Dinesh, an avid movie collector and music lover, had a growing problem. His laptop was bursting at the seams with countless movies, albums, and family photos. Every time he wanted to watch a movie or listen to her carefully curated playlists, he had to sit around his laptop. And if he wanted to share something with his friends, it meant copying with USB drives or spending hours transferring files.

One Saturday evening, after yet another struggle to connect his laptop to his smart TV via a mess of cables, Dinesh decided it was time for a change. He needed a solution that would let his access all his media from any device in his house – phone, tablet, and TV. He needed a media server.

Dinesh fired up his browser and began his search: “How to stream media to all my devices.” He gone through the results – Plex, Jellyfin, Emby… Each option seemed promising but felt too complex, requiring subscriptions or heavy installations.

Frustrated, Dinesh thought, “There must be something simpler. I don’t need all the bells and whistles; I just want to access my files from anywhere in my house.” He refined her search: “lightweight media server for Linux.”

There it was – MiniDLNA. Described as a simple, lightweight DLNA server that was easy to set up and perfect for home use, MiniDLNA (also known as ReadyMedia) seemed to be exactly what Dinesh needed.

MiniDLNA (also known as ReadyMedia) is a lightweight, simple server for streaming media (like videos, music, and pictures) to devices on your network. It is compatible with various DLNA/UPnP (Digital Living Network Alliance/Universal Plug and Play) devices such as smart TVs, media players, gaming consoles, etc.

How to Use MiniDLNA

Here’s a step-by-step guide to setting up and using MiniDLNA on a Linux based system.

1. Install MiniDLNA

To get started, you need to install MiniDLNA. The installation steps can vary slightly depending on your operating system.

For Debian/Ubuntu-based systems:

sudo apt update
sudo apt install minidlna

For Red Hat/CentOS-based systems:

First, enable the EPEL repository,

sudo yum install epel-release

Then, install MiniDLNA,

sudo yum install minidlna

2. Configure MiniDLNA

Once installed, you need to configure MiniDLNA to tell it where to find your media files.

a. Open the MiniDLNA configuration file in a text editor

sudo nano /etc/minidlna.conf

b. Configure the following parameters:

• media_dir: Set this to the directories where your media files (music, pictures, and videos) are stored. You can specify different media types for each directory.

media_dir=A,/path/to/music  # 'A' is for audio
media_dir=V,/path/to/videos # 'V' is for video
media_dir=P,/path/to/photos # 'P' is for pictures

• db_dir=: The directory where the database and cache files are stored.

db_dir=/var/cache/minidlna

• log_dir=: The directory where log files are stored.

log_dir=/var/log/minidlna

• friendly_name=: The name of your media server. This will appear on your DLNA devices.

friendly_name=Laptop SJ

• notify_interval=: The interval in seconds that MiniDLNA will notify clients of its presence. The default is 900 (15 minutes).

notify_interval=900

c. Save and close the file (Ctrl + X, Y, Enter in Nano).

3. Start the MiniDLNA Service

After configuration, start the MiniDLNA service

sudo systemctl start minidlna

To enable it to start at boot,

sudo systemctl enable minidlna

4. Rescan Media Files

To make MiniDLNA scan your media files and add them to its database, you can force a rescan with

sudo minidlnad -R

5. Access Your Media on DLNA/UPnP Devices

Now, your MiniDLNA server should be up and running. You can access your media from any DLNA-compliant device on your network:

• On your Smart TV, look for the “Media Server” or “DLNA” option in the input/source menu.
• On a Windows PC, go to This PC or Network and find your DLNA server under “Media Devices.”
• On Android, use a media player app like VLC or BubbleUPnP to find your server.

6. Check Logs and Troubleshoot

If you encounter any issues, you can check the logs for more information

sudo tail -f /var/log/minidlna/minidlna.log

To setup for a single user

Disable the global daemon

sudo service minidlna stop
sudo update-rc.d minidlna disable

Create the necessary local files and directories as regular user and edit the configuration

mkdir -p ~/.minidlna/cache
cd ~/.minidlna
cp /etc/minidlna.conf .
$EDITOR minidlna.conf

Configure as you would globally above but these definitions need to be defined locally

db_dir=/home/$USER/.minidlna/cache
log_dir=/home/$USER/.minidlna 

To start the daemon locally

minidlnad -f /home/$USER/.minidlna/minidlna.conf -P /home/$USER/.minidlna/minidlna.pid

To stop the local daemon

xargs kill </home/$USER/.minidlna/minidlna.pid

To rebuild the database,

minidlnad -f /home/$USER/.minidlna/minidlna.conf -R

For more info: https://help.ubuntu.com/community/MiniDLNA

Additional Tips

• Firewall Rules: Ensure that your firewall settings allow traffic on the MiniDLNA port (8200 by default) and UPnP (typically port 1900 for UDP).
• Update Media Files: Whenever you add or remove files from your media directory, run minidlnad -R to update the database.
• Multiple Media Directories: You can have multiple media_dir lines in your configuration if your media is spread across different folders.

To set up MiniDLNA with VLC Media Player so you can stream content from your MiniDLNA server, follow these steps:

Let’s see how to use this in VLC

On Machine

1. Install VLC Media Player

Make sure you have VLC Media Player installed on your device. If not, you can download it from the official VLC website.

2. Open VLC Media Player

Launch VLC Media Player on your computer.

3. Open the UPnP/DLNA Network Stream

1. Go to the “View” Menu:
   • On the VLC menu bar, click on View and then Playlist or press Ctrl + L (Windows/Linux) or Cmd + Shift + P (Mac).
2. Locate Your DLNA Server:
   • In the left sidebar, you will see an option for Local Network.
   • Click on Universal Plug'n'Play or UPnP.
   • VLC will search for available DLNA/UPnP servers on your network.
3. Select Your MiniDLNA Server:
   • After a few moments, your MiniDLNA server should appear under the UPnP section.
   • Click on your server name (e.g., My DLNA Server).
4. Browse and Play Media:
   • You will see the folders you configured (e.g., Music, Videos, Pictures).
   • Navigate through the folders and double-click on a media file to start streaming.

4. Alternative Method: Open Network Stream

If you know the IP address of your MiniDLNA server, you can connect directly:

1. Open Network Stream:
   • Click on Media in the menu bar and select Open Network Stream... or press Ctrl + N (Windows/Linux) or Cmd + N (Mac).
2. Enter the URL:
   • Enter the URL of your MiniDLNA server in the format http://[Server IP]:8200.
   • Example: http://192.168.1.100:8200.
3. Click “Play”:
   • Click on the Play button to start streaming from your MiniDLNA server.

5. Tips for Better Streaming Experience

• Ensure the Server is Running: Make sure the MiniDLNA server is running and the media files are correctly indexed.
• Network Stability: A stable local network connection is necessary for smooth streaming. Use a wired connection if possible or ensure a strong Wi-Fi signal.
• Firewall Settings: Ensure that the firewall on your server allows traffic on port 8200 (or the port specified in your MiniDLNA configuration).

On Android

To set up and stream content from MiniDLNA using an Android app, you will need a DLNA/UPnP client app that can discover and stream media from DLNA servers. Several apps are available for this purpose, such as VLC for Android, BubbleUPnP, Kodi, and others. Here’s how to use VLC for Android and BubbleUPnP, two popular choices

Using VLC for Android

1. Install VLC for Android:
   • Download and install the VLC app from the Google Play Store.
2. Open VLC for Android:
   • Launch the VLC app on your Android device.
3. Access the Local Network:
   • Tap on the menu button (three horizontal lines) in the upper-left corner of the screen.
   • Select Local Network from the sidebar menu.
4. Find Your MiniDLNA Server:
   • VLC will automatically search for DLNA/UPnP servers on your local network. After a few moments, your MiniDLNA server should appear in the list.
   • Tap on the name of your MiniDLNA server (e.g., My DLNA Server).
5. Browse and Play Media:
   • You will see your media folders (e.g., Music, Videos, Pictures) as configured in your MiniDLNA setup.
   • Navigate to the desired folder and tap on any media file to start streaming.

Additional Tips

• Ensure MiniDLNA is Running: Make sure your MiniDLNA server is properly configured and running on your local network.
• Check Network Connection: Ensure your Android device is connected to the same local network (Wi-Fi) as the MiniDLNA server.
• Firewall Settings: If you are not seeing the MiniDLNA server in your app, ensure that the server’s firewall settings allow DLNA/UPnP traffic.

Some Problems That you may face

1. minidlna.service: Main process exited, code=exited, status=255/EXCEPTION - check the logs. Mostly its due to an instance already running on port 8200. Kill that and reload the db. lsof -i :8200 will give PID. and `kill -9 <PID>` will kill the process.
2. If the media files is not refreshing, then try minidlnad -f /home/$USER/.minidlna/minidlna.conf -R or `sudo minidlnad -R`

In this blog, we will learn about IP addresses and netmasks.

IP

The Internet Protocol (IP) is a unique identifier for your device, similar to how a mobile number uniquely identifies your phone.

IP addresses are typically represented as four Octets for IPv4, with each octet being One byte/Octets in size, and eight octets for IPv6, with each octet being two bytes/Octets in size.

Examples:

• IPv4: 192.168.43.64
• IPv6: 2001:db8:3333:4444:5555:6666:7777:8888

For the purposes of this discussion, we will focus on IPv4.

Do we really require four Octets structure with dots between them?

The answer is NO

The only requirement for an IPv4 address is that it must be 4 bytes in size. However, it does not have to be written as four octets or even with dots separating them.

Let’s test this by fetching Google’s IP address using the nslookup command.

Convert this to binary number using bc calculator in Bash shell.

And you can see it’s working.

This is because the octet structure and the dots between them are only for human readability. Computers do not interpret dots; they just need an IP address that is 4 bytes in size, and that’s it.

The range for IPv4 addresses is from 0.0.0.0 to 255.255.255.255.

Types of IP Addresses

IP addresses are classified into two main types: Public IPs and Private IPs.

Private IP addresses are used for communication between local devices without connecting to the Internet. They are free to use and secure to use.

You can find your private IP address by using the ifconfig command

The private IP address ranges are as follows:

10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255

Public IP addresses are Internet-facing addresses provided by an Internet Service Provider (ISP). These addresses are used to access the internet and are not free.

By default

Private IP to Private IP communication is possible.
Public IP to Public IP communication is possible.

However:

Public IP to Private IP communication is not possible.
Private IP to Public IP communication is not possible.

Nevertheless, these types of communication can occur through Network Address Translation (NAT), which is typically used by your home router. This is why you can access the Internet even with a private IP address.

Netmasks
Netmasks are used to define the range of IP addresses within a network.

Which means,

You can see 24 Ones and 8 Zeros.

Here, we have converted 255 to binary using division method.

255 ÷ 2 = 127 remainder 1

127 ÷ 2 = 63 remainder 1

63 ÷ 2 = 31 remainder 1

31 ÷ 2 = 15 remainder 1

15 ÷ 2 = 7 remainder 1

7 ÷ 2 = 3 remainder 1

3 ÷ 2 = 1 remainder 1

1 ÷ 2 = 0 remainder 1

So, binary value of 255 is 11111111

By using this, we can able to find the number of IP addresses and its range.

Since we have 8 zeros, so

Number of IPs = 2 ^8 which equals to 256 IPs. SO, the usable IP range is 10.4.3.1 – 10.4.3.254 and the broadcast IP is 10.4.3.255.

And we can also write this as 255.255.255.0/24 . Here 24 denotes CIDR (Classless Inter-Domain Routing).

Thats it.

Kindly let me know in comments if you are any queries in these topics.

In this blog, we are going to see how to increase or decrease the size of the static partition in Linux without compromising any data loss and how to do that in Online mode without unmounting.

I already explained the basic concepts of partition in very detail in my previous blog. You can refer to that blog by clicking here.

In this practical, the Oracle VirtualBox is used for hosting the Redhat Enterprise Linux (RHEL8) Virtual Machine (VM).

The first step is to attach one hard disk. So, I attached one virtual hard disk with the size of 40GiB. That disk is named “/dev/sdc”. You can check the disk name and all other disks present in your VM by running the following command.

fdisk -l

Then, we have to do partition by using “fdisk” command.

fdisk /dev/sdc

Then, enter “n” in order to create a new partition. Then enter the partition number and specify the number of sectors or GiB. Here, we entered 20 GiB in order to utilize that much storage unless we do partition, we can’t utilize any storage.

We had created one partition named as “/dev/sdc1”. Next step is to format the partition. Here, we used Ext4 filesystem(format) to create an inode table.

Next step is to create one directory using “mkdir” command and mount that partition in that directory since we can’t directly use the hardware device no matter it is either real or virtual.

One file should be created inside that directory in order to check the data loss after Live scaling of static partition.

Ok, now the size of the static partition is 20 GiB, we are going to do scaling up to 30GiB without unmounting the partition. For this, again we have to run the following command.

fdisk /dev/sdc

Then delete the partition. Don’t bother about the data, it won’t lose.

Then enter “n” to create the new partition and specify your desired size. Here, I like to scale up to 30GiB. And then one warning will come and it says that “Partition 1 contains an ext4 signature” and ask us what to do with that either remove the signature or retain.

If you don’t want to lose the data, then enter “N”. Then enter “w” to save the partition. you can verify your partition size by running “fdisk -l” command in terminal. Finally, you increased the size of static partition.

First part is done. Then next step is to format the partition in order to create the file system. But this time, we will not use “mkfs” command, since it will delete all the data. We don’t need it. We have to do format without comprising the data. For that we have to run the following command.

resize2fs  /dev/sdc1

Finally, we done format without comprising the data. We can check this by going inside that mount point and check whether the data is here or not.

Yes, data is here. It is not lost even though we created new partition and formatted the partition.

Live Linux Static Partition scaling without any data loss

In this blog, we are going to see how to increase or decrease the size of the static partition in Linux without compromising any data loss and done in Online mode.

I already explained the basic concepts of partition in very detail in my previous blog. You can refer to that blog by clicking here.

In this practical, the Oracle VirtualBox is used for hosting the Redhat Enterprise Linux (RHEL8) Virtual Machine (VM).

The first step is to attach one hard disk. So, I attached one virtual hard disk with the size of 40GiB. That disk is named “/dev/sdc”. You can check the disk name and all other disks present in your VM by running the following command.

fdisk -l

Then, we have to do partition by using “fdisk” command.

fdisk /dev/sdc

Then, enter “n” in order to create a new partition. Then enter the partition number and specify the number of sectors or GiB. Here, we entered 20 GiB in order to utilize that much storage unless we do partition, we can’t utilize any storage.

We had created one partition named as “/dev/sdc1”. Next step is to format the partition. Here, we used Ext4 filesystem(format) to create an inode table.

Next step is to create one directory using “mkdir” command and mount that partition in that directory since we can’t directly use the hardware device no matter it is either real or virtual.

One file should be created inside that directory in order to check the data loss after Live scaling of static partition.

Ok, now the size of the static partition is 20 GiB, we are going to do scaling up to 30GiB without unmounting the partition. For this, again we have to run the following command.

fdisk /dev/sdc

Then delete the partition. Don’t bother about the data, it won’t lose.

Then enter “n” to create the new partition and specify your desired size. Here, I like to scale up to 30GiB. And then one warning will come and it says that “Partition 1 contains an ext4 signature” and ask us what to do with that either remove the signature or retain.

If you don’t want to lose the data, then enter “N”. Then enter “w” to save the partition. you can verify your partition size by running “fdisk -l” command in terminal. Finally, you increased the size of static partition.

First part is done. Then next step is to format the partition in order to create the file system. But this time, we will not use “mkfs” command, since it will delete all the data. We don’t need it. We have to do format without comprising the data. For that we have to run the following command.

resize2fs  /dev/sdc1

Finally, we done format without comprising the data. We can check this by going inside that mount point and check whether the data is here or not.

Yes, data is here. It is not lost even though we created new partition and formatted the partition.

Reduce the size of the Static Partition

You can also reduce the Static Partition size. For this, you have to follow the below steps.

• Unmount
• Cleaning bad sectors
• Format
• Mount

First step is to unmount your mount point since it is online, somebody will using it.

umount /partition1

Then we have to clean the bad sectors by running the following command

e2fsck -f /dev/sdc1

Then we have to format the size you want. Here we want only 20 GiB and we will reduce the remaining 10 GiB space. This is done by running following command.

resize2fs /dev/sdc1 20G

Then we have to mount the partition.

Finally, we reduced the static partition size.

Above figure shows that Data is also not lost during scaling down.

Thank you all for your reads. Stay tuned for my next article, because it is Endless.

Hosting your own WordPress website is interesting right!! Ok, come on let’s do it!!

We are going to do this practical from Scratch. From the Creation of our Own VPC, Subnets, Internet Gateway, Route tables to Deployment of WordPress.

Here, we are going to use Amazon Web Service’s RDS service for hosting our own WordPress site. Before that, let’s take a look at a basic introduction to RDS service.

Amazon Relational Database Service is a distributed relational database service by Amazon Web Services (AWS). It is a web service running in the cloud designed to simplify the setup, operation, and scaling of a relational database for use in applications. Administration processes like patching the database software, backing up databases and enabling point-in-time recovery are managed automatically.

Features of AWS RDS

• Lower administrative burden. Easy to use
• Performance. General Purpose (SSD) Storage
• Scalability. Push-button compute scaling
• Availability and durability. Automated backups
• Security. Encryption at rest and in transit
• Manageability. Monitoring and metrics
• Cost-effectiveness. Pay only for what you use

Ok, let’s jump onto the practical part!!

We will do this practical from scratch. Since it will be big, so we divided this into 5 small parts namely

• Creating a MySQL database with RDS
• Creating an EC2 instance
• Configuring your RDS database
• Configuring WordPress on EC2
• Deployment of WordPress website

Creating a MySQL database with RDS

Before that, we have to do two pre-works namely the Creation of Virtual Private Cloud(VPC), Subnets and Security groups. These are more important because in order to have a reliable connection between WordPress and MySQL database, they should be located in the same VPC and should have the same Security Group.

Since Instances are launched on Subnets only, Moreover RDS will launch your MySQL database in EC2 instance only that we cannot able to see since it is fully managed by AWS.

We are going to create our own VPC. For that, we have to specify IP range and CIDR. We specified IP and CIDR as 192.168.0.0/16.

What is CIDR?. I explained this in my previous blog in very detail. You can refer here.

Lets come to the point. After specifying the IP range and CIDR, enter your VPC name.

Now, VPC is successfully created with our specified details.

Next step is to launch the subnet in the above VPC.

For Creating Subnets, you have to specify which VPC the lab should launch. We already have our own VPC named “myvpc123”.

And then we have to specify the range of Subnet IP and CIDR. Please note that the Subnet range should come under VPC range, it should not exceed VPC range.

For achieving the property of High Availability, We have to launch minimum two subnets, so that Amazon RDS will launch its database in two subnets, if one subnet collapsed means, it won’t cause any trouble.

Now, two Subnets with their specified range of IPs and CIDR are launched successfully inside our own VPC and they are available.

Next step is to create a security group in order to secure the WordPress and MySQL databases. Note that both should have the same Security Group or else it won’t connect.

For creating a Security Group, we have to specify which VPC it should be launched and adding a Description is mandatory.

Then we have to specify inbound rules, for making this practical simple, we are allowing all traffic to access our instance.

Now, the Security Group is successfully created with our specified details.

Now let’s jump into part 1 which is about Creating a MySQL database with RDS.

Select Create database, then select Standard create and specify the database type.

Then you have to specify the Version. Version plays a major role in MySQL when integrating with WordPress, so select the compactible version or else it will cause serious trouble at the end. Then select the template, here we are using Free-tier since it won’t be chargeable.

Then you have to specify the credentials such as Database Instance name, Master username and Master password.

Most important part is a selection of VPC, you should select the same VPC where you will launch your EC2 instance for your WordPress and we can’t modify the VPC once the database is created. Then select the Public access as No for providing more security to our database. Now, the people outside of your VPC can’t connect to your database.

Then you have to specify the security group for your database. Note that the Security Group for your database and WordPress should be the same or else it will cause serious trouble.

Note that Security Groups is created per VPC. After selecting Security Group, then click Ok to create the RDS database.

Creating an EC2 instance

Before creating an instance, there should be two things you configured namely Internet Gateway and Route tables. It is used for providing outside internet connectivity to an instance launched in the subnet.

Internet Gateway is created per VPC. First, we have to create one new Internet Gateway with the specified details.

Then you have to attach Internet Gateway to the VPC

Next step is to create Routing tables. Note that Route table is created per Subnet.

We have to specify which VPC in which your subnet is available to attach routing table with it, specify Name and click create to create the route table.

Then click Edit route to edit the route details namely destination and target. Enter destination as 0.0.0.0/0 for accessing any IP anywhere on the Internet and target is your Internet Gateway.

After entering the details, click Save routes.

We created a Route table, then we have to attach that table to your Subnet. For that click Edit route table association and select your subnet where you want to attach the route table with it.

Now, lets jump into the task of creating an EC2 instance.

First, you have to choose the AMI image in which you used for creating an EC2 instance, here I selected Amazon Linux 2 AMI for that.

Then you have to select Instance type, here I selected t2.micro since it comes under free tier.

Then you have to specify the VPC, Subnet for your instance and you have to enable Auto-assign Public IP in order to get your Public IP to your instance.

Then you have to add storage for your instance. It is optional only.

Then you have to specify the tags which will be more useful especially for automation.

Then you have to select the Security Group for your instance. It should be the same as your database have.

And click Review and Launch. Then you have to add Keypair to launch your EC2 instance. If you didn’t have Keypair means, you can create at that time.

Configuring your RDS database

At this point, you have created an RDS database and an EC2 instance. Now, we will configure the RDS database to allow access to specific entities.

You have to run the below command in your EC2 instance in order to establish the connection with your database.

export MYSQL_HOST=<your-endpoint>

You can find your endpoint by clicking database in the RDS dashboard. Then you have to run the following command.

mysql --user=<user> --password=<password> dbname

This output shows the database is successfully connected to an EC2 instance.

In the MySQL command terminal, you have to run the following commands in order to get all privileges to your account.

CREATE USER 'vishnu' IDENTIFIED BY 'vishnupassword';
GRANT ALL PRIVILEGES ON dbname.* TO vishnu;
FLUSH PRIVILEGES;
Exit

Configuring WordPress on EC2

For Configuring WordPress on EC2 instance, the first step is to configure the webserver, here I am using Apache webserver. For that, you have to run the following commands.

sudo yum install -y httpd

sudo service httpd start

Next step would be download the WordPress application from the internet by using wget command. Run the following code to download the WordPress application.

wget https://wordpress.org/latest.tar.gz
tar -xzf latest.tar.gz

Then we have to do some configuration, for this follow the below steps.

cd wordpress
cp wp-config-sample.php wp-config.php
cd wp-config.php

Go inside the wp-config.php file and enter your credentials (including your password too)

Then, Goto this link and copy all and paste it to replace the existing lines of code.

Next step is to deploy the WordPress application. For that, you have to run the following commands in order to solve the dependencies and deploy WordPress in the webserver.

sudo amazon-linux-extras install -y lamp-mariadb10.2-php7.2 php7.2

sudo cp -r wordpress/* /var/www/html/

sudo service httpd restart

That’s it. You have a live, publicly-accessible WordPress installation using a fully-managed MySQL database on Amazon RDS.

Then if you enter your WordPress instance IP in your browser, you will land your WordPress home page.

After you filled in your credentials, you will get your own homepage.

That’s it. You launched your own application in your own instance and your database is managed by AWS RDS service.

Thank you all for your reads. Stay tuned for my next article.

This is a series of Python learning blog from parottosalna community by kaniyam foundation

This blog is based on this video "Python Meet & Greet - Part 2 | Parotta Salna" - Day 1 of Python learning Introduction class

To watch the full series check this youtube playlist

Objectives

1. Introduction to Python Program
2. About Linux user groups and their activites in Tamilnadu
3. Contact numbers and links
4. Forum questions asking methods
5. Today Tasks

• Linux groups and meetups in tamilnadu

  • Kanchi linux user group
    • https://kanchilug.wordpress.com/
    • Every week online meeting and discuss about tech and linux updates
  • FSHM - Pondicheery
    • https://www.fshm.org/
  • Chennaipy - Chennai
    • Monthly meetup
    • having Mailing list

• To get updates for the linux meetups you can check the kaniyam.com website calender

• The know for meetups check for meetup.com

• These groups are volunteer group for knowledge sharing

• GNU Linux

• Windows or Mac are properaty software

• Linux is made by the people for the people

• GNU image for alternative photoshop

• The only thing is after modify the software, it should be reelase it with original license

• muthuramalingam tamil python - Youtube channel

• To eliminate Thayakkam

  • This is what i know, and I am sharing it with you

• By asking questions in forums you are creating a knowledge database

• Ask questions in mailing list in chennaipy.org

• By using tanglish you are not strong in either english or in tamil.

• Things to remember when asking question

  • Don't ask your questions in one line
  • If possible add error code
  • If you have any question, always ask in public

• Programming is like cooking

• UI/UX - Javascript or HTML or CSS

• Srinivasan is using Ubuntu KDE distribution of Linux

• Srinivasan's Phone number: 9841795468

• Dhanasekaran and Srinivasan is organising the class

• Every week saturday teaching reactJS

• Today Exercise

  • Install Python
  • Login in colab

• Freetamilebook.com

• python books

  • Bytes of python

• Telegram link: https://t.me/+2Q_uTW7j9xtkMmVl

This is a series of Python learning blog from parottosalna community by kaniyam foundation

This blog is based on this video "Python - Meet & Greet - Part 1 | ParottaSalna" - Day 1 of Python learning Introduction class

To watch the full series check this youtube playlist

Objectives:

1. Why Python ?
2. Course Syllabus
3. Python Installation - Windows, Linux
4. Collab Notebook
5. Where to see updates & recordings.
6. Where to ask questions ?
7. Our Expectations
8. Basic Print Command
9. About FOSS, FOSS Communities.

• Applications of Python language

  • https://www.python.org/about/apps/

• Syllabus

  • https://parottasalna.com/python-development/
  • Each concepts includes - Basic, Intermediate and Advanced

• Resources provided the team

  1. Blog
  2. Infographic PDF with important concepts
  3. Quiz
  4. Task like exercises

• Learn -> Write blog -> Teach someone

• python is open source

• Python Colab in google for temperavery

  • Each program set is called cell

• To ask questions

  • Ask in Tamil linux forum
  • Direct question in whatsup after class upto 2 hours
  • Few minutes before the class

• To check updates for class

  • Check in Kaniyam website
  • Check in python syllabus session
  • Youtube channel live notification
  • Direct message to mentors

• To find answer for my question

  1. First check in google search
  2. Then ask question

• Expectations

  • To write blog notes after each classes

• Programming

  • Print command
    • print("") this the format of the print command
    • To run the code python print or python print.py

• Python is ready install in linux, if not install it with brew command

• Mentor will use VScode and colob for teaching

• Telegram link: https://t.me/+2Q_uTW7j9xtkMmVl

Alex Pandian was the system administrator for a tech company, responsible for managing servers, maintaining network stability, and ensuring that everything ran smoothly.

With many scripts running daily and long-running processes that needed monitoring, Alex was constantly flooded with notifications.

Alex Pandian: “Every day, I have to gothrough dozens of emails and alerts just to find the ones that matter,”

Alex muttered while sipping coffee in the server room.

Alex Pandian: “There must be a better way to streamline all this information.”

Despite using several monitoring tools, the notifications from these systems were scattered and overwhelming. Alex needed a more efficient method to receive alerts only when crucial events occurred, such as script failures or the completion of resource-intensive tasks.

Determined to find a better system, Alex began searching online for a tool that could help consolidate and manage notifications.

After reading through countless forums and reviews, Alex stumbled upon a discussion about ntfy.sh, a service praised for its simplicity and flexibility.

“This looks promising,” Alex thought, excited by the ability to publish and subscribe to notifications using a straightforward, topic-based system. The idea of having notifications sent directly to a phone or desktop without needing complex configurations was exactly what Alex was looking for.

Alex decided to consult with Sam, a fellow system admin known for their expertise in automation and monitoring.

Alex Pandian: “Hey Sam, have you ever used ntfy.sh?”

Sam: “Absolutely, It’s a lifesaver for managing notifications. How do you plan to use it?”

Alex Pandian: “I’m thinking of using it for real-time alerts on script failures and long-running commands, Can you show me how it works?”

Sam: “Of course,”

with a smile, eager to guide Alex through setting up ntfy.sh to improve workflow efficiency.

Together, Sam and Alex began configuring ntfy.sh for Alex’s environment. They focused on setting up topics and integrating them with existing systems to ensure that important notifications were delivered promptly.

Step 1: Identifying Key Topics

Alex identified the main areas where notifications were needed:

• script-failures: To receive alerts whenever a script failed.
• command-completions: To notify when long-running commands finished.
• server-health: For critical server health alerts.

Step 2: Subscribing to Topics

Sam showed Alex how to subscribe to these topics using ntfy.sh on a mobile device and desktop. This ensured that Alex would receive notifications wherever they were, without having to constantly check email or dashboards.

# Subscribe to topics
ntfy subscribe script-failures
ntfy subscribe command-completions
ntfy subscribe server-health

Step 3: Automating Notifications

Sam explained how to use bash scripts and curl to send notifications to ntfy.sh whenever specific events occurred.

“For example, if a script fails, you can automatically send an alert to the ‘script-failures’ topic,” Sam demonstrated.

# Notify on script failure
./backup-script.sh || curl -d "Backup script failed!" ntfy.sh/script-failures

Alex was impressed by the simplicity and efficiency of this approach. “I can automate all of this?” Alex asked.

“Definitely,” Sam replied. “You can integrate it with cron jobs, monitoring tools, and more. It’s a great way to keep track of important events without getting bogged down by noise.”

With the basics in place, Alex began applying ntfy.sh to various real-world scenarios, streamlining the notification process and improving overall efficiency.

Monitoring Script Failures

Alex set up automated alerts for critical scripts that ran daily, ensuring that any failures were immediately reported. This allowed Alex to address issues quickly, minimizing downtime and improving system reliability.

# Notify on critical script failure
./critical-task.sh || curl -d "Critical task script failed!" ntfy.sh/script-failures

Tracking Long-Running Commands

Whenever Alex initiated a long-running command, such as a server backup or data migration, notifications were sent upon completion. This enabled Alex to focus on other tasks without constantly checking on progress.

# Notify on long-running command completion
long-command && curl -d "Long command completed successfully." ntfy.sh/command-completions

Server Health Alerts

To monitor server health, Alex integrated ntfy.sh with existing monitoring tools, ensuring that any critical issues were immediately flagged.

# Send server health alert
curl -d "Server CPU usage is critically high!" ntfy.sh/server-health

As with any new tool, there were challenges to overcome. Alex encountered a few hurdles, but with Sam’s guidance, these were quickly resolved.

Challenge: Managing Multiple Notifications

Initially, Alex found it challenging to manage multiple notifications and ensure that only critical alerts were prioritized. Sam suggested using filters and priorities to focus on the most important messages.

# Subscribe with filters for high-priority alerts
ntfy subscribe script-failures --priority=high

Challenge: Scheduling Notifications

Alex wanted to schedule notifications for regular maintenance tasks and reminders. Sam introduced Alex to using cron for scheduling automated alerts.S

# Schedule notification for regular maintenance
echo "Time for weekly server maintenance." | at 8:00 AM next Saturday ntfy.sh/server-health

Sam gave some more examples to alex,

Monitoring disk space

As a system administrator, you can use ntfy.sh to receive alerts when disk space usage reaches a critical level. This helps prevent issues related to insufficient disk space.

# Check disk space and notify if usage is over 80%
disk_usage=$(df / | grep / | awk '{ print $5 }' | sed 's/%//g')
if [ $disk_usage -gt 80 ]; then
  curl -d "Warning: Disk space usage is at ${disk_usage}%." ntfy.sh/disk-space
fi

Alerting on Website Downtime

You can use ntfy.sh to monitor the status of a website and receive notifications if it goes down.

# Check website status and notify if it's down
website="https://example.com"
status_code=$(curl -o /dev/null -s -w "%{http_code}\n" $website)

if [ $status_code -ne 200 ]; then
  curl -d "Alert: $website is down! Status code: $status_code." ntfy.sh/website-monitor
fi

Reminding for Daily Tasks

You can set up ntfy.sh to send you daily reminders for important tasks, ensuring that you stay on top of your schedule.

# Schedule daily reminders
echo "Time to review your daily tasks!" | at 9:00 AM ntfy.sh/daily-reminders
echo "Stand-up meeting at 10:00 AM." | at 9:50 AM ntfy.sh/daily-reminders

Alerting on High System Load

Monitor system load and receive notifications when it exceeds a certain threshold, allowing you to take action before it impacts performance.

# Check system load and notify if it's high
load=$(uptime | awk '{ print $10 }' | sed 's/,//')
threshold=2.0

if (( $(echo "$load > $threshold" | bc -l) )); then
  curl -d "Warning: System load is high: $load" ntfy.sh/system-load
fi

Notify on Backup Completion

Receive a notification when a backup process completes, allowing you to verify its success.

# Notify on backup completion
backup_command="/path/to/backup_script.sh"
$backup_command && curl -d "Backup completed successfully." ntfy.sh/backup-status || curl -d "Backup failed!" ntfy.sh/backup-status

Notifying on Container Events with Docker

Integrate ntfy.sh with Docker to send alerts for specific container events, such as when a container stops unexpectedly.

# Notify on Docker container stop event
container_name="my_app"
container_status=$(docker inspect -f '{{.State.Status}}' $container_name)

if [ "$container_status" != "running" ]; then
  curl -d "Alert: Docker container $container_name has stopped." ntfy.sh/docker-alerts
fi

Integrating with CI/CD Pipelines

Use ntfy.sh to notify you about the status of CI/CD pipeline stages, ensuring you stay informed about build successes or failures.

# Example GitLab CI/CD YAML snippet
stages:
  - build

build_job:
  stage: build
  script:
    - make build
  after_script:
    - if [ "$CI_JOB_STATUS" == "success" ]; then
        curl -d "Build succeeded for commit $CI_COMMIT_SHORT_SHA." ntfy.sh/ci-cd-status;
      else
        curl -d "Build failed for commit $CI_COMMIT_SHORT_SHA." ntfy.sh/ci-cd-status;
      fi

Notification on ssh login to server

Lets try with docker,

FROM ubuntu:16.04
RUN apt-get update && apt-get install -y openssh-server
RUN mkdir /var/run/sshd
# Set root password for SSH access (change 'your_password' to your desired password)
RUN echo 'root:password' | chpasswd
RUN sed -i 's/PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config
RUN sed 's@session\s*required\s*pam_loginuid.so@session optional pam_loginuid.so@g' -i /etc/pam.d/sshd
COPY ntfy-ssh.sh /usr/bin/ntfy-ssh.sh
RUN chmod +x /usr/bin/ntfy-ssh.sh
RUN echo "session optional pam_exec.so /usr/bin/ntfy-ssh.sh" >> /etc/pam.d/sshd
RUN apt-get -y update; apt-get -y install curl
EXPOSE 22
CMD ["/usr/sbin/sshd", "-D"]

script to send notification,

#!/bin/bash
if [ "${PAM_TYPE}" = "open_session" ]; then
  echo "here"
  curl \
    -H prio:high \
    -H tags:warning \
    -d "SSH login: ${PAM_USER} from ${PAM_RHOST}" \
    ntfy.sh/syed-alerts
fi

With ntfy.sh as an integral part of daily operations, Alex found a renewed sense of balance and control. The once overwhelming chaos of notifications was now a manageable stream of valuable information.

As Alex reflected on the journey, it was clear that ntfy.sh had transformed not just the way notifications were managed, but also the overall approach to system administration.

In a world full of noise, ntfy.sh had provided a clear and effective way to stay informed without distractions. For Alex, it was more than just a tool—it was a new way of managing systems efficiently.

import java.util.Scanner;

Scanner sc = new Scanner(System.in);

A simple text scanner that can parse primitive types and strings using regular expressions.
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.

Scanner sc = new Scanner(System.in);
System.out.println("Enter the value:");
int value =sc.nextInt();
System.out.println(value);

• int –> nextInt()
• long –>nextLong()
• short –>nextShort()
• float –> nextFloat()
• double –> nextDouble()
• boolean –> nextBoolean()
• String –> nextLine() & next()

reference:https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html

import java.util.Scanner;

Scanner sc = new Scanner(System.in);

A simple text scanner that can parse primitive types and strings using regular expressions.
A Scanner breaks its input into tokens using a delimiter pattern, which by default matches whitespace. The resulting tokens may then be converted into values of different types using the various next methods.

Scanner sc = new Scanner(System.in);
System.out.println("Enter the value:");
int value =sc.nextInt();
System.out.println(value);

• int –> nextInt()
• long –>nextLong()
• short –>nextShort()
• float –> nextFloat()
• double –> nextDouble()
• boolean –> nextBoolean()
• String –> nextLine() & next()

reference:https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html

To know the user is using id command

id username

sudo

permits the user to execute a command as a super user at the admin level

su

su --> switch user
su -username
id 
exit

Zip

zip filename file
zip filename *.txt

zip -sf filename.zip
to view the zipped file.

unzip

unzip filename 

to make another directory to unzip the file or rename the exisisting file.

ulimit

to manage the resources of the particular user.

ulimit -a

soft limit cannot more than hard limit

cat  /etc/security/limits.conf

type> can have the two values:

-“soft” for enforcing the soft limits

– “hard” for enforcing hard limits

type

to know where the command it will present

type command

which 

where the command will locate

which mv

whatis

to know the description of the command

whereis

locate the binary, source, and manual page files for a command

apropos

search the manual page names and descriptions

change attribute

which makes the file unchangeable in the same location. but will copy the file in another location and edit the file.

sudo chattr +i filename

lsattr

sudo chattr -i file

it will convert unchangeable file to changeable file

sudo chattr -R +i dir1
sudo chattr -R -i dir1

to change the directory to unmutable

pidof ---> find the process ID of running program
vi test --> new process
ps -ef | grep vi 
pidof vi
pwdx 8279
to know the present working directory of vi using pid.

nice value

NI –> (-20 to 19) highest priority to lowest priority range.

1 to 19 –> non root users will aslo set the ni values

-20 to -1 –> root user only set the value

to modify the program priority.

ps -l --> process list
to change the priority of the running program
nice -n 11 ps -l

renice

changing the priority of the running program.

user-management

useradd

create a new user or update default new user information.

tail /etc/passwd –> userslist

adduser –> adduser, addgroup – add a user or group to the system

sudo passwd sample
to set a password for sample user.
sudo passwd -Sa
to check all the users having password or not.
set a password for the sample user

after setting the passwd for sample user

sudo passwd -d sample
d --> delete
NP --> no passwd

user-delete

sudo userdel sample
sudo userdel -r sample --> to delete with home

Group

to create group with user

to create a group

addgroup :

deletegroup :

sudo groupdel groupname
sudo delgroup groupname

sudo usermod -aG sudo username
permission to using i commands for new user
to give sudo or root previlage for new user.

To know the user is using id command

id username

sudo

permits the user to execute a command as a super user at the admin level

su

su --> switch user
su -username
id 
exit

Zip

zip filename file
zip filename *.txt

zip -sf filename.zip
to view the zipped file.

unzip

unzip filename 

to make another directory to unzip the file or rename the exisisting file.

ulimit

to manage the resources of the particular user.

ulimit -a

soft limit cannot more than hard limit

cat  /etc/security/limits.conf

type> can have the two values:

-“soft” for enforcing the soft limits

– “hard” for enforcing hard limits

type

to know where the command it will present

type command

which 

where the command will locate

which mv

whatis

to know the description of the command

whereis

locate the binary, source, and manual page files for a command

apropos

search the manual page names and descriptions

change attribute

which makes the file unchangeable in the same location. but will copy the file in another location and edit the file.

sudo chattr +i filename

lsattr

sudo chattr -i file

it will convert unchangeable file to changeable file

sudo chattr -R +i dir1
sudo chattr -R -i dir1

to change the directory to unmutable

pidof ---> find the process ID of running program
vi test --> new process
ps -ef | grep vi 
pidof vi
pwdx 8279
to know the present working directory of vi using pid.

nice value

NI –> (-20 to 19) highest priority to lowest priority range.

1 to 19 –> non root users will aslo set the ni values

-20 to -1 –> root user only set the value

to modify the program priority.

ps -l --> process list
to change the priority of the running program
nice -n 11 ps -l

renice

changing the priority of the running program.

user-management

useradd

create a new user or update default new user information.

tail /etc/passwd –> userslist

adduser –> adduser, addgroup – add a user or group to the system

sudo passwd sample
to set a password for sample user.
sudo passwd -Sa
to check all the users having password or not.
set a password for the sample user

after setting the passwd for sample user

sudo passwd -d sample
d --> delete
NP --> no passwd

user-delete

sudo userdel sample
sudo userdel -r sample --> to delete with home

Group

to create group with user

to create a group

addgroup :

deletegroup :

sudo groupdel groupname
sudo delgroup groupname

sudo usermod -aG sudo username
permission to using i commands for new user
to give sudo or root previlage for new user.

sudo apt install mariadb-server mariadb-client

sudo systemctl status mariadb.servcie

to check the mariadb services.

sudo systemctl enable mariadb.service

sudo systemctl start mariadb.service

sudo systemctl stop mariadb.service

sudo mysql_secure_installation

enter into the database using

mysql -u root -p

to view the default databases which present in mariadb using

show databases;

create new database using 
create database name;
show created database
show databases:
to use the exsisting database
use databasename;

sudo apt install mariadb-server mariadb-client

sudo systemctl status mariadb.servcie

to check the mariadb services.

sudo systemctl enable mariadb.service

sudo systemctl start mariadb.service

sudo systemctl stop mariadb.service

sudo mysql_secure_installation

enter into the database using

mysql -u root -p

to view the default databases which present in mariadb using

show databases;

create new database using 
create database name;
show created database
show databases:
to use the exsisting database
use databasename;

apache -> Hypertext transfer protocol webserver.

sudo apt install apache2 -y

install apache2 webserver in ubuntu.

sudo systemctl status apache2
apache2 status check

sudo systemctl enable apache2

persistently run across the reboot

cd /var/www/html

ubuntu default apache webpage.

sudo vim /etc/hosts

customize the localhost name 127.0.0.1 localhost to eladhruv.in. it will reflect only in local server.

rm index.html  -->  it removes default webpage
we customize the default page.