Linux and FOSS

Today's installment of Mastering the Linux Shell comes with a warning. Actually, it comes with a few warnings. .And a viewer advisory. Well, actually a reader advisory. 

So what constitutes a process on your Linux system?  The short answer is : Everything. 

In your long and illustrious career as Linux gurus, you are going to hear a lot about processes, process status, monitoring processes, or even killing processes. Gasp! Reducing the whole discussion to its simplest form, all you have to remember is that any command we run is a process.  Processes are also sometimes referred to as jobs. 

The session program which executes our typed commands (the shell, or terminal if you prefer) is a process.  The tools I am using to write this article such as my desktop, the browser, the server somewhere out on the internet . . . these are creating several processes and sub-processes.  Every terminal session you have open, every link to the Internet, every game you have running, the little clock in the corner; all these programs will generate one or more processes on your system.  In fact, there can be hundreds, even thousands of processes running on your system at any given time.   To see your own processes, try the following command.

You know how you get those emails that suggest you can find out anything about anyone? They claim to be able to locate any person and tell you who they are, where they are from, the date they were born, and what their background is . . . You'll be happy to know this isn't the subject of this article. It's a lot more fun than that.

In my last article, I introduced the idea of permissions in the Linux world. Some users can read or write a file, while others can only read the same. A user may also belong to a group and share the permissions of that group which might also involve the ability to execute, or run a file as a program.

Under Linux, access to files and directories is controlled by a system of permissions. Those permissions define who can see a file, whether they can modify it in any way, and in the case of some files, whether the commands within that file (or the file itself) can be executed. By executed, we mean "can we run that program?".

Information begets information and eventually, there's just too much of it. I don't really believe that -- I'm an information junkie -- but there's no question that if you never delete anything, eventually, you will either use up all your disk space, or you'll have a terrible mess on your hands.