Installing Docker On CentOS

Docker is the hottest infrastructure technology to hit the tech world in a long time.  The appeal of Docker is that it allows the infrastructure team to utilize the capacity of the servers to near full capacity.  Docker is a container.  A container is like a micro virtualization minus the operating system.  It only contains enough infrastructure to host an app, without the fat.  Hence the term container is used to describe it.

SQL: MAX() And MIN() Aggregate Functions

The MAX() function gets the highest value in the specified column, and the MIN() function gets the lowest value in the specified column

SELECT MAX(UnitPrice) AS HighestPrice, MIN(UnitPrice) AS LowestPrice
FROM Products

The query above gets the highest and lowest prices for the Products table in the Northwind database


 

Iaas With AWS: VPC With Public And Private Subnets, Create NAT Gateway For Private Subnet

 In the previous post  we created a public and private subnet in our VPC.  In this post we are going to create a NAT gateway so that our private instances can access the internet.  That's useful when there's a need to update the instance.  For example if we ping google.com right now there will be 100% package lost in our private instance because we cannot get to the internet.  After we attach the instance to the NAT gateway we will be able to ping google.

It would go on for a while but eventually it would say the package is lost.

Now let's create our NAT Gateway, it is important that we delete the NAT Gateway if it's not in use because you have to pay for it.

JavaEE: Install The Eclipse IDE On Windows

In this post we are going to install the Eclipse IDE for Java development.

Here are the steps to install Eclipse:

1. Go to https://eclipse.org/downloads click on the "Download 64-bit" button

Linux Administration: Disk Partitions Getting Partition Information With df And fdisk Commands

 As a Linux administrator there will be times when you go in blind and do not know why system you are logging into, one way to CSI your way through the system is with the fd and fdisk command.  Which will tell you who murdered Sideshow Bob.  Not really it will just tell you the systems disk information and the partition it has.  The first command you can run is the df command, if you run it by itself it would look a little cryptic.  So most of the time you will see people run it with the -h option

The df command which is an abbreviation of the words disk free is a command used to display the amount of available disk space for file systems.  It gives you amount of disk space available for each mount points.

The next command you can run is the fdisk command, as with df if you just type fdisk by itself, you won't get anything useful.  So you usually see it with the -l option

fdisk gives you the disk partition information as you can see we have two partitions and mount points, the first is a boot partition which does not have a lot of space which it does not need a lot of space.  The second partition has the bulk of space and is the system that we as users and administrators interact with.  It also tells you the swap size and mount points.  The home sector is also shown, you will often see the system administrator use this command when the system is running out of space.

SQL: Sort By Multiple Columns

SELECT UnitPrice, ProductName
FROM Products
ORDER BY UnitPrice DESC, ProductName

The query above sorts the results based on the most expensive products, and then the product name. Useful if you want a secondary sort criteria. For example if there are multiple products that are $14.00 then those products will be sorted by their names after the price has been sorted.

SQL: DATEPART Function

The DATEPART function extracts the date part of a date, for example using the 'yyyy' expression allows you to extract the year from a given date. The query below queries all the employees who were hired in the year 1994 in the Northwind Employees table.

SELECT FirstName + ' ' + LastName  AS Employee, HireDate
FROM Employees
WHERE DATEPART(yyyy,HireDate) = 1994

Iaas With AWS: VPC With Public And Private Subnets

 In most scenarios you don't want to expose all of your servers to be public facing.  You probably want to configure your network so that only the server that is hosting your web application is public facing.  What you want to do is put your web application on the public subnet and your backend servers on the private subnet.  This private subnet can access the internet through a NAT gateway for software updates and other functions that require internet access.  However, the outside world cannot establish a connection to servers in the private subnet.  The NAT gateway resides in the public subnet, acting as a bridge between the public subnet and private subnet.

JavaEE: Install Tomcat 9 On Windows

2. Under "Binary Distributions" select the last link

Linux Administration: Message Of The Day

As a Linux administrator you can set the message of the day for users to see when they are logged in.  It could be a reminder of a maintenance schedule or just to say high.  Or if you want to get fired a fake hacked message...j/k...lol  It does seemed like someone hacked your system sometimes when you see it as a user though.

The file that controls the Message of The Day message (pun) is located in /etc/motd 

All you have to do is modify the file to display the message to the users in your system.

So vi /etc/motd and type in your message and the next time a user logs in he will see the message

One caveat is that it will only appear in text terminal session login such as logging in using Putty you will not see the message if you log in using the GUI.

Unfortunately, you've been told that you've been hacked by Kanya's evil twin brother, who's a better rapper!