CST 8177 - Lab 8

Automating Tasks: homebak

Student Name	Student number	Lab section

Objectives

To learn and understand basic bash scripting language
To automate tasks
To develop basic PDL

Lab Outcome

A good working understanding of how shell scripting works and how to create simple task automation

In-Lab Demo - Demo the homebak script and explain its commands.

Part I: Basic bash scripting

Exercise #1: Creating a script

In this exercise, you will write a script called greetings.

Note: Scripts that are created on a local machine are typically stored in /usr/local/bin or /usr/local/sbin depending and who may run the script. Before you name a script, verify with the command whereis if the name has already been used for a command. If it has, choose a different name for the script. Personal scripts are often placed in ~/bin.

The script will contain a comment section with:

the name of the script
course number & name
your name and student ID
the purpose of this script

Note: Make certain you have the above information in every script file you create from now on.

Your script will:

Greet the user using the user's login name
Print the date and the time.
Print the name of the machine.
Print a list of all files in the user's home directory using the environment variable that contains the user's home directory.
Print the search path using the environment variable that contains the user's search path.

To accomplish this follow the steps below:

Step #1

Login as a user.
Switch to the root account.
Create a bin directory in root's home directory and change into it.

Step #2

Create a file in vi called greetings insert the first line:

#! /bin/bash

This is the line that indicates to the shell that this is file to be interpreted by /bin/bash. Broken down into its components, this line uses:
#! - indicates a script file (hash-bang line)
/bin/bash - the path in which the shell bash resides

Step #3

Add the lines indicated below. Ensure that your script shows your OWN information!

# Name: greetings

# Course: CST8177 - Linux 2

# (your name) - Student ID (your id)

# Purpose: greet the user and display some information

Step #4

Greet the user using the user's login name. Use printenv(1) to identify the environment variable that contains the user's login name

Tip: Execute printenv and use grep to search for the entries that contain the account name.

Use the echo command to display the content of the environment variable that contains the user's login name.

Example: echo $USER

Save and exit when you are done.
Change the permissions so that everyone can execute the file.
Execute the script to ensure everything is working properly.

Step #5

Next, you want to print the date and time. This information can be obtained using the date(1) command, with some options thrown in for formatting to make it look good. Re-open your file and add the next command:

Example: Enter the following line exactly as shown below.

echo "It is $(date +%A" "%e" "%B" "%Y", "%R" "%p)."

Note: Notice that we put the date command inside round brackets and preceded by a $ sign, to tell the shell that this is a command to be executed outside the scope of the echo command and for its stdout to be returned.

Now run it to make sure it works properly.

Step #6

Next you want to display a list of all files in the user's home directory using the appropriate environment variable.

Save the file, exit and run it again to make sure it works properly.

Step #7

You want to show the search path.

Note: To display the search path use the echo command to display the contents of the environment variable used for the search path: PATH.

Save the file, exit and run it again to make sure it works properly.

Step #8

Display the time and date again after waiting 1 minute (note: don't actually wait for 1 minute - that's a very long time; test it with only 3 to 5 seconds instead).

Note: Use the sleep(1) command.

Save the file, exit and run it again to make sure it works properly.

Step #9: Installing and testing the script

Copy the script to the /usr/local/bin directory.

Step #10

The PDL or description for this script is simple because the flow of execution (flow control) is sequential.

START greetings

DISPLAY user name

DISPLAY date

SHOW user's home directory

SHOW current search path

WAIT for a few seconds

DISPLAY date

END greetings

The complete script is shown below:

# Name: greetings

# Course: CST8177 - Linux 2

# (your name) - Student ID (your id)

# Purpose: greet the user and display some information

echo "Hi $LOGNAME!"

echo "It is $(date +%A", "%B" "%e" "%Y)."

ls $HOME

echo $PATH

sleep 3

date

Part II: Automating administrative tasks

Back up all home directories at regular intervals

Specifications

Create a small script, named homebak (for home backup) that accomplishes all of the following (create a script header as above):

Send a message to all users currently logged in (use the wall(1) command) to warn them of the impending operation and wait 5 minutes before proceeding (Note: While working on the script use a 5-second wait period).
Prevent users from logging in during the backup (see nologin(5)). When should this login prevention start, and when should it end?
Backup all home directories to /var/local/backup in a single gzipped tar archive. Use a file name that includes the month and day of the backup, specifically: home-back-MM-DD.tgz.
Submit a message to the system logger at facility user and priority info. The log file you will use is to be located in the default log directory and named userlog. You may have to add an entry to the logging rules.
Note: When logging, identify the name of your utility and keep the format of the log message as close as possible to the standard log message format.
The backup is scheduled to occur weekly. Set it up as a system maintenance task in /etc/crontab, NOT as root's task.

Solution

Write a point-form description of this script: describe WHAT or WHY, but not HOW.

Example: State that the script is preventing users from logging in, but not how this is implemented: "PREVENT user logins"

Write a Test Plan
Develop your script from the description; for testing, replace long-running commands with faster forms and modify commands that create big files so they create smaller ones.
Execute your Test Plan, confirming that any test output is correctly formed.
Remove your replacement statements and run your Test Plan again, confirming that all files and records are correctly formed.
Add your weekly task to the system maintenance facility. Test this by adjusting the date/time for entry and then restoring it.

Result

Print out your script and any other material for inclusion in your Lab Book.

Record the output of an ls -l for your new home backup .tgz file:

______________________________________________________________________________

Record the entry in rsyslog.conf file if you needed to add one:

______________________________________________________________________________

Describe your scheduling setup, recording any entries made here:

______________________________________________________________________________

You may have had a problem with the scheduling. How did you fix it?

______________________________________________________________________________

You have created a new log file (userlog). Next you have to manage the number of log files kept and their frequency using - name the tool to use:

______________________________________________________________________________

Identify any files that need to be modified to enable log rotation for the newly created log file and record your changes:

______________________________________________________________________________