Computer Systems And Networks: How To Create A Linux System Change Logger Script

Specification

For the preparation of the report on Linux system change Logger script we have selected Ubuntu as the Linux operating system for running the bash script. The script is developed with the common pre-installed command line tools without relying on the additional program or tools or libraries. The main content of the log file is the time stamped details of the significant changes of the current processes, currently logged in users. Plugged in devices, disk usage information for the different directories, state of network and details of the interface and other relevant information that is used for monitoring the computer.

For the creation of the shell script a new file is needed to be created and the shell script should be started with #!/bin/bash and for saving the file .sh is used as the extension and permission is needed to be added to be file for allowing the user to read and write. For allowing permission “ chmod +x mySysMonitor.sh” is types in the terminal after the creation of the file. For running the shell script ./mySysMonitor.sh command is used. It executes the command and stores in the output in the mySysMonitor.log file. The log file is used for comparing the output with the previous result and finding any changes made to the system from the previous time the shell script was executed.  

Echo command is used for labelling the output and identification of each of the output of the command. For the development of the shell script the nano editor is used in the terminal and firstly the current process running in the system is identified using the “ps” command. The current users logged in the system can be identified using the “who” command and for finding the devices plugged in with the system the “lsusb” command is used and it returns a list of the devices that are connected with the system using the USB ports. For the identification of the overall usage of the disk “df” command is used and for getting the details of the usage for the home directory the path is needed to be defined and the command used is “df -h /home/jay” is needed to be typed where jay is the username of the account. For listing the other key directories the “df -h” command is used and it return the usage of the disk space of the directories present in the system. The interface used for communicating with the network and their states can also be identified using the “ip link show” command and for getting any other relevant information we have selected the information of the applications currently installed in the system. For displaying the application installed the “ls /usr/share/applications | awk -F ‘.desktop’ ‘ { print $1}’ – ” command is used. It helps in identification of the new application installed in the system and maintain the changes in the system.

The shell script prepared for management of the change log is given below:

#! /bin/bash

#Author : – Jay

Design Consideration

#Date : – 29 November, 2018

#Checking if this script is being executed as ROOT. For maintaining proper directory structure, this script must be run from a root user.

if [ $EUID != 0 ]

then

  echo “Please run this script as root so as to see all details! Better run with sudo.”

  exit 1

fi

#Declaring variables

#set -x

num_proc=`ps -ef | wc -l`

Users_Currently_logged_in=`who`

Devices_Plugged_in=`lsusb`

total_root_size=`df -h /dev/sda1 | tail -1 | awk ‘{print$2}’`

overall_disk_usage=`df -h /boot|awk ‘{print $5 ” “$6}’`

Users_home_directory=`df -h /home|sed -n ‘2p’ |awk ‘{print $5 ” “$6}’`

ip_add=`ip link show | grep “inet addr” | head -2 | tail -1 | awk {‘print$2’} | cut -f2 -d:

ping -c 1 google.com &> /dev/null && echo -e “Internet: Connected” || echo -e “Internet: Disconnected”;`

root_fs_pc=`df -h /dev/sda1 | tail -1 | awk ‘{print$5}’`

os_name=`uname -v | awk {‘print$1′} | cut -f2 -d’-‘`

upt=`uptime | awk {‘print$3′} | cut -f1 -d’,’`

#load_avg=`uptime | cut -f5 -d’:’`

load_avg=`cat /proc/loadavg  | awk {‘print$1,$2,$3’}`

ram_usage=`free -m | head -2 | tail -1 | awk {‘print$3’}`

ram_total=`free -m | head -2 | tail -1 | awk {‘print$2’}`

inode=`df -i / | head -2 | tail -1 | awk {‘print$5’}`

os_version=`uname -v | cut -f2 -d’~’ | awk {‘print$1′} | cut -f1 -d’-‘ | cut -c 1-5`

#Creating a directory if it doesn’t exist to store reports first, for easy maintenance.

if [ ! -d ${HOME}/health_reports ]

then

  mkdir ${HOME}/health_reports

fi

html=”${HOME}/health_reports/Server-Health-Report-`hostname`-`date +%y%m%d`-`date +%H%M`.html”

email_add=”change this to yours”

for i in `ls /home`; do sudo du -sh /home/$i/* | sort -nr | grep G; done > /tmp/dir.txt

#Generating HTML file

echo “<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN” “https://www.w3.org/TR/html4/loose.dtd”>” >> $html

echo “<html>” >> $html

echo “<link rel=”stylesheet” href=”https://unpkg.com/[email protected]/build/pure-min.css”>” >> $html

echo “<body>” >> $html

echo “<fieldset>” >> $html

echo “<center>” >> $html

echo “<h2>Linux Server Report” >> $html

echo “<h3><legend>Script authored by Jay</legend></h3>” >> $html

echo “</center>” >> $html

echo “</fieldset>” >> $html

echo “<br>” >> $html

echo “<center>” >> $html

echo “<h2>System Details : </h2>” >> $html

echo “<table class=”pure-table”>” >> $html

echo “<thead>” >> $html

echo “<tr>” >> $html

echo “<th>num_proc</th>” >> $html

echo “<th>Users_Currently_logged_in</th>” >> $html

echo “<th>Devices_Plugged_in</th>” >> $html

echo “<th>Uptime</th>” >> $html

echo “</tr>” >> $html

echo “</thead>” >> $html

echo “<tbody>” >> $html

echo “<tr>” >> $html

echo “<td>$num_proc</td>” >> $html

echo “<td>$Users_Currently_logged_in</td>” >> $html

echo “<td>$Devices_Plugged_in</td>” >> $html

echo “<td>$upt</td>” >> $html

echo “</tr>” >> $html

echo “</tbody>” >> $html

echo “</table>” >> $html

echo “<h2>Resources Utilization : </h2>” >> $html

echo “<br>” >> $html

echo “<table class=”pure-table”>” >> $html

echo “<thead>” >> $html

echo “<tr>” >> $html

echo “<th>Overall Disk Usage</th>” >> $html

echo “<th>The user’s home directory</th>” >> $html

echo “<th>Other key directories</th>” >> $html

echo “<th>Network Interface and their states</th>” >> $html

echo “<th>Used RAM(in MB)</th>” >> $html

echo “<th>Total RAM(in MB)</th>” >> $html

echo “<th>iNode Status</th>” >> $html

echo “</tr>” >> $html

echo “</thead>” >> $html

echo “<tbody>” >> $html

echo “<tr>” >> $html

echo “<td><center>$$total_root_size</center></td>” >> $html

echo “<td><center>$root_fs_pc</center></td>” >> $html

Extensive test result and exemplary log and screen output

echo “<td><center>$Users_home_directory</center></td>” >> $html

echo “<td><center>$ip_add</center></td>” >> $html

echo “<td><center>$ram_usage</center></td>” >> $html

echo “<td><center>$ram_total</center></td>” >> $html

echo “<td><center>$inode</center></td>” >> $html

echo “</tr>” >> $html

echo “</tbody>” >> $html

echo “</table>” >> $html

while read size name;

do

  echo “<td>$size</td>” >> $html

  echo “<td>$name</td>” >> $html

  echo “</tr>” >> $html

  echo “</tbody>” >> $html

done < /mySysMonitor.log

echo “</table>” >> $html

echo “</body>” >> $html

echo “</html>” >> $html

echo “Report has been generated in ${HOME}/health_reports with file-name = $html. Report has also been sent to $email_add.”

#Sending Email to the user

cat $html | mail -s “`hostname` – mySysMonitor” -a “MIME-Version: 1.0” -a “Content-Type: text/html” -a “From: Jay <[email protected]>” $email_add

The shell script runs and the output is stored in the mySysMonitor.log file temporarily and server health report.html file for displaying it on the web browser and the screenshot is given in the following screenshot. 

The changes in the file is analysed using the tail -f command the changes identified in the log file is given in the following screenshot. 

The tail -f command helps in identification of the significant changes that are made in the log file for the management of the computer system and increase the network security.

Conclusion

The report is prepared for the development of a shell script for monitoring the changes in the computer system that have been made from the previous time. The shell script is created for the Linux ubuntu environment and might generate some error if it is executed in another Linux environment. For testing the compatibility of the shell script Ubuntu operating system is used. The main advantage of the change logger script is that it can be used for monitoring the current activity of the user and help in securing the network from any unwanted malware or application that is installed in the client machine. The management of the permission for running the shell script is needed to be managed and the user should be restricted to modify the shell script for eliminating the risk of manipulation of the result of the script and is the main disadvantage of bash shell scripting. 

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