Anders,
Please see comments below:
On Thursday 22 January 2004 10:58 am, Anders Bruun Olsen wrote:
> This would not get over the problem that all the users would need an
> account on both servers and the fact that their settings wouldn't
> migrate from one server to the other.
Well, there's no way you could do these things with any dhcp daemon anyway, no
matter how cleverly configured.
If you set up NIS for user authentication and use an NFS mounted volume for
user home directories, then the solution I suggested would work just fine. If
you are sysadmining an LTSP installation, you should already know this. I
assume you are a Windows sysadmin and new to Unix.
You need to know that Linux servers just don't go down unless the hardware
fails, or the sysadmin is incompetant. I have an installation where the
entire enterprise (24 users, email, web server, database, firewall, dns,
dhcp, ...) is running on _one_ dual processor system. The users access it
using LTSP thin clients. The system has been up for 50 days. The last time it
was down was for a kernel upgrade.
If you want true high availability then the cost and complexity will be
substantial. You may find that it is much less expensive to put all your
software on one fast server with RAID'd disks. keep a complete set of spare
parts handy so you could fix a hardware failure and have the server back up
again quickly.
>
> > Put an entry in the crontab to run this script every minute.
>
> I believe this would put quite a load on the server - CPU time which in
> my opinion could be used better for other things.
Better upgrade that '386 man!
Seriously, you need to look at this quantitatively. What makes you think that
a tiny job that runs once a _minute_ would put excessive load on the CPU? It
would probably take a few _milliseconds_ of CPU time at the most. Compared to
the CPU load of things like Gnome, KDE, Mozilla, Java, and Open Office, this
is serveral _orders_of_magnitude_ smaller, or negligable.
In terms of wasted CPU, you should be concerned about processes like "java_vm"
and "wineloader", which are often particularly obnoxious. For example, one
user can bring the system to it's knees when they hit a web page with 20 java
applets on it, each one spawning a different "java_vm" that is eating all the
CPU it can get!
My solution to this is the following script, which runs once per minute:
-----------------------------------------------------------------------------------------------------------------------------
#!/bin/sh
#
# 3/21/01 created by JDR
# Checks for processes that are rampant, and kills them if they remain
# continue to run.
#
#
KILL_PROCNAMES=''
NICE_PROCNAMES='java_vm wineloader wineserver'
KILL_LIST=/tmp/manageRampantProcs_kill.lst
NICE_LIST=/tmp/manageRampantProcs_nice.lst
REFFILE=/var/run/crond.pid
# This is the %CPU utilization that gets our attention
THRESHOLD=15
function getPidCpu ()
# Get a list of PID's and %CPU utilization given a list of command names.
{
THRESH=$1
shift
unset CMDSTR
# Get ps entries for all processes we are monitoring
while [ -n "$1" ];do
CMDSTR="$CMDSTR -C $1"
shift
done
# Run ps command, strip decimal part of %CPU
ps --no-headers $CMDSTR -o 'pid pcpu'| sed 's/\.[0123456789]*$//' | \
(
while read PID CPU; do
#ps --no-header -p $PID 1>&2
if [ -n "$CPU" ] && let "$CPU > $THRESH"; then
echo $PID
fi
done
)
}
function getOffendingPids ()
# Search the supplied list of PID's, and return those that are using more CPU
than the threshold
{
THRESH=$1
shift
# check pid's for offending processes
while [ -n "$1" ]; do
CPU=$(ps --no-headers -p $1 -o 'pcpu'| sed 's/\.[0123456789]*$//')
if [ -n "$CPU" ] && let "$CPU > $THRESH"; then
echo $1
fi
shift
done
}
######################## main() ############################
# If the list is legitimate, search for processes still
# using too much CPU.
if [ -e "$NICE_LIST" ] && [ "$NICE_LIST" -nt "$REFFILE" ]; then
PIDS=$(getOffendingPids $THRESHOLD $(cat $NICE_LIST))
if [ -n "$PIDS" ]; then
renice +19 -p $PIDS &>/dev/null
fi
fi
if [ -e "$KILL_LIST" ] && [ "$KILL_LIST" -nt "$REFFILE" ]; then
PIDS=$(getOffendingPids $THRESHOLD $(cat $KILL_LIST))
if [ -n "$PIDS" ]; then
kill -s SIGTERM $PIDS &>/dev/null
# Give honest processes a chance to exit gracefully
sleep 5
PIDS=$(ps --no-header -p $(cat $KILL_LIST) -o 'pid')
if [ -n "$PIDS" ]; then
kill -s SIGKILL $PIDS &>/dev/null
fi
fi
fi
# Generate update list of files to watch
getPidCpu $THRESHOLD $KILL_PROCNAMES >$KILL_LIST
getPidCpu $THRESHOLD $NICE_PROCNAMES >$NICE_LIST
exit 0
---------------------------------------------------------------------------------
--
=============================================================
John D. Robertson, Computer / Engineering Consultant
Robertson & Robertson Consultants, Inc.
3637 West Georgia Rd.
Pelzer, SC 29669
Phone: (864) 243-2436
Fax: (864) 243-3023
Email: [EMAIL PROTECTED]
WWW: http://www.rrci.com
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