Date: Wed, 01 May 2002 23:48:08 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: kudzu@tenebras.com Cc: Ian Dowse <iedowse@maths.tcd.ie>, utsl@quic.net, "Andrew P. Lentvorski" <bsder@allcaps.org>, freebsd-fs@freebsd.org Subject: Re: Non-standard root filesystems Message-ID: <3CD0E128.980AA927@mindspring.com> References: <200205012115.aa68752@salmon.maths.tcd.ie> <3CD04F45.1040704@tenebras.com>
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Michael Sierchio wrote: > Ian Dowse wrote: > > I never said anything about using union filesystems; you can just > > mount another filesystem directly over /, and it hides the underlying > > root filesystem. > > Covering mounts are also broken, IIRC, with the same cache coherency > problem. I may be mistaken, but the problem is with NULLFS, which > is required for covering mounts. He's talking a fully covering mount, not a stacking mount. The coherency issues are particular to the stacking process, and to the "unionfs", which is a stacking FS. The "union" mount option, which is handled internally to the FS framework itself, has different problems. The main problem with covering mounts is what happens to inferior mount points, when you cover a mount point higher up in the mount hierarchy (e.g. "What happens to an already mounted "/usr/" when you cover over "/"?"), and "slip under" (e.g. "How do I replace, rather than cover, an FS at a mount point?"). -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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