Date: Fri, 30 Mar 2012 19:42:18 +0000 From: Chris Rees <crees@freebsd.org> To: Adrian Chadd <adrian@freebsd.org> Cc: freebsd-current@freebsd.org, "C. P. Ghost" <cpghost@cordula.ws>, sthaug@nethelp.no Subject: Re: Using TMPFS for /tmp and /var/run? Message-ID: <CADLo839w4sWyqVh0bG1bXHQ41T48EM-Yry8AnH8rqOdYydCC2A@mail.gmail.com> In-Reply-To: <CAJ-VmonpQ7hBxd3k8RmxKmQ0s=EKmvcjmA1Yji6bp24Uc0Cvgg@mail.gmail.com> References: <4F746F1E.6090702@mail.zedat.fu-berlin.de> <4F74BCE8.2030802@vangyzen.net> <CACM2%2B-7Ahn6J=CTASe0g48%2BSD2vvLVd_hG3DRZmvO31QszG5Xw@mail.gmail.com> <20120330.151848.41706133.sthaug@nethelp.no> <CADGWnjXj5W_UCHPExNjxHgq3EZHP1GwocnK4kOHLch5y3gNG0A@mail.gmail.com> <CADLo83-c3jNd9XAyCMhqrEP3x9nvX1=Q9j7foEB37zRy3QZWDA@mail.gmail.com> <CAJ-VmonpQ7hBxd3k8RmxKmQ0s=EKmvcjmA1Yji6bp24Uc0Cvgg@mail.gmail.com>
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On 30 March 2012 19:36, Adrian Chadd <adrian@freebsd.org> wrote: > On 30 March 2012 10:56, Chris Rees <crees@freebsd.org> wrote: >> On 30 March 2012 17:31, C. P. Ghost <cpghost@cordula.ws> wrote: >>> On Fri, Mar 30, 2012 at 3:18 PM, =A0<sthaug@nethelp.no> wrote: >>>>> > However, if you always want to use tmpfs instead of stable storage, >>>>> please do not. =A0Some people expect /tmp to be persistent. =A0This i= s why >>>>> /etc/defaults/rc.conf has clear_tmp_enable=3D"NO". =A0Changing this w= ould break >>>>> the POLA. >>>>> > >>>>> This is a mistake. >>>>> >>>>> The default should be clear_tmp_enable=3D"YES" >>>>> if only to uncover those broken configurations that expect /tmp to be >>>>> persistent. >>>> >>>> If you want to break POLA and make a lot of people angry, sure. >>>> Otherwise no. >>> >>> I couldn't agree more. Not clearing /tmp on reboot has been >>> the norm for way too long and it is too late to change now. >>> It's not just POLA, it also involves deleting data of unaware >>> users, and that should be avoided. >>> >>> Anyone willing to change policy w.r.t. /tmp can do so on their >>> own machines. Nothing is preventing them from doing so. >>> But by changing defaults, one should err on the side of >>> caution and remain conservative, IMHO. >> >> >From man hier: >> >> /tmp/ =A0 =A0 =A0temporary files that are not guaranteed to persist acro= ss >> system reboots >> >> This assumption that people often make 'People will be astonished by >> this'-- I would like to have someone speak up and actually say "Yes, I >> use *temporary* directories for long-term storage" rather than the >> assumption that they are around. >> >> Software that assumes this should be fixed, and it won't be until the >> bug is exposed (I'll look at eaccelerator-- it probably should store >> its cache in /var/db). >> >> Maintaining the status quo because of some hypothetical scenario isn't >> really productive. >> > Let me tell you a story. > > Someone decided that ext4 could have a decent speed up if it > implemented the posix standard for not flushing files on close(). > After all, if you needed it to be guaranteed to be written to disk, > you would call a flush routine first, before you called close(). > > So they did this. > > Then people testing out ext4 discovered that upon crash, their > kde/gnome profiles were corrupted. > > Why? Because KDE/Gnome authors hadn't ever called flush before > close(), and they weren't the only ones. They didn't read the > standard, they only used the system and fixed bugs whenever their > system behaved against their expectations. They didn't notice that the > system was being different from the standard. > > Guess what ext4 did? :) > > Don't mis-estimate POLA. Well, having thought about what this conversation was *really* about, I may have unintentionally derailed it a little. My original intention was to say to Oliver, please, don't be discouraged from using tmpfs for /tmp, and make sure you send PRs to the upstream of any programs that misbehave as such. Let's not make judgement on people who treat /tmp as persistent quite yet ;= ) Chris
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