SSH to your Linux Server using Google Authenticator app

In this section, we will learn how to secure your ssh connection with MFA using Google authenticator app.

Before we start go ahead and download the google authenticator app to your mobile device.

After you successfully downloaded and install the google authenticator app on your mobile device go to your Linux server and install the google-authenticator PAM module by typing this command:

swarm@swarm3:~$ sudo apt install libpam-google-authenticator
Reading package lists... Done
Building dependency tree       
Reading state information... Done
libpam-google-authenticator is already the newest version (20191231-2).
0 upgraded, 0 newly installed, 0 to remove and 75 not upgraded

After the installation complete type following command:

swarm@swarm3:~$ google-authenticator

  • Follow the instructions and scan the bar-code by your google authenticator mobile app
  • You can type yes for every question that you encounter during the process of setting up the Google authentication app
  • After completion save the emergency scratch codes in a secure location, you will need it in case you lose your phone
  • You can do this process for every user on your Linux server.

Now we will need to enable “ChallengeResponseAuthentication” in the ssh config file.

swarm@swarm3:~$ sudo vi /etc/ssh/sshd_config

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication yes

Don’t forget to save the file by pressing :qw

Restart the SSH service:

swarm@swarm3:~$ sudo systemctl restart ssh

The final step is to add the google authentication module to the PAM ssh config file:

swarm@swarm3:~$ sudo vi /etc/pam.d/sshd

Add this line to the end of the config file and save the file:

auth required

That’s it, now you can ssh to your server using google authentication

Verfication code: Enter the code that presented in your google authenticator app in your mobile device.

SSH Key-Pairs.

Remotely Connect to Linux Servers with SSH key-pairs

SSH: Authentication with Key-pairs

On your client machine:

  • Create ssh key pair by using the command ssh-keygen
    • It will create 2 files (Private key and Public key) in the .ssh folder.
[menit@fedora .ssh]$ ls 
  • It is recommended that you will use a passphrase to encrypt your private key
[menit@fedora .ssh]$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/menit/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/menit/.ssh/id_rsa
Your public key has been saved in /home/menit/.ssh/
The key fingerprint is:
SHA256:E+n8J9Sjbdbi5A7uyu7LVAm2Y8fNBtSawvCyoR7l3Y4 menit@fedora
The key's randomart image is:
+---[RSA 3072]----+
|          ..     |
|      .  o  .    |
|       += .o     |
|      +++=o*     |
|     + =So* *    |
|    o o..B.+ o   |
|   . .  .o= B .  |
|    .  +E..X .   |
|       oB+o.+    |

How to Deploy your public key to your manage servers.

  • To connect to your Linux servers using ssh keys you will need to transfer the public key to your remote servers

There are 2 methods to transfer the public key to your server

The first method is to install the public key from your own host to your remote server using this command:

  • This command will create on the remote host .ssh folder and a file named authorized_keys and he will copy-paste the public key to this file.
ssh-copy-id -i /home/menit/.ssh/ username@

  • The second method is to copy your public key and paste it to your remote server under the .ssh folder to file named authorized_keys (if you can’t find such file you just need to create it.

Now you can connect to your machine using this command

[menit@fedora .ssh]$ ssh swarm@

Connect to your remote server without the passphrase

To avoid the need to enter a passphrase every time you ssh to a remote host you can use sshagent to Cache your Authentication Credentials into the host memory.

[menit@fedora .ssh]$ ssh-agent bash
[menit@fedora .ssh]$ ssh-add id_rsa
Enter passphrase for id_rsa: ***********
Identity added: id_rsa (menit@fedora)

How to ssh to a remote host using the Root User account.

  1. On the remote host, you will need first to enable the login as root option: To enable it to remove # from the line “PermitRootLogin prohibit-password”
swarm@swarm3:/etc/ssh$ vim /etc/ssh/sshd_config

#LoginGraceTime 2m
PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

Exit and Save the file by pressing :wq

  1. Switch to you root account in the remote server and pass the Public ssh key to the authorized_keys file under the .ssh folder.
root@swarm3:~/.ssh# ls

How to type sudo command with a password

To grant you user sudo permissions you will need to edit this config file:

[menit@fedora .ssh]$ sudo visudo

Under Allow people in group wheel paste this command

#Allow users to run all commands

This is how it’s should be looked like in the config file:

## Allows people in group wheel to run all commands
%wheel  ALL=(ALL)       ALL

#Allow users to run all commands

It’s important you enter your new line entry at the bottom of the config file because the visudo file is processed from the top to bottom.

Install Zabbix Server 5.0 LTS on CentOS 8.

Zabbix Server depends on the following software applications:

  • MySQL database server
  • Apache web server
  • PHP with required extensions
  • For this installation I used this image CentOS-8.2.2004-x86_64-minimal

If you’re not a fan of SELinux, I recommend to you set it in Permissive mode.

setenforce 0 && sed -i 's/^SELINUX=.*/SELINUX=permissive/g' /etc/selinux/config

Install and configure Zabbix server for your platform

a. Install Zabbix repository

# rpm -Uvh <>
# dnf clean all

b. Install Zabbix server, frontend, agent

# dnf install zabbix-server-mysql zabbix-web-mysql zabbix-apache-conf zabbix-agent

Install MySQL Server on CentOS 8

Install MySQL Database Server

sudo dnf install mysql-server

Activate the MySQL service using the command below:

sudo systemctl start mysqld.service
sudo systemctl enable mysqld

Secure MySQL by changing the default password for MySQL root:

Enter current password for root (enter for none): Press the Enter
Set root password? [Y/n]: Y
New password: <Enter root DB password>
Re-enter new password: <Repeat root DB password>
Remove anonymous users? [Y/n]: Y
Disallow root login remotely? [Y/n]: Y
Remove test database and access to it? [Y/n]: Y
Reload privilege tables now? [Y/n]: Y

Once Database server is installed, you need to create a database for Zabbix user:

c. Create initial database

Run the following on your database host.

Don’t forget to change the password befor you copy this code.

mysql -uroot -p
mysql> create database zabbix character set utf8 collate utf8_bin;
mysql> create user zabbix@localhost identified by 'password';
mysql> grant all privileges on zabbix.* to zabbix@localhost;
mysql> quit;

Import Zabbix Server database schema

zcat /usr/share/doc/zabbix-server-mysql*/create.sql.gz | mysql -uzabbix -p zabbix

d. Configure the database for Zabbix server

Edit file /etc/zabbix/zabbix_server.conf


Configure PHP for Zabbix frontend

e. Configure PHP for Zabbix frontend

Edit file /etc/php-fpm.d/zabbix.conf, uncomment and set the right timezone for you.

; php_value[date.timezone] = Asia/Jerusalem

File Example:

php_value[max_execution_time] = 300
php_value[memory_limit] = 128M
php_value[post_max_size] = 16M
php_value[upload_max_filesize] = 2M
php_value[max_input_time] = 300
php_value[max_input_vars] = 10000
php_value[date.timezone] = Asia/Jerusalem

Configure firewall

firewall-cmd --add-service={http,https} --permanent
firewall-cmd --add-port={10051/tcp,10050/tcp} --permanent
firewall-cmd --reload

Start Zabbix server and agent processes

f. Start Zabbix server and agent processes

Start Zabbix server and agent processes and make it start at system boot.

systemctl restart zabbix-server zabbix-agent httpd php-fpm
systemctl enable zabbix-server zabbix-agent httpd php-fpm

Open Zabbix URL: http://<server_ip_or_name>/zabbix in your browser.

Confirm that all pre-requisites are satisfied.

Configure DB settings

Finish installation

Configure Email notification’s

AWS S3 Bucket – Secure File Sharing

In this blog post, we will create s3 bucket with a policy that only allow us to connect to a specific folder in the bucket and from specific ip.

The Main Advantages of this service:

  • Unlimited storage
  • Low Cost
  • Ability to transfer data to Cold/Archive Storage
  • Limit Access by IP and Folder
  • Have backup/redundancy
  • Can be created in any region.


  • Hard to manage Users
  • Need basic knowledge with JSON and AWS
  • Limited to specific sftp client that support S3 Buckets

Lets Start,first lets create S3 Bucket

To create a bucket

  1. Sign in to the AWS Management Console and open the Amazon S3 console at
  2. Choose Create bucket.
  3. In Bucket name, enter a DNS-compliant name for your bucket. The bucket name must:
    • Be unique across all of Amazon S3.
    • Be between 3 and 63 characters long.
    • Not contain uppercase characters.
    • Start with a lowercase letter or number.After you create the bucket, you can’t change its name. For information about naming buckets, see Rules for bucket naming in the Amazon Simple Storage Service Developer Guide. Important Avoid including sensitive information, such as account numbers, in the bucket name. The bucket name is visible in the URLs that point to the objects in the bucket.
  4. In Region, choose the AWS Region where you want the bucket to reside. Choose a Region close to you to minimize latency and costs and address regulatory requirements. Objects stored in a Region never leave that Region unless you explicitly transfer them to another Region. For a list of Amazon S3 AWS Regions, see AWS service endpoints in the Amazon Web Services General Reference.
  5. In Bucket settings for Block Public Access, choose the Block Public Access settings that you want to apply to the bucket. (Please leave all settings enabled )
  6. After you successfully created a bucket Lets enter to the bucket and create Home Folder and inside the Home Folder we will create 2 more folder 1 in the name Devops and the second IT.

Now lets Create the IAM Policy

To create your own IAM policy

  1. Sign in to the AWS Management Console and open the IAM console at
  2. Choose Policies, and then choose Create Policy. If a Get Started button appears, choose it, and then choose Create Policy.
  3. In the create policy select the JSON Tab and paste this code. (Don’t forget to change the <Bucketname> and <YourpublicIP> in the JSON file to your actual bucket and your public ip where you coming from)
  4. Click on Review Policy give the policy a name and click on Create Policy
    "Version": "2012-10-17",
    "Statement": [
            "Sid": "AllowUsersToAccessFolder2Only",
            "Effect": "Allow",
            "Action": [
            "Resource": [
            "Effect": "Allow",
            "Action": [
            "Resource": [
            "Condition": {
                "StringLike": {
                    "s3:prefix": [
            "Effect": "Deny",
            "Action": "*",
            "Resource": "*",
            "Condition": {
                "NotIpAddress": {
                    "aws:SourceIp": [
                "Bool": {
                    "aws:ViaAWSService": "false"

After we created the policy lets create a IAM User and attached to him the new policy that we just created.

Creating IAM users (console)

You can use the AWS Management Console to create IAM users.

To create one or more IAM users (console)

  1. Sign in to the AWS Management Console and open the IAM console at
  2. In the navigation pane, choose Users and then choose Add user.
  3. Type the user name for the new user.
  4. Select the type of access this set of users will have. We will select programmatic access

Type the name of the policy that you previously created

Click next and Create A user.

Save the access key ID and secret access key in a secure location we will use it to connect to our bucket.

Thats it!! Lets now connect to our S3 Bucket

  1. Download Winscp
  2. File Protocol – Amazon S3
  3. Click on advance and put the remote directory
  4. Enter the key ID and Access key and click login

[AWS] Deploy Ansible for linux and Windows Domain Joined

Installation Details

  • Infrastructure: AWS
  • AMI ID: RHEL-8.2.0_HVM-20200423-x86_64-0-Hourly2-GP2 (ami-07dfba995513840b5)
  • Instance type : t2.medium
  • Instance Hardware: 2vcpu , 4G Memory.

Before we start

Install Vim:

sudo yum install vim

Update Packages

sudo yum update

Prepare For Installation

Change the Hostname:

sudo vim /etc/hostname

Add DNS in hosts file.

sudo vim /etc/hosts

Install epel Repo:

yum -y install [<>](<>)

Install Ansible:

sudo yum install ansible

General Configuration Ansible

Create user:

sudo useradd ansible

Generate password:

passwd ansible 

Login with ansible user:

sudo su - ansible

Give Sudo Permissions:

  1. Change user to root
sudo su -
  1. Give ansible sudo privileges (Centos)
[root@itansible ~]# usermod -aG wheel ansible
[root@itansible ~]# sudo su - ansible
[ansible@itansible ~]$ id ansible
uid=1001(ansible) gid=1001(ansible) groups=1001(ansible),10(wheel)

[ansible@itansible ~]$ sudo visudo
## Read drop-in files from /etc/sudoers.d (the # here does not mean a comment)
#includedir /etc/sudoers.d
ansible         ALL=(ALL)       NOPASSWD: ALL
ec2-user        ALL=(ALL)       NOPASSWD: ALL

login back to you ansible user and Create SSH key pair.

[ansible@itansible ~]$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/ansible/.ssh/id_rsa):
/home/ansible/.ssh/id_rsa already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase): ******

Configure Linux Managed Hosts:

  1. Create user and password name ansible
  2. Copy the ssh public key from ansible master to to the managed hosts.
# On the managed host, switch to ansible user
Type the command  =  cd .ssh/
# Create authorized_keys file
vim authorized_keys
# Go to ansible master and copy the public key:
cat ~/.ssh/ [select and copy to your clipboard]
# ssh into ansible managed hosts, and append the contents of that to the authorized_keys file:
[paste your clipboard contents to the authorized_keys file:]
  • Give sudo permissions (Ubuntu)
ansible@ip-10-64-118-34:~$ sudo visudo

# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

# Allow members of group sudo to execute any command
%sudo   ALL=(ALL:ALL) ALL

# See sudoers(5) for more information on "#include" directives:

#includedir /etc/sudoers.d
ansible     ALL=(ALL) NOPASSWD:ALL

Configure Ansible for Linux

  1. log in to the Ansible Master with the user ansible
  2. Create a linux project directory in ansible home folder
mkdir linux
  1. in the linux directory create 2 file.
[ansible@itansible linux]$ ls
ansible.cfg  inventory
  1. Configure ansible.cfg file like this:
remote_user = ansible
host_key_checking = false
inventory = inventory
become = true
become_method = sudo
become_user = root
become_ask_pass = false
  1. Configure inventory file like this:

  1. Test the connection examples:
[ansible@itansible linux]$ ansible all -m command -a "id ansible"
itansible-slave | CHANGED | rc=0 >>
uid=1001(ansible) gid=1001(ansible) groups=1001(ansible),27(sudo)

[ansible@itansible linux]$ ansible all -m user -a name=test
itansible-slave | CHANGED => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python3"
    "changed": true,
    "comment": "",
    "create_home": true,
    "group": 1002,
    "home": "/home/test",
    "name": "test",
    "shell": "/bin/sh",
    "state": "present",
    "system": false,
    "uid": 1002

Configure Ansible for Windows

  1. log in to the Ansible Master with the user ansible
  2. Create a windows project directory in ansible home folder
mkdir windows

Installing the Kerberos Library

# via Yum (RHEL/Centos/Fedora)
sudo yum -y install gcc python-devel krb5-devel krb5-libs krb5-workstation
sudo yum -y pip3 install "pywinrm>=0.2.2"

Configuring Kerberos

Edit your /etc/krb5.conf (which should be installed as a result of installing packages above) and add the following information for each domain you need to connect to:

ansible@ip-10-64-118-34:~$ cat /etc/krb5.conf
default_realm = (Enter your domain)
dns_lookup_realm = true
dns_lookup_kdc = true

Testing a kerberos connection

If you have installed krb5-workstation (yum) or krb5-user (apt-get) you can use the following command to test that you can be authorised by your domain controller.

kinit user@MY.DOMAIN.COM

To see what tickets if any you have acquired, use the command klist


Create Inventory,Config,Variables file

[ansible@itansible windows]$ ls
ansible.cfg group_vars inventory winvars winvars.yml

Create Inventory file

[ansible@itansible windows]$ vim inventory


Create config file

[ansible@itansible windows]$ vim ansible.cfg

host_key_checking = false
inventory = inventory

Create Group_vars directory and variables file

mkdir group_vars
[ansible@itansible group_vars]$ vim windows
ansible_user: user@ARGUS-LOCAL
ansible_password: password
ansible_connection: winrm
ansible_winrm_transport: kerberos
ansible_winrm_server_cert_validation: ignore

Configure Windows Managed Hosts

To configure the Windows Server for remote management by Ansible requires a bit of work. Luckily the Ansible team has created a PowerShell script for this. Download this script from [here] to each Windows Server to manage and run this script as Administrator.

Log into WinServer1 as Administrator, download ConfigureRemotingForAnsible.ps1 and run this PowerShell script without any parameters.

Once this command has been run on the windows 10 , return to the Ansible master Controller host.

Test Connectivity to the Windows Server

If all has gone well, we should be able to perform an Ansible PING test command. This command will simply connect to the remote WinServer1 server and report success or failure.

Type: ansible windows -m win_ping
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