The surprising powerful world of Linux

Welcome back to the roadmap of Penetration Testing where we’ll go through the world of Linux. I hope you would have set up and would be ready with loaded guns. So, let’s get this started to know: What is Linux?

I’ll provide you brief about how does the world of Linux look from the inside. If you have not completed what we have done before, I recommend you to go back and complete that first because the fun will get ruined if the flow break.

Opening the doors of Linux

So, we’re about to start with the new world. But first, I have something for you. You can subscribe to the mailing list and I’ll let you know whenever the roadmap has a new stop at weekends.

File Structure

For Linux, everything is a file or a process. There are certain details of the file structure you need to know about.

• Directory — It’s the list of other files. A folder of files
• Link — It’s a way to make a file to be available in more than one place
• Special File — These contain mechanisms of input and output
• Sockets — These provide information about internal networking
• Pipes — It provides a way for processes to communicate

Common Commands

Linux is all about your flex with its command. Here are a few of them. Open the terminal and try these:

ls - list a directory's contentcd - move to another directoryrm - remove a filechmod - change ownership of the filepwd - print name of the current directorymkdir - create a new directoryrmdir - remove an empty directorywhereis - find some files in the systemcp - copy a filemvmove a filezip - compress directory or filedf - list partitions of the systemifconfig - know about your network interfacenetstat - shows local or remote established connectionsnslookup - detail about name serversnano - file editortouch - create new filefree -h - check free memorycat - display content of a file

If you won’t try, just reading these won’t help. Open the browser if you need help with some commands. Go over the terminal, try it!

Common applications

Linux has some common applications that you will encounter in every distro and these will be your main targets.

• Apache: It’s an open-source web server.
• MySQL: A most popular database. Somewhere data will be stored 😉
• Sendmail: This is Linux-based mail server
• Postfix: It’s an alternate for sendmail
• PureFTP: It’s a default FTP server used in all Unix-based systems.

Looks like that’s good enough to know about Linux. Now, let’s meet the members of this world. To work with them, you’ll need to meet them and talk. Soon, they’ll become your good friends.

Subdirectories to meet

Open terminal and type cd / && ls . What will be listed now are the ones with whom you need to become friends, for now knowing them will be fine.

/bin - It contains common programs used by the system and various errors/var - Contains all variables and temporary files created by the user/boot - Contains startup and the kernel data/dev - Contains references to all the hardware/etc - Contains system configuration files/initrd - Contains information about booting not available in all distros/lib - Contains library files like files a system program will need/lost-found - Contains the files that were saved during failures. Like lost and found department of your school/misc - It's like the others storage in your phone/mnt - Mount point for external systems/net - It is the mount point for the remote file system/opt - Contains third party software/proc - A virtual file system that contains information about system resources/root - Home of the administrative user/sbin - Contains programs for use/tmp - Temporary space of the system

It’s your time to explore now! That’s it from my side about the world of Linux. Meet them, greet them, and know about them.

We’ll meet next to know about How to gather information? Till then, take yourself into the world we went to today. Spend time and explore as much as possible. Meet you soon!