LPI 101-500 – 109.4: Configuring the client-side DNS
- 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 System. DNS ensures that names are assigned to IP addresses. For example, google. com can be reached under the IP address 172, 217, 1899.
For example, DNS ensures that this IP address is assigned the address google. com so that we can enter google. com into our browser instead of the IP address. This procedure is also called name resolution. A DNS server takes on these tasks. The DNS server is not part of the ipg One exam. This topic is waiting for you in the arpeg Two exam. This topic is about the client side DNS configuration. So how do I configure my computer to use DNS correctly? And how do I find and fix DNS problems? There are various programs that can be used to resolve names. Before we get to these programs, I would like to point out that this basically also works with a ping command.
So for example and as a result we receive among other things, the IP address of the website Linuxcruiser. com and it is this IP address here 80, 413, 6164 and 98. But as I said, only marginally. To do name resolution One uses a program like ns lookup. If you have been a Windows user before, you may have heard this before because nslookup is also available in Windows. To find out the IP address of this website here I’ll simply enter nslookup and then Linuxcouser. com and we get the IP address. Here it is this one. It is the same as this one. Here ns lookup can also be used in an interactive mode and ns lookup is now waiting for an input.
So for example and then we have the IP address, or maybe google. com. And here we have the IP Four address. And here we have the IP Six address. Okay, sorry, it was exit. So with Exit we can leave the interactive mode of nslookup again. And it’s lookup is now a bit out of date. Nowadays you tend to use Host or Dig, but ns lookup still has its authorization because it just works and you can use it across platforms as it also exists in Windows. Let’s look at the first alternative host. Also at this point the note that Host and Host name are two completely different commands. You can’t get confused here. hostname executed without any option just gives us the host name of the local system.
Host is used for name resolution. The host contacts the so called name server for its queryhostgoogle. com and the result is displayed a little differently than with ls lookup, but the result is the same. We get the IP address of the website, we get the IP six address of the website and so on. So the V option provides a very detailed information hostbgoogle. com and you see some more information here. What this all means is irrelevant. For the Epic one exam we can also execute a corresponding request backwards. It’s called a reverse query here.
However, the result is often not satisfactory. Let’s take the IP address of the website google. com as an example host and then the IP address is this one here copy, insert, paste and as a result in this case we are only given the server name on which the website is hosted. So we would not know that this server or these server names belong to google. com. By the way, how does the host program know which DNS server to use? In this case, the host accesses the etsy resolve confile. So let’s take a look again at Cresolve. The first line is crucial.
The so called name server has the IP address one hundred and twenty seven, zero, zero, fifty three. And the result of hostgoogle. com does not tell us which name server is being used with. If we use the V option, then yes, we get the information that this name server is used. We saw it in the last example. Let me show that again. Let me scroll a little bit up. And here you see received 44 bytes. From here is the name server. And here again the name server. The last command in the series would be Diggooglecom. Here we get more information than if we use nslookup or Host. In Dig the V option does not mean verbose, but a version.
So it shows us the version of Dig and it’s version 916 one. The last command in this chapter is Gatant. We have already talked about this in another video. With gatent databases based on text file can be queried. We tried this before with password. Let’s memorize in etsy password and get tend password procedure or to produce the same result cat at the password or get tend password. It’s the same. The commendation Guitant appears again in this chapter because it can also be used on the etsy host file. Host file. So detand host and here we get the information of the host file.