Unable to mount USB Flash memory created on CentOS

[James B. Byrne]

On Fri, July 28, 2017 15:24, Polytropon wrote:
>> > Is the USB stick (usually /dev/da0 or /dev/da0s1 or something
>> > like that) _really_ mounted?
>>
>> Not that I can see. That appears to be the essence of the problem.
>
> Can you _manually_ mount the USB stick? For example, with
> something like
>
> 	% mount -t ext2fs -o ro /dev/da0 /media/da0
>
mount -t ext2fs -o ro /dev/da0 /media/da0
mount: /media/da0: No such file or directory

> No matter if the file browser will automatically open a window for
> /media/da0 (in this example), you can check again the output of
>
> 	% mount -v | grep da0
>

#  mount -v | grep da0
#


> and of course
>
> 	% ls /media/da0
>
> to see if the files you are expecting are really there.
>

# ls /media/da0
ls: /media/da0: No such file or directory
# ls /media/
#



>
>> > Check what's on the USB stick, using
>> >
>> > 	% gpart show da0
>> >
>> # gpart show da0
>> =>       63  122915265  da0  MBR  (59G)
>>          63       8001       - free -  (3.9M)
>>        8064  122907264    1  !12  [active]  (59G)
>
> Hmmm... that looks really strange... check with "old-fashioned"
> fdisk again:
>
> 	% fdisk da0

# fdisk da0
******* Working on device /dev/da0 *******
parameters extracted from in-core disklabel are:
cylinders=7651 heads=255 sectors/track=63 (16065 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=7651 heads=255 sectors/track=63 (16065 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 12 (0x0c),(DOS or Windows 95 with 32 bit FAT (LBA))
    start 8064, size 122907264 (60013 Meg), flag 80 (active)
	beg: cyl 1/ head 0/ sector 1;
	end: cyl 905/ head 60/ sector 61
The data for partition 2 is:
<UNUSED>
The data for partition 3 is:
<UNUSED>
The data for partition 4 is:
<UNUSED>

>
> Is there an ext2 partition? The output you presented looks like
> a situation where there's nothing the system can automatically
> detect and mount.

Well, this exact usb stick was mounted and working up to the point
that I inserted a second one.  I have moved files from and to the
device earlier today.

>
> (I don't have an ext2 USB stick at hand so I cannot check how
> the gpart and fdisk output should look like for a valid TOC with
> an ext2 partition.)
>
> Can you re-initialize the USB stick on the Linux system? Just in
> case partitioning data has been damaged...
>

No, I cannot.  The stick contains my backup of the critical data from
my original workstation that was dying and has since passed on.  The
contents were moved to the device using rsync.  This USB key was used
straight from a sealed package and I did not format it.


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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
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