Date: Wed, 6 Oct 1999 19:55:21 -0700 (PDT) From: David Wolfskill <dhw@whistle.com> To: bright@wintelcom.net, pwd@apple.com Cc: FreeBSD-Hackers@FreeBSD.ORG Subject: Re: Apple's planned appoach to permissions on movable filesystems Message-ID: <199910070255.TAA99394@pau-amma.whistle.com> In-Reply-To: <199910070011.RAA00348@scv2.apple.com>
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>Date: Wed, 6 Oct 1999 17:11:41 -0700 >From: Pat Dirks <pwd@apple.com> >>This is very interesting, as a timesaver to the second option >>(overwriting) you could use the timestamp on the file's permissions >>to determine if the UID/GIDs are valid (if they are stale old uids, >>or new uid's after a chown/chgrp) >That'd be an intriguing optimization. It would require maintaining a >timestamp for every file and directory on the disk to note the time of >the last change, though, in addition to the filesystem's timestamp, >wouldn't it? I suppose you could check that the owner/group IDs are >corrected if the "last changed date" is ever updated and ignore the >owner/group IDs if the last changed date is before the filesystem's >timestamp and thereby incrementally update individual >filesystems/directories on the filesystem without a lengthy delay at >"adoption" time. Please be careful here. There is absolutely *no* (meta-)information that can be trusted on a "foreign" medium, unless one can trust each process (computer-originated or otherwise) that has had the ability to modify anything on the medium. [Bad analogy follows. Sorry, I can't help myself.] Suppose you give a kid a sucker. The kid might keep it in his mouth until it's all consumed, but that's not especially probable. More likely, it's repeatedly placed in his mouth & taken back out. Often, putting it back in his mouth is a reasonable thing to do... but it depends on where the sucker has been in the mean time. Cheers, david -- David Wolfskill dhw@whistle.com UNIX System Administrator voice: (650) 577-7158 pager: (888) 347-0197 FAX: (650) 372-5915 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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