Question on unmounting storage device

[technossomy]

I have a 1GB USB stick attached and mounted on FreeBSD running KDE3. I loaded some files onto it and tried to unmount through the standard mounting tray and the error message read that I could only forcefully unmount and will lose data. The file /etc/fstab read:

# Device        Mountpoint              FStype          Options Dump    Pass#
/dev/ad4s1a     /                       ufs             rw      1       1
/dev/ad4s1b     none                    swap            sw      0       0
/dev/ad4s1d     /var                    ufs             rw      2       2
/dev/ad4s1e     /usr                    ufs             rw      2       2
/usr/tmp        /tmp                    nullfs          rw      0       0
procfs          /proc                   procfs          rw      0       0
linprocfs       /usr/compat/linux/proc  linprocfs       rw      0       0

After forcefully unmounting, the same file read:

# Device        Mountpoint              FStype          Options Dump    Pass#
/dev/ad4s1a     /                       ufs             rw      1       1
/dev/ad4s1b     none                    swap            sw      0       0
/dev/ad4s1d     /var                    ufs             rw      2       2
/dev/ad4s1e     /usr                    ufs             rw      2       2
/usr/tmp        /tmp                    nullfs          rw      0       0
procfs          /proc                   procfs          rw      0       0
linprocfs       /usr/compat/linux/proc  linprocfs       rw      0       0

In other words, if the file is the same, what is the matter here?

[Freston]

fstab is a file defining statical mount points, it wont get corrupted through these exercises

But I don't see your USB device in it. So it might be a permission issue. Devices not in fstab are handled differently, and that may lead to problems sometimes. But before that, lets not overlook the obvious.


Was the device still busy? Something like a filebrowser opened onto your device or a console with the device in the current path, marks the device as busy and will cause the unmount to fail.
And, if as I believe the FreeBSD default is, the write is asynchronous, any illegal or forced unmount will cause loss of data. That is because copying files to an external device (because of asynchonity) is actually not written to device but just set aside as a 'task to do later'. It's not until the device gets unmounted that the write is executed.