Replace ssh key of the AWS EC2 machine

You can follow the below steps to change the SSH key for a AWS EC2 machine.

Step 1)

Check that you have existing ssh key working and we can log in to the machine using it. You can also directly login via a new function in AWS console.

Step 2)

Generate a new SSH key via Amazon Web Console

Step 3)

Get the public key from it. Using the command below

ssh-keygen -y -f ~/Downloads/second.pem

If working on Windows system using this

Step 4)

Login to the machine and edit the file.

vi ~/.ssh/authorized_keys

Add the new public key and check that you are able to login with the new key

Step 5)

Change permission of new key to 400 and try to login

Step 6)

If login is successful delete the old key from authorized keys file

Tips for AWS Professional certification exams

I recently gave AWS Professional exam and found certain things that are useful to be documented and share with all.
This post is generally about non-technical things. For technical pointers please see the other related posts.
AWS professional exams not only test your AWS knowledge but, also test our mental and physical strength. You have to sit there for 3 hours staring at the screen and read large large texts in questions and answers.
Below are the things which can be useful for you
Stretch at regular intervals
After every 30-45mins just stand up and stretch your legs, or just stretch your hands while sitting, this will keep your blood circulation moving and helps to keep you active.
Time management
AWS professional exams are the fight against time, you need to keep a constant tab on your clock which ticks on the screen. As a rough guideline try to complete 30 questions in the first 60mins, 30 in the next 60mins and keep the remaining 15 questions in 30mins. Try to spend just 2 mins per question and mark any thing which you are doubtful for a review and go ahead.
Time left >>>>> Questions pending
170 >>>>> 75
110 >>>>> 45
50 >>>>> 15
20 >>>>>  0
In the last 20mins try to review any questions which you have marked during the first pass.
Question reading
Read what is really asked first. Don’t start reading the question from the top to bottom and then read the answers. Don’t do this.
Just to make it clear, see the example question below from the AWS Solutions Architect Professional exam.
Your company’s on-premises content management system has the following architecture:

  • Application Tier – Java code on a JBoss application server
  • Database Tier – Oracle database regularly backed up to Amazon Simple Storage Service (S3) using the Oracle RMAN backup utility
  • Static Content – stored on a 512GB gateway stored Storage Gateway volume attached to the application server via the iSCSI interface

Which AWS based disaster recovery strategy will give you the best RTO? 

A) Deploy the Oracle database and the JBoss app server on EC2. Restore the RMAN Oracle backups from Amazon S3. Generate an EBS volume of static content from the Storage Gateway and attach it to the JBoss EC2 server.

B) Deploy the Oracle database on RDS. Deploy the JBoss app server on EC2. Restore the RMAN Oracle backups from Amazon Glacier. Generate an EBS volume of static content from the Storage Gateway and attach it to the JBoss EC2 server.

C) Deploy the Oracle database and the JBoss app server on EC2. Restore the RMAN Oracle backups from Amazon S3. Restore the static content by attaching an AWS Storage Gateway running on Amazon EC2 as an iSCSI volume to the JBoss EC2 server.

D) Deploy the Oracle database and the JBoss app server on EC2. Restore the RMAN Oracle backups from Amazon S3. Restore the static content from an AWS Storage Gateway-VTL running on Amazon EC2
When you see this question, the first thing which you should read is the text underlined. This will give you an idea of what is really needed. Then quickly go up and read the full questions and start reading the answers options. Keep on eliminating the answers till to are able to find the correct answer as per what is asked for the underlined text.

While reading keeps on eliminating the wrong answers and iterate until you are able to reach the most suitable answer as per the ask of the question. If you are stuck with a choice of 2 and not able to decide on the final one, mark that question for review, randomly mark one choice as the answer, note on the notepad provided with question number and choices for which the final battle is to be decided. You can come back to this question later at the end of the exam if time permits. This happens very rarely that you will get time to review. So, we have to mark something in the first pass and then later decide if we get time in the review.

Water bottleA clear water bottle is allowed, keep it next to you and drink a sip when your brain starts steaming in the middle of the exam. It will happen that brain will be jammed in the middle at the regular intervals and you will need some fuel to keep it going :)

Thank you for reading. I am done with AWS Devops Professional and now preparing for the SA Pro.  What are your tips for the AWS professional exams?

How to pass AWS Devops Engineer Professional Exam


I recently cleared AWS Devops Engineer Professional exam.

Below is what I did and hopefully can be helpful to you as well for the exam.


  • Stephane Udemy course. I did everything he told. Readings (He suggests lots of things to read) + Watched videos 2 times and labs. I did all 3 Associate exams also following Stephane. So, he does assume that we know the basics.
  • AWS Official Devops exam readiness. This course tells about how to approach the question and the test. I highly suggest you to take this and it is a free course.

Practice tests

This exam tests your time management. So keep an eye on the watch on your side. Try to finish 30 questions in first hour, 30 in second hour and 15 in the remaining time plus for the questions you marked for the review. I was very slow and managed to finish the exam only 5 mins to spare.

Good luck

How to pass AWS Certified Developer exam

I cleared AWS Certified Developer Associate exam with 968 scores. Below is my blueprint for success which you can follow.

Study material
  • Udemy Stephane Maarek course
  • Linux Academy course
Practice tests
  • Whizlabs
  • Udemy Stephane Maarek practice tests 
If you are short of time, then just do the Stephane Maarek course and practice with Whizlabs and Udemy Stephane Maarek practice test.

Good luck




Convert webpage to pdf using Python

If you dont want to use Python then one easy way is to use website

If you want to use Python then see the library below

Gradle proxy settings

If you are behind the corporate proxy, you can configure Gradle to use the proxy by following settings.

Create a file called ~/.gradle/

Generally is in «USER_HOME»/.gradle/, where «USER_HOME» is your home directory.
That’s typically one of the following, depending on your platform:
C:\Users\<username> (Windows Vista & 7+)
/Users/<username> (macOS)
/home/<username> (Linux)

Add the settings related to proxy.

Also add the HTTPS proxy settings

If your proxy is a CNTLM then you can also configure

* Set the http.proxyUser system property to a value like domain/username.
• Provide the authentication domain via the http.auth.ntlm.domain system property.