Date: Thu, 15 Nov 2012 13:48:56 +0000 From: Arthur Chance <freebsd@qeng-ho.org> To: "Ronald F. Guilmette" <rfg@tristatelogic.com> Cc: freebsd-questions@freebsd.org Subject: Re: Advanced Format Drive ? Message-ID: <50A4F2C8.5040308@qeng-ho.org> In-Reply-To: <21828.1352983292@tristatelogic.com> References: <21828.1352983292@tristatelogic.com>
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On 11/15/12 12:41, Ronald F. Guilmette wrote: > > In message <alpine.BSF.2.00.1211142250370.58597@wonkity.com>, > Warren Block <wblock@wonkity.com> wrote: > >> On Wed, 14 Nov 2012, Ronald F. Guilmette wrote: >> >>> I'm looking at the examples section of the gpart(8) man page. May I >>> assume that if I just want to merely ``try out'' GPT... you know... >>> taking it out on the road for a first time test run... that I can >>> just do the first five (5) commands listed under EXAMPLES and then >>> that will be enough to go ahead and try installing FreeBSD into the >>> created freebsd-ufs partition? >>> >>> Even assuming that the answer is yes, I have still more questions... >>> Where are these magic numbers coming from?? I am specifically talking >>> about the number "34" in the "-b 34" option and also the number "162" >>> in the "-b 162" option. Tha man page just tosses those into the example >>> command lines without saying a word about them. And you can probably >>> guess what it is that is especially troubling to me about them... neither >>> one of them is divisible by 8 (i.e. 4KB/512B). So would the examples >>> in the current gpart(8) man page produce an Epic Fail when and if they >>> were used with a modern "Advanced Format" drive? >> >> -b is the beginning block of a partition. 34 is a magic value, the size >> of a standard GPT partition table. > > It probably wouldn't have hurt anything to mention that in the gpart man > page. > > And what about 162? Is that magic too? If so, how? I seriously do not > know. The man example should be taken as a whole. You've got /sbin/gpart add -b 34 -s 128 -t freebsd-boot ad0 which gives you a 128 block partition starting at block 34, so the next free block is 162, and the next partition is explicitly started there in /sbin/gpart add -b 162 -s 1048576 -t freebsd-ufs ad0 No magic, just arithmetic. :-)
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