etc/nologin, xinetd, systemd.socket In topic 107 one, we talked about the Etsy password file. Among other things. Here I demonstrated how you can prevent a certain person from logging into the system. Once again. To remember, there are amp teen users here who are not allowed to log in simply because user bin or the user has been no login. No login, no login no log in here can be found instead of the shell used. This tells the system that this user is not authorized to log in. There…

find, chage, passwd, ulimit, lsof, fuser This is now the first video on the last major issue, which is safety. You are already familiar with most of the commands that you will find on the overview page for this chapter 110 one. This topic is only about using them to increase the security of the system or to detect security threads. Let’s start with Find. First, files can be found using Find. For example, if you want to display all text files in a folder, then you could use Find…

nslookup, host, dig, getent If you look at the lpic page, which commands and or files are discussed in this chapter, you will notice that three files were already discussed in chapter 109 Two, namely etsy Hosts@cresolve. com and Etsynsville. There the files were discussed in connection with the topic of persistent network configuration. Accordingly, we will not go into it again. In this chapter I briefly explained what DNS is in one of the last videos. To repeat briefly one or two sentences again DNS stands for Domain Name…

ifconfig, hostname This chapter is called Basic Network Troubleshooting. The description says candidates should be able to solve network problems on client computers. That sounds worse than it is. You won’t find a bug in the exam that you need to fix. You just need to know the tools that could fix them. And of course you need to know how to use them. And there are different programs here that can take on different tasks. The tasks in this area would be general connectivity routing and the connections themselves….

nmcli So we are now on the subject of persistent network configuration. I have now switched to my live system here, so I’m no longer using the virtual system for this lesson. This is because I wanted to show something with a WiFi connection that does not work with my virtual system. Because an Ethernet interface is virtualized here and not a WiFi interface, I have not yet figured out how to change that and whether you can do it at all. Accordingly, I am now on my live system…

Subnet masks We come to the subnet mask. The computer can use the subnet mask to determine which network it is itself in. Because, as already briefly mentioned, a computer can only communicate directly with another computer if they are in the same network segment. If they are not, the computer knows that it has to send the data, data to the router. We have just talked about the network classes, and the subnet masks have always been mentioned here. Without going into more detail, you will notice that we…

OSI model, ports, address classes So we are back to a completely new topic. Topic 109 deals with the basics of networks in general, and specifically the basics of Internet protocols. This topic becomes not very practical, but very theoretical. I don’t like it either, but unfortunately it has to be. Okay, well, let’s start first of all, very briefly about the story. I wouldn’t expect there to be any questions, but it’s useful to be able to say at least a little. The Internet as we know it today…

CUPS, lpr, lpq, lpadmin, lpc This chapter deals with managing printers and printing processes. The printing system used almost exclusively under Linux is called Cups. Cups stands for common Unix printing solution or common Unix printing system. In most operating systems, including including Linux, the printing process is similar. I’m talking about the concept of the queue here. A file that is selected for printing via a program is first placed in a so called printer queue by a print client program, for example Lpr. If there are several files…

sendmail, postfix, mailq Before we go into practice, we must first discuss three terms so that you understand the relationships a little better. This chapter deals exclusively with the socalled mta, but I have to mention the other services too. The transmission of emails is usually done by three programs. First we have the mua, then the mda and the mta. mua stands for mail user agent. A male user Agent is an email client program that each of us probably works with on a daily basis, or at least…

syslog, rsyslog In the Linux environment. It is the absolute standard that various events are recorded in log files. This includes events from various programs, but also events from the Linux system itself. In a professional environment, you can hardly do without logs. If something doesn’t work, you can consult the relevant log files and then usually find out what is wrong in the relevant case. In order for the corresponding log files to be written at all, linux needs a program that takes on these tasks. As almost always,…