Introduction

SSH (Secure Shell) is a popular, secure protocol for remote access to servers and other network devices. When you launch an EC2 instance, you can connect to it using SSH to manage the server, install and update software, configure settings, and perform other administrative tasks.

• Prerequisites
• Connecting over Unix-based systems
• Connecting over Windows

Prerequisites

Before you can connect to an EC2 instance over SSH, you need the following:

• Running EC2 instance and accessible over the network.
• The EC2 instance’s IP address or public DNS.
• The appropriate security group configured to allow SSH access (port 22) from your IP address or network.
• The private key file (.pem) corresponding to the key pair used when launching the instance.

Remember to keep your private key file secure and not share it with anyone. It is the key to accessing your EC2 instance.

If you encounter any issues while connecting, double-check that your instance is running, that the security group allows SSH access from your IP address, or that you are using the correct private key file.

Connecting over Unix-based systems

To connect to your EC2 instance via SSH at Unix-based systems like Linux, macOS, or others, follow these steps:

Locate the private key file

Find the private key file (.pem) you downloaded when you created the EC2 instance.

Make sure you have the correct permissions to use the private key file. On Linux or macOS, you can set the permissions using the command:

chmod 400 /path/to/your/private-key.pem

Connect to the EC2 instance using SSH

Open a terminal or command prompt and use the `ssh` command to connect to your EC2 instance:

ssh -i /path/to/your/private-key.pem ec2-user@<public-dns-or-ip>

• Replace /path/to/your/private-key.pem with the real path to your private key file.
• Replace <public-dns-or-ip> with the public DNS or IP address of your EC2 instance.
• If you’re using a different username than ec2-user (e.g., for Ubuntu instances, it’s usually ubuntu), modify the command accordingly.

Here’s an example of the SSH command:

 ssh -i ~/Downloads/my-key-pair.pem ec2-user@ec2-1-25-67-980.us-west-2.compute.amazonaws.com

Accept the server’s host key

If it’s your first time connecting to the instance, the server may prompt you to accept its host key. Type yes and press Enter to continue.

Connection to EC2 instance

Success! You should now have successfully connected to your EC2 instance via SSH.

Connecting over Windows

If you’re using Windows and don’t have the ssh command available, you can use an SSH client like PuTTY:

• First, convert your private key file (.pem) to a format compatible with PuTTY (.ppk) using PuTTYgen. If you do not know how, just check the section below.
• Open PuTTY and enter the public IPv4 DNS or IP address of your EC2 instance in the “Host Name (or IP address)” field. Keep “Connection type” as “SSH”.
• From the “Connection” category in left tree navigation, select “SSH -> Auth” and click on “Credentials”.
• For “Private key file for authentication” click on “Browse” and select the private key file (.ppk).
• Click on “Open” to initiate the SSH connection. At “Putty Security Alert”, click “Yes” to accept the server’s host key.

Generating a .ppk file from a .pem file

To convert your private key file (.pem) to a .ppk file for use with PuTTY, follow these steps:

• Open PuTTY Key Generator (PuTTYgen) and click on “Load” to select your private key file (.pem).
• Click on “Save private key” to convert the key to PuTTY’s .ppk format and save it to a location of your choice.
• You can now connect the converted .ppk file with PuTTY to your EC2 instance.

Conclusion

This article has shown how to connect to an Amazon EC2 instance over SSH. Following the steps outlined above, you can securely access your EC2 instance and manage it remotely using SSH.

Be sure to store your private key file securely and avoid sharing it with others, as it serves as the gateway to accessing your Amazon EC2 instance.

If you face any connection issues, verify that your instance is operational, that your security group permits SSH access from your IP address, and that you employ the correct private key file.

Did you find connecting to your EC2 instance over SSH easy? Do you have tips or another way to connect to an EC2 instance? Let us know in the comments below. We’d love to hear your ideas and experiences.

Thanks for reading!

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I had stuck on the problem when I needed to provide private key .pem file type for the OpenSSL command. However, the private key was saved in .der file type, so I needed to convert it.

There is a way to convert .pem file type on the Windows operating system to .der without using command line. Go to the Windows search bar and search for KeyStore Explorer. Open the KeyStore Explorer program. After opening the KeyStore Explorer, you should get the program screen like this:

KeyStore opened

Click on the icon Examine a Certificate. From a system select your .der file. After selecting the .der you should get the KeyStore image like this:

KeyStore – .der file opened

Now all you need to do is to click on the PEM button. It will open you content of the .der file in .pem format.

KeyStore – .der file turned to .pem

You have now two options:

• You can either copy .pem file content into the system memory with Copy option.
• Or you can export .pem file content on you machine disk with Export option.

Note : Never show or publish content of your private keys!

Conclusion

This article has shown how to turn .pem file type into the .der file type on Windows.

Did you find turning files easy? Do you have your trick or know another way how to turn .pem file type into the .der file type? Let us know in the comments below the article. We would like to hear your ideas and stories.

How to set hot swap with Trava Open JDK in your IntelliJ Idea

1. Install to your computer Trava Open JDK. You can find installation binaries at Trava Open JDK on GitHub. If you are Windows user, I would give you a tip to just download Windows binaries and unpack them to folder where you have the rest of JDKs. Exp. C:/Program files/Java/ .
2. In IntelliJ Idea go to Project Structure and under Platform Settings add to SDKs Trava Open JDK. Also under Project Settings in Project SDK select Trave Open JDK as JDK for your project.
3. And as last step change in IntelliJ Spring Boot runner configuration Running Application Update Policies. Change On ‘Update’ action and set it to Update classes and resources and On frame deactivation set the same to Update classes and resources. You can check image below for more details.

And that is all. You can start your app now, and your code will be hot-swapped on frame deactivation. Or you can command hot-swap manually with ctrl + shift + f9.

How to install Azure CosmosDB Emulator

First of all, we need to install Azure CosmosDB Emulator locally. Go to https://docs.microsoft.com/en-us/azure/cosmos-db/local-emulator#installation, download the windows installation package and install Azure Cosmos DB Emulator.

When installing Azure Cosmos DB Emulator passed successfully on your Windows machine, start the emulator (if it did not start automatically).

If it is already running you can find it minimized in the system hidden in the running application system and either click Open Data Explorer … or visit https://localhost:8081/_explorer/index.html page. You can now get finally into the Azure CosmosDB Emulator.

Exporting security certificates

Azure Cosmos DB Emulator uses a secure connection with your application. We need to extract and register your certificate for communication with the emulator.

Let’s type “Manage user certificates” into Windows Start console or open Windows Certificate Manager (running certlm.msc in the run prompt). Go to Personal->Certificates folder and export certificate with DocumentDbEmulatorCertificate name. The whole tutorial how to do it can be found at Microsoft Azure website explaining how to export the Azure Cosmos DB SSL certificate.

You can name your file when exporting arbitrary. However, we will name it for our example documentdbemulatorcert.cer.

Now when I have extracted the SSL certificate, I need to upload it into the correct Java SDK location.

Check which version of Java do you use in your project. In IntelliJ idea you can use either keyword shortcut [ctrl] + [shift] + [alt] + [s] or go to File->Project Structure->SDKs and check which version your Spring Boot application uses or where SDK is located.

Copy certificate into the Java SDK directory. It should be copied into the %JAVA_HOME%/jre/lib/security location.

If you use OpenJDK, OpenJDK does not contain jre folder. Just copy it into %JAVA_HOME%/lib/security location.

Registering certificate

The nearly last thing we need to do is to register the certificate into the system.

We need to open the Windows Command prompt as an administrator and navigate at JDK’s folder at jdk\jre\lib\security.

Hint: A little hint if you are more familiar with Linux based systems than Windows. If you open a folder in Windows, copy the path to the folder and place it into quotation marks in the command prompt. Executing the command changes the directory instantly.

Then, upon the folder, we need just to run the following command to register the certificate into the keystore on your system:

keytool -keystore cacerts -importcert -alias documentdbemulator -file documentdbemulatorcert.cer

Hint: Keytool is a tool located in your Java installation, so you need to have jdk/bin on your PATH for this to work.

If you need a hint with registration, check this tutorial at Microsoft Azure website where you learn how to add a root certificate to the certification authority certificates storage. However instead of bc2025.cer name in tutorial use name of your certificate.

Otherwise, when the prompt asks for a password, type your password. More likely you didn’t change it, so default password is changeit. Following, you get a question, if you trust this certificate. Answer it simply yes.

That is it. The certificate is registered, and Azure Cosmos DB Emulator should be now created securely and with ease.

Using emulator with local Spring Boot app development

And all we need to do now is just run the Spring Boot application. If you implemented a connection to Cosmos DB and registered connection properties to application.properties or application.yml you can successfully run the application.

azure:
   cosmosdb:
    uri: https://localhost:8081
    key: VERY_LONG_KEY
    database: YOUR_DB_NAME

To fill up application.yml you will need to implement your own data:

You can find VERY_LONG_KEY in your Azure Cosmos DB Emulator Data Explorer under the Quick start tab.

And all we need to do now is just run the Spring Boot application. If you check now Data Explorer under Explorer tab, you can find now your database with all the defined structures.

Troubleshooting

In case you already successfully installed the Azure CosmosDB Emulator and you want to restart the database, you have an option to reset data. Data reset comes handy when you get an authentication issue over HTTPS with your Azure CosmosDB certificate on the application run.

Pick up “Reset data” from the Azure CosmosDB Emulator mini-panel dialogue window from your start button. Operation is not reversible; it will clean up all your caches and the internal state of the Azure CosmosDB Emulator database and reset the certificate.

Then it would be best if you continued extracting the certificate from the list of certificates according to the description in Exporting Security Certificates. However, before registering the certificate back to Java keytool, you need to remove the old alias on the certificate with a command like this:

keytool -delete -alias documentdbemulator -keystore cacerts -storepass changeit

Notes: behind -alias you place the name of the certificate, -keystore is the name of a file containing the certificates and behind -storepass is your password (default is changeit).

Issue

I got into trouble with my Spring Boot application on my development machine. The application port occupancy prevented my local Spring development environment from running. By default, Spring uses port 8443. So, I needed to make the port free to run my application without needing to rewrite the port number in the application config file.

Solution

Here is a simple solution on how to set the occupied port free on Windows OS:

Step 1

You must run the Windows Command Line as an Administrator or Git Bash. Then, run the command below with the port number in the port number placeholder.

netstat -ano | findstr :MY_PORT_NUMBER

The number on the right side (PID – process identifier) is the number of processes currently using the port.

Step 2

For this, you can use only the Windows Command Line. First, you need to kill the process using the port so the port can be set free. Type the following command with process PID to the command line:

taskkill /PID YOUR_PID_NUMBER /F

Prefix /F, in this case, means forcefully terminates the process.

If everything went smoothly, you should get the following message:

SUCCESS: The process with PID YOUR_PID_NUMBER has been terminated.

In the end, rerun the first command to check whether the process is on or not. If you get an empty line, the process successfully ends, and the required port is free.

Conclusion

This article shows how to kill the Windows operating system port quickly.

Did you find releasing ports easy? Do you have your trick, or do you know another way how to kill specific port on the Windows operating system? Let us know in the comments below. We would like to hear your ideas and stories.