Date: Sun, 25 Aug 2002 01:49:05 -0700 From: Marcel Moolenaar <marcel@xcllnt.net> To: Julian Elischer <julian@elischer.org> Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/geom geom_gpt.c Message-ID: <20020825084904.GA3192@dhcp01.pn.xcllnt.net> In-Reply-To: <Pine.BSF.4.21.0208241557190.73088-100000@InterJet.elischer.org> References: <200208242242.g7OMgInd018655@freefall.freebsd.org> <Pine.BSF.4.21.0208241557190.73088-100000@InterJet.elischer.org>
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On Sat, Aug 24, 2002 at 03:58:59PM -0700, Julian Elischer wrote:
> have I got this right....
>
> ad0a ->ad0p1
>
> ??
>
> please give examples....
Peter explained it already, but here's a real-life example:
itanium% sudo ./gpt -rvvv show da0
gpt show: /dev/da0: mediasize=9186603008; sectorsize=512; blocks=17942584
gpt show: /dev/da0: MBR at sector 0
gpt show: /dev/da0: MBR partition: type=239, start=63, size=208782
gpt show: /dev/da0: MBR partition: type=165, start=208845, size=17719695
gpt show: /dev/da0: Pri GPT at sector 1
gpt show: /dev/da0: GPT partition: type=c12a7328-f81f-11d2-ba4b-00a0c93ec93b, start=63, size=208782
gpt show: /dev/da0: GPT partition: type=516e7cb6-6ecf-11d6-8ff8-00022d09712b, start=208845, size=13525391
gpt show: /dev/da0: GPT partition: type=516e7cb5-6ecf-11d6-8ff8-00022d09712b, start=13734236, size=4194304
gpt show: /dev/da0: Sec GPT at sector 17942583
start end size contents
0 0 1 MBR
1 1 1 Pri GPT header
2 33 32 Pri GPT table
34 62 29
63 208844 208782 GPT partition
208845 13734235 13525391 GPT partition
13734236 17928539 4194304 GPT partition
17928540 17942550 14011
17942551 17942582 32 Sec GPT table
17942583 17942583 1 Sec GPT header
The first MBR partition (type=239) is an EFI partition (FAT filesystem).
The second should be well-known. In the FreeBSD slice is a BSD label
with 2 partitions: root and swap.
The GPT equivalent has 3 partitions. The first (starting at LBA 63)
mirrors the MBR EFI partition. The other two are an UFS partition
and a swap partition (see sys/gpt.h for the UUIDs) and exactly
mirror the BSD partitions inside the FreeBSD slice.
Thus, with GPT we have a non-nested (ie linear) partitioning scheme:
da0s1 = da0p1
da0s2a = da0p2
da0s2b = da0p3
The non-nested partitioning is not inherent. It's still possible to
have BSD disklabels inside MBR slices inside GPT partitions and I
have reserved a GPT partition type for BSD disklabels. If you use
this partition type, you do get the well-known slice naming, but
it's mostly for compatibility and/or inter-operability.
FYI,
--
Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net
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