[Pkg-sysvinit-devel] Bug#386945: initscripts: User Mode Linux (UML) doesn't start because /dev/shm is mounted noexec

[Mario 'BitKoenig' Holbe]

On Mon, Sep 11, 2006 at 11:24:03AM +0200, Petter Reinholdtsen wrote:
> I suspect we need to provide some other tmpfs for users such as UML
> and ifupdown.

Please be very careful when you do so. Even now the tmpfs for /dev/shm
allows every user to eat up half of the RAM virtually anonymous by means
of the page-cache not being owned by any process. Preventing this pages
from getting swapped is easy to achieve by just touching them regulary.
This is not a big issue, though. However, if you create another default-
sized tmpfs, this becomes an issue because users then will be able to
effectively lock up all available RAM and thus force the OOM-Killer to
kill random foreign processes (including daemons etc.).

This is the main reason for me to bind-mount /dev/shm to /tmp and any
other tmpfs on my system while accepting to live with a potentially
polluted POSIX-shm-namespace (which is virtually never used anyways :)).


just my 2 cents
   Mario
-- 
Independence Day: Fortunately, the alien computer operating system works just
fine with the laptop. This proves an important point which Apple enthusiasts
have known for years. While the evil empire of Microsoft may dominate the
computers of Earth people, more advanced life forms clearly prefer Macs.
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