Okay, thanks everyone for their feedback. I think I have a workable solution now.
Peter ----- Original Message ----- From: "Oliver Fromme" <o...@lurza.secnetix.de> To: freebsd-hackers@FreeBSD.ORG, pste...@maxiscale.com Sent: Friday, March 6, 2009 11:15:11 AM GMT -08:00 US/Canada Pacific Subject: Re: How to tear down a geom mirror? Peter Steele wrote: > > Yes. The "clear" commands usually just zero-out the last sector of the > > underlying provider (doesn't matter if it's a drive, slice or something > > altogether different) so you don't have to do it manually. > > So, as a generic solution then I could just iterate through all > slices of all drives and run "gmirror clear" on each, and run dd > to clear the first sectors. What btw is in these first sectors? I > use this command because I saw it being done in one of the gmirror > tutorials. I understand what the gmirror clear command does, but what > is the dd command clearing? It clears the MBR (slice table) and GPT or disklabel (partition table), if any. Depending on how many sectors you clear, it will also destroy the beginning the file system, e.g. the first UFS superblock. By the way, if you cannot use "gmirror clear" for any reason, you can also easily clear the last sector on any devices using the information from diskinfo. For example: DEV=/dev/ad0s1a set -- $(diskinfo $DEV) BLOCKSIZE=$2 MEDIASIZE=$4 LASTSEC=$(( $MEDIASIZE - 1 )) dd if=/dev/zero of=$DEV bs=$BLOCKSIZE seek=$(( $MEDIASIZE - 1 )) count=1 That's pretty much what "gmirror clear /dev/ad0s1a" does. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "One of the main causes of the fall of the Roman Empire was that, lacking zero, they had no way to indicate successful termination of their C programs." -- Robert Firth _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "freebsd-hackers-unsubscr...@freebsd.org"
