Thanks a lot for the instructions! I'm attaching the mbr and partition table with this email.
I'm pretty sure I had 1 partition on the card, since my /etc/fstab mounts mmcblk0p1. I think something corrupted my disk first, and then what I've done to the disk after noticing the corruption: 1. fdisk, it says use "w" will correct the error, so I did. But then the one parition is gone. 2. fdisk again, create a single partition, then "w" My mistake was that I didn't create a backup copy of the MBR. A hard lesson learned :( Also, why is that my hexedit doesn't take the "-s" option? It's version 0.9.7, and can't edit bigger than 4.2GB. My SD card is A-DATA brand, class 6, and 16GB. I'm using Linux, and fdisk version (util-linux-ng 2.14.1) Regards, Paul Liu On 11/3/09, Jan de Kruyf <[email protected]> wrote: > hallo, > Almost sounds like you had only the root master-boot-record /dev/mmcblk0 > before and now you have added 1 main partition /dev/mmcblk0p1. > > If (and only if) that is the case we have to undo the the 1st partition + > check that no nilfs is overwritten. > and I would have to urgently study fdisk to see exactly what it writes when > and where. > The last time I did tricks like these is quit a few years ago. > > It is the Linux version of fdisk is it?? > > So here is the plan of action: > hexdump the master boot record to file. > like this: > > dd if=/dev/mmcblk0 of=backup-mmcblk0.mbr count=1 bs=512 > > then dump any partitions of the device in a format useful as input to > sfdisk. For example, > % sfdisk -d /dev/mmcblk0 > mmcblk0 .out > sfdisk is a tool provided with the util-linux > package<http://www.kernel.org/pub/linux/utils/util-linux/>. > > > or you could use hexdump to get machine readable or man readable images. > Here is the man readable version: > hd -n512 /dev/mmcblk0 > backup-mmcblk0.mbr > hd -n512 /dev/mmcblk0p1 >backup-mmcblk0p1.mbr > etc. > > By the way boor records always end with '55 AA'. > > Keep your files in a safe place in case we mess something we can at least go > back to the present situation. > If you could dd the whole drive to a file, now that would be magic indeed! > but you must have the space on a harddrive. > count=... is the number of sectors in the above line (dd ...) that you dump > to file. > Hexedit will tell you the number of sectors is you start it with -s option > and then go to the last sector. > DONT stop hexedit with control-x use cntl-c. > DONT use high level or even midlevel tools on a stuffed disk, it normally > messes more than it solves. > unless of course you really,really know what you are doing. > Fiddling the bytes is in general safe and gives results, if a man keeps a > cool head. > > Please send me the fdisk version, the size of the card, and the mbr dump to > feast my eyes on. > > cheers, > > Jan de kruyf. > > > > On Tue, Nov 3, 2009 at 1:27 AM, Paul L <[email protected]> wrote: > >> just want to add that I've always been using 1 partition on this >> device, it's actually /dev/mmcblk0p1. But hexedit /dev/mmcblk0p1 >> doesn't show that 34 34 at line begining with 0x400, only hexedit >> /dev/mmcblk0 shows it. Not sure if this is a problem. >> >> Any help is greatly appreciated! >> >> >> On 11/2/09, Paul L <[email protected]> wrote: >> > Thanks for the tips. When I first used the SD card, I used fdisk to >> > create the partition. >> > >> > The device is /dev/mmcblk0, and hexedit -d -s /dev/mmcblk0 shows that >> > at the line 0x0400, it is indeed 34 34. What should I do then? >> > >> > I tried gparted, but apparently it has no support for nilfs2. >> > >> > Regards, >> > Paul Liu >> > >> > On 11/2/09, Jan de Kruyf <[email protected]> wrote: >> >> Did you first format this card with fdisk? >> >> did you give it the exact same info this time around? >> >> >> >> Can you read /dev/'sdcard' ? (sdcard being the device in the dev >> >> directory >> >> where the card lives) >> >> >> >> If yes can you run hexedit -s /dev/sdcard1 in a terminal as root? >> >> and go to address 0400 - 04B0 to see if nilfs still exists? >> >> >> >> be very careful no to save any data in hexedit, it will definitely and >> >> finally >> >> destoy your data. >> >> >> >> 0400 looks vagely like this: >> >> 00000400 02 00 00 00 00 00 34 34 00 01 00 00 D3 56 F0 B9 >> >> ......44.....V.. >> >> 00000410 39 BF D9 73 02 00 00 00 CA 02 00 00 00 00 00 00 >> >> 9..s............ >> >> 00000420 00 B4 66 65 01 00 00 00 01 00 00 00 00 00 00 00 >> >> ..fe............ >> >> 00000430 00 08 00 00 05 00 00 00 01 00 00 00 00 00 00 00 >> >> ................ >> >> 00000440 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> >> ................ >> >> 00000450 00 48 16 00 00 00 00 00 73 95 DC 4A 00 00 00 00 >> >> .H......s..J.... >> >> 00000460 00 00 00 00 00 00 00 00 73 95 DC 4A 00 00 00 00 >> >> ........s..J.... >> >> 00000470 00 00 32 00 01 00 01 00 73 95 DC 4A 00 00 00 00 >> >> ..2.....s..J.... >> >> 00000480 00 4E ED 00 00 00 00 00 00 00 00 00 0B 00 00 00 >> >> .N.............. >> >> 00000490 80 00 20 00 C0 00 10 00 4C 73 DD 3D 01 EC 45 85 .. >> >> .....Ls.=..E. >> >> 000004A0 94 28 44 42 3D F6 EF EC 56 61 72 36 34 00 00 00 >> >> .(DB=...Var64... >> >> 000004B0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> >> ................ >> >> 000004C0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> >> ................ >> >> >> >> the 34 34 in the top line say this is nilfs. >> >> >> >> >> >> cheers >> >> >> >> jan de kruyf >> >> >> >> >> >> >> >> >> >> On Mon, Nov 2, 2009 at 9:06 PM, Paul L <[email protected]> wrote: >> >> >> >>> Due to some careless handling of my laptop, the SD card popped out >> >>> when the machine is still running. When I put it back in and reboot >> >>> the machine, it says "partition table error". I then ran fdisk and >> >>> recreated the single partition. Then I can no longer mount the nilfs2 >> >>> partition that was on the SD card! >> >>> >> >>> Can any one help to me recover the file system? I believe all data are >> >>> still there, but just some bits and pieces are missing for the mount >> >>> to work. Any help is greatly appreciated! >> >>> >> >>> PS: I've a deadline to meet in 4 hours, not sure if I can get my stuff >> >>> back in time... so help please! >> >>> >> >>> -- >> >>> Regards, >> >>> Paul Liu >> >>> >> >>> Yale Haskell Group >> >>> http://www.haskell.org/yale >> >>> _______________________________________________ >> >>> users mailing list >> >>> [email protected] >> >>> https://www.nilfs.org/mailman/listinfo/users >> >>> >> >> >> > >> > >> > -- >> > Regards, >> > Paul Liu >> > >> > Yale Haskell Group >> > http://www.haskell.org/yale >> > >> >> >> -- >> Regards, >> Paul Liu >> >> Yale Haskell Group >> http://www.haskell.org/yale >> _______________________________________________ >> users mailing list >> [email protected] >> https://www.nilfs.org/mailman/listinfo/users >> > -- Regards, Paul Liu Yale Haskell Group http://www.haskell.org/yale
mmcblk0.out
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backup-mmcblk0.mbr
Description: Binary data
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