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A System Monitoring Dashboard

Issue 137

From Issue #137
September 2005

Jul 28, 2005  By John Ouellette
 in
This simple set of shell scripts keeps you informed about disks that are filling up, CPU-hog processes and problems with the Web and mail servers.

Listing 1. smtp.pl tests outgoing mail through the SMTP server.


#!/usr/bin/perl -w
#
# Title  :   smtp.pl
# Author :   John_Ouellette@yahoo.com
# Files  :   smtp.pl
# Pupose :   Send email through SMTP server
#            Called from monitor_smtp.sh
#
# Submit as

use Net::SMTP;

my $rcpt   = $ARGV[2] || 'mygroup@somewhere';
my $sender = $ARGV[1] || 'root@host01';
my $host   = $ARGV[0];


#Start Script

my $smtp =Net::SMTP->new($host, Debug => 1);
my $input="test msg for server $host";

$smtp->mail("$sender");
$smtp->to("$rcpt");
$smtp->data();
$smtp->datasend("To: $rcpt\n") ;
$smtp->datasend("From: $sender\n") ;
$smtp->datasend("Subject: $host test\n") ;
$smtp->datasend("$input");
$smtp->dataend();
$smtp->quit;

Do I Have That Perl Module Installed?

An easy way to check whether you have any Perl module installed is by issuing this from the command line: 

$ perl -e "use Net::SMTP";

If nothing prints, you have that module installed. If you're missing the module, you get an error that looks like this: 


$perl -e "use Net::OTHER";
Can't locate Net/OTHER.pm in @INC (@INC contains:
/usr/lib/perl5/5.8.3/i386-linux-thread-multi /usr/lib/perl5/5.8.3
/usr/lib/perl5/vendor_perl/5.8.0 /usr/lib/perl5/vendor_perl .) at -e line
1.
BEGIN failed--compilation aborted at -e line 1.

This error indicates a lack of the module in question.

Finally, we come to our stats script, monitor_stats.pl. This script logs in to each host and runs the commands: 


df -k
swapon -s
top -n 1 | head -n 20
hostname
uptime

It then displays the results in a browser (Figure 2) and saves the result in a log, again sorted by date on the filesystem. It serves as a simple dashboard to give quick stats on each server.

The benefit of this monitoring design is threefold:

  1. We have a history of CPU, disk and swap usage, and we easily can pinpoint where problems may have occurred.

  2. Tedious typing to extract this information for each server is reduced. This comes in handy before leaving work to resolve potential problems before getting paged at night.

  3. Management quickly can see how well we're doing.

We are using the insecure rsh protocol in this script to show you how to get this set up quickly, but we recommend that you use SSH with properly distributed keys to gain security.

Figure 2. monitor_stats.pl in Action

Conclusion

With the use of this new system monitoring dashboard, my team's productivity has increased and and its confidence in monitoring has soared, because we no longer are wasting time chasing down false positives. A history of system performance has been a real time saver in diagnosing problems. Finally, easy installation allows users with basic skills to conquer a complex system administration problem in one business day.

Resources for this article: /article/8269.

John Ouellette is a system administrator with nine years of experience in Microsoft Windows NT and UNIX. He believes the command line is king and loves chicken parmigiana. He can be reached at john_ouellette@yahoo.com.

______________________

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Nagios

Will_'s picture
Submitted by Will_ (not verified) on Fri, 12/18/2009 - 08:57.

I believe Nagios already does this.

Also checking the page ...

ecazarez's picture
Submitted by ecazarez on Wed, 08/17/2005 - 14:42.

We have also scripts for monitoring a web server. Additionally to know that the web service is up and running we were interested in knowing that the page haven't had changes, so we did this:

- Precalculated and stored de md5 from the page we want to check
- Every few minutes (crontab line), get the page and calculate the md5 for the page we get and compare it with the precalculated. If they are different, there is a problem.

The calculus is an onliner:


fetch -q -o - http://www.thepage.tocheck | md5

Also, to avoid the problem of installing some modulus in Perl to send email, we use this:


sub send_mail {
# Send email messages using the sendmail process
# parameters:
# $from_address, addres to use in From field
# $subject, Subject for the message
# $body, Message body
# $to_address, address(es) destination for the message
my ( $from_address, $subject, $body, $to_address) = @_;
open(SENDMAIL, "|/usr/lib/sendmail -t") or warn "Cannont open sendmail: $!\n";
print SENDMAIL <<MESSAGE;
To: $to_address
From: $from_address
Subject: $subject
$body
.

MESSAGE
close SENDMAIL;
}

So, not having the module is not a problem for sending emails :)

Sendmail

jcoyle's picture
Submitted by jcoyle (not verified) on Mon, 09/26/2005 - 09:27.

How would you include you sendmail script in the web_monitor.sh ?

script errors

GZILL's picture
Submitted by GZILL on Sat, 07/30/2005 - 14:15.

I get a ": bad interpreter" error when running monitor_web.sh after having configured web servers, email addy and correcting the path to wget. Please advise.

line endings

Russ's picture
Submitted by Russ (not verified) on Mon, 08/15/2005 - 23:02.

I had to fix the line endings of the script after downloading it to Windows XP and moving the tgz file to my Debian box. Try

tr -s "\r" "\n" < monitor_web.sh > b && mv b monitor_web.sh;

You'll have to re-enable the executable bit.

bash or ksh ?

Anonymous's picture
Submitted by Anonymous (not verified) on Wed, 08/03/2005 - 15:28.

is the first line pointing to bash or ksh?
make sure its bash if using linux as most distros don't have ksh by default.

permissions ok?

Anonymous's picture
Submitted by Anonymous (not verified) on Wed, 08/03/2005 - 10:26.

have you set perms to 755 on the script?

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