2010/9/15 Arno Wagner <arno@xxxxxxxxxxx>: > On Wed, Sep 15, 2010 at 01:02:25AM +0200, Ma Begaj wrote: >> >> > This confirms that you did create the LUKS container at the >> >> > right place, namely the LUKS header is at 64 x 512 B offset. >> >> >> >> 64x512 =32768 >> >> 32768 ?!= ?32256 >> >> >> >> 512 bytes is partition table? should it be 32780? >> >> I am probably missing something. >> > >> > No, you see what I missed. Your LUKS sector is at 63 sectors >> > offset, not 64. However the partition starts at 64 and therefore >> > the LUKS sector is not at its start. >> > >> > I don't know what went wrong here, but partitions 1-4 are special in >> > that you can change them without any changes to the disk except >> > in the first sector (for partitions >= a chained partition sector >> > is writte to disk and that can kill a LUKS header and do other dmage). >> > >> > This smeans you can just delete the partiton with fdisk and create >> > a new one, which will the start at sector 63 and should have >> > your LUKS container in it. It will not be 4kB alingned, though. >> > You should unplug and replug the disk after the partition creation. >> > >> > If this goes wrong, you still have the first 100MB as backup. >> >> ;-)). you are the man :). >> >> Working like a charm. Deleted partition, created new starting at 63, >> unplug/plug and luks partition is there. Thanks. >> >> I owe you at least a drink. > > You are welcome. Made my now day too ;-) > >> >> I don't know enough about partition tables and headers but it looks like >> >> /dev/sdm1 is starting little bit too far and LUKS header stays before the >> >> beginning of /dev/sdm1 (first partition). >> > >> > Indeed. >> > >> >> Only obvious reason (at lease for me) ?for this could be in this 4Kb >> >> sector size. >> > >> > I think something has gone wrong when you did the alignment. >> > Did you first create a not-4kB aligned partition and delete >> > that again? If so the kernel would could remembered the partition >> > but not that it got deleted and replaced (that needs a disk unplug). >> > The reason is that the kernel sees partition changes only under some >> > circumstances. >> >> Wow great assumption. I did exactly that. I was doing this remotely >> (I was not able to unplug) and I forgot first time to set 4kB sector size. >> I deleted partition (which already was luksFormated too) and recreated >> it again but this time in 4kB format. > > Its easy to have the idea when you already messed that up yourself > once ;-) Well, I will not forget my experience either ;-). > >> Thanks a lot. >> >> >> One more question because this is going pretty well now :) : >> >> Do you have an idea how could I recreate 4kB aligned partition >> without deleting data from the disk? This is more facultative question, >> because I know have my data. > > Difficult. You would need to shift the wole partitoon by > one sector. > >> I thought about shrinking this partition, creating a second parition >> with 500gb to copy all data on this new partition, creating first paritition >> in 4kB aligned format, copying all data back to this partition etc. > > That would work if you can shrink. At least my standard > tool (Gnu parted) cannot do much with XFS. > > Best option would be if you could temporary store all the date > somewhere else on the machine and repartition. > > The other option is to live with it, USB2 is very slow anyways, > sector alignment may not even matter that much. Well, I was "pre-thinking" (this word sounds nice ;-) ) and I bought a USB3 case for the HDD although my old server still only have USB2 ports. >> That could maybe even work if XFS would support shrinking. But it >> does not as I can remember ;-). Could partition start be moved from >> sector 63 to sector 64 and keep working filesystem (of couse at the same >> time risking to destroy some of the data)? Or is this (if possible) would >> destroy filesystem totally? > > Well, you could either use dd_rescue or write a program in C that > moves the raw partition. From your fdisk -ul output, I conclude > that there is no space left at the end of the disk, so you would > have to move the start from sector 63 to sector 60. That > should still work. Another option is to do away with partitioning > and move the start from sector 63 to 0. Your filesystem is then > on /dev/sdm. > > A possible commandline for dd_rescue would be something like this > (moving the partition to the start of the disk) > > dd_rescue -s 63 -S 0 -b /dev/sdm /dev/sdm > > Looks good, but better assume a 99% probability of complete data > loss. Connection problems, read errors, all can kill the data. > And this will take something like > 10 days for 2TB on USB2. Good that I was not patient enough ;-). I backed up everything, deleted and recreated partition again. Thanks. M. p.s.: I should contact you for a drink when I visit which city? ;-) _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
