Run a command during boot time

I wanted to add a command to crontab so that it is executed every time Linux boots so that I do not have to enter the command manually. I wanted to turn off the red light on my microphone outlet in Ubuntu.

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SHA256 using OpenSSL library (Linux)

I love cryptography and it was one of my favorite subjects in college. So recently when at work, I was asked to compute SHA256 for some data, I did some reading and learnt a lot of new stuff. I love learning anything new so enjoyed this exercise a lot. One of those days when work can be actually fun!

“A cryptographic hash (sometimes called ‘digest’) is a kind of ‘signature’ for a text or a data file. SHA-256 generates an almost-unique 256-bit (32-byte) signature for a text. A hash is not ‘encryption’ – it cannot be decrypted back to the original text (it is a ‘one-way’ cryptographic function, and is a fixed size for any size of source text). This makes it suitable when it is appropriate to compare ‘hashed’ versions of texts, as opposed to decrypting the text to obtain the original version. Such applications include stored passwords, challenge handshake authentication, and digital signatures.” (taken from here).

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Using Crontab

Crontab command is used to edit crontab files. These files have a list of commands that are to be executed on a particular day at a given time. They are most useful when you want to run some tests or some cleanup commands or something that needs to be run regularly – say weekly or monthly. The commands specified are executed automatically and logs can also be collected from those commands, along with an email that will be sent to the user. I had not used this feature until recently when I was asked to use them at my job. These crontab files are maintained per user, so each user can configure his own commands to be run.

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Ubuntu on my Macbook

I own a Macbook Pro for sometime now and had installed windows on it along with Mac OS. Windows kept crashing every few days and I had to reinstall it repeatedly. Finally, I got fed up and removed it completely from my Macbook. I have always loved Ubuntu as it is extremely user friendly and is powerful, owing to the fact that it has Linux Kernel. Having used Ubuntu while I was in University, I have a special kind of liking towards it. That was when I decided that I want to install Ubuntu on my Macbook.

How did I install Ubuntu?

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