Using Scripts to Automate Tasks

Important system statistics like status of services and resource utilization are usually lost in log files hidden away. Use our shell script to extract such vital information so you can make use of it more easily

Wednesday, March 08, 2006

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In our last issue we took you through a Windows script that helps you add users in a Windows Active Directory. Continuing this series further, this month we will take you through a Linux script related to server monitoring. Server and network monitoring is an important part of any enterprise sysadmin's tasks. By 'monitoring' we mean an automated mechanism to test, track and report on the availability and condition of the system services.  

This article's sample script takes a snapshot of things like disk space, users logged in, mail queue, Inetd Services, RAM, Swap Space, CPU SPEED, services, network connections, print queues etc and mails all the details to you, thus, enabling you to do remote monitoring. We have put a copy of this script on this month's PCQLive CD. There are two scripts-sysinfo.sh and mailsysinfo.sh. The first one collects all the information of the server and stores it in a htm file called  info.html in /tmp directory.Before you start using the script make sure that a mail server is running on your Linux server.

To schedule these scripts to run at particular time we are going to use Cron daemon, which is a Linux task scheduler. Cron wakes up every minute and looks for jobs it has to execute at that moment. Details of which job to execute and when to execute are present in its configuration file called crontab.

Our sysinfo script generates this output which is then e-mailed by mailsysinfo

There are different ways to use Cron. In the /etc directory you will probably find some sub-directories called 'cron.hourly', 'cron.daily', 'cron.weekly' and 'cron. monthly'. If you place a script into one of those directories it will be run either hourly, daily, weekly or monthly, depending on the name of the directory. Here we want our script to run daily at particular time. To edit the crontab file, browse to 

/etc/crontab 

and open crontab file with your favorite text editor. Its will look something like this. Each line in this file has the following  format:

minute   hour   day   month   dayofweek   command

Now add the following line to it.

30 22 *  *  *  /root/desktop/mailsysinfo.sh

Where '*' is a wild-card meaning 'ALL', and  /root/desktop/mailsysinfo.sh is the path script is. You will have to change the path according to where you have kept the scripts, but make sure that both the scripts are in the same directory. Save the file and close it. Our script is scheduled to run everyday at 10:30 PM.You can change the time to what you want but remember that cron works on a 24 hourly clock.

Script editing
The only script you need to edit here is mailsysinfo.sh, unless you are planning to add new fields to sysinfo.sh. Here you need to change the e-mail address.

Explanation
We shall now explain what both the scripts that we have discussed in this story deliver.

Script 1: mailsysinfo.sh
The following script first executes sysinfo.sh file and then mails the output file info.html using the mail utility.

/opt/sysinfo.sh; cat /tmp/info.html | mail -s "subject of the mail" username@domain.com

Cron allows one to schedule commands to be run at intervals. Here we schedule our mailsysinfo script to run at 10:30 PM

The mail utility allows you to compose, send, receive, forward and reply to mail. Here –s is for the subject and after it's the e-mail address to which you want to send the e-mail.

Script 2: sysinfo.sh
This is the Script which retrieves all the information from the system and saves the output in a html file.

HOSTNAME=`hostname`
VERSION=`cat /proc/version`
DATE=`date`
OUT="/tmp/info.html"

Here HOSTNAME and VERSION are two variables defined containing the command hostname and VERSION contains version of the kernel respectively. OUT is another variable which stores the path of the output file of the script.

PMODEL=`cat /proc/cpuinfo | grep vendor_id | awk -F\: '{print $2}'`
PNAME=`cat /proc/cpuinfo  | grep model | awk -F\: '{print $2}'`
PSPEED=`cat /proc/cpuinfo | grep MHz | awk -F\: '{print $2}' | awk -F\. '{print $1}'`

In this part three variables are defined which store the output of  /proc/cpuinfo according to the given parameters. /proc/ cpuinfo contains information about the system CPU (or CPUs for a multi-processor machine).  'awk' is a utility for handling text processing tasks.

With -F, awk uses a set of patterns it reads from the file.

echo " Disk Configuration" >> $OUT
df -hv  >> $OUT
echo "ifconfig -a"        >> $OUT 
ifconfig -a                      >> $OUT

Here 'df' displays the amount of disk space available on the file system. '–h' argument prints the sizes in human readable format.  'ifconfig –a' causes ifconfig to print information on all interfaces.Other than simply e-mailing this information as shown above, it is possible to build complex scripts that also perform corrective action when problems arise like -clearing a disk of unnecessary file if the disk fills up. So while you make yourself comfortable with this script, we assure you that you won't leave empty handed.

Swapnil Arora

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