Date: Tue, 24 May 2011 23:04:30 +0400 From: "Andrey V. Elsukov" <ae@FreeBSD.org> To: Victor Balada Diaz <victor@bsdes.net> Cc: stable@freebsd.org Subject: Re: gpart usage Message-ID: <4DDC013E.5040107@FreeBSD.org> In-Reply-To: <20110524172718.GG1291@equilibrium.bsdes.net> References: <20110524132028.GE1291@equilibrium.bsdes.net> <4DDBC4A9.7040404@FreeBSD.org> <20110524150951.GF1291@equilibrium.bsdes.net> <4DDBD73B.7090600@FreeBSD.org> <20110524172718.GG1291@equilibrium.bsdes.net>
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[-- Attachment #1 --] On 24.05.2011 21:27, Victor Balada Diaz wrote: >>> So the 16 sector offset in BSD label is really needed or isn't? >> >> First 8 KBytes of the freebsd partition are reserved for the boot code >> (/boot/boot). The table of BSD partitions itself is located in the >> second sector. So, if you plan to create freebsd-ufs partition you can >> create it without any offset. But if it will be not an UFS partition, >> then i would created it with offset, otherwise you can wipe the BSD label. > > Who's the one reserving the 16 sector (8 KBytes) offset? the UFS filesystem? the BSD slice/disklabel > provider? the MBR provider? BSD slice provider. > If i understood it correctly, it would be like: > > Sector 0: usual IBM-PC MBR, MBR provider doesn't need anything more > Sector 1-62: Reserved by MBR scheme (dunno why, but seems to be the case, probably CHS alignment) start: 63 Yes, currently we are actively discussing about this in the freebsd-geom@ maillist. > Sector 63: BSD scheme unused because on disk metadata is stored on second sector Here is saved the boot1 stage of /boot/boot. > Sector 64: BSD scheme (disklabel) on disk data (148 + 8 * 16 = 276 bytes according to sys/disklabel.h) GEOM_PART_BSD supports up to 20 partitions. > Sectors 65-(63+16): Reserved by ??? for /boot/boot Here is saved the boot2 stage of /boot/boot. > Sectors (63+16)+: partitions If you will not use offset for the first BSD partition, then you can wipe BSD scheme with this command: # dd if=/dev/zero of=/dev/da0s1a count=2 -- WBR, Andrey V. Elsukov [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (FreeBSD) iQEcBAEBAgAGBQJN3AFDAAoJEAHF6gQQyKF6DoYH/i6bPG1tkPpWdvZMaNWe5n8l HKP0LlKRwQ/t8x9txvwkCKjzwrRlPKyLF0+VvLxXRTIZfbEmZ0jjsOfUEr4VdUx7 t+2KI/k7Jd6/3jeab7JlHERhUkqZhfdn6BzsUQy9DP4f7+vaey747NpRxh5CYC1p 4FOP6MhjyDmnwKNLr9T1cVHmyPn3NKHwomHv6NPoAtJp/ECGURewcob1ovaoYAam 6Ag4Udndlh+93qfxn0Wxwlxf5wDyegTcP5U+K4lvV6NnYPltn2/syWGIK66n9VCf 3bYbwTJ57PQ/uW1NwgbdypH2QLyK6hsuUFSXKQNNrMxTbGacZ4Nhq3n1QjrNFps= =vbI/ -----END PGP SIGNATURE-----
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