Hi,

I am happy to say I have a xymon client running on Openwrt. I thought other people might find this useful in three ways:

1. If you are running openwrt you can take this code and run a xymon client to monitor your openwrt system.

2. People using other small unix-like systems can use the same design to run a xymon client, even if the code doesn't fit exactly.

3. My approach uses only shell scripts, none of the xymon binaries need to be cross compiled. So anyone struggling to compile xymon client for a foreign system can use this approach; all they need to do is add a few shell scripts and they don't need to compile anything.

Details below.

jonty

• Equipment

I used the following pieces to put this together:

1. xymon 4.3.0 from : http://sourceforge.net/projects/xymon
2. openwrt 10.03 from : http://openwrt.org
3. Linksys WAG354G modem and router : 150MHz, 4MB flash, 16MB ram

• Design

I already have a xymon server running in my network. It monitors web servers, mail servers, and so on. I wanted to add monitoring to the broadband modem, which runs openwrt.

The broadband modem must send xymon status messages to the xymon server every five minutes. These messages are generated by the shell scripts xymonclient-linux.sh and xymonclient.sh. These are started every five minutes by cron.

1. xymonclient-linux.sh - This is part of the source of xymon 4.3.0. It generates the "body" of each message by running tools such as df, ps, and top. I had to make a few changes to this so it would run on openwrt but I tried to keep these changes as small as possible (see below).

2. xymonclient.sh - This started from the source of xymon 4.3.0 but had to change so much you could consider this a rewrite. The purpose of this script is to take the output from xymonclient-linux.sh, add a "header" and "footer" to the output, and then transmit the finished message over the local network to the xymon server (see below).

3. cron - The xymon package includes a tool called xymonlaunch which runs other parts of the package to a configured schedule. But the schedule on this client is so simple it can be handled by cron, which is already included in openwrt (see below).

No other parts of the xymon package are used on openwrt. The two shell scripts xymonclient-linux.sh and xymonclient.sh use only core linux utilities which are already included in openwrt. There is no need to copy xymon binaries or config files to openwrt.

• xymonclient-linux.sh

I copied this script from the source of xymon 4.3.0 onto openwrt and put it in the file /bin/xymonclient-linux.sh. I ran it to see what happened. It executed but it produced a few errors. Redirecting the usual output to /dev/null let me see just the errors and start fixing them:

openwrt$ /bin/xymonclient-linux.sh >/dev/null

1. Configure openwrt busybox to include the core utilities: who, nohup. These tools are missing from a standard build of openwrt but they are needed by the xymonclient. See http://wiki.openwrt.org/doc/howto/build

2. Add the package procps. This includes a "real" ps, rather than the minimal ps that is part of busybox. It also includes vmstat.

3. The df tool in openwrt busybox doesn't support -l or -x. And openwrt uses a rom filesystem as root. So the commands to run df become:

echo "[df]" EXCLUDES=cat /proc/filesystems | grep nodev | awk '{print $2}' | xargs echo iso9660 rom root | sed -e 's! !|!g' df -P | grep -v -E "$EXCLUDES" | sed -e '/^[^ ][^ ]*$/{

4. If you run ps you will get the simple one in openwrt busybox. But if you run /usr/bin/ps you will get the full featured one from the procps package. So the command to run ps becomes:

echo "[ps]" /usr/bin/ps -Aww -o pid,ppid,user,start,state,pri,pcpu,time,pmem,rsz,vsz,cmd

5. Top is not configured by the install utility. So the command to run it becomes:

echo "[top]" top -b -n 1

6. To run vmstat we don't have the usual xymon configuration variables such as MACHINEDOTS to build temporary files. Fortunately we can use mktemp and do something simple:

echo "[vmstat]" TMPFILE=mktemp -t nohup sh -c "vmstat 300 2 1>$TMPFILE 2>&1; mv $TMPFILE /tmp/xymon_vmstat" </dev/null >/dev/null 2>&1 & if [ -f /tmp/xymon_vmstat ]; then echo "[vmstat]" cat /tmp/xymon_vmstat rm -f /tmp/xymon_vmstat fi

• xymonclient.sh

This script is a wrapper around xymonclient-linux.sh. When it runs it has to add a header and a footer to the output and then copy the output over the network to the xymon server. The server is running on some machine in the local network and listening at port 1984. If you use the code below put the address of your xymon server machine in the XYMSRV variable.

The original script xymonclient.sh is part of xymon 4.3.0. But this uses a few of the xymon binaries to generate parts of the header and footer, then it uses another binary to transmit the message. I decided to replace the calls to binaries with core utilities that are already included in openwrt. In particular I used netcat to transmit the message over the network.

I started from the original xymonclient.sh script that is part of xymon 4.3.0 and simplified it step by step to reduce it to only what is needed. I ended up with a top-to-bottom rewrite of the script. I put this in /bin/xymonclient.sh :

#!/bin/sh

Configuration for the local machine.

This is hardcoded until I find a better way to do it.

MACHINE=hostname | tr . , SERVEROSTYPE=linux CONFIGCLASS=linux XYMSRV=192.168.1.1

Must make sure core utilities return standard (english) texts.

LANG=C LC_ALL=C LC_MESSAGES=C export LANG LC_ALL LC_MESSAGES

Use a temporary file to build the status message

TMPFILE=mktemp -t

Header line describes the source of this status message

echo "client $MACHINE.$SERVEROSTYPE $CONFIGCLASS" >> $TMPFILE

Information from core utilities

/bin/xymonclient-linux.sh >> $TMPFILE

Client version

echo "[clientversion]" >> $TMPFILE echo "" >> $TMPFILE

System clock

NOW=date "+%Y-%m-%d %H:%M:%S" echo "[clock]" >> $TMPFILE date -d "$NOW" "+epoch: %s" >> $TMPFILE date -d "$NOW" "+local: %Y-%m-%d %H:%M:%S %Z" >> $TMPFILE date -d "$NOW" -u "+UTC: %Y-%m-%d %H:%M:%S GMT" >> $TMPFILE

Transmit status message to server

nc $XYMSRV 1984 < $TMPFILE

Remove temporary file

rm -f $TMPFILE

Done

exit 0

• cron

All that is needed is a single line in /etc/crontabs/root on the openwrt machine that tells crond to run xymonclient.sh every five minutes:

*/5 * * * * /bin/xymonclient.sh