On 10/16/2015 05:35 PM, Ranjan Maitra wrote:
> On Fri, 16 Oct 2015 12:24:22 +0800 Ed Greshko <ed.greshko@xxxxxxxxxxx> wrote:
>
>> On 10/16/2015 12:14 PM, Ranjan Maitra wrote:
>>> I don't know and I am not an expert. However, from experiment, observation and inference, I have noticed that unless the usb is mounted, dd does not copy to the device. (This happened as recently as last week).
>> Sure it does....
>>
>> [root@meimei tmp]# cat ones
>> 111111111111111111111111111111111111111111111111111111111111111111111111111111
>> 1111111111111111111111111111111111111111111111111111111111111111111111111111111
>> 111111111111111111111111111111111111111111111111111111111111111111111111111111
>>
>> [root@meimei tmp]# df
>> Filesystem 1K-blocks Used Available Use% Mounted on
>> devtmpfs 4071532 0 4071532 0% /dev
>> tmpfs 4082428 327808 3754620 9% /dev/shm
>> tmpfs 4082428 1520 4080908 1% /run
>> tmpfs 4082428 0 4082428 0% /sys/fs/cgroup
>> /dev/sda2 50264772 17507156 30181232 37% /
>> tmpfs 4082428 96 4082332 1% /tmp
>> /dev/sdb1 480589520 12122308 444031552 3% /home
>> /dev/sda1 487652 135783 322173 30% /boot
>> /dev/sda5 894266040 397001636 451815240 47% /opt
>> tmpfs 816488 0 816488 0% /run/user/985
>> ds:/volume1/video 2879621632 1108568832 1770950400 39% /home/egreshko/Videos
>> tmpfs 816488 28 816460 1% /run/user/1029
>>
>> [root@meimei tmp]# dd if=ones of=/dev/sdg
>> 0+1 records in
>> 0+1 records out
>> 239 bytes (239 B) copied, 0.00298501 s, 80.1 kB/s
>>
>> [root@meimei tmp]# cat /dev/sdg | more
>> 111111111111111111111111111111111111111111111111111111111111111111111111111111
>> 1111111111111111111111111111111111111111111111111111111111111111111111111111111
>> 111111111111111111111111111111111111111111111111111111111111111111111111111111
>>
>> "f�f�Vf�f!�uf�����r���f�F�������fa��b
>> f�fFf��0�r�>�}U�����{Z_����
>> ^���>b��<
>> u��▒���
>>
> And this got copied to the USB device? (I did not say that it was not copied to an arbitrary location, only that it did not get copied to the USB device). Further, it messed up the mount point till reboot.
>
Of course it was written to the device. That is what /dev/sdg is...
brw-rw----. 1 root disk 8, 96 Oct 16 18:32 /dev/sdg
You need to learn about "block devices". /dev/sdg is the entire device. In this case a USB thumb drive. In my case,
brw-rw----. 1 root disk 8, 96 Oct 16 18:32 /dev/sdg1 also exists, when the thumb drive is inserted, since there is a single partition defined on the drive.
These are *not* mount points.
--
In reality, some people should stick to running Windows and others should stay away from computers altogether.
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