Re: [uml-user] limits?

[BlaisorBlade <bla...@ya...>]

Alle 21:20, marted=EC 27 gennaio 2004, Sven 'Darkman' Michels ha scritto:
> Hi there,
>
> anyone played around with ulimits etc. and UML?
> Or can give some recomendations for setting maxfd's etc.
> when running a mailsystem into an UML?
> I don't want
> my host getting out of fd's if something went wrong
> in a UML etc. ;)
>
> Regards,
> Sven
>
> PS: maybe some general recommendations for proc
> tweaks would be also nice :)

=46irst, see man proc about that. You could probably increase host's fd wit=
h=20
/proc/sys/fs/file-max.

About the specific question:
=2D you don't get an inode /file descriptors on the host for every inode on=
 the=20
guest (and you can ulimit only open files, i.e. file descriptors); that=20
happens only with hostfs. And if you put a server inside your UML, you must=
=20
avoid using hostfs, as it's not secure at all (and you must also chroot you=
r=20
UML to avoid that some user loads a hostfs module).

=2D you get, in SKAS mode, one open file for each process inside the guest:=
 look=20
at /proc/<UML pid>/fd to see that there are many descriptors referring to=20
/proc/mm.

=2D so, a person who used to ulimit to 1024 the open files got problems whe=
n a=20
lot of threads started. IIRC he got a kernel panic (it will be fixed at som=
e=20
time, so that the process creation should just fail), so if you ulimit=20
processes inside UML be sure to reduce also the maximum number of processes=
=20
inside UML (via /proc/sys/kernel/threads-max inside the guest).

Bye
=2D-=20
cat <<EOSIGN
Paolo Giarrusso, aka Blaisorblade
Linux Kernel 2.4.23/2.6.0 on an i686; Linux registered user n. 292729
EOSIGN