Bill Marcum wrote:
> On Fri, Nov 24, 2006 at 12:05:06PM +0100, Mirto Silvio Busico wrote:
>
>> Hi all,
>> I'm trying to star qemu but I have problems.
>>
>> I'm using Etch and qemu 0.8.1-1
>>
>> When I try to start I receive an error message stating that I have not
>> enough shared memory.
>>
>> the mount command says:
>> devshm on /dev/shm type tmpfs (rw)
>>
>> If I do what qemu suggest:
>> umount /dev/shm
>> mount -t tmpfs -o size=144m none /dev/shm
>>
>> the emulation starts correcty
>>
>> Here my questions:
>>
>> 1. is this the expected behaviour?
>> 2. where can I find documentation about shm device and temporary file
>> systems?
>>
>
> For a start, you can read the comments in /etc/init.d/mountvirtfs
>
Well, in my /etc/init.d/ directory there is no such file.
A grep of shm in this directory says:
=============================================================
msb01:/etc/init.d# grep shm *
checkroot.sh: domount tmpfs shmfs /tmp \
mountdevsubfs.sh: # Mount a tmpfs on /dev/shm
mountdevsubfs.sh: domount tmpfs shmfs /dev/shm
-onoexec,nosuid,nodev$SHM_OPT
mtab.sh:# /dev/pts and /dev/shm.
mtab.sh: domtab tmpfs /dev/shm "devshm" $SHM_OPT
udev: if mountpoint -q /dev/shm/; then
udev: umount -n -l /dev/shm/
umountfs: /|/proc|/dev|/.dev|/dev/pts|/dev/shm|/proc/*|/sys)
umountnfs.sh: /|/proc|/dev|/dev/pts|/dev/shm|/proc/*|/sys)
msb01:/etc/init.d#
=============================================================
So, looking at mountdevsubfs.sh (there is no great comment inside) I see:
=============================================================
TMPFS_SIZE=
[ -f /etc/default/tmpfs ] && . /etc/default/tmpfs
KERNEL="$(uname -s)"
. /lib/lsb/init-functions
. /lib/init/mount-functions.sh
do_start () {
#
# Mount a tmpfs on /dev/shm
#
SHM_OPT=
[ "${SHM_SIZE:=$TMPFS_SIZE}" ] && SHM_OPT=",size=$SHM_SIZE"
domount tmpfs shmfs /dev/shm -onoexec,nosuid,nodev$SHM_OPT
=============================================================
Looking at /etc/default/tmpfs I find a file containing:
=============================================================
# SHM_SIZE sets the maximum size (in bytes) that the /dev/shm tmpfs can use.
# If this is not set then the size defaults to the value of TMPFS_SIZE
# if that is set; otherwise to the kernel's default.
#
# The size will be rounded down to a multiple of the page size, 4096 bytes.
SHM_SIZE=
=============================================================
That explains the size determination.
>
>> 3. how can I change the shm device?
>>
>>
> Create an /etc/default/tmpfs containing the line
> TMPFS_SIZE=144M
>
> The default size is half of available memory, so I suppose your system
> has 256M or less?
>
Yes it have 256Mb
Thanks for your help
Mirto
>
>
--
__________________________________________________________
Mirto Silvio Busico ICT Consultant
Tel. +39 333 4562651
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