kloareg
Posts: 11
Joined: Sat Sep 29, 2012 7:19 pm

cannot copy bootable SD card

Wed Oct 10, 2012 6:44 pm

I have two 4GB Transcend sdhc cards (1 class 4, 1 class 6). I can install Wheezy on either and both work. If one of them crashes (happens e.g. when using Tightvncserver) and I try to copy the good image from one card to the other (using sudo dd if= etc. in Ubuntu) the copied image won't boot, despite the records counted in and out being identical. Can anyone please suggest what I might be doing wrong? If it's of any help, the last 2 lines displayed when trying to boot are:
PANIC:VFS:Unable to mount root fs on unknown block (179.2)
Entering kdb (current:0xcb 82ac80,pid1) due to keyboard failure

Thanks in advance for any suggestions.
Kloareg
If at first you don't succeed, give up!

kloareg
Posts: 11
Joined: Sat Sep 29, 2012 7:19 pm

Re: cannot copy bootable SD card

Wed Oct 10, 2012 6:55 pm

P.S. to the above - if I try to mount the copied SDHC card in Ubuntu I get:

Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sdd2,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

Kloareg
If at first you don't succeed, give up!

lb
Posts: 281
Joined: Sat Jan 28, 2012 8:07 pm

Re: cannot copy bootable SD card

Wed Oct 10, 2012 7:38 pm

Did you perhaps copy to or from partitions (/dev/sdc1, etc.) instead of the whole card?

drgeoff
Posts: 11382
Joined: Wed Jan 25, 2012 6:39 pm

Re: cannot copy bootable SD card

Wed Oct 10, 2012 9:50 pm

Have you experienced this with both card 1 to card 2 and card 2 to card 1 copying or has it always been the same one of the two cards as the source and the other as destination?
Quis custodiet ipsos custodes?

dextrus
Posts: 119
Joined: Tue Jan 24, 2012 10:10 pm
Location: Eastleigh, Hampshire
Contact: Website

Re: cannot copy bootable SD card

Wed Oct 10, 2012 10:26 pm

What worries me is that you try and copy the "good" image from one card to the other card, irrespective of the card. You are not keeping a stable "known" image. I don't know how many times you have done this but I do wonder if an error has crept in at some point, and is now on both cards.

Another way of putting this would be, surely you have kept a "clean" image somewhere other than a card you are going to be using?

It could also be card failure of course, and I assume you've checked that the card is not a fake?

/Dextrus
Have more FUN with your Pi. Visit www.pi-fun.com

kloareg
Posts: 11
Joined: Sat Sep 29, 2012 7:19 pm

Re: cannot copy bootable SD card

Thu Oct 11, 2012 12:07 pm

Many thanks for the above comments. Since my original post I have tried copying from card 1 to card 3 (Dane-elec Proline 200x 4GB class 10) and that worked OK (yes I do put sdd and sdf without a partition number).
So I guess that card 2 could be a fake or defective in some way, although if I copy the downloaded Wheezy image to it and do the update, upgrade etc. it works fine.
I'll play around a bit more with card 2, but in the meantime perhaps it's best to close this topic, and I'll get back later if I find more anomalies.
Thanks again,
Kloareg
If at first you don't succeed, give up!

dextrus
Posts: 119
Joined: Tue Jan 24, 2012 10:10 pm
Location: Eastleigh, Hampshire
Contact: Website

Re: cannot copy bootable SD card

Thu Oct 11, 2012 8:17 pm

Fake cards report incorrect size (of course), but also report that writes have worked, when in fact they haven't. The trouble is, fake cards do have capacity (2gb, although I had one recently with 8) and that you have to read the data back to find the error. In normal use, we don't do this so you don't find out until weeks or months later.

I've posted a few times on this subject, sorry, but a) Make backups, and b) Your internet-purchased SD card is quite likely a fake. It's *awash* with fakes.

/Dextrus
Have more FUN with your Pi. Visit www.pi-fun.com

drgeoff
Posts: 11382
Joined: Wed Jan 25, 2012 6:39 pm

Re: cannot copy bootable SD card

Thu Oct 11, 2012 11:02 pm

dextrus wrote:Fake cards report incorrect size (of course), but also report that writes have worked, when in fact they haven't. The trouble is, fake cards do have capacity (2gb, although I had one recently with 8) and that you have to read the data back to find the error. In normal use, we don't do this so you don't find out until weeks or months later.

I've posted a few times on this subject, sorry, but a) Make backups, and b) Your internet-purchased SD card is quite likely a fake. It's *awash* with fakes.

/Dextrus
But the OP in the first post said that he can install Wheezy on both cards and they both work.

The reason for my question in the fourth post was my thinking that although both cards are nominally 4 Gbyte, in reality they may have slightly different capacities. That is, one is larger than the other. Clearly the small one can be copied to the larger one but not vice versa. But maybe the lost bits would not matter anyway.
Quis custodiet ipsos custodes?


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