Re: [K12OSN] Random logouts, inability to log in

[Les Mikesell <les futuresource com>]

On Fri, 2004-01-02 at 11:18, Julius Szelagiewicz wrote:

> 	the value i was referring to is 'memory in use'. The system was
> done by fresh install. I freely admit to being very weakly versed in
> Linux, which all too often leads me to expect behavior similar to that of
> HP-UX. I was spooked by the fact that 20 terminals could essentially max
> out the 4GB server memory, i was even more spooked by the apparent *non*
> realeasing of memory as proceses went away - going down to 8 users didn't
> change memory usage display in top. Reading between the lines in your
> mesage, i gather that memory is not added explicitly to the free pool, but
>  just marked as unused?

Actually it is still used, buffering valid contents of the previous
activity but will be released and re-used as needed for something
else.  All disk read/write activity and program loads are buffered
in available memory so the slow disk activity doesn't have to be
repeated in the likely event that something else wants to read the
same thing.  In the also-likely event that something wants memory for
a new use, the least-recently used buffers are invalidated and reused
or if you are down to the miminum, something is pushed into swap.
If things are working normally, you should see a general slowdown
as you start to need swap activity but nothing should completely die
until swap space is all consumed.

> 	I agree that the lack of swap use doesn't suggest memory
> starvation, but sudden logins accompanied by apparent data loss and or
> corruption *feel* like it.

Is there a difference between activity on the clients and server
in this respect?  That is, if you log in on the console does anything
ever go wrong?  If it really is memory the failures should be the
same.  If it only happens on the clients you more likely have some
kind of network problem that is either killing your X connection or
failing as some program code tries to page in over NFS.

> 	My big problem is that this is a production box in a middle of the
> fight over the desktop. Managers and users want M$, I want Linux. For the
> time being i'm making slow progress (at high political cost). What i can't
> afford is the system that fails - I got them spoiled, the business system
> stays up forever (3 years, 3 outages, 2 caused by vast power fluctuations
> and power failures and 1 caused by a mysterious hardware problem - no
> data loss).
> 

Note that your business system can probably survive a lot of network
issues without affecting data much.  The ltsp clients can't, although
the server should retain everything successfully saved.

> 	my previous experiences with upgrades of K12 (2.x to 3.0 to 3.1.0)
> wer very positive, so i just went for it. now i'm thinking that maybe i
> want to hear about a few reasonably large installs doing wel for a few
> months first ;-)

I've used the recent kernels enough to know that there is not a generic
problem that causes random program crashes and others would have
reported more problems if there were.  You have some specific issue
with your hardware and/or network.  If updating the kernel triggered
it, a likely suspect is the network card.  I had trouble recently
with a 3com chip on an old Dell motherboard but blamed it more on age
than the new driver.  Switching to an Intel PCI card fixed it
regardless.

---
   Les Mikesell
    les futuresource com