DevOps and Linux practice pt. 2

After setting up our development environment and practicing a little bit with cron in part 1, it’s time to do something useful with it. But first, lets make sure that my repository and account are safe.

1.- Setting up 2FA

GitHub has the option to connect with 2 factor authentication to your account, I have activated this option and now after signing up in an unknown device they ask for a number that they send to my phone via SMS. Now, whenever I try to push from the terminal when I’m not logged in it won’t accept my password account, this happens because with 2FA I have to generate a token and use that token as my password. I use two tokens, one for Linux and the other for Windows, they both have the minimal permissions to let me push into the repository but not delete or modify anything important from that repository or others as well.

2.- Setting up SHH keys

To avoid copying and pasting that token each time I want to use my account in the terminal there is a alternative, the SSH keys. To generate one I followed this complete tutorial, now I can connect with the key from any place I want.

3.- Cron server update automation

Now for the cron practice, I already changed the bash script to do a pull instead of just printing hello world. Also, I considered to change the cron file to run the script every 12 hours. I’m still not sure how often I should update, or how often companies do it in a real life development environment, but 12 hours seemed reasonable for me because it updates the server when people(me) are supposedly not updating the repository. However, the problem with this is that if someone pushes a broken piece of code, it will not be fixed until the next 12 hours or that someone corrects the bug and pulls manually from the server. For this practice I need to watch consistent changes, so I’m going to change the script to do a pull each minute. Whenever the server pulls any change, the website updates with a refresh if it is a simple change like a text line in the html, but I need to run it again if something like new dependencies and a JS script were added. I’m not sure if this happens because I’m using NodeJS to run the server or if this is a normal behavior, but Node already has some solutions related to this, check this site if you want to see how to use the node demon or you want to avoid refreshing the web page each time the server updates. I’m not implementing any of this for now, but I will consider it for the next practices. To ensure that the server is not running two copies of the same script there are several techniques, a simple solution is to create a file and after making the pull deleting the file. Before creating the file we should check if it already exists, if it does, then wait until the script that created it deletes it; if it doesn’t exists; then there is no concurrency and everything should execute normally.  I added this solution in the bash script, to do that I had to learn first how to do it. This bash cheat sheet helped me a lot, I think is a very useful resource when you are coding scripts.


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