Date: Sat, 18 Mar 2006 16:59:13 +0200 (EET) From: Dmitry Pryanishnikov <dmitry@atlantis.dp.ua> To: Jos Backus <jos@catnook.com> Cc: freebsd-current@freebsd.org Subject: Re: [patch] NetBSD disklabel support for geom_bsd Message-ID: <20060318162413.K32225@atlantis.atlantis.dp.ua> In-Reply-To: <20060318050116.GA19952@lizzy.catnook.local> References: <20060317012428.N52721@atlantis.atlantis.dp.ua> <863bhh3y05.fsf@xps.des.no> <20060317174743.GA13507@lizzy.catnook.local> <20060317213430.R31244@atlantis.atlantis.dp.ua> <20060317204704.GA16269@lizzy.catnook.local> <20060318032023.K40573@atlantis.atlantis.dp.ua> <20060318050116.GA19952@lizzy.catnook.local>
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Hello! On Fri, 17 Mar 2006, Jos Backus wrote: >> Well, as I wrote in my previuos letter, it's my mistake that FreeBSD >> uses slice-relative offsets while NetBSD uses absolute offsets. Actually, >> both systems use absolute offsets, and offset conversion isn't required >> (but just accidently happens harmless). > > I thought they were relative too. So this means one cannot move either FreeBSD And when disklabel shows contents of label, it (or, maybe, geom_bsd nowadays) auto-converts absolute media offsets to slice-relative. It was another source of my confusion. > or NetBSD partitions without modifying the label, requiring the moving tool > (such as PM) having to understand the label format. Seems like a downside to > me. Yes, exactly, but it's not something that we can easily change: it seems that all *BSD's do it in this way. RELENG_4 auto-converts offsets to slice-relative when you read label off the slice. I suppose that it should allow transferring slice image to "dangerously dedicated" (sliceless) media of the same size, and getting valid disklabel as a result. Nice idea, but in some situations it can hurt. Once I had to remotely replace Linux with FreeBSD on some co-location. I've prepared disk slice for FreeBSD at colo, locally created the same (as at colo) HDD layout on my disk, locally installed FreeBSD-4.11, dd'ed slice contents to a file, transferred it to the colo, dd'ed it it that slice, switched active partition to this slice, rebooted the machine. Machine didn't come up! It was due to the label auto-conversion on fly: when I've dd'ed slice to a file on local FreeBSD system, absolute offsets were converted to relative. Of course, Linux at colo didn't change them back to absolute ;) Sincerely, Dmitry -- Atlantis ISP, System Administrator e-mail: dmitry@atlantis.dp.ua nic-hdl: LYNX-RIPE
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