Message-Id: <199705051203.OAA05820@grendel.sylaba.poznan.pl> Comments: Authenticated sender is From: "Mark Habersack" Organization: PPP (Pesticide Powered Pumpkins) To: physmsa AT cantua DOT canterbury DOT ac DOT nz (Mr M S Aitchison) Date: Mon, 5 May 1997 14:04:13 +0100 MIME-Version: 1.0 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Subject: Re: A few FS notions Reply-to: grendel AT hoth DOT amu DOT edu DOT pl CC: opendos AT delorie DOT com In-reply-to: <199705020534.RAA18805@cantua.canterbury.ac.nz> Precedence: bulk Once upon a time (on 2 May 97 at 17:34) Mr M S Aitchison said: > I really like these file system ideas. It should be possible and > efficient to allow (say) a Macintosh file system to be mounted in one > place in the tree, an hpfs one in another, and each have attributes > available when in that area. I'm not sure that second files are the > best way to do it, but I'm not sure (Tim probably has the best feel for what > would work well over bnetworks; I certainly don't like systems where some > special file is stored in the root directory that is missing when > subdirectories are exported). Such an additional file would be tied to a "regular" one with a link in the same dirent that describes the file and thus copied together with the regular file! > The only problem might be when a search needs to take corresponding > (but slightly incompatible) attributes from each. (Not a problem > in the sense "we can't do it" but "this is going to take some > discussion"). For example: > > 1. A program asks for the icon (if it exists) for a particular file; > if the file is on an OS/2 system or a Unix system or whatever (which do > have mechanisms at the moment fort associating icons with files) the icon > is supplied *converted from whatever native format* it had. > > 2. Two file systems have Access Control Lists (or something like that) but > how do you match up the user ID's and groups? In some systems > (e.g. the Linux mount "squashing" options, and the username mapping file > that Multinet's nfs under VMS has) you can manually supply a conversion > in some form; but ideally it should hook into pluggable authentication > modules or NIS or something like that. I think that for the moment we are discussing a hypothetic new file system. Relation between several file systems is a different thing (and a lot tougher!). I suspect that making two (or more) different file systems work together and provide more or less the same information would require creating a VFS to cope with all the possible incompatibilities. But what you suggest about the IFS is great: "I (the user/application/kernel/whatever) don't care where did you take the information from. I just wanna see it" - that way the general and common functions like "dir', "ls", "move", "cp" etc. would exist in a single copy for all file systems. > 3. Some files have bare-bones FAT permissions, others have owner-group-world > flags; do we have to map them all down to a "readonly" bit appropriate > for that user? Or make up owner-group-world bits (e.g. from a default > umask to use Unix terminolgy). That would depend on the target file system. In case of FAT, you have no choice - just the R/O bit... > 4. Macs might say the creator was some mac version of Word Perfect; we are > in DOS - is it good enough to claim the creator was a PC Word Perfect? > (Remember that Mac MS Works file formats in some versions are definately > different to PC ones). > > I think we need "classes" of file, as well as specific creators, to cope > with the last situation at least. You could probably get away with a single > byte to describe the type of system and the type of program teh file came > from. Just what I suggested in the other posting: a system-wide database of registered *applications* and their custom file types! ++++++++++ Well I'm out in a car, and it's just full of stupid girls, and I've forgotten how to speak, and I just can't remember a word And my eyes feel like they're bursting, and they're splitting like plums, and I'm writhing, and I'm writhing, and I'm writhing in the snakepit. ----------