usb bootable stick

Ranjan Maitra maitra.mbox.ignored at inbox.com
Fri Oct 16 12:38:56 UTC 2015


On Fri, 16 Oct 2015 18:37:26 +0800 Ed Greshko <ed.greshko at greshko.com> wrote:

> On 10/16/2015 05:35 PM, Ranjan Maitra wrote:
> > On Fri, 16 Oct 2015 12:24:22 +0800 Ed Greshko <ed.greshko at 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 at meimei tmp]# cat ones
> >> 111111111111111111111111111111111111111111111111111111111111111111111111111111
> >> 1111111111111111111111111111111111111111111111111111111111111111111111111111111
> >> 111111111111111111111111111111111111111111111111111111111111111111111111111111
> >>
> >> [root at 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 at 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 at 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.
> 

OK, I stand corrected, thanks!

Ranjan

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