Re: [gentoo-user] is "scp" reliable?

[cal <cal@mail.meme.technology>]

On 5/29/21 5:42 PM, thelma@sys-concept.com wrote:
>>> Another mystery.
>>> I copied the file to USB 1TB sandisk.  
>>> md5sum check OK same as my computer 
>>>
>>>
>>> md5sum /run/media/joseph/SSD-1TB/business/backup/VDI/windows-7_pro_May-23-21.ova 
>>> 6f3348f1fb915af9c45806d947558a37  /run/media/joseph/SSD-1TB/business/backup/VDI/windows-7_pro_May-23-21.ova
>>>
>>> I mount the same USB 1TB sandisk on another computer and running md5sum on same file gives me different number,  why???
>>>
>>> md5sum /run/media/fd/SSD-1TB/business/backup/VDI/windows-7_pro_May-23-21.ova 
>>> c478cb48e2f7961cb0e3eb452df6e642  /run/media/fd/SSD-1TB/business/backup/VDI/windows-7_pro_May-23-21.ova
>>>
>> Did you sync and unmount the partition before ejecting the drive from
>> the first computer?  With a file this large being copied, it is likely
>> that a large amount of data remains buffered/cached and will not be
>> fully written to the flash memory even after the copy command completes.
>>
>> On the first machine, you would still see the correct md5sum because the
>> kernel abstracts this fact away from you.  But if you rip out the drive
>> and take it somewhere else without flushing those caches, you're going
>> to get an incomplete file.
>>
>> Check if the file on the drive still md5sums the same if you plug it
>> back into the first machine.  Check what size it is, and whether there
>> are a lot of 0s at the end indicating an unfinished write.
>>
>> cal
> 
> Yes, I unmounted the USB device every time. 
> And yes, I plug the USB device back to original machine and md5sum is correct, same as the original. 
> 
> I copied the large file over network to another box and md5sum of:  windows-7_pro_May-23-21.ova is correct same as on the original box.
> 
> I run this:   "rsync -avh [source] [destination] && rsync -avhc [source] [destination]"
> 
> above code rsync files folder on first run and if complete without issue, will run rsync again immediately while performing same file name comparison by using hash of entire file.
> 
> This i what I got:
> 
> rsync -avh windows-7_pro_May-29-21.ova fd@10.0.0.138:/home/fd/business/VDI/ && rsync -avhc windows-7_pro_May-29-21.ova fd@10.0.0.138:/home/fd/business/VDI/
> sending incremental file list
> windows-7_pro_May-29-21.ova
> 
> sent 30.29G bytes  received 35 bytes  115.81M bytes/sec
> total size is 30.28G  speedup is 1.00
> sending incremental file list
> windows-7_pro_May-29-21.ova
> WARNING: windows-7_pro_May-29-21.ova failed verification -- update discarded (will try again).
> windows-7_pro_May-29-21.ova
> ERROR: windows-7_pro_May-29-21.ova failed verification -- update discarded.
> 
> sent 33.44M bytes  received 6.47M bytes  123.38K bytes/sec
> total size is 30.28G  speedup is 758.62
> rsync error: some files/attrs were not transferred (see previous errors) (code 23) at main.c(1330) [sender=3.2.3]
> 
>  
> 
rsync is emitting errors indicating the file was not transferred
correctly.  At this point I would call into question whether your second
machine is the problem rather than any of the tools you're using.  If
you have a third machine that is easy to test.  Otherwise I would run
memtest86+ and smartctl.

cal