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Re: TMPDIR - Do we also need a drive backed TPMDIR ?

On Thu, 21 Jul 2016 17:19:27 +0530
Ritesh Raj Sarraf <rrs@debian.org> wrote:

> Hi,
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=831998
> This bug is an example of the problem. I am bringing it here to know
> views of fellow developers.
> I am not sure if there's an fd.o defined standard for environment
> variables, but a quick web search pointed to the IEEE and Open Group
> link.
> http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html
> None of the standards talk about where TMPDIR should be pointing to.
> On GNU/Linux, I recollect it pointing to /tmp and always wondered
> what environment variable would point to /var/tmp
> On the Debian front, I can't recollect what our official stand is. I
> could find a conversation at the following link. It is fairly recent
> from 2012. https://lists.debian.org/debian-devel/2012/06/msg00311.html
> My /tmp is on tmpfs. I just don't recollect if it was the default or
> I enabled it explicitly. Currently, it is managed by systemd, but I
> do recollect initscripts providing similar feature.
> ● tmp.mount - Temporary Directory
>    Loaded: loaded (/usr/share/systemd/tmp.mount; enabled; vendor
> preset: enabled)
>    Active: active (mounted) since Wed 2016-07-20 21:50:05 IST; 19h ago
>     Where: /tmp
>      What: tmpfs
>      Docs: man:hier(7)
>            http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
>    CGroup: /system.slice/tmp.mount
> Jul 20 21:50:05 learner systemd[1]: tmp.mount: Directory /tmp to
> mount over is not empty, mount
> Jul 20 21:50:05 learner systemd[1]: Mounting Temporary Directory...
> Jul 20 21:50:05 learner systemd[1]: Mounted Temporary Directory.
> Now, back to the actual problem. For many applications, we rely on
> the TMPDIR environments. Tools like Python's modules help use these
> variables and not worry about the underneath platform.
> Under Linux, with /tmp more commonly on tmpfs, how are developers
> dealing with it? tmpfs is limited and multi gigabyte operations may
> end up filling it all (as is the case in the debdelta bug report
> above).

As a drive backend, why doesn't swap work for this? There's no mention of swap in the original bug report.

> The whole idea of tmpfs for /tmp was performance. Email attachments
> could be temporarily opened under tmpfs
> But what do we do about larger operations where temporary data may
> have the possibility of being huge. I think most video/audio
> transcoding workflows may be hit by this.
> Should there be another TPMDIR? Like DTMPDIR, pointing to the
> underneath disk, where size is limited by the capacity available to
> partition/disk ?
> This could allow developers to choose one over the other based on
> their needs. It could also help standardize it as a fallback.
> -- 
> Given the large number of mailing lists I follow, I request you to CC
> me in replies for quicker response


Neil Williams

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