I'm trying to execute a fsck (e2fsck) on my system. Though I boot into single-user mode I'm not able to umount my /dev/sda1 root filesystem. Of course I can't run a fsck on my root partition (/dev/sda1 with / as mountpoint) without my root filesystem being unmounted.

When I try (in single-user mode of course) to run umount /dev/sda1 I get "device is busy". After I ran fuser -km /dev/sda1 my system doesn't give any error when I execute umount -l /dev/sda/1. Unfortunately, I don't notice any difference when I execute mount.

When I try to fsck my /dev/sda1 I see a warning that contains:
I would like to execute the fsck command on my system without using a live cd.

You can run fsck against a file system mounted in read only mode. When you boot into single user mode the kernel should mount / as read only.

If you cannot get / mounted in read only mode then I suggest that you use a live CD to run fsck.

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Steve Stites

Use mount with "remount,rw" as options - no umount.

syg00, don't you mean

mount /dev/sda1 / -oremount,ro

Nope - the OP wants to fsck root - needs (should) be rw.
This works fine BTW - been there, done that.

Of course, fsck can trash files whilst doing it's job; that applies equally with root. Problem is (with root) you can wind up with a dead system.
That is the OPs choice - presumably s/he has read my sigline.

Thanks for the clarification syg00. Nice sigline by the way, my own is inspired by yours.

I mounted / in read only mode. I'll show you a part of my /boot/grub/menu.lst:

It seems to me that / doesn't have to be mounted in read only mode in order to execute a fsck.

mount -o remount,ro / didn't make any difference.

I'm starting to believe it should be mounted as rw, though this sounds very dangerous to me.

I executed touch /forcefsck in /root and after I rebooted I have removed it.

It doesn't. What read only mode does is prevent other programs from updating the file system control blocks at the same time that fsck is updating the control blocks. Such simultaneous updates will scramble the file system.

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Steve Stites