Date: Sun, 08 Feb 1998 13:32:20 -0800 From: Mike Smith <mike@smith.net.au> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: mike@smith.net.au (Mike Smith), hackers@FreeBSD.ORG Subject: Re: Bootblock sizes (was bad144 ravings) Message-ID: <199802082132.NAA00992@dingo.cdrom.com> In-Reply-To: Your message of "Sun, 08 Feb 1998 20:51:05 %2B0100." <199802081951.UAA13052@labinfo.iet.unipi.it>
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> > Let us look at some sizes (in bytes). The 'Bare' bootblock has serial > > console support, but nothing else fancy. > > > > Config Size Feature bulk > > ------ ---- ------------ > > Bare 6560 0 (room for 608 bytes) > > is this /usr/mdec/boot2 ? In which case, why (on 2.2.1 at least) the > first 512 bytes are all zero ? So that the bootblock can live in the same area of the disk as a disklabel. > (for the records, I was playing these days with simple compression > algorithms, like the "pred.c" in iijppp, or some other simple things > (so that the code to uncompress is reasonably small) but the savings > are not big (perhaps 100 bytes, including the extractor overhead). This > excludes the first 512 zeros, which probably can be easily ripped off ? In my case at least, that part of the disk is not actually empty: 00000200 57 45 56 82 05 00 00 00 77 64 30 73 32 00 00 00 |WEV.....wd0s2...| 00000210 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00000220 00 00 00 00 00 00 00 00 00 02 00 00 3f 00 00 00 |............?...| 00000230 40 00 00 00 bd 01 00 00 c0 0f 00 00 c0 60 1b 00 |@............`..| 00000240 00 00 00 00 00 00 00 00 10 0e 01 00 00 00 00 00 |................| 00000250 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * 00000280 00 00 00 00 57 45 56 82 a9 95 08 00 00 20 00 00 |....WEV...... ..| 00000290 00 20 00 00 00 f0 00 00 00 00 00 00 00 00 00 00 |. ..............| 000002a0 07 00 00 00 00 20 03 00 00 f0 00 00 00 00 00 00 |..... ..........| 000002b0 01 00 00 00 c0 60 1b 00 00 00 00 00 00 00 00 00 |.....`..........| 000002c0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 000002d0 00 00 00 00 00 d0 07 00 00 10 04 00 00 00 00 00 |................| 000002e0 07 00 00 00 c0 80 0f 00 00 e0 0b 00 00 00 00 00 |................| 000002f0 07 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| 00000300 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| * The first four bytes there are DISKMAGIC (see /sys/sys/disklabel.h). -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe hackers" in the body of the message
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