mounting error on LFS 11.2 chapter 7.3: mount: /mnt/lfs/sys: sysfs already mounted on /sys.

hananelroe · 09-28-2022, 09:55 AM

when I try to run:

Code:

mount -vt sysfs sysfs $LFS/sys

it outputs:

Code:

mount: /mnt/lfs/sys: sysfs already mounted on /sys.

so I try:

Code:

umount -f /sys

and it outputs:

Code:

umount: /sys: target is busy.

how can I fix it?

hazel · 09-28-2022, 10:14 AM

It looks to me as if you may have tried to mount sysfs on $LFS/sys twice! Of course the second time won't work. This kind of mistake is easy enough to make in a fit of absent-mindedness.

You can use the mount command without arguments at any time to check on what is currently mounted. And if, at any time, you do want to umount $LFS/sys, then use $LFS/sys in the command and not just /sys. Trying to unmount /sys definitely won't work.

xlfs-0.2 · 11-23-2022, 01:11 AM

You cannot be cd(1) or $PWD in the directory when you unmount it. (try cd / first)

Also if there are running programs with open files you cannot unmount it. Try lsof(1) to see all files open.

Try fuser /mnt to see who is using /mnt

Already said, if it's already mounted elsewhere you cannot unmount it - but you might not know where it is. Use mount(1) without args to see what is mounted.

The are very typical things to do (hopefully rarely).

Keith Hedger · 11-23-2022, 07:14 AM

Use

Code:

mountpoint $LFS/sys

It will tell you if anything is mounted there.