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In this video, we'll talk about options to repair file systems. Actually, you need to

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understand what is going on. And that is because many problems are fixed automatically when

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you boot because file system journal on XFS or the transaction log on XFS. This journal

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and transaction log mean that file systems basically are auto-healing. So when you are

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booting and an error was encountered, the file system will do a rollback of the previous

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situation and you'll be all set. EXT file systems can be checked manually as well using

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the fscheck utility, which is a utility that you can also use to repair. And on some more

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cases, you might need to have to do that. On XFS, it's even more rare with the XFS repair

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utility is available. If you are going to use these utilities, you need to make sure

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that you are in emergency mode because normally these utilities require the file system not to

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be opened at all. So let me show you how you can start these utilities.

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Starting here. So to start it, I need to reboot and get access to the group boot prompt.

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Getting access to the group boot prompt is always a little bit of a guess. You need to

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press escape at the right moment. And as you can see, I just succeeded. So here we see the

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default kernel that my system wants to start. I'm pressing E for edit. And then I'm looking

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up the line that starts with Linux and ends with R-A-G-B and quiet, which is default on CentOS.

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I'm giving it the option init is slash bin slash bash. Init is bin bash is the most

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minimal troubleshooting mode. And the nice thing about this minimal troubleshooting mode

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is that your file systems are not yet mounted in a read-writable way. And also you are not

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required to enter a root password. You just get access to a root shell. Now there I'm going to

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use LSBLK where I can see my block devices and none of these block devices is mounted.

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So I need to use the appropriate utility. And in order to do so, I am going to use slash user

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slash sbin where all of my XFS utilities are. And there we can see there is the XFS repair utility.

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So let's do that on dev sda1, which should be by my boot device. And oh boy, there I can see that

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XFS repair is failing. Bad primary superblock. And why is it giving me bad primary superblock?

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Well, that is because I made a mistake. And we did it on a VFAT file system. In order to use

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XFS repair and other repair utilities, they're file system specific. So you need to be on the

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right file system.