external HD

[Basil Chupin]

On 21/01/13 19:06, TuxMario DeTreb wrote:
>
> Le 21/01/2013 06:26, Basil Chupin a écrit :
>> On 21/01/13 15:51, Errol Sapir wrote:
>>> I backup on a Toshiba external HD. Suddenly Kubuntu doesn't read or 
>>> recognize the fact that I place an external HD in the USB. I tried 
>>> even connecting it to the "direct" USB at the back of the computer 
>>> instead of to the front one which I always used. The HD is 
>>> recognized when I boot to windows. I am using Kubuntu 12.10.
>>> Any suggestions?
>>> TIA
>>> Errol
>>
>> Did you "Safely Remove" it when you used it last in whatever OS you 
>> used it in?
>>
>> And when you say that Windows "recognises" it, can Windows actually 
>> read the contents of the drive? (I am assuming here that the HDD is 
>> formatted in some weird Windows file system, right? :-) .)
>>
>> BC
>>
> Hello
>
> I had some times issues with USB port when one unmounting USB set was 
> not correctly done.
>
>   * t
>   * another one is to complete umount process by  commands
>

Depends on what you actually mean by "reboot" - issuing the "reboot" 
command or merely hitting the "reset"/"reboot" button.

Data is not always immediately written to a device but is stored in RAM 
or the HDD cache and is
waiting to be written to the device. With externals and USB flash sticks 
when the data IS written to them then a flag is set on that device 
indicating that there is no data yet to be written to it.

If you do a normal "reboot" or "shutdown" the operating system makes 
sure that any unwritten data is written out to the appropriate device - 
and then the flag is set.

If you suffer a power loss or hit the "reset/reboot" button this does 
not happen - and the flag is not set, indicating that there is missing 
data which is yet to be written to the device.

So, be careful when you say, "Simpler solution was a reboot" :-) .

Unmounting the device is the same as doing a correct reboot or Safely 
Remove the device - any unwritten data is written out to the device.

Having said all of this, I know that when I was running Windows and shut 
the system down without first Safely Removing the USB or the external 
device I quite often ended up with problems. Moral of this is: Safely 
Remove such devices when you need them.

BC

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