From owner-freebsd-current Fri Jul 26 11:44:57 1996 Return-Path: owner-current Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id LAA15645 for current-outgoing; Fri, 26 Jul 1996 11:44:57 -0700 (PDT) Received: from halloran-eldar.lcs.mit.edu (halloran-eldar.lcs.mit.edu [18.26.0.159]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id LAA15637 for ; Fri, 26 Jul 1996 11:44:54 -0700 (PDT) Received: by halloran-eldar.lcs.mit.edu; (5.65/1.1.8.2/19Aug95-0530PM) id AA05293; Fri, 26 Jul 1996 14:43:37 -0400 Date: Fri, 26 Jul 1996 14:43:37 -0400 From: Garrett Wollman Message-Id: <9607261843.AA05293@halloran-eldar.lcs.mit.edu> To: Joe Greco Cc: imp@village.org (Warner Losh), jkh@time.cdrom.com, freebsd-current@freebsd.org Subject: Re: cvs commit: src/sys/dev/ccd ccd.c src/sys/dev/vn vn.c src/sys/sys conf.h src/sys/i386/isa fd.c mcd.c scd.c wcd.c wd.c wt.c s In-Reply-To: <199607261830.NAA17041@brasil.moneng.mei.com> References: <199607261727.LAA28387@rover.village.org> <199607261830.NAA17041@brasil.moneng.mei.com> Sender: owner-current@freebsd.org X-Loop: FreeBSD.org Precedence: bulk < said: > I don't have anything useful to suggest other than to note that Sun took the > easy way out of this problem by implementing a "devfs-on-ufs", i.e. they use > UFS and have a procedure for "automatically" creating new instances of > devices. Well, perhaps this is an indication of the correct way to implement persistence. Filesystems keep device nodes as they currently exist, but they don't actually do anything---they are just place-holders that return ENXIO or some such if you try to do anything to them. However, if a devfs layer is stacked on top of a directory containing such a node, then the devfs hides any device nodes that are not available in the running system, and ``adopts'' the permissions of the underlying nodes for its own local devices. That way, upgrading an old system to devfs would Just Work. Attempts to change the permissions of a node would cause a new node to be created in the underlying filesystem, and the permissions changed on that, as well. This fixes the persistence problem, leverages our stackable filesystem infrastructure in a useful way, and makes devices work again over NFS. (This wouldn't support renaming of devices, but I don't know if that's at all useful if we have symbolic links instead.) Julian, does this sound reasonable to you? -GAWollman -- Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same wollman@lcs.mit.edu | O Siem / The fires of freedom Opinions not those of| Dance in the burning flame MIT, LCS, ANA, or NSA| - Susan Aglukark and Chad Irschick