Linux – Force unmount of a device, how to

linuxUbuntu

I've mounted a block device (internal hard disk) to say ~/HD, and I'm trying,

~# umount ~/HD

It answers,

umount: device is busy.

Now I kill all processes manually by examining

~# fuser -m ~/HD

I also make sure that really no process is accessing the ~/HD path

~# lsof | grep HD

Still umount ~/HD says device is busy even with -f option.

PS: I don't want to use the -l option of umount, since the mounted device is actually an encrypted mapper device, which in turn won't get unmounted unless mapper device is clearly unmounted.

So basically my question is how to really force umount to unmount a device OR How can a device still be marked as busy while no processes are accessing it (or at least fuser and lsof don't report it) and what can I do about it?

I'm on Ubuntu 9.10 x64.

Best Answer

You will see this behavior if you have mounted something else on a subdirectory of ~/hd. In this case, neither fuser nor lsof will show anything. If you haven't mounted anything under ~/hd ('mount' will answer this question), then I'm not sure what to check.

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Linux – Hard Reset USB in Ubuntu 10.04

I have Ubuntu 14.04.4. I have no idea if this works in 10.04. I tested it on Cyborg Rumble Pad (and a generic USB flash drive).

Just after I connect the device:

dmesg | grep usb | tail -n 20

I get (maybe among other things):

[ 2875.790610] usb 2-1.2: new full-speed USB device number 7 using ehci-pci
[ 2875.887485] usb 2-1.2: New USB device found, idVendor=0738, idProduct=cb02
[ 2875.887489] usb 2-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2875.887490] usb 2-1.2: Product: Cyborg Rumble Pad - PC/Xbox 360
[ 2875.887492] usb 2-1.2: Manufacturer: Saitek
[ 2875.887493] usb 2-1.2: SerialNumber: 0CFE6B97

The crucial part is 2-1.2 string. It identifies the USB port. Good news is it should not change unless I plug the device into another port, so I need to obtain the string just once.

Next I go to the right place:

cd /sys/bus/usb/drivers/usb

and invoke as root (e.g. sudo bash first):

echo 2-1.2 > unbind ; sleep 3 ; echo 2-1.2 > bind

The result is my Rumble Pad reinitializes itself as if it was plugged out and in again. I tested my USB flash drive as well. It (its LED) behaves as if nothing happened, still my KDE reacts and asks if I want to mount.

All the time the device is powered. This method will not work if your modem resets itself because of the lack of power.

Linux – Unmounting Detachable devices (eSATA,USB storage) in Linux

You can write a bash script to scan all the file descriptors listed in /proc (assume you have that) and list/kill the processes.

/proc/$m/fd/$n is the n-th file descriptor for PID m presented as a symbolic link. busybox does have readlink support, so you should be able to automatic it.

Edit: Just to say this is essentially re-implementing lsof, but it's actually fairly simple.

Best Answer

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