding no.
If lines are commented out, remove the hash sign # to uncomment them. Save the file and exit. Restart the SSH service by typing the following command:
sudo systemctl restart sshd
Create Key-Pair by each user, so login with a common user on SSH Server Host and work like follows.
# create key-pair
debian@dlp:~$ssh-keygen
Generating public/private rsa key pair. Enter file in which to save the key (/home/debian/.ssh/id_rsa): # Enter or input changes if you want Created directory '/home/debian/.ssh'. Enter passphrase (empty for no passphrase): # set passphrase (if set no passphrase, Enter with empty) Enter same passphrase again: Your identification has been saved in /home/debian/.ssh/id_rsa Your public key has been saved in /home/debian/.ssh/id_rsa.pub The key fingerprint is: SHA256:H+lFm+3c93VekrLiFCYAwoWDUVs43s4JEze8wr8QzG8 debian@dlp.srv.world The key's randomart image is: ..... ..... debian@dlp:~$ll ~/.ssh total 8 -rw------- 1 debian debian 2655 Aug 17 13:48 id_rsa -rw-r--r-- 1 debian debian 574 Aug 17 13:48 id_rsa.pub
debian@dlp:~$mv ~/.ssh/id_rsa.pub ~/.ssh/authorized_keys
Transfer the private key created on the Server to a Client, then it’s possible to login with Key-Pair authentication. Below is an example to connect from a linux shell.
Before going into how to use the scp command, let’s start by reviewing the basic syntax. The scp utility expressions take the following form:
scp [OPTION] [user@]SRC_HOST:]file1 [user@]DEST_HOST:]file2
OPTION – scp options such as cipher, ssh configuration, ssh port, limit, recursive copy ..etc
[user@]SRC_HOST:]file1 – Source file.
[user@]DEST_HOST:]file2 – Destination file
Local file should be specified using an absolute or relative path while remote file names should include a user and host specification.
scp provides a number of options that control every aspect of its behavior. The most widely used options are:
-P Specifies the remote host ssh port.
-p Preserves files modification and access times.
-q Use this option if you want to suppress the progress meter and non-error messages.
-C. This option will force scp to compresses the data as it is sent to the destination machine.
-r This option will tell scp to recursively copy directories.
Most of you have probably used a tunnel with an SSH connection. What you probably weren’t aware of is that you can use a dynamic tunnel to access all remote infrastructure. Furthermore, you can specify a port and a destination IP to have direct access. This process is achieved through your PuTTY configuration.
In this procedure, we will use Internet Explorer, Firefox and an RDP connection to demonstrate the use of a tunnel with an SSH connection, as well as configuring the tunnel with several other protocol types.
Local Port Forwarding
Step 1 – Load the Session
In your PuTTY configuration, configure the Host Name and Port of your remote SSH computer. Enter your Saved Sessions name, and click Save. If your session already exists, Load it as shown below:
For legal reasons, Some people need to display a warning banner on their Linux machine before login so that a person requires to acknowledge the contents of the banner before entering the password. To do this, edit a/etc/issue.net file and fill it with the desired context.
Edit the /etc/issue.net file:
sudo nano /etc/issue.net
Here is mine banner as a sample, you can add your’s here:
######################################################### # Authorized access only! # # Disconnect IMMEDIATELY if you are not an authorized user!!! # # All actions Will be monitored and recorded # ###############################################################
First if you have any pre-installed SSH server that has gone bad, remove it-
on Redhat Architechture
Type the following commands as the root user:
# chkconfig sshd off
# service sshd stop
# yum erase openssh-server
You need to edit and update firewall rules that allows inbound connections to SSHs tcp port # 22. Edit /etc/sysconfig/iptables and /etc/sysconfig/ip6tables. In each file find and delete the line that access connection to port # 22. A sample entry:
Method-1:
Create the cryptographic Key on FreeBSD / Linux / UNIX workstation, enter:
ssh-keygen -t rsascp .ssh/id_rsa.pub vivek@rh9linux.nixcraft.org:.ssh/authorized_keys2
Linux: Debian / Ubuntu Linux Remove SSHD Server
Type the following commands:
# apt-get –purge remove openssh-server
Now reinstall the openssh again using-
Voila# apt-get install openssh-server
Src: http://www.cyberciti.biz/faq/howto-unix-linux-remove-delete-opensshd-server/