Hi, On Tue, 29 Jun 2010, Jefferson Ogata wrote: > On 2010-06-29 19:44, Eberhard Moenkeberg wrote: >> On Tue, 29 Jun 2010, J. Epperson wrote:
>>> Arrived home very tired and in a lapse of judgement tried to configure a >>> new USB backup drive on my PERC3 based home server, with a new cat roaming >>> between me and the monitor. Created a new partition on the existing >>> /dev/sda instead of the new /dev/sdb. System is still running, and I"m >>> doing an rsync to the new drive now. >>> >>> Can some kind soul help me remember how to repair this surgically instead >>> of rebuilding the filesystem and reloading it? If not, I deserve it. >> >> You just need to revert the partition table change. >> If you do not have a backup of the master boot record (LILO would have >> one), you can use the df output to estimate the right cylinder numbers. > > /proc/partitions is possibly a better reference. > >> If you need trial and error to find the boundaries, "tune2fs -l /dev/sdaX" >> is a non-destructive test. > > Doubtful that will work; it will refer to the old partition table the > kernel is still using. Yes, it works only after reboot. > You should be able to use dmsetup to create device nodes with offset > into /dev/sda if you want to do this. But you should be able to find > your filesystem headers with dd and xxd (or any hexdump program). A very good idea, to avoid the reboot. > Where to look: > > - The first partition starts one track into the disk; typically that's > 63 512-byte sectors. > > - The second, third, and fourth partitions are usually on cylinder > boundaries, with a cylinder typically being 63 * 255 512-byte sectors. > > - If you had more than four partitions, then the last physical partition > has a partition table at the beginning. The first logical partition will > begin one track into that physical partition. > > What to look for: > > - For ext3 filesystems, a superblock begins 1024 bytes into the > partition. At offset 0x38 in the superblock you should find the magic > number 0x53ef (big-endian). > > - For swap partitions, look at the first 4096 bytes. At the end of that > page you should find the string SWAPSPACE2. > > - For LVM physical volumes you should see an LVM label 512 bytes from > the beginning of the partition. A nice collection. Thanks, I will keep it in case i get into partition table trouble. Viele Gruesse Eberhard Moenkeberg ([email protected], [email protected]) -- Eberhard Moenkeberg Arbeitsgruppe IT-Infrastruktur E-Mail: [email protected] Tel.: +49 (0)551 201-1551 ------------------------------------------------------------------------- Gesellschaft fuer wissenschaftliche Datenverarbeitung mbH Goettingen (GWDG) Am Fassberg 11, 37077 Goettingen URL: http://www.gwdg.de E-Mail: [email protected] Tel.: +49 (0)551 201-1510 Fax: +49 (0)551 201-2150 Geschaeftsfuehrer: Prof. Dr. Bernhard Neumair Aufsichtsratsvorsitzender: Dipl.-Kfm. Markus Hoppe Sitz der Gesellschaft: Goettingen Registergericht: Goettingen Handelsregister-Nr. B 598 ------------------------------------------------------------------------- _______________________________________________ Linux-PowerEdge mailing list [email protected] https://lists.us.dell.com/mailman/listinfo/linux-poweredge Please read the FAQ at http://lists.us.dell.com/faq
