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Hello, everyone, and welcome to this lesson.

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In this lesson, we are going to understand a very important concept about network repositories and

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Kali Linux.

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Now what are repositories?

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So it's basically a place from where you can fetch, download and install all the tools or softwares

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that you want in your Linux machine.

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Kali by default has its own repo that you can update and fetch tools or any programs that you want.

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But sometimes there are some tools or other programs which are not in the official repository.

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So to do that, you have to manually add new repositories in your operating system.

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Once you add this new repo path, it allows you to fetch, download, and install those new tools or

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programs.

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So in this lesson, we are going to walk through that.

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What are sources start list repositories?

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How you can come across an error when you want to install a specific software which is not in the official

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repo.

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How to fix it by adding a new path in the source start list and update the repository of our Kali Linux

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machine and then successfully install that software that you want.

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So the first thing that we are going to see is we are going to read these sources start list file which

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is inside Etsy apt.

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When you go over here by default in the Linux default installation, this is the official repo that

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you will see now when you navigate to the next directory which is sources dot list dot D, you can see

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over here there are three list files which are been added explicitly which allows you to install Google

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Chrome, protonvpn, sublime text dot list, etc..

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Now let us try to read one of the list file.

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So let's say we are reading Google Chrome dot list here.

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You can see this file is automatically configured which is written in comment.

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You may comment out this entry, but any of the modifications may be lost.

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Here you can see the architecture is AMD 64.

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The version of the program that is going to be downloaded is for Debian.

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It is going to be downloaded from this specific URL, which is DL, which stands for download or Google.com

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Linux Chrome for Debian, the stable main version.

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I hope you guys understood this.

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Now let us see the next one.

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This one is for Protonvpn stable dot list.

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It says that this is a Debian download.

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This is a specific URL which has been signed by a keyring, which is a valid certificate which allows

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to download files officially from the server.

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Let us see the next one.

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Let's see what's next.

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So let's say I want to install this program, which is signal now signal like any other application

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like Telegram or WhatsApp.

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It allows you to do communication.

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This specific software is not in the official repository, which means you cannot install it directly

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by typing the command app to get install signal.

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So once we go on this website here we see the Linux Debian based install instructions which we are going

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to follow in which we primarily are going to give the repository path to our Linux machine and then

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we are going to fetch the tool and install it successfully.

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So here you can see there are three steps.

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Step one, to install our official public software signing key, which will validate that the request

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that is going is valid and you will be able to download the software.

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Next is adding the repository to your list of repositories and finally the command to install this tool.

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Let's see what happens if we directly run the command without giving the path to the repo.

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In our source short list you can see our machine will give an error like this which says unable to locate

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package, this is because it is unable to identify the signal desktop package into the official default

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repository which it is trying to fetch from.

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Okay.

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So we are going to follow the steps one by one.

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The first step is to give the official signing key in our system.

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The next step is going to download the repository to our sources start list.

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So I'm going to copy paste the command over here.

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Here you can see this is exactly the same thing that we saw in Chrome and Protonvpn, which says the

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architecture is aimed 64 for Debian assigning key and from there the program or the tool needs to be

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downloaded from.

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Let us verify this by going in the same directory.

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And you can see over here signal dot list.

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One more list has been created successfully and when we try to read this list it is exactly as same

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as for Google Chrome and Protonvpn.

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Great.

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So now we have successfully added the list in our Kali Linux.

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Now we need to update our repositories.

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So for that we have to run the command, which is sudo apt update when we run this command.

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It allows our Linux machine to update the repo path and fetch the tools from new given source to start

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list.

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As you can see get one request says that it has successfully updated its repo path to fetch programs

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from update signal dot org.

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Next we saw google.com.

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The third one is update start signal dot org.

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Again, these are all the custom path that we have added that we want to fetch the programs from the

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next hit.

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As you can see over here are basically the default rip apart from where it is trying to fetch, if there

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has been new programs that has been added or any new packages that have been updated.

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It will take few seconds to update its official repository and we just have to wait in for here.

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Once this step is completed successfully, we would now be able to run the command, which is to install

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the signal package.

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As we saw before, when we ran that specific command, it gave us an error.

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But let us see this time what will happen?

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Will it again give an error or will it allow us to install?

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So it's almost complete.

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So we are going to base the command this time and hit enter and you can see it is successfully installing

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the package that we want.

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Here we can see previously we got the error while installing the signal text drop package.

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We successfully ran the first command to add the list file in our system and the key ring as well.

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After that we did an APT update and then we were successfully able to install the package in our system.

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I hope you guys understood this.

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Thank you.