Date: Tue, 22 May 2007 09:57:34 +0200 From: Ivan Voras <ivoras@fer.hr> To: freebsd-hackers@freebsd.org Subject: GPT boot loader? Message-ID: <f2u7pf$7as$1@sea.gmane.org>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD0F433E148B0D5BEABDA97F3 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi! I've had the opportunity to talk to Adam Martin, Marcel Moolenaar and Peter Wemm about making GPT bootable, but not all of them at the same time, so I'd like this thread to be the meeting point on the subject. (Adam and Peter have offered to modify the boot loader chain, but differently.) Summary: The idea is to replace bsdlabels with GPT. The problem is that GPT is intended to be used with EFI and not to be bootable by regular BIOS machines. For FreeBSD, there are two distinct cases: 1. the machine is GPT-only, there are no other MSDOS and bsdlabel partiti= ons 2. the machine is dual-boot or has some other need to retain MSDOS partitions. The second case is more convoluted as it means the MBR will hold a regular MSDOS partition table, and one of those partitions will hold a GPT - which is trivially done with GEOM but completely non-standard. The problems: On EFI based machines this firmware deals with partition issues so there's no problem, but BIOS machines will probably need some tweaking, up to the point of using more-or-less nonstandard GPT format. GPT details are available here: http://technet2.microsoft.com/windowsserver/en/library/bdeda920-1f08-4683= -9ffb-7b4b50df0b5a1033.mspx?mfr=3Dtrue and some useful tips are here: http://developer.apple.com/technotes/tn2006/tn2166.html Some of the breaking points are small "details" such as the requirement that the protective MBR be marked non-bootable, that there's no "bootable" flag among the official flags, and that the fields in the GPT are supposed to be disk-absolute (which is not a problem on FreeBSD but may be on other systems). Full support for GPT will require modifying boot0..boot2 but also the loader executable (since it parses UFS). I'd like to hear more from Adam and Peter (and others!) about their ideas= =2E.. --------------enigD0F433E148B0D5BEABDA97F3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGUqJuldnAQVacBcgRAoJUAKDGSJsJ3oBCicCZijzVuxE7dMb/PQCdEPUV zWzA4TpmB07OSiDnKHWNnpM= =3WJR -----END PGP SIGNATURE----- --------------enigD0F433E148B0D5BEABDA97F3--
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