Perl script to monitor free disk space and send email alert

lee · **Posted:** Sun Jan 04, 2009 4:21 pm

I was looking around for some scripts to see if other people had made a diskspace check script, there were a few but they all seem to depend on modules that don't install too well. I wanted one that didn't require any modules since a few of the systems I work on are a pain to get modules on and it seems like this is simple enough to do without requiring them.

So I made this script to take care of that problem. It's based off of the df command and grabs the results, does some math and makes a decision to send an email or not based on the threshold levels set. There are 2 notification levels, warning and critical that will send emails. If the free disk space is higher than those 2 levels, it will not send out an email. Remember to set permissions and a cronjob for this script to run like so:
35 10 * * * /root/scripts/diskspace.pl
This would run every day at 10:35am. And permissions...
chmod 755 diskspace.pl

Code:

#!/usr/bin/perl -w
# Script to check free diskspace and email notifications.  Change the email and alert levels and you should be good to go.
#                                                               created by lb
use strict;
 
# Alert levels Warning and Critical - Below what percent level of free disk space do you want an alert?
my $alert1 = 30;        #Warning level free space below 30%
my $alert2 = 10;        #Critical level free space below 10%
 
# Put the email address to notify here
my $email = 'you@foo.com';
 
my ($size,$used,$avail,$use,$mounted);
my $message;
my @list;
my $sysname = `/bin/uname -n`;
chomp $sysname;
my @df = `/bin/df`;
my $df;
foreach $df (@df) {
        if ($df =~ /\/\n/) {
        @list = split(/\s+/, $df);
        }
        else {next;}
}
 
# Check the usage
my $diskfree = (($list[3]) / ($list[2]+$list[3])) * 100.00;
 
# Round the number off to 2 decimals
$diskfree = sprintf("%.2f", $diskfree);
 
# See if free disk space is below any of our levels
if ( ($diskfree < $alert1) && ($diskfree > $alert2) ) {
        $message = "Warning Diskspace threshold reached...free space below $alert1% at $diskfree%\n";
        &mailer;
        }
 
elsif ( ($diskfree < $alert1) && ($diskfree < $alert2) ) {
        $message = "Critical Diskspace threshold reached...free space below $alert2% at $diskfree%\n";
        &mailer;
        }
 
else {
        $message = "Free diskspace is good at $diskfree%\n";
        }
 
#Output to terminal (comment out if you wish)
print $message;
print "~" x 75, "\n@df","~" x 75,"\n","From system: $sysname\n";
 
#Subroutine for Mail, notifies on warning and critical levels.
sub mailer {
         open(MAIL, "|/usr/sbin/sendmail -t") or die "Cannot open sendmail!: $!";
         print MAIL "To: $email\n";
         print MAIL "From: $sysname\n";
         print MAIL "Subject: $message\n\n";
         print MAIL "$message";
         print MAIL "~" x 75, "\n@df","~" x 75,"\n","From system: $sysname";
         close(MAIL);
}

If all is well the commandline response will look like the following:

[root@rain]# perl diskspace.pl
Free diskspace is good at 97.76%
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
305410304 6505676 283390620 3% /
/dev/sda1 194442 19731 164672 11% /boot
tmpfs 900456 48 900408 1% /dev/shm
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From system: rain

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Perl script to monitor free disk space and send email alert

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