How to release /dev entry of unplugged storage device while a program has a file open

10110111 · 11-06-2009, 01:41 PM

I plug a USB device, it gets a /dev entry, e.g. sdf, i mount its filesystem, then some program opens a file on this filesystem. I unplug this device, its /dev entry disappears, but if i replug this device again, it gets another name - sdg.
How can i force the program to close the file so the filesystem is ready to be unmounted without using "lazy unmount" to release the device name, BUT so that the program doesn't crash after trying to make I/O to this file, and, of course, without having to kill the program?

unSpawn · 11-08-2009, 03:46 AM

Quote:

Originally Posted by 10110111

How can i force the program to close the file so the filesystem is ready to be unmounted without using "lazy unmount" to release the device name, BUT so that the program doesn't crash after trying to make I/O to this file, and, of course, without having to kill the program?

If the filesystem a file resides on is no longer available then it would be not be a design flaw or application error but rather a human misunderstanding of concepts to assert it is still valid to write to it.

10110111 · 11-09-2009, 12:32 PM

Quote:

design flaw or application error

I didn't mean any of this. There exist some programs which is wouldn't like to stop running, but i need them to release any file pointers which make OS give newly inserted devices not next unused name, but some greater one (e.g. sdg instead of sdf), leaving sdf inexistant in /dev at all. So, the question is how to do this.

tredegar · 11-09-2009, 02:44 PM

To make USB devices appear in the same place always you need to use udev

Please read this introduction / tutorial / examples.

Then come back here with your results (success or fail).

unSpawn · 11-09-2009, 03:21 PM

Quote:

Originally Posted by 10110111

There exist some programs which is wouldn't like to stop running, but i need them to release any file pointers

As far as I know there are only two possibilities: a) kill the application or b) do not unplug and change the device. As far as releasing file pointers there is no middle way I know of.