Date: Sun, 22 Jul 2012 15:12:59 -0500 (CDT) From: Robert Bonomi <bonomi@mail.r-bonomi.com> To: freebsd-questions@freebsd.org Subject: Re: fsck on FAT32 filesystem? Message-ID: <201207222012.q6MKCxPe025704@mail.r-bonomi.com> In-Reply-To: <20120722181402.9fec82f0.freebsd@edvax.de>
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> From: Polytropon <freebsd@edvax.de> > Date: Sun, 22 Jul 2012 18:14:02 +0200 > Subject: Re: fsck on FAT32 filesystem? > > By the way, I remember I had a DD.EXE program on my old DOS > system. I'm not sure if such a tool could operate on devices > (instead of filesystem-based representations as "drive letters"), > but it actually _was_ a DOS-based "copy & convert" utility > for the PC. :-) MSDOS/PCDOS had -no- O/S functions to directly access actual disk devices. The ONLY fuctionality provided to the user, by the "O/S" was filesystem based access. To get 'raw' device access, one had to bypass the O/S entirely, and use direct BIOS calls (INT 13h). And, _if_ you went the INT 13H route, you had to include your own custom code in your app for MS 'partition' handling, and possible multiple logical drives inside a single 'extended partition'. There was a fairly widely available "INT 13H" program called 'rawrite" that would copy a file (inside the filesystem on a letter-named drive) to a raw disk device. Commonly used for making bootable UNIXesque floppies under DOS/Windows, from an 'image' file. There was a companion 'rawread', that was much less widely distributed -- few people needed to make a complete disk image file of a physical drive (or logical 'drive letter') under windows. Rawread/rawwrite would work for 'cloning' a *SMALL* physical drive, but *ONLY* if the 'bad sectors' were in the same place(s). They _weren't_ smart enough to write the data intended for what turned out to be a 'bad sector' on the target drive to "somewhere else", and update the FAT accordingly. They only worked on small drives because they only spoke 'CHS' sector addressing, not LBA.
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