##rsh_cluster_update.pl
##to execute this script either save it off on your machine and execute it with the command "perl rsh_cluster_update.pl (or whatever you call it)
##or copy this segment to the first line "#!/usr/bin/perl -w", exactly as is, make the file executable, and execute it.

##this version of the cluster update script is intended to be run when using rsh as the communication tool within the cluster.  unlike the version
##used under ssh, it doesn't use perl modules to accomplish copying and remote restarting of the mosix daemons, but directly calls the system
##rcp and rsh commands with appropriate commands.  i actually prefer the module approach for portability and elegance, but there don't seem to 
##any modules that directly pertain to rcp, and portability between operating systems is not a major concern in this context.  

use strict;
use Socket;
##mfs mount point scalar
my $mfs_mount='//mfs';

##configuration file repository path
my $source_dir = '//home//mosix//';

##open a directory handle to the mfs mount point
opendir(MFS_HANDLE,$mfs_mount);

##array to hold the directories under the mount point and a scalar to hold the current array member as the script iterates over the array.
my @mfs_dirs;
my $mfs_dirs;

##read the contents of the directory handle into the array
@mfs_dirs=readdir MFS_HANDLE;

##the following scalar will hold the results of mosctl commands after they are written to files by the executed command
my $response;

##this scalar holds the full path version of the restart command, relative to the root of whatever machine is pertinent
my $restart = '//etc/init.d//mosix restart';

##scalar to hold the results of the test conducted during the array iteration
my $testvar;


##the following 3 scalars hold the fully qualified names of the configuration files being distributed
my $map_file=$source_dir.'mosix.map';
my $hosts_file=$source_dir.'hosts';
my $default_mosix_file=$source_dir.'mosix';

##the following three scalars will hold the destination file name when they are constructed within the loop
my $dest_map_file;
my $dest_hosts_file;
my $dest_default_mosix_file;

##this scalar will hold the binary address of the relevant host
my $addr;

##array to hold the information returned by the gethostbyaddr() function
my @host;

##scalar to hold the hostname, first element of the array returned by the gethostbyaddr() function
my $host;

##for each element of the @mfs_dirs array (for each directory under /mfs)
foreach $mfs_dirs(@mfs_dirs)  {
		##$testvar is true if the dirctory name contains a digit
		$testvar=($mfs_dirs=~/^\d/);
		
		##if $testvar is true ...
		if ($testvar)  {
			
			##it is possible that since the cluster controller (re)started mosix a machine that was in the cluster is no longer there,
			##for whatever reason.  to prevent that from breaking the script execution, we'll check to make sure that machine is up.
			##execute the mosctl command with the isup argument and the mosix number of the machine, which is what the directory
			##number represents, and write the result to a file
			system("mosctl isup $mfs_dirs > mos_stat");
			
			##open a read file handle on the result of the operation above
			open(STATUS,'<mos_stat');
			
			##read the top (and only) line from the file handle into the $response scalar
			$response=<STATUS>;
			
			##if the machine is up ...
			if ($response=~/yes/)  {
				
				##determine the hostname of the machine by executing the mosctl command with the whois option, and write the
				##response to a file
				system("mosctl whois $mfs_dirs > mos_host"); 
				
				##as above, open a file handle on the resultant file and read in the only line there
				open(HOST,'<mos_host');
				$response=<HOST>;
				
				##convert the returned address to packed binary representation
				$addr=inet_aton($response);
				
				##use that representation to get the host information
				@host=gethostbyaddr($addr, AF_INET);
				
				##store the first element of that array into the $host scalar
				$host=$host[0];
				
				##construct three scalars holding the destination files
				$dest_map_file="root@".$host.":/etc/mosix/mosix.map";
				$dest_hosts_file="root@".$host.":/etc/hosts";
				$dest_default_mosix_file="root@".$host.":/etc/default/mosix";	
				
				##execute the copying operations 
				system("rcp $map_file $dest_map_file");
				system("rcp $hosts_file $dest_hosts_file");
				system("rcp $default_mosix_file $dest_default_mosix_file");
				
				##execute the restart command
				system("rsh $host $restart");
				close(HOST);
				system("rm mos_host");
			}
			close(STATUS);
			system("rm mos_stat");
		}
	}