Cannot "Umount /media/mmc2" - Device busy
 

I encountered problems to connect my n810 to a PC via USB. While the external memory card is connected successfully, the internal card cannot be accessed via the PC (running a Ubuntu system). When I try to unmount the card the following statement is displayed:
umount: cannot umount /media/mmc2: Device or resource busy
Searching the forums I found only a reference in the German n800.de forum. Yet, the proposed workaround (to connect directly w/o intermediate usb-hub) does not work for me. Up until now, the only solution I have found is to reboot the system. Which is feasible yet not very convinient.

Maybe somebody knows a way how to calm down the memory card - preferable w/o killing all processes by hand?

icke

Re: Cannot "Umount /media/mmc2" - Device busy
 

You need to make sure NOTHING is accessing the card.. and I do mean nothing.

If even a terminal is open and you are just "cd"'d into the media card.. it's considered busy. Or if your terminal is open as "user" who is in /media/mmc2, and you sudo su - to "root", and you cd out of the directory as root, and try to umount it.. "user" is still in the directory even though the active terminal is not. So you must first exit "root", change directories in "user", then go back to root and umount.

Or if a media application is running and even is aware there might be, possibly, a music file on your media card.. it could also be busy.

Or if you are booted into the media card with a cloned OS.. it's obviously busy..

If you are absolutely sure NOTHING you care about is currently accessing that device.. you CAN force linux to do as you wish by issuing:

umount -l /media/mmc2

Which is a "lazy" unmount.. it doesn't check anything and *can* cause some filesystem corruptions if done in the middle of read/write operations and things of that nature. It's typically a bad, evil, command that should only be used.. well, never :D. But I still find use for it sometimes.

Re: Cannot "Umount /media/mmc2" - Device busy
 

Relatedly, I have used console tools to establish a swap partition on mmc1. But sometimes I want to take out mmc1 to use it with a card reader on the PC. How can I do this safely without throwing the tablet into a tailspin and having to force a reboot?

Thanks.

Re: Cannot "Umount /media/mmc2" - Device busy
 

swapoff [filename]

Re: Cannot "Umount /media/mmc2" - Device busy
 

Thank you very much for the quick reply. Meanwhile I had to reboot the system as I encountered another issue (with the external card). Unfortunately, I could not solve it.

So my next steps will be to use the search function and maybe to open the next thread.

Again, thank you very much for your help.
Yours,
icke

Re: Cannot "Umount /media/mmc2" - Device busy
 

You could try typing

to find out what process has open files on it. Prefixing the invocation with sudo i think digs out processes with root privileges which otherwise wouldn't be shown. I assume lsof is there by default, I'm not sure.

In my case, the results I get (for mmc1) are like this:

fnord

Re: Cannot "Umount /media/mmc2" - Device busy
 

Bundyo, how do I determine the name of the swap file? I just assumed it was "swap"?!

Re: Cannot "Umount /media/mmc2" - Device busy
 

It's going to be the partition you created for it.. IE:

swapoff /dev/mmcblk1p2

Re: Cannot "Umount /media/mmc2" - Device busy
 

cool, thanks. And then "swapon ..." to turn it back on?

Re: Cannot "Umount /media/mmc2" - Device busy
 

o_O I have a swap partition, too ...

Curious,
icke

Re: Cannot "Umount /media/mmc2" - Device busy
 

There's this old thread that Fanoush is pointing to as a solution. It has worked for me.

http://www.internettablettalk.com/fo...ad.php?t=17689

hope it's useful.

Re: Cannot "Umount /media/mmc2" - Device busy
 

Dear Saturn,

Thank you very much for the link. I will give it a try and see how it works out.

icke

Re: Cannot "Umount /media/mmc2" - Device busy
 

Turn off any 'virtual memory' extension setting in the control panel.

Re: Cannot "Umount /media/mmc2" - Device busy
 

Well, to turn off the virtual memory might be a way. Yet, I am using the virtual memory to enhance the performance. So, an easy workaround is more desireable than to tinker with the settings (off / on).

Thanks,
icke

Re: Cannot "Umount /media/mmc2" - Device busy
 

If you leave the virtual memory extension "on" then you have occupied your card, it can't be exported. Those 'swapoff' suggestions in other posts are workarounds trying to turn off the vm extension feature behind its back, so to speak.

BTW, I've started using the vm ext. feature, and the 'enhances performance' meme is nothing but an urban myth. It does not enhance performance (and it was never explained why it should, when it doesn't on a desktop computer). Instead, it does exactly what it's for: It is an overflow catch, i.e. it keeps the device (or rather, programs) from crashing due to using too much memory. If you monitor the swap usage during normal use you will see that it's very close to empty at all times and can't possibly free any RAM for programs (the only way of enhancing performance). So, to conclude, the 'enhanced performance' is all in the imagination. That doesn't mean the feature shouldn't be used (after all, I use it myself now), but it does come with a cost: You can't export the card through USB as long as you use it.

Re: Cannot "Umount /media/mmc2" - Device busy
 

Dear TA-t3, Thanks for the clarification =b
So I keep on happily using the swap memory. Not because its faster - because its more stable.

icke