DEV Community: K Dhanesh

How to create New VM in CLI

K Dhanesh — Mon, 24 May 2021 19:05:04 +0000

KVM to Create New VM using CLI Commands, Tested in ubuntu 16.04 its working fine

sudo virt-install \
--virt-type=kvm \
--name centos7 \
--ram 6144 \
--vcpus=8 \
--os-variant=rhel7 \
--hvm \
--cdrom=/RootPartitions/CentOS-7-x86_64-DVD-1810.iso \
--network network=default,model=virtio \
--graphics vnc \
--disk path=/RootPartitions/centos7-0.1.img,size=30,bus=virtio


# Spin a New VM with Bridge Network

sudo virt-install \
--virt-type=kvm \
--name centos7 \
--ram 6144 \
--vcpus=8 \
--os-variant=rhel7 \
--hvm \
--cdrom=/RootPartitions/CentOS-7-x86_64-DVD-1810.iso \
--network bridge=br0,model=virtio \
--graphics vnc \
--disk path=/RootPartitions/centos7.img,size=30,bus=virtio

Basic Virsh Commands

sudo virsh list --all. # to all the VM in the Host Machine 
sudo virsh destroy <vm-nam> # Stopping or Shutting down the VM
sudo virsh dumpxml vm-name > vm-name.xml # Export the VM setting in XML Formate
sudo cat vm-name.xml | grep source # to list the attached Partition
sudo lvremove /partition/name # remove the LVM Partition 
sudo rm -rf /RootParition/Centos.img # To remove the .img and .qcow2 partitions
sudo virsh undefine <vm-name> # Removing the VM from the Host Machine, before execute
sudo virsh vncdisplay # to display the VNC port number

How to Connect the Private VM from the Local machine

Host Machine should have the Public and Private Network and VM should configured via bridge network from Privat network.

Using SSH tunnel we can connect the VM, before pls install VNC viewer in your local - https://www.realvnc.com/en/connect/download/viewer/

From Local Machine

ssh -L localhost:5900:VM-IP:VNC-Port-Number username@hostmachine.com

For Example

HostMachine: dhanesh.vm-test.com (Public IP)
HostMachine: UserName: dhanesh
VM PrivateIP: 192.168.100.100
VM VNC Port: 12

ssh -L localhost:5900:192.168.100.100:5912 dhanesh@dhanesh.vm-test.com

Finally open the VNC viewer and type localhost:5900 you can able to see the VM from your local machine.

Ensure that all the Network settings are working fine.

Wordpress along with Rails app with Apache2 and Passenger

K Dhanesh — Thu, 20 May 2021 17:30:33 +0000

Wordpress along with Rails app with Apache2 and Passenger

Intro

This document helps to run Wordpress blog along with Rails app in a same server and make it available / accessible via Rails App. In this example we want to run a Rails app that accsesible via domain name www.dhanesh-example.com and also want to run a Wordpress instance that accessible via /blog.

user access the www.dhanesh-example.com or any paths (except /blog /api), it will refer to the Rails app
user access the www.dhanesh-eample.com/blog or any paths inside /blog path scope it will refer to wordpress.

Steps

New or Running Rails project path /var/www/html/rails_app
Install passenger gem
Install apache2 and passenger module
Create virtual host for Rails app
Download, Extract, and rename the wordpress folder to blog
Move the blog folder to /var/www/html/blog and configure our wordpress instance
Create MySQL database for our wordpress instance
set WP_HOME and WP_SITEURL wordpress config to http://www.dhanesh-example.com/blog
Add gem 'rails-reverse-proxy' to your Gemfile and run bundle install, Commit the Gemfile and Gemfile.lock
Create controller to handle reverse proxy from Rails to wordpress
Create new route that will point access to /blog path to our reverse proxy controller.

ADDITIONAL DETAILS

Configure Rails, Passenger, Apache2

Install passenger gem and continue with installing apache2 passenger module by run passenger-install-apache2-module. Follow any instructions from the installation guide until all requirements met.

Note: don't forget the important part from the installation guide that will ask you to load passenger module in your apache2 configuration file /etc/apache2/apache2.conf

Create new virtual host by creating new config file in /etc/apache2/sites-available/dhanesh-example.conf folder. Use this configuration for the virtual host:

<VirtualHost *:80>
    ServerName dhanesh-example.com
    ServerAlias www.dhanesh-example.com
    ServerAdmin dhanesh@example.com
    DocumentRoot /var/www/html/rails_app/current/public
    RailsEnv production
    ErrorLog /var/log/apache2/app-name/error.log
    CustomLog /var/log/apache2/app-name/production.log combined
    <Directory "/var/www/html/rails_app/current/public">
        Options FollowSymLinks
        Require all granted
    </Directory>
</VirtualHost>

Wordpress Configuration

Update the wp-config.php set WP_HOME and WP_SITEURL to http://www.dhanesh-example.com/blog.

define('WP_SITEURL', 'http://dhanesh-example.com/blog');
define('WP_HOME',    'http://dhanesh-example.com/blog');
define('FS_METHOD', 'direct');

Configuring Reverse proxy from Rails to Wordpress

Install rails-reverse-proxy gem

Create a controller that will handle reverse proxy from Rails to wordpress. In my example, the controller name is WordpressController with the following codes:

# app/controllers/wordpress_controller.rb
class WordpressController < ApplicationController
  include ReverseProxy::Controller
  def index
    reverse_proxy "http://dhanesh-example.com:80" do |config|
      config.on_missing do |code, response|
        redirect_to root_url   and return
      end
    end
  end
  end

You could change the http://dhanesh-example.com:80 part with any host and any port where your wordpress instance running.

Next, you need to add new route to config/route.rb that will point any request to /blog path in our Rails app to our reverse proxy controller (WordpressController). Here is my config/routes.rb:

Rails.application.routes.draw do
  match 'blog' => 'wordpress#index', via: [:get, :post, :put, :patch, :delete]
  match 'blog/*path' => 'wordpress#index', via: [:get, :post, :put, :patch, :delete]

  get 'home/index'
  root to: 'home#index'
end

When there is request to /blog path, our Rails app will point it to apache server and looking for a folder with name blog, that's why we need to rename our wordpress folder into blog.

Configure virtual host for wordpress

Edit the previously created config file in dhanesh-example.conf folder. Add the following configurations to the virtual host:

    Alias /blog /var/www/html/blog
    <Directory /var/www/html/blog>
        Allow From all
        Options +Indexes
        AllowOverride all
    </Directory>

    <Location /blog>
      PassengerEnabled off
    </Location>

Restart the Apache server again.

Test

dhanesh-example.com it will display rails page and try to access dhanesh-example.com/blog it will point to the wordpress blog

Example Vhost Entry

<IfModule mod_ssl.c>
<VirtualHost *:443>
    RailsEnv production
    ServerName dhanesh-example.com
    #ServerAlias www.dhanesh-example.com
    DocumentRoot "/var/www/html/rails_app/current/public"
    PassengerRuby /home/dhanesh/.rvm/gems/ruby-2.6.3/wrappers/ruby
    #DocumentRoot "/var/www/html"
    ErrorLog "/var/log/apache2/example.com/error.log"
    CustomLog "/var/log/apache2/example.com/access.log" common
    <Directory "/var/www/html/rails_app/current/public">
    #<Directory "/var/www/html">
        Options All
        #DirectoryIndex maintenance.html
        AllowOverride All
        Order allow,deny
        Allow from all
    </Directory>
    Alias /blog /var/www/html/blog
    <Directory /var/www/html/blog>
        Options FollowSymLinks
        AllowOverride Limit Options FileInfo
        DirectoryIndex index.php
        Order allow,deny
        Allow from all
    </Directory>
    <Directory /var/www/html/blog/wp-content>
        Options FollowSymLinks
        Order allow,deny
        Allow from all
    </Directory>
    <Location /blog>
        PassengerEnabled off
    </Location>
    #RewriteEngine on
    #RewriteRule index\.html index.php [NC,R]
    # Remove the www
    #RewriteCond %{HTTP_HOST} ^www.URL$ [NC]
    #RewriteRule ^(.*)$ http://URL/ [R=301,L]
    Include /etc/letsencrypt/options-ssl-apache.conf
    SSLCertificateFile /etc/letsencrypt/live/dhanesh-example.com/fullchain.pem
    SSLCertificateKeyFile /etc/letsencrypt/live/dhanesh-example.com/privkey.pem
</VirtualHost>
</IfModule>

Thank you

Python Script to get the AWS EC2 Instance Details

K Dhanesh — Thu, 20 May 2021 17:17:23 +0000

Used python version 3.7 and Boto3, Kindly configure the AWS IAM Credentials in your local or workstation

AWS Profile Configuration

aws configure --profile name(my_proile)

import boto3
import sys
import time

session=boto3.Session(profile_name="my_profile", region_name="us-east-1") #boto3 session, aws profile 

ec2_resource=session.resource(service_name="ec2") # resource object method

'''
client object method, commented because this script using resource object method
ec2_client=session.client(service_name="ec2")
'''

#using Resource Object
'''
for each_instances in ec2_resource.instances.all():
    print(each_instances.id, each_instances.state['Name'])
'''

for instance in ec2_resource.instances.all():
     print(
            "Id: {0}\nPlatform: {1}\nType: {2}\nPublic IPv4: {3}\nAMI: {4}\nState: {5}\n".format(
         instance.id, instance.platform, instance.instance_type, instance.public_ip_address, instance.image.id, instance.state
         )
     )

Practise the Linux Basic Commands

K Dhanesh — Thu, 20 May 2021 17:02:51 +0000

Unix Tools

Bash Commands

uname -a                ## Get the Kernel Version
lsb_release -a          # Release or Distibution info
cat /etc/SuSE-release   # Suse Linux Version Check
cat /etc/debian_version # Debian Version check

Basic Commands to know the Server status

uptime                  # it will shows how long the system has been running
hostname                # System Host Name
hostname -i             # To Display to the ip address of the Host, Linux based distribution
man hier                # File system hierarchy Description
last reboot             # to know the system reboot history

Hardware informations

Kernel Detected HW

dmesg                   # Detect Hardware and Boot messages
lsdev                   # Info about the installed Hardware like PCI Card
dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8  # Read BIOS

Linux

cat /proc/cpuinfo                # CPU Model
cat /proc/meminfo                # Hardware Memory
grep MemTotal /proc/meminfo      # Physical Memory
watch -n1 'cat /proc/interrupts' # watch changecable interrupts
free -m                          # To know the used & free memory ( -m for MB)
cat /proc/devices                # Configured devices
lspci -tv                        # PCI Device info
lsusb -tv                        # USB Device info
lshal                            # List all devices with properties
dmidecode                        # DMI/SMBIOS: hw info from the BIOS

Free BSD

sysctl hw.model                 # CPU Model
sysctl hw                       # More information about hardware
sysctl hw.ncpu                  # No. of active CPU's Installed
sysctl vm                       # Memory Usage
sysctl hw.realmem               # Hardware Memory (Physical)
sysctl -a | grep mem            # Kernel memory settings and info
sysctl dev                      # Configured devices
pciconf -l -cv                  # PCI Device info
usbdevs -v                      # USB Device info
atacontrol list                 # ATA Device info
camcontrol devlist -v           # SCSI Device info

Load, Statistics and Messages

Folowing Commands are useful to find out what is going on the system realtime.

top                             # display & update the top CPU processes
mpstat 1                        # display processors related statistics
vmstat 2                        # virtual memory statistics
iostat 2                        # I/O statistics - 2sec intervals
systat -vmstat 1                # system statistics - 1sec intervals
systat -tcp 1                   # tcp connections (try also -ip)
systat -netstat 1               # active network connections - BSD
systat -ifstat 1                # network traffic through active interfaces - BSD
systat -iostat 1                # CPU and Disk throughput - BSD
ipcs -a                         # info on system V interprocess
tail -n 500 /var/log/messages   # Last 500 Kernel/syslog messages
tail /var/log/warn              # System Warnings messages see syslog.conf

Users

id                                                  # To display the active user ID with login & group
last                                                # To know the last logins on the server
who or w                                            # Who is logged on the server currently in simple type "w"
groupadd admin                                      # Adding group "admin"
useradd -c "Dhanesh Kumar" -g admin -m colin        # Creating user "Dhanesh Kumar", with "admin" group
usermod -a -G <group> <user>                        # Adding existing user to the group - Debian Based
groupmod -A <user> <group>                          # Adding existing user to the group - Suse Linux
userdel dhanesh                                     # delete the user "dhanesh" (linux / Solaris)
adduser dhanesh                                     # FreeBSD add user joe (interactive)
rmuser dhanesh                                      # FreeBSD delete user joe (interactive)
pw groupadd admin                                   # Use pw on FreeBSD
pw groupmod admin -m newmember                      # Add a new member to a group
pw useradd dhanesh -c "Dhanesh Kumar" -g admin -m -s /bin/tcsh
pw userdel dhanesh; pw groupdel admin

/etc/shadow - Encrypted passwords are stored

Temporarily prevent system logings for all user except ROOT user, with nologin.

echo "Apologies no login now" > /etc/nologin     #(linux)
echo "Apologies no login now" > /var/run/nologin #(FreeBSD)

Limits in Linux

Some application requires higer limits on open files and sockets (like a proxy web server, database). The default limits are usually too low.

Shell/Script

Python Script to get the Docker Containers status

K Dhanesh — Mon, 17 May 2021 04:18:53 +0000

Used docker-py SDK

Installed using pip command

pip install docker-py

Python Script

import os
import datetime
from docker import Client

cli = Client(base_url='unix://var/run/docker.sock')
containers = cli.containers()
for container in range(len(containers)):
 for key in containers[container]:
    print(containers[container][key])

# Output

b8c2a832a4f107b86981d3b346d5627e0554312465fde358f1072b61cc940961
['/etcd']
quay.io/coreos/etcd:v2.2.1
sha256:142eb4c815648ddd1146ce61f85ee577fce794a54489873134b2d9714f396ac6
/etcd -name etcd0 -advertise-client-urls http://localhost:2379,http://localhost:4001 -listen-client-urls http://0.0.0.0:2379,http://0.0.0.0:4001 -initial-advertise-peer-urls http://localhost:2380 -listen-peer-urls http://0.0.0.0:2380 -initial-cluster-token etcd-cluster-1 -initial-cluster etcd0=http://localhost:2380 -initial-cluster-state new
1618796211
[{'IP': '0.0.0.0', 'PrivatePort': 2379, 'PublicPort': 2379, 'Type': 'tcp'}, {'IP': '0.0.0.0', 'PrivatePort': 2380, 'PublicPort': 2380, 'Type': 'tcp'}, {'IP': '0.0.0.0', 'PrivatePort': 4001, 'PublicPort': 4001, 'Type': 'tcp'}, {'PrivatePort': 7001, 'Type': 'tcp'}]
{}
running
Up 4 days
{'NetworkMode': 'default'}
{'Networks': {'bridge': {'IPAMConfig': None, 'Links': None, 'Aliases': None, 'NetworkID': '6e5820ead0cfa5c34baee87737f99e5b2b05601d02435760631a914815e0fcb8', 'EndpointID': 'efe94e05a72f0197f891bb49ec6b4882d8da72fc10819cdc38831bbf145001df', 'Gateway': '172.17.0.1', 'IPAddress': '172.17.0.2', 'IPPrefixLen': 16, 'IPv6Gateway': '', 'GlobalIPv6Address': '', 'GlobalIPv6PrefixLen': 0, 'MacAddress': '02:42:ac:11:00:02', 'DriverOpts': None}}}
[{'Type': 'bind', 'Source': '/usr/share/ca-certificates', 'Destination': '/etc/ssl/certs', 'Mode': '', 'RW': True, 'Propagation': 'rprivate'}]