[Pkg-sysvinit-devel] Bug#630615: Bug#630615: RAMTMP should default to no

Michael Biebl biebl at debian.org
Wed Jun 15 21:38:37 UTC 2011


Hi Roger!

Thanks for answering in such detail. I'll try to comment on a few points.

Am 15.06.2011 22:46, schrieb Roger Leigh:
> On Wed, Jun 15, 2011 at 05:33:59PM +0100, Roger Leigh wrote:

> 
> The FHS defines the persistence/lifetime for /tmp and /var/tmp.
> It does not make any recommendations about size.

Yep, that's also how I read and understand the FHS.

> Historical practice is that /tmp is small, and /var/tmp is
> rather larger.  When using Sun/Solaris systems back around 2000,
> /tmp was always a tmpfs (it's the default), and /var/tmp was
> disc.  Solaris tmpfs didn't have size limits (filling it would
> hang the system--I remember an undergrad being told off for
> trying to download a RedHat ISO image to /tmp and killing the
> system).  On these systems files in /tmp were cleaned hourly,
> and files in /var/tmp weekly.  Files needing longer-term storage
> went in /var/preserve (cleaned every few months) or on other
> storage.

As a fun fact, I made the opposite experience. At university (where $HOME was
shared via NFS and had rather strict quotas) students where told to use /tmp for
larger downloads.
But then, this was not on a Solaris system.

> In the IRC discussion, it was mentioned that some DVD authoring
> applications were using /tmp to create/store 4GiB disc images.
> Also, backup software used /tmp to store multi-gigabyte backups
> during its operation.  I would argue that any application expecting
> to be able to store such large files in /tmp has wholly unrealistic
> expectations.

If I look at todays installers for Linux distros, like openSUSE, Redhat, Ubuntu
or Debian, the default option creates a large /tmp, as it is a subdirectory of
/. I don't know of any Linux distribution which uses tmpfs for /tmp.
/tmp on a separate partition is an option which not all installers offer and
needs to be chosen explicitly.

So while we don't guarantee any minimum sizes for /tmp, applications expecting a
large /tmp is not completely unrealistic.

I acknowledge that my concern is more targetted at a typical desktop/laptop
user, which certainly has different usage of software than a server installation.

> Initial setup:
> I would like to see the Debian installer support setup of /tmp to
> permit
> - disabling of /tmp on tmpfs
> - setting of a tmpfs size other than 20% core
> - allocation of sufficient backing store (swap) during partitioning
> If we wanted to guarantee a minimum tmpfs size here, we could ensure
> that there's sufficient swap to up the limit from 20% to something
> more, or an absolute value rather than a percentage.

Having RAMTMP=no and letting d-i enable it if it finds a minimum amount of ram
would be a good compromise imho.

Michael


-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

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