In the last post we created our ACME Bank database in MySQL, the next step is to get the values from the Values table in the Asp.Net Core WebApi controller.  

Let's create some test data so that we could retrieve the values from the database.  The Values table could contain anything.  So I am going to store famous philosophers throughout history.  These philosophers are so famous that they only have one name: 

You can run the SQL insert statement below to seed the data in MySQL:

INSERT INTO acmebank.Values (
    Name
)
VALUES
    (
        'Socrate'
    ),
    (
        'Plato'
    ),
    (
        'Spock'
    ),
    (
	'Thanos'
    );

So your Values table should look like this when you executed the insert query

 In Linux there's a service often called the Central Logger which generates logs for itself or if permited collects logs for other servers.  The service name is rsyslog and the configuration file is located in /etc/rsyslog.conf

One of the more common usage scenario is that once you scaled out your infrastructure and have hundreds of servers you don't want to log into every servers that are having problems if you need to troubleshoot an issue.  That would take forever, so it is useful to have a centralize logging location.

The command to install the package is dnf install rsyslog -y

To start and enable the service you can type the command 

• systemctl start rsyslog
• systemctl enable rsyslog

In the conf file /etc/rsyslog.conf there's a line that specifies the remote server to send you logging information to, if the server is going to be the client and not the central logger.  Look for the line#

#'.' @@remote-host:514

If you want to send you logs to another server replace the remote-host with the host's IP address or fully qualified hostname and as you can see it will be sending traffic through port 514

Now you can run the service with the command systemctl start rsyslog

 In this post we are going to create our first Entity Framework migration and creating an actual database in MySQL. 

In order to do that we need to add a few NuGet packages to our Asp.Net Core project including the Entity Framework Core package.  But, before we do that we want to find out what what version of .NET Core we are running.  Obviously I have it memorized, but for the rest of you, you can type the command dotnet --version to figure out what the version is :)  It's always a good idea to try and match the package version with the .NET Core runtime you have.  It's one of the more annoying thing with Angular and Asp.Net Core, it's changing constantly. So as you can see my version 3.1.xxx so I should try to install packages that are made for 3.1.x.

The first package we are going to install is the Microsoft.EntityFrameworkCore.  So open the ACMEBank.API project with Visual Studio Code.  Press Ctrl+Shift+P and type NuGet and select

 User Data in an instance allows you run commands while your instance boots up.  In the previous posts we just plain vanilla instances so far.  But in this post we are going to install the Apache Httpd service when we create our instance using User Data.

Here are the steps to create an instance with User Data:

SELECT ProductName,UnitPrice
FROM Products
WHERE ProductName LIKE 'Chef%'

 In this post we are going to install the Apache Web Server, which is the most common web server in the world.  With a web server you can serve up web sites or business products on the web.  Therefore it's kind of like giving your Linux system a purpose to exist.

The service you have to install is called httpd and the configuration files are located in the following directories

• /etc/httpd/conf/httpd.conf
• /var/www/html/index.html

1. systemctl start httpd
2. systemctl enable httpd

5.  To view the web page you typing ifconfig to see the server's IP address

SELECT SUM(UnitsInStock) AS TotalInventory
FROM Products

An instance metadata is data about your instance that you can use to configure your instances.  They are divided into categories.  Anyone who have access to the instance can view the metadata, therefore you should not store anything sensitive that could be accessed such as "User Data"

You can get more information here at Amazon's website:

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/instancedata-data-retrieval.html

You can access your metadata with this URL http://169.254.169.254/latest/meta-data/

Here are the steps to retrieve your instance data:

 1.  Connect to your AWS Linux instance and type curl http://169.254.169.254/latest/meta-data/

 In this post we are going to install MySQL Workbench on Fedora.  MySQL Workbench is a great GUI database management tool for MySQL.  Even though we can do everything we need with MySQL on the terminal it's nice sometime to see the tables and data visually.

Here are the steps to install MySQL Workbench:

1, Go to the yum repository for MySQL at https://dev.mysql.com/downloads/repo/yum/ select the Fedora repository, and click "Download"

 Sendmail is the most common Linux mail service, it is lightweight and is used in administrative tasks as well as sending mail.  In this post we are going to install and configure Sendmail and go over how to use it. Sendmail is the mechanism to send mail, it's not the mail server itself.

First let's install the Sendmail service, type dnf install sendmail -y after sendmail is installed you can install another package which will configure sendmail for you, type dnf install sendmail-cf -y to install that package

One it is installed you need to define your smtp relay server in the file /etc/mail/sendmail.mc file in the line that says dnl define(`SMART_HOST', `smtp.your.provider')dnl this is the one service that you need to have some infrastructure in place before you can use it.  Remember to remove the dnl when you specify the smtp server because dnl means comment in the sendmail.mc file.

Once you have your smtp relay server defined, you can start the sendmail service with the systemctl restart sendmail command

SELECT e.FirstName + ' ' + e.LastName AS Name, t.TerritoryDescription,t.TerritoryID
FROM Employees e
INNER JOIN EmployeeTerritories et ON et.EmployeeID = e.EmployeeID
INNER JOIN Territories t ON t.TerritoryID = et.TerritoryID

 In this post we are going to connect to a Windows instance using RDP.  In order for us to connect to the Windows instance we need to get the password for the server using the key pair that we downloaded from the last post when we created the instance, the .pem file.

Here are the steps to connect to the Windows instance using RDP:

1.  Navigate the EC2 "Instances" page, check the instance and click "Connect"

2. On the next screen click on "Get Password"

 In this post we are going to circle back to MySQL and continue setting up our MySQL database, so that we can use it in our application.  Since we don't want to use our root for log in and we turned off root login for remote connection.  We have to create a dedicated user for our application.  Here are the steps to create a dedicated dev use in MySQL

1. Log into MySQL with root using this command mysql -u root -p

2.  In the MySQL prompt type CREATE User 'devuser'@'localhost' IDENTIFIED BY 'P@ssw0rd'; to create the user, obviously if this is your production environment you would want to use a more secure password

3. Then type GRANT ALL PRIVILEGES ON *.* TO 'devuser'@'localhost' WITH GRANT OPTION; to grant the user all the privileges on all the objects

4. Now type FLUSH PRIVILEGES; to update and apply the privileges

 Now that we have a good understanding of how time works in a Linux ecosystem.  We want to sychronize our time with the chrony package.  There's also the ntp package but it's been deprecated so the way to do this right now is the to do it with the chrony package.

Here are the steps to synchronize time with chrony:

1. First you wan to install the package by running the command dnf install chrony -y it might already be installed

2. Once it's installed type the command systemctl enable chronyd and systemctl start chronyd to start the time sychronization

3. If you want to see more information about the time synchronization on the server you can run the chronyc tracking command

Before we run our Asp.Net Core application for the first time we are going to copy a controller from Asp.Net Core 2.2 to help us create the skeleton for our application.  A skeleton are the plumbings we do at the beginning of our application to make sure all the mechanisms work.  It's called the ValuesController which has been replaced with a more complicated WeatherForecastController.  The ValuesController is just a lot easier to work with to get things set up.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;

namespace ACMEBank.API.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class ValuesController : ControllerBase
    {
        // GET api/values
        [HttpGet]
        public ActionResult> Get()
        {
            return new string[] { "value1", "value2" };
        }

        // GET api/values/5
        [HttpGet("{id}")]
        public ActionResult Get(int id)
        {
            return "value";
        }

        // POST api/values
        [HttpPost]
        public void Post([FromBody] string value)
        {
        }

        // PUT api/values/5
        [HttpPut("{id}")]
        public void Put(int id, [FromBody] string value)
        {
        }

        // DELETE api/values/5
        [HttpDelete("{id}")]
        public void Delete(int id)
        {
        }
    }
}

SELECT EmployeeID, (FirstName + ' ' + LastName) AS Name
FROM Employees
WHERE EmployeeID IN (SELECT EmployeeID 
       FROM EmployeeTerritories 
       WHERE TerritoryID=01581) 

• They are not the most efficient performance wise
• You can only retrieve a single column in the subquery, retrieving multiple columns will throw an error

 NTP stands for Network Time Protocol, in a nutshell what this service does is that it synchronizes your servers so that communications is reliable between servers.  The reason NTP is needed is because there are three types of time in computer networking.  They are the following:

1. Hardware time
2. System time
3. NTP

NTP is graded by Stratums with a scale, yeah buzzwords! So if you have a stratum of 1 that means you are the champ you are at atomic clock synchronization, and if you are at 16 you are a chump!  Best explanation ever!

Anyways to check if you are using NTP you can type the timedatectl status on the terminal

As you can see I am a champ, because the timedatectl status command tells me that my system clock is synchronized and my NTP service is active, and if you say otherwise, "I will break you!".  It's my blog sorry.  Besides showing the status timedatectl is also useful in setting the time it will check to see if the time you set is reasonable for instance you can set the time to 1999 because you wanted to party like it's 1999.  Let's see what happens time using the command timedatectl set-time "1999-01-01 00:00:00" 

 For those of you who works with Visual Studio, working with C# comes out of the box, but with Visual Studio Code you need to install some extensions from the Marketplace to make it suitable for C# development.  

Here are the extensions you need to install:

• C#: This extension by Microsoft gives us IntelliSense, references, code editing and highlighting and debugging support

• C# Extensions: This extension let's you create C# files, like classes and interfaces also some keyboard shortcuts like creating.  This one seems to be no longer in development for a long time, but it works fine.

• NuGet Package Manager: This extension let's us install new NuGet packages which we will need from time to time.

 AWS has a very generous free tier account, but there will be times when you forget to clean up your work and are stuck with the bill.  There's a setting in AWS that allows to set the limits on your account so that you won't get charged for resources or get a surprise on your bill.  

Here are the steps to set a billing alarm:

1. First thing you have to do is sign in as the root user

 In this post we are going to use the .NET Core CLI to create a web api application for our app.  The first thing to do is create an a folder to hold our files.  Since we are using Linux you want to sudo su into the terminal and create the following folder /opt/app/ACMEBank.  Once that's done cd into it and you are ready to type in the command to create the Web Api.

Here are the steps:

1. What you want to do first is to make sure that you have .NET Core install by typing in dotnet --info, there should be information on your .NET Core install.  If you don't have .NET install you can follow the directions in this post.

 The dig and nslookup commands are useful commands that you can use to lookup information about a network.  The dig command gives you more information about a network.  For example for my network I have a DNS server setup in it, if I wanted to display the DNS information on my server I would simply type dig masterdns.acmebanking.com and I would get the following:

As you can see it gives you a lot of information about the DNS server like the IP that the server resolves to.  However, there are times when you just want something quick and brief on what the IP resolves to. For example you might know the IP address but not the hostname or vice versa and you want to lookup the information on the part that is know that's when nslookup comes in handy.  For example let's say you know the IP address 192.168.0.15 but you don't know the hostname.  You can lookup the hostname by typing nslookup 192.168.0.15 and you would get the hostname that resolves to the IP address

 SELECT COUNT(*) NumberOfProductsByCategory
FROM Products
GROUP BY CategoryID

 So far we have connected to our EC2 instance with the terminal on Linux and Putty on Windows.  There is another option that you can perform and it only requires that you have a browser.  You must have an Amazon Linux Version 2 instance for this to work, at least that's what I think.

On the instances page on the AWS console click on the "Connect" button while the instance is selected

The most important thing for most modern dynamic application these day is choosing a database to store your data.  If you are on a Windows environment then you use SQL Server database that is a fine choice. But if you are on Linux MySQL is a great choice also.  In this post we are going to go through how to install MySQL server on our Fedora development machine.

Here are the steps to install MySQL on Fedora Linux:

1. First we need to add the MySQL repository to our machine by tying in the following command in the terminal

sudo dnf -y install https://dev.mysql.com/get/mysql80-community-release-fc32-1.noarch

 The chattr command in Linux is one of the more useful commands that you've probably used but have no idea what it's use is, it just works!  That's probably the most dangerous phrase in IT.  Well just from the command you can tell that controls the file modify attribute of the file.  Well not really I mean how is chattr related to file attributes.  I guess it's change attribute.  It's pretty easy to use + means to add an attribute, - means to remove an attribute, and = means you want to assign an attribute.  You can also add attributes with the -R option to reclusively on a directory.

One of the senario I used often is when I want to make a file immutable, I'll just type chattr +i filename.  For instance if I and setting a DNS server and I don't want the DHCP scripts to change the resolv.conf file every time I restart the NetworkManager.service I would just type chattr +i /etc/resolv.conf to make the file immutable.  If I try to modify the file I would get the following error message saying I can't modify the file.

It's just as easy to make it writable again, it would just be chattr -i /etc/resolv.conf

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 On the previous post we connect to our EC2 instance using SSH on Linux now I will show you how to connect to the EC2 instance using Putty on Windows

Here are the steps to connect to our EC2 instance on Windows:

1. Download and install Putty from here 

2. Open PuttyGen from the start menu, and select your .pem file and convert it to a .pkk file

Once it's open select "File", then "Load private key", then select your .pem file

In this post we going to get our development environment with NodeJS, VSCode and Postman

The Urls are the following, if you are developing in Linux you should install the Linux version.  All these tools are cross platform so you can develop in either Windows, Linux or MacOS:

.NET Core: https://dotnet.microsoft.com/download

Node.JS: https://nodejs.org/en/

Visual Studio Code: https://code.visualstudio.com/#alt-downloads

Postman: https://www.postman.com/downloads/

For .NET Core make sure you download the "recommended" version and not the preview version. Also with NodeJS, usually it has LTS status.

Installing .NET Core SDK and NodeJS On Fedora

In order to install .NET Core SDK on Fedora open the terminal and type in the following

sudo dnf install dotnet-sdk-3.1 -y

The -y tells Fedora to skip the y/N prompt and just go on with the install

Once the SDK is installed you can verify the install with the command dotnet --version