I copy files from an SD card to the NAND file system, or vice versa using cp command line.

If I don't wait 3-4 minutes, and remove the disk, the files are not copied.
Also, if I try copying files from one directory to another - the 'ls -l' shows that the files have been copied (time, size have changed), but if I power off the system too quickly (without waiting 3-4 minutes) the files have been erased with nothing copied.

How can I check, flush or guarantee that the entire file has been copied correctly?

Using Ubuntu 10.4 on ARM.

Thanks,
Mechi

Depending on how you too quickly power off the system the data just did not got written to the disk but only to the cache. On normal shutdowns the disk cache is written to the disk. Also I just read that it only waits a few second till the synchronisation happened.

Use the sync command to have the cache beeing written to the disk. To check on the actuall cache or if there are still data lingering to be written I'm not so sure if free will tell you. Maybe this link can shed some more light: http://www.linuxatemyram.com/play.html. Or take a journey into the /proc directory and see if you can find some info there.

When you power off the system, what are you doing? Just pulling the plug? You should issue "poweroff" or "shutdown -h now".

Yes the sync command is also the correct thing to do here, and then it wouldn't matter if you didn't shut off the system.

Hi,

Be sure to learn the use of 'man command'. From 'man sync';I like to provide this to users;
Hope this helps.
Have fun & enjoy!

Thanks for all of the ideas and extra information.
I will definitely try them, though on embedded Linux not all of the functions are supported in the BusyBox. I do see the 'sync' function in /bin.
Thanks again,
Mechi