On 10/16/2015 05:35 PM, Ranjan Maitra wrote:
> On Fri, 16 Oct 2015 12:24:22 +0800 Ed Greshko <ed.gres...@greshko.com> 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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