In this video, we'll talk about options to repair file systems. Actually, you need to
understand what is going on. And that is because many problems are fixed automatically when
you boot because file system journal on XFS or the transaction log on XFS. This journal
and transaction log mean that file systems basically are auto-healing. So when you are
booting and an error was encountered, the file system will do a rollback of the previous
situation and you'll be all set. EXT file systems can be checked manually as well using
the fscheck utility, which is a utility that you can also use to repair. And on some more
cases, you might need to have to do that. On XFS, it's even more rare with the XFS repair
utility is available. If you are going to use these utilities, you need to make sure
that you are in emergency mode because normally these utilities require the file system not to
be opened at all. So let me show you how you can start these utilities.
Starting here. So to start it, I need to reboot and get access to the group boot prompt.
Getting access to the group boot prompt is always a little bit of a guess. You need to
press escape at the right moment. And as you can see, I just succeeded. So here we see the
default kernel that my system wants to start. I'm pressing E for edit. And then I'm looking
up the line that starts with Linux and ends with R-A-G-B and quiet, which is default on CentOS.
I'm giving it the option init is slash bin slash bash. Init is bin bash is the most
minimal troubleshooting mode. And the nice thing about this minimal troubleshooting mode
is that your file systems are not yet mounted in a read-writable way. And also you are not
required to enter a root password. You just get access to a root shell. Now there I'm going to
use LSBLK where I can see my block devices and none of these block devices is mounted.
So I need to use the appropriate utility. And in order to do so, I am going to use slash user
slash sbin where all of my XFS utilities are. And there we can see there is the XFS repair utility.
So let's do that on dev sda1, which should be by my boot device. And oh boy, there I can see that
XFS repair is failing. Bad primary superblock. And why is it giving me bad primary superblock?
Well, that is because I made a mistake. And we did it on a VFAT file system. In order to use
XFS repair and other repair utilities, they're file system specific. So you need to be on the
right file system.