invisible process

[Thierry ITTY]

I'm working on a internet gateway for my home based on RH9
I want it to be "small" (P200/64MB) and "silent" (spin down disks and so on)
So I recompiled the kernel (2.4.20-x) with any unuseful thing disabled (ie
no audio, no video, no usb, and so on), even no module support (2 nics and
ext2/3 compiled in)

it works fine, I just noticed a very strange thing : some processes became
invisible !

I mean, sshd, named, for example, are not listed in "top" or "ps ax"
thought they exist.
"netstat -nap" shows ports listening, but with no associated processes
(sshd, named...)
"ls -al /proc" shows only a very few processes (which I can see in "top" or
"ps ax")

But, still stranger, "/var/run/sshd.pid" contains a pid number, which is
_not_ listed in /proc, but a "cd /proc/<sshd.pid>" works (and then "pwd"
and so on) and the directory is a valid /proc process sub-dir, with correct
exe link, for example.

When I connect to this gateway throught sshd, the forked sshd process
becomes visible

The same is true for named (excepted for the last remark)

When I need to shut it down, I get messages that the filesystems are still
busy, I think the "sending kill to all processes" can't find the invisible
ones, and they gon on running, keeping the filesystems busy

If I use a standard, or not-that-much-optimized custom kernel, I have no
invisible processes

I really wonder what this can come from, though it doesn't prevent my
gateway to work fine...

Any clue somebody ?

Thierry