Itis 2110 Lab 8 Installing a Web Server Apache

Part 1: New Linux Techniques

Create and execute a script file

A script file is basically a small, low level program. The commands in the script file are executed by the shell (bash in this lab). Scripts are handy to automate tasks. Some of the things that can be done by a script:

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  make decisions (using if statements)
  
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  loop
  
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  call other scripts to be executed
  
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  read and write files
  
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  execute system commands
  

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  Parameters passed to a script are denoted by $1, $2, $3, … where $1 is the 1^st parameter, $2 is the 2^nd, etc.
  
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    The number of parameters is $#
    
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  Conditionals are done by an if…elif…else…fi structure
  
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    The if and elif are followed by a command that evaluates to true or false
    
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    The elif and else are optional
    
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      elif can be repeated
      
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      Only one else may be used, if needed
      
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    The if is closed with the fi statement
    
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    To stop a script use exit n
    
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      n = 0 is a normal exit
      
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      n = 1 is an error exit
      
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    If a value needs to be checked the test command is used
    
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      Numbers use conditionals like –gt, -lt, and -eq (greater than, less than, equal)
      
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        E.g. test 1 –gt 2
        
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      Strings use = or != (equal and not equal)
      
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    There are other comparisons that can be done, check the internet
    
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  Variables are case sensitive, and are UPPER case by convention for environment variables
  

Script one

cd ~

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  The first line tells the system which shell to run (bash in this case
  
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  The next two line are variables that are used for the fully qualified name of the interfaces and resolv.conf files
  
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    To use a variable in a script you put a $ in front of the name
    
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  The forth line stops the NIC card
  
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    $1 is the first (and only in this case) parameter passed to the script
    
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  The fifth line starts the vi editor to edit the interfaces file
  
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  The sixth line is commented out. It is to edit the resolv.conf file. To edit that file uncomment that line.
  
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  The next line restarts the NIC card
  
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  The last two lines add the IP address of two servers in the lab to the resolv.conf file
  

chmod 744 netcofig.sh

This will make the file readable, writeable and executable by your user id and only readable by those in the group and rest of the world. Note that although the file is now executable by your userid, it will fail the ifdown and ifup commands since only root can do those commands.
To run the script enter: ./netconfig.sh eth0

The script expects one parameter, the name of the NIC card, in this case eth0. Change eth0 if it is different on your system. That beginning period and slash is important. The ./ is the "command" (it really means to run the program from the current directory) to run the following script program netconfig.sh in the PWD and that program is not in your PATH. Remember the script you created has a command to start vi. The script will pause at the vi command until you close vi. When vi opens make the desired changes to the interfaces file. When done save and close. The script will then continue by starting the NIC card, and then appending the nameserver information string to the end of the resolv.conf file.

Script two:

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  Change to the networks file: cd /etc/network
  
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  Create the templates:
  
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    cp interfaces interfaces.static
    
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    cp interfaces interfaces.dhcp
    
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  Edit both templates with the values you wish to have in them
  

Then create the following script named go:

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  Make the script executable:
  
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    chmod 755 go
    
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  Run the script:
  
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    ./go static
    
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      Will load the static
      
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    ./go dhcp
    
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      Will load the dhcp
      
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    ./go dog
    
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      Will print the error message
      

**Document the working and one of the tests with a bad parameter.

Scripts can make repetitive tasks easier. Scripts by convention end in .sh, but that is for human use only. The permissions for the script must be eXecutable for the owner, group or world to run them. The scripts go and go2 have no extension and they work perfectly well.