EX200 Red Hat Certified System Administrator RHCSA – Red Hat Certified System Administrator (RHCSA) exam preparation

1. What does the RedHat Certified System Administrator exam include?

Welcome everybody. Today I’m going to go ahead and jump into the first section of our preparation for the Red Hat Certified System Administrator exam. Anyway, one of the first things that I wish to cover here is globing or wildcards. Anyway, if you type in this term on the net, you’re going to get a lot of things, a lot of results for your search and you’ll have a lot of explanations. But basically what it is, how I would describe it, is just searching for things, allowing you to actually execute a command on a file without actually knowing the full name of the file. It can be extremely convenient. And these are some of the things that people that administrators and many people don’t consider administrators to be people, just so you know, tend to use on daily basis. So look over here on the left side. I have these things set up for you. I have set them up for the LS command, but I have just as easily could have typed in, for example, here, RM so remove or something of a kind and you would have pretty much the same effect, except the command would be different.

Anyway, so over here we have name of the file. So this can be pretty much anything. I for us have created a set of files with extremely innovative names. This one is it random, random, random file, semi random file and TTT dest. I know extremely innovative and original names, but what can you really do about it? My imagination is such that it is awesome. Anyway, let’s stick to the subject. You have name of the file. See, it’s written here. So this name of the file can be is it random? This is the file. And then I have an Asterisk at the end. What this Asterisk means is any character or whatever follows along. So this doesn’t necessarily need to be a letter, it can be a number, it can be a sign, it can be any character that you can think of that is supported asterisk pretty much substitutes it. Let me show you how this works. So now I have issued ll command. I do believe that I have mentioned it before. Ll is pretty much the same as LSpace L, so you get the same output, but it’s quicker to type in Ll. But Ll is less universal as it is not installed on a lot of systems out there, especially on the server editions. Sometimes it tends to be what I mean by server editions is the one is operating systems without any GUI or whatsoever, although it’s quite easily installable from the repository.

So that should be a problem. Let’s just go ahead and clear the screen. I’m just going to use Ll for the sake of convenience. I could have also used LS. No problem, same thing, just quicker typing, I suppose, with Ll. Anyway, let’s go ahead and type in Ll space and the name of the file will be, is it random? And if I type in this, I know exactly what the name of the file is. If I press Enter. Oh, I have missed it. Great. Random. Excellent. So you see, I will get a listing for the file. Is it random? However, what would have happened if I didn’t know the file? And in this particular directory on desktop, I only have these five files. But take a look at this LSC. Press Enter. Look at how many files there are here. Imagine if you were looking for something in here and you didn’t know the whole name and you wanted to get the listing for it. Sure, you could use, locate or find or something of a kind, but hey, you just want to get the listing, you know, that it’s in here somewhere. So what you would do, and this is usually used in scripting or it can be used in a vast variety of situations.

Let me just show you what you would do. You would type in LS and you would type in or Ll is it? And then I would put in Nasax. I get the same output. Now, what does this mean? Basically what you are telling to the computer with this command. Let me just see if I can now I’m going to stick it to the previous, maybe not. I’ve just zoomed it in a little bit. I do believe that you can all see it without any problems. If there are any problems with actually seeing it, do let me know in the discussions, I’ll see what I can do about it. But I’m pretty sure everybody can see this anyway. I have typed in Ll space part of the name of the file, and then I’ve placed an Asterisk at the end. Press Enter.

What did I get? I got pretty much the same output from Ll. Is it random? So you see two exactly same outputs. But in the first one, in the first command, I didn’t actually need to type in the whole file name. I didn’t even need to know it. I just needed to know the letters with which the file actually starts. But you don’t even need to know that.

You can just type in the Asterisk sign can go at the beginning or at the end, or yeah, there we go. It can go in a variety of positions if I put it like this, and if I delete rent. There we go. What did we get? We got exactly the same output once again. And we didn’t know the letters with which the file name started. We didn’t know how it ended. We just knew approximately that it was something of a kind. But the capital letters do matter here. So just use the part of the name of the file that you are absolutely certain of and then use wild Cards. You can see how I’ve placed them here. And then type it in very simple, no complication there. If you need to list something or let’s say I want to remove all files, this can be quite dangerous because you won’t be able to retrieve it later on, but you can type in I want to remove all files there we go. That have these characters in them in this order and with this set of capital and lowercase letters. So you can delete all of that.

This is especially useful, for example, if you have, for example, a number of files. For example, is it random? Underline zero one. So let’s see if we can do that. Let’s create those touch. We’ll use touch to create these files. So I have Is it random? Zero one, is it random? Zero two is three. If I press Enter and if I do ll again and I’m going to say is it? And place an asterisk sign. So I have basically four files which contain the same beginning, but have different endings. And I suppose if I wanted to remove these files, I could go ahead and type in RM and type in Is it random? And then delete that. And then after that, I would basically type in an underline and type in one, and so on and so forth. And imagine if I had 100 of these files, what would I do? Like, type in RM 100 times? No, of course not. That would be, I don’t want to say stupid, but it would definitely be inefficient.

It would consume a ton load of your time, which you cannot spare, especially not the exact or anything like that. Rather, instead, what I would simply do is type in RM is at random, and I don’t want to delete the first one, rather instead I want to delete the other one. So I’m just going to say, give it the underline here and place an Asterisk sign here, press Enter, and if I do Ll again, you see, they don’t exist anymore. They’re gone. If I do Ll with the Asterisk, as I have done before, again, I am let me just clear the screen. There you go. Again. I only have Is it random? I no longer have Is it random? 010203, or anything of a kind. They could have ended with something completely nonsensical, like, I don’t know, eight, 50, something like that. It does not matter.

The Asterisk covers all of your characters. The asterisks is anything. It’s a complete wild card and generally not recommended to use with RM unless you are absolutely certain that those are the files that have that ending. And you should always double check to make sure what sort of files will be deleted by getting a listing first and then see what comes in the listing. Then you can pass whatever you want from there to the RM anyway. That’s definitely useful. But you will also have something else. You have the next one, which is a question mark. Question mark represents a single character. So if I do the same thing here, let’s give it the full name. Is it random? And we’re just going to place a question mark instead of M. Again, question mark also stands for any character but a single character. So just a single character, no more. Let me just show you. Is it random? I don’t know. Five whatever. And there we go. It just substituted a single character, which is a considerable difference from this. Let me just show you the difference between the wild card between these two wild cards.

I guess if I press enter with a question mark, it’s just going to substitute the last letter, nothing else. And if I type in asterisk here, I’m going to get two files because it’s going to say pretty much everything that follows. This is also a valid output. Anyway, these things, as I said, are used on daily basis in administration and they’re extremely useful. They save you a download of Time. You would not believe how much. Anyway, there are these three down below which function on basis of different logic, but fairly similar, and we’re going to do them in the follow up tutorial for the time being. I’m going to call it here and wish you a lot of luck with this.

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