Date: Sat, 28 Apr 2012 13:52:02 -0400 From: Alejandro Imass <ait@p2ee.org> To: freebsd-questions@freebsd.org Subject: Re: UFS Crash and directories now missing Message-ID: <CAHieY7Tcv%2Bo-KbmLtPVHWXSphJX7b5f0QMO46yM-DOju4S9S7Q@mail.gmail.com> In-Reply-To: <201204281731.q3SHVaiM061997@mail.r-bonomi.com> References: <201204281731.q3SHVaiM061997@mail.r-bonomi.com>
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On Sat, Apr 28, 2012 at 1:31 PM, Robert Bonomi <bonomi@mail.r-bonomi.com> w= rote: > > Alejandro Imass <aimass@yabarana.com> wrote: >> On Sat, Apr 28, 2012 at 11:39 AM, Robert Bonomi >> <bonomi@mail.r-bonomi.com> wrote: >> > =A0Alejandro Imass <aimass@yabarana.com> wrote: >> >> After a little more research, ___it it NOT unlikely at all___ that >> >> under high distress and a hard boot, UFS could have somehow corrupted >> >> the directory structure, whilst maintaining the data intact. >> > >> > This is techically accurate, *BUT* the specifics of the quote "corrupt= ion" >> > unquote in the case under discussion make it *EXTREMELY* unlikely that= this >> > is what happened. >> > >> > 99.99+++% of all UFS filesystem "corruption' issues are the result of = a >> > system crash _between_ the time cached 'meta-data' is updated in memor= y >> > and that data is flushed to disk (a deferred write). >> > >> > The second most common (and vanishingly rare) failure mode is a powerf= ail >> > _as_ a sector of disk is being written -- resulting in 'garbage data' >> > being written to disk. >> > >> > The next possibility is 'cosmic rays'. =A0If running on 'cheap' hardwa= re >> > (i.e., without 'ECC' memory), this can cause a *SINGLE-BIT* error in >> > data being output. >> > >> > The fact that the 'corrupted' filesystem passed fsck -without- any rep= orted >> > errors shows that everything in the filesystem meta-data was consisten= t >> > >> [...] >> >> > I think it is safe to conclude that the probabilities -greatly- favor >> > alternative #1. >> > >> >> OK. So after your comments and further research I concur with you on >> the mv but if it wasn't a human, then this might be exposing a serious >> security flaw in the jail system or the way EzJail implements it. > > BOGON ALERT!!! > I admit my ignorance on how the filesystem works but I don't think your condescending remarks add a lot of value. The issue here is this actually happened and there is a flaw somewhere other than "the stupid administrator did it".
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