Using Scripts to Automate Tasks

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 Minute="30" Hour="10">
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