path: root/src/config-db/slxconfig-demuxer

#! /usr/bin/perl
# -----------------------------------------------------------------------------
# Copyright (c) 2006, 2007 - OpenSLX GmbH
#
# This program is free software distributed under the GPL version 2.
# See http://openslx.org/COPYING
#
# If you have any feedback please consult http://openslx.org/feedback and
# send your suggestions, praise, or complaints to feedback@openslx.org
#
# General information about OpenSLX can be found at http://openslx.org/
# -----------------------------------------------------------------------------
# slxconfig-demuxer
#    - OpenSLX configuration demultiplexer
# -----------------------------------------------------------------------------
use strict;
use warnings;
use Switch;


my $abstract = q[
slxconfig-demuxer
    This script will read information about all systems, clients and
    groups from the OpenSLX configuration database, mix & match the individual
    configurational attributes and then demultiplex the resulting information
    to a set of configuration files. These files are used by any OpenSLX-client
    during boot to find out which systems to offer for booting.

    The resulting files will be put into the OpenSLX-tftpboot-path.

    Please use the --man option in order to read the full manual.
];

use Config::General;
use Digest::MD5 qw(md5_hex);
use File::Basename;
use File::Find;
use File::Path;
use List::Util qw(first);
use Getopt::Long qw(:config pass_through);
use Pod::Usage;

# add the lib-folder and the folder this script lives in to perl's search
# path for modules:
use FindBin;
use lib "$FindBin::RealBin/../lib";
use lib "$FindBin::RealBin";
# development path to config-db stuff

use OpenSLX::Basics;
use OpenSLX::ConfigDB qw(:support);
use OpenSLX::ConfigFolder;
use OpenSLX::OSPlugin::Roster;
use OpenSLX::Utils;

my (
    $systemConfCount,
        # number of system configurations written
    $systemErrCount,
        # number of systems that had errors
    $bootEnvErrCount,
        # number of boot environments that had errors
    $clientSystemConfCount,
        # number of (system-specific) client configurations written
    $initramfsCount,
        # number of initramfs that were created
    @targetSystems,
        # systems to create initramfs for, defaults to all systems
    %bootEnvMap,
        # objects encapsulating the bootloader specific configurations
    %option,
        # cmdline option hash
);

if ($> != 0) {
    die _tr("Sorry, this script can only be executed by the superuser!\n");
}

GetOptions(
    'dhcp-export-type=s' => \$option{dhcpType},
    'dry-run'            => \$option{dryRun},
    'help|?'             => \$option{helpReq},
    'man'                => \$option{manReq},
    'version'            => \$option{versionReq},
  )
  or pod2usage(2);
pod2usage(-msg => $abstract, -verbose => 0, -exitval => 1) if $option{helpReq};
if ($option{manReq}) {
    # avoid dubious problem with perldoc in combination with UTF-8 that
    # leads to strange dashes and single-quotes being used
    $ENV{LC_ALL} = 'POSIX';
    pod2usage(-verbose => 2);
}
if ($option{versionReq}) {
    slxsystem('slxversion');
    exit 1;
}

openslxInit();

my $openslxDB = OpenSLX::ConfigDB->new();
$openslxDB->connect();

my $clientConfigPath = "$openslxConfig{'private-path'}/config/stage3";
# make sure that the default config folders exist:
if (createConfigFolderForDefaultSystem()) {
    # this path should have been generated by earlier stage (slxsettings), so
    # we indicate that there is some kind of problem:
    warn _tr(
        "Completed client-config-folder '%s', since at least some parts of it didn't exist!",
        $clientConfigPath
    );
}

# protect against parallel execution of this script
my $demuxerLock = grabLock('slxconfig-demuxer');

my $tempPath = "$openslxConfig{'temp-path'}/slxconfig-demuxer";
if (!$option{dryRun}) {
    rmtree($tempPath);
    mkpath($tempPath);
    if (!-d $tempPath) {
        die _tr("Unable to create or access temp-path '%s'!", $tempPath);
    }
}

my $deleteInFinalize = 0;

my @demuxableSystems
    = grep { $_->{name} ne '<<<default>>>' } $openslxDB->fetchSystemByFilter();
if (@ARGV) {
    # create initramfs only for systems given on cmdline
    for my $systemName (@ARGV) {
        if ($systemName eq '<<<default>>>') {
            warn _tr(
                'The default-system can not be demuxed - it will be skipped.'
            );
            next;
        }
        my $system = first { $_->{name} eq $systemName } @demuxableSystems;
        if (!$system) {
            warn _tr(
                'The system "%s" is unknown and will be ignored.', $systemName
            );
            next;
        }
        push @targetSystems, $system;
    }
}
else {
    # create initramfs for all systems
    @targetSystems = @demuxableSystems;
    $deleteInFinalize = 1;
}

writeConfigurations();

my $wr = $option{dryRun} ? 'would have written' : 'wrote';
my $errCount = $systemErrCount ? $systemErrCount : 'no';
my $systemStatusString 
    = $systemErrCount ? "$errCount system(s) had errors" : 'all systems ok';
$errCount = $bootEnvErrCount ? $bootEnvErrCount : 'no';
my $bootEnvStatusString 
    = $bootEnvErrCount 
        ? "$errCount boot environment(s) had errors" 
        : 'all boot-environments ok';
print "\n", unshiftHereDoc(<<"End-of-Here");
    $wr $systemConfCount system-specific and $clientSystemConfCount client-specific configurations
    $initramfsCount initramfs were created
    $systemStatusString
    $bootEnvStatusString
End-of-Here

$openslxDB->disconnect();

rmtree([$tempPath]);

# allow all boot-environments to clean up and active the new configuration
foreach my $bootEnv (values %bootEnvMap) {
    $bootEnv->finalize($deleteInFinalize);
}

exit;

################################################################################
###
################################################################################
sub folderContainsFiles
{
    my $folder = shift;

    return 0 unless -d $folder;

    my $result = 0;
    my $wanted = sub {
        if ($result) {
            # skip anything else if we have found a file already
            $File::Find::prune = 1;
        }
        $result = 1 if -f;
    };
    find({wanted => $wanted, follow_fast => 1}, $folder);
    vlog(2, "result for folderContainsFiles($folder): $result\n");
    return $result;
}

sub digestAttributes
{   # returns a digest-string for the given attribute hash, in order to
        # facilitate comparing different attribute hashes.
    my $object = shift;

    my $attrs = $object->{attrs} || {};
    my $attrsAsString 
        =   join ';', 
            map { "$_=$attrs->{$_}" }
            sort
            grep { defined $attrs->{$_} } 
            keys %$attrs;

    vlog(3, "Attribute-string: $attrsAsString");
    return md5_hex($attrsAsString);
}

sub writeAttributesToFile
{
    my $object   = shift;
    my $fileName = shift;

    return if $option{dryRun};

    my $content = "# attributes set by slxconfig-demuxer:\n";
    my $attrs = $object->{attrs} || {};
    # filter out any plugin-specific attributes (we only want to handle
    # the attributes relevant to the core here)
    my @attrs = sort grep { index($_, '::') == -1 } keys %$attrs;
    foreach my $attr (@attrs) {
        my $attrVal = $attrs->{$attr};
        next if !defined $attrVal;
        $content .= qq[$attr="$attrVal"\n];
    }
    # Overwrite attribute file even if it exists, to make sure that our users
    # will never try to fiddle with machine-setup directly in the file-system. 
    # The config-DB is the keeper of that info!
    spitFile($fileName, $content);
    if ($openslxConfig{'log-level'} > 2) {
        vlog(0, "--- START OF $fileName ---");
        vlog(0, $content);
        vlog(0, "--- END OF $fileName --- ");
    }
    return;
}

sub writeSlxConfigToFile
{
    my $slxConf  = shift;
    my $fileName = shift;

    return if $option{dryRun};

    my $content = '';
    foreach my $key (sort keys %$slxConf) {
        $content .= qq[$key="$slxConf->{$key}"\n];
    }
    spitFile($fileName, $content);
    return;
}

sub copyExternalSystemConfig
{   # copies local configuration extensions of given system from private config
    # folder (var/lib/openslx/config/stage3/...) into a temporary folder
    my $systemName = shift;
    my $targetPath = shift;
    my $clientName = shift;    # optional

    if ($targetPath !~ m[^$tempPath]) {
        # bail if target-path isn't within temp folder, as we do not dare
        # executing 'rm -rf' in that case!
        die _tr("system-error: illegal target-path <%s>!", $targetPath);
    }
    return if $option{dryRun};

    slxsystem("rm -rf $targetPath");
    mkpath $targetPath;

    # first copy default files ...
    my $defaultConfigPath = "$clientConfigPath/default";
    vlog(2, "checking $defaultConfigPath for default config...");
    if (-d $defaultConfigPath) {
        slxsystem("cp -a $defaultConfigPath/* $targetPath");
    }
    # ... now pour system-specific configuration on top (if any) ...
    my $systemSpecConfigPath = "$clientConfigPath/$systemName/default";
    vlog(2, "checking $systemSpecConfigPath for system config...");
    if (folderContainsFiles($systemSpecConfigPath)) {
        slxsystem("cp -a $systemSpecConfigPath/* $targetPath");
    }
    if (defined $clientName) {
        # ... and finally pour client-specific configuration on top (if any):
        my $clientSpecConfigPath = "$clientConfigPath/$systemName/$clientName";
        vlog(2, "checking $clientSpecConfigPath for client config...");
        if (folderContainsFiles($clientSpecConfigPath)) {
            slxsystem("cp -a $clientSpecConfigPath/* $targetPath");
        }
    }
    return;
}

sub createTarOfPath
{
    my $buildPath       = shift;
    my $tarName         = shift;
    my $destinationPath = shift;

    my $tarFile = "$destinationPath/$tarName";
    vlog(1, _tr('creating tar %s', $tarFile));
    return if $option{dryRun};

    mkpath $destinationPath;
    my $tarCmd = "cd $buildPath && tar czf $tarFile *";
    if (slxsystem("$tarCmd") != 0) {
        die _tr("unable to execute shell-command:\n\t%s \n\t(%s)", $tarCmd, $!);
    }
}

sub bootEnvironmentForType
{
    my $bootTypeIn = shift || 'pxe';
    
    my %bootTypeMap = (
        'pxe'     => 'PXE',
        'preboot' => 'Preboot',
        'pbs'     => 'PBS',
    );
    my $bootType = $bootTypeMap{lc($bootTypeIn)}
        or die _tr(
            "'%s' is not one of the supported boot-types (pxe,preboot)", 
            $bootTypeIn
        );

    if (!$bootEnvMap{$bootType}) {
        my $bootEnv = instantiateClass("OpenSLX::BootEnvironment::$bootType");
        $bootEnv->initialize( {
            'dry-run' => $option{dryRun},
        } );
        $bootEnvMap{$bootType} = $bootEnv;
    }
    
    return $bootEnvMap{$bootType};
}



################################################################################
###
################################################################################
sub writeBootloaderMenus
{
    my @infos = @_;

    # iterate over all clients and write a bootloader configuration for each
    my @clients = $openslxDB->fetchClientByFilter();
    foreach my $client (@clients) {
        # fetch all infos relevant to this client (including the bootable 
        # systems)
        my %systemIDs;
        @systemIDs{$openslxDB->aggregatedSystemIDsOfClient($client)} = ();
        my @systemInfos = grep { exists $systemIDs{$_->{id}} } @infos;

        # now write bootloader menu with all bootable systems for this client
        my $bootEnv = bootEnvironmentForType($client->{attrs}->{boot_type});
        my $externalID = externalIDForClient($client);
        my $success = eval {
            $bootEnv->writeBootloaderMenuFor(
                $client, $externalID, \@systemInfos
            );
            1;
        };
        if (!$success) {
            print STDERR $@;
            $bootEnvErrCount++;
        }
    }
    return;
}

sub writeDhcpConfig
{
    vlog(0, _tr("sorry, exporting dhcp data is not implemented yet!"));
    my $dhcpModule = "OpenSLX::ConfigExport::DHCP::$option{dhcpType}";
    if (!eval { require $dhcpModule } ) {
        die _tr("unable to load DHCP-Export backend '%s'! (%s)\n",
            $dhcpModule, $@);
    }
    my $dhcpBackend = $dhcpModule->new();
    my @clients     = $openslxDB->fetchClientByFilter();
    $dhcpBackend->execute(\@clients);
    return;
}

sub writeClientConfigurationsForSystem
{
    my $info      = shift;
    my $buildPath = shift;
    my $attrFile  = shift;
    my $bootType  = shift;
    my $clients   = shift || [];

    foreach my $client (@$clients) {
        next if $client->{name} eq '<<<default>>>';
            # skip default client, as it doesn't need any config-tgz
      
        next if ($client->{attrs}->{boot_type} || 'pxe') ne $bootType;
            # skip clients with non-matching boot type

        my $externalSystemID   = $info->{'external-id'};
        my $externalClientName = externalConfigNameForClient($client);
        my $clientConfigPath
            = "$clientConfigPath/$externalSystemID/$externalClientName";

        # merge configurations of groups, default client and system into the
        # current client (overwriting only values the client does not specify)
        $openslxDB->mergeDefaultAndGroupAttributesIntoClient($client);
        mergeAttributes($client, $info);

        # compute a digest value of the merged attributes ...
        my $clientAttrDigest = digestAttributes($client);
        vlog(
            2,
            _tr(
                "attribute-digest for client '%s' is '%s'", $client->{name},
                $clientAttrDigest
            )
        );
        # ... and export client-specific config only if attributes are different
        # from system and/or a client-specific config-folder exists:
        if ($clientAttrDigest ne $info->{'attr-digest'}
            || -d $clientConfigPath)
        {
            vlog(
                1,
                _tr(
                    "creating config-tgz for client %d:%s", $client->{id},
                    $client->{name}
                )
            );
            $clientSystemConfCount++;

            # merge default, system and client configuration folders into
            # a configuration folder specific to the current client:
            copyExternalSystemConfig(
                $externalSystemID, $buildPath, $externalClientName
            );

            # add plugin configuration and note if the client adds any active
            # plugin (as opposed to current state)
            my $activeClientPlugins = writePluginConfigurations(
                $info, $buildPath, $client->{attrs}
            );
            my @additionalActivePlugins = grep {
                my $activeClientPlugin = $_;
                ! grep { 
                    $activeClientPlugin eq $_
                } @{$info->{'active-plugins'}};
            } @$activeClientPlugins;
            if (@additionalActivePlugins) {
                push @{$info->{'active-plugins'}}, @additionalActivePlugins;
                my $additionalActivePluginStr
                    = join ',', @additionalActivePlugins;
                vlog(0, _tr(
                    "client '%s' activates additional plugins: %s", 
                    $client->{name}, $additionalActivePluginStr
                ));
            }
            
            # check attributes against illegal values and write them into
            # a file if they're ok:
            my $attrProblems = OpenSLX::AttributeRoster->findProblematicValues(
                $client->{attrs}, $info->{'vendor-os'}->{name}, 
                $info->{'installed-plugins'}
            );
            if ($attrProblems) {
                my $complaint = join "\n", @$attrProblems;
                $complaint =~ s{^}{client $client->{name}: }gms;
                warn $complaint;
            }
            writeAttributesToFile($client, $attrFile);

            # create a tar containing the external configuration folder
            # and client attribute file, this time referring to the client
            # via its external ID (the PXE-style MAC), as the TGZ needs to
            # be accessed from the client-PC, which doesn't know about the
            # name it is referred to in the openslx-config-DB:
            my $externalClientID = externalIDForClient($client);
            my $bootEnv = bootEnvironmentForType($bootType);
            switch ($bootType) {
            	case 'pxe' {
	                createTarOfPath(
		                $buildPath, "${externalClientID}.tgz",
		                "$bootEnv->{'target-path'}/client-config/$externalSystemID"
		            );
    	        } 
                case 'preboot' {
                    # for preboot types
                    my $cname = $client->{name};
                    createTarOfPath(
                        $buildPath, "${cname}.tgz",
                        "$bootEnv->{'target-path'}/client-config/$externalSystemID"
                    );
                }
                case 'pbs' {
                    # for preboot types
                    my $cname = $client->{name};
                    createTarOfPath(
                        $buildPath, "${cname}.tgz",
                        "$bootEnv->{'target-path'}/client-config/$externalSystemID"
                    );
                }
            }
        }
    }
    return;
}

sub writePluginConfigurations
{
    my $info      = shift || confess 'need to pass in info-hash!';
    my $buildPath = shift || confess 'need to pass in build-path!';
    my $attrs     = shift || {};

    my $pluginConfPath  = "$buildPath/initramfs/plugin-conf";

    my @activePlugins;
    foreach my $pluginInfo (@{$info->{'installed-plugins'}}) {
        my $pluginName = $pluginInfo->{plugin_name};
        vlog(2, _tr("checking configuration of plugin '%s'", $pluginName));

        # skip inactive plugins
        next unless $attrs->{"${pluginName}::active"};
        push @activePlugins, $pluginName;
        
        my $plugin = OpenSLX::OSPlugin::Roster->getPlugin($pluginName);
        my $requiredPlugins = $plugin->getInfo()->{required} || [];
        my @missingPlugins 
            =   grep {
                    my $required = $_;
                    ! grep {
                        $_->{plugin_name} eq $required
                    } @{$info->{'installed-plugins'}};
                }
                @$requiredPlugins;
        if (@missingPlugins) {
            die _tr(
                'the plugin "%s" requires the following plugins to be installed: "%s"!', 
                $pluginName, join(',', @missingPlugins)
            );
        }

        next if $option{dryRun};

        mkpath([ $pluginConfPath ]);

        vlog(2, _tr("writing configuration file for plugin '%s'", $pluginName));
        # write plugin configuration to a file:
        my $content;
        my @pluginAttrs = grep { $_ =~ m{^${pluginName}::} } keys %$attrs;
        foreach my $attr (sort @pluginAttrs) {
            my $attrVal = $attrs->{$attr};
            if (!defined $attrVal) {
                $attrVal = '';
            }
            my $attrName = substr($attr, index($attr, '::')+2);
            $content .= qq[${pluginName}_$attrName="$attrVal"\n];
        }
        my $fileName = "$pluginConfPath/${pluginName}.conf";
        spitFile($fileName, $content);
        if ($openslxConfig{'log-level'} > 2) {
            vlog(0, "--- START OF $fileName ---");
            vlog(0, $content);
            vlog(0, "--- END OF $fileName --- ");
        }
    }
    return \@activePlugins;
}

sub createBootEnvironmentsForSystem
{
    my $info      = shift;
    my $buildPath = shift;
    my $attrFile  = shift;
    my $clients   = shift || [];

    my %bootTypes;
    foreach my $client (@$clients) {
        my $type = $client->{attrs}->{boot_type} || 'pxe';
        $bootTypes{$type}++;
    }

    foreach my $bootType (sort keys %bootTypes) {
        vlog(0, _tr("creating boot environment (system part) for $bootType"));
    
        my $bootEnv = bootEnvironmentForType($bootType);

        # only create a default.tgz if required by boot environment
        if ($bootEnv->requiresDefaultClientConfig()) {
            writeAttributesToFile($info, $attrFile);
    
            my $systemPath
                = "$bootEnv->{'target-path'}/client-config/$info->{'external-id'}";
            createTarOfPath($buildPath, "default.tgz", $systemPath);
        }
    }

    foreach my $bootType (sort keys %bootTypes) {
        vlog(0, _tr("creating boot environment (client part) for $bootType"));
    
        my $bootEnv = bootEnvironmentForType($bootType);

        writeClientConfigurationsForSystem(
            $info, $buildPath, $attrFile, $bootType, $clients
        );

        # let boot environment copy the kernel and create the initramfs
        $initramfsCount 
            += $bootEnv->writeFilesRequiredForBooting($info, $buildPath);
    }

    return;
}

sub writeSystemConfiguration
{
    my $info           = shift;
    my $isTargetSystem = shift;

    $info->{'initramfs-name'} = "initramfs-$info->{id}";

    # if this is not a target system, we shall not write any configurations,
    # but we simply incorporate inherited attributes
    if (!$isTargetSystem) {
        $openslxDB->mergeDefaultAttributesIntoSystem($info);
        return;
    }
    
    # write configuration files for this system
    my $buildPath = "$tempPath/build";
    copyExternalSystemConfig(externalIDForSystem($info), $buildPath);

    $openslxDB->mergeDefaultAttributesIntoSystem(
        $info, $info->{'installed-plugins'}
    );
    $info->{'attr-digest'} = digestAttributes($info);
    vlog(
        2,
        _tr(
            "attribute-digest for system '%s' is '%s'", $info->{name},
            $info->{'attr-digest'}
        )
    );

    # check if rootfs in corresponding vendor-OS matches the current
    # version and add a warning if it does not:
    my $rootfsVersionPath 
        = "$openslxConfig{'private-path'}/stage1/$info->{'vendor-os'}->{name}/opt/openslx/rootfs.version";
    chomp(my $rootfsVersion 
        = slurpFile($rootfsVersionPath, { failIfMissing => 0 } ));
    chomp(my $currVersion = qx{slxversion});
    if ($currVersion !~ m{M$} && $rootfsVersion ne $currVersion) {
        warn _tr(
            "eglibc rootfs for system '%s' may not be up-to-date - consider updating the vendor-OS!",
            $info->{name}, $rootfsVersion, $currVersion
        );
    }

    my $attrProblems = OpenSLX::AttributeRoster->findProblematicValues(
        $info->{attrs}, $info->{'vendor-os'}->{name}, 
        $info->{'installed-plugins'}
    );
    if ($attrProblems) {
        my $complaint = join "\n", @$attrProblems;
        $complaint =~ s{^}{system $info->{name}: }gms;
        warn $complaint;
    }

    my $activePlugins 
        = writePluginConfigurations($info, $buildPath, $info->{attrs});
    $info->{'active-plugins'} = $activePlugins;
    my $activePluginStr 
        = @$activePlugins ? join ',', @$activePlugins : '<none>';
    vlog(0, _tr("active plugins: %s", $activePluginStr));

    # create all required (pre-)boot-environments (PXE, CD, ...)
    my $attrFile  = "$buildPath/initramfs/machine-setup";
    my @clientIDs = $openslxDB->aggregatedClientIDsOfSystem($info);
    my @clients   = $openslxDB->fetchClientByID(\@clientIDs);
    createBootEnvironmentsForSystem($info, $buildPath, $attrFile, \@clients);

    slxsystem("rm -rf $buildPath") unless $option{dryRun};

    $systemConfCount++;

    return;
}

sub writeConfigurations
{
    $initramfsCount = $systemConfCount = $systemErrCount 
        = $clientSystemConfCount = 0;
    my @infos;
    foreach my $system (@demuxableSystems) {
        my $isTargetSystem 
            = first { $_->{name} eq $system->{name} } @targetSystems;
        if ($isTargetSystem) {
            vlog(
                0, 
                _tr("\ndemuxing system %d : %s", $system->{id}, $system->{name})
            );
        }
        else {
            vlog(
                0, 
                _tr(
                    "\nlinking demuxed system %d : %s into bootloader menu",
                    $system->{id}, $system->{name}
                )
            );
        }

        my $success = eval {
            my $info = $openslxDB->aggregatedSystemFileInfoFor($system);
            $info->{'external-id'} = externalIDForSystem($system);

            writeSystemConfiguration($info, $isTargetSystem);

            push @infos, $info;
            1;
        };
        if (!$success) {
            print STDERR $@;
            $systemErrCount++;
        }
    }
    my $imageBaseDir = "$openslxConfig{'public-path'}/images";
    rmtree($imageBaseDir)   unless $option{dryRun};
    writeBootloaderMenus(@infos);
    if (defined $option{dhcpType}) {
        writeDhcpConfig();
    }
    return;
}

=head1 NAME

slxconfig-demuxer - OpenSLX configuration demultiplexer

=head1 SYNOPSIS

slxconfig-demuxer [options] [<system-name> ...]

=head3 Script Options

    --dry-run                    avoids writing anything, for testing

=head3 General Options

    --help                       brief help message
    --man                        full documentation
    --version                    show version

=head1 DESCRIPTION

B<slxconfig-demuxer> will read information about all systems, clients and
groups from the OpenSLX configuration database, mix & match the individual
configurational attributes and then demultiplex the resulting information
to a set of configuration files. These files are used by any OpenSLX-client
during boot to find out which systems to offer for booting.

If you invoke the script with one or more system names, only these systems
will be demuxed. All other systems (which are expected to have been demuxed
before) will just be linked into the bootloader menu.

The resulting files will be put into the OpenSLX-tftpboot-path.

=head2 FILE CREATION

The following set of files will be created:

=over 8

=item B<Basic PXE Setup>

The basic PXE files (F<menu.c32>, F<pxelinux.0>) will be copied into
F<$SLX_PUBLIC_PATH/tftpboot> to make them available to any PXE-client via tftp.

=item B<PXE Client Configurations>

For each client, a PXE configuration file will be generated and written to
F<$SLX_PUBLIC_PATH/tftpboot/pxelinux.cfg/01-<MAC-of-client>>. This file will
contain information about the systems this client shall offer for booting.
For each of these systems, the kernel cmdline options required for that
particular system setup is specified (via PXE's APPEND option).

Any client that is not known to OpenSLX (so it will not have a specific
configuration file) will use the configuration from the default client 
(appropriately named 'default').

=item B<System Kernels and Initialram-Filesystems>

For each bootable system, that system's kernel will be copied to
F<$SLX_PUBLIC_PATH/tftpboot/<vendor-os-name>/kernel and an OpenSLX-specific initramfs
required for booting that particular system is generated (by means of
slxmkramfs) and put into F<$SLX_PUBLIC_PATH/tftpboot/<vendor-os-name>/initramfs.

These two files (kernel & initramfs) will be referenced by the PXE client
configuration of all clients that offer this specific system for booting.

=item B<OpenSLX Client Configurations>

For each system, an OpenSLX configuration archive will be generated and written 
to F<$SLX_PUBLIC_PATH/tftpboot/client-config/<system-name>/default. Furthermore, 
every client of that system whose attributes differ from the system's default
will get its own configuration archive generated here, too (e.g. 
F<$SLX_PUBLIC_PATH/tftpboot/client-config/<system-name>/01-<MAC-of-client>.tgz>).

Each of these archives will contain the file F<initramfs/machine-setup>, 
specifying all the attributes of that particular system and/or client 
(e.g. whether or not it should start the X-server).

Furthermore, each system-specific archive may contain additional system files 
that are required for that system (e.g. a special PAM-module required for LDAP 
authentication). These files are copied from
F<$SLX_PRIVATE_PATH/config/stage3/default> and
F<$SLX_PROVATE_PATH/config/stage3/<system-name>>.

On top of that, each client may have its own set of system files, too (e.g.
some config files required to install a special kind of hardware available only
on that client). These files are copied from 
F<< $SLX_PROVATE_PATH/config/stage3/<system-name>/01-<MAC-of-client> >>.

=back

=head2 MIXING & MATCHING (THE DEMUXER)

In the OpenSLX configuration database, each system, group and client may have
several configurational attributes set to a specific value that will cause
a client booting that system to behave in a certain way. The mixing of all
these different attributes into one set that is relevant for a specific client
booting one specific system is one important task of the slxconfig-demuxer.

As an example, let's assume one system setup that is configured to boot directly
into a special application that demands a rather low screen-resolution of
1024x768 pixels, as otherwise the text would be unreadable due to very small
fonts being used by that app. In order to achieve this, the administrator can
set the I<hw_monitor>-attribute of the B<system> to '1024x768'.
Let's say one of the clients, however, is connected to a very old monitor that
has problems with this resolution and only supports 800x600 pixels. In that
case, the administrator can set the I<hw_monitor>-attribute of that B<client> to
'800x600'. The mixing & matching process would make sure that this specific
client would run that system with a resolution of 800x600, while all other
clients would run that system in 1024x768.

So the slxconfig-demuxer demultiplexes the individual configurational attributes
into a concrete set of configuration settings for specific clients and their
offered systems, making sure that each client/system combination uses the
appropriate settings.

=head1 OPTIONS

=head3 Script Options

=over 8

=item B<<     --dry-run >>

Runs the script but avoids writing anything. This is useful for testing, as
you can learn from the logging output what would have been done.

=back

=head3 General Options

=over 8

=item B<<     --help >>

Prints a brief help message and exits.

=item B<<     --man >>

Prints the manual page and exits.

=item B<<     --version >>

Prints the version and exits.

=back

=head1 SEE ALSO

slxsettings, slxos-setup, slxos-export, slxconfig

=head1 GENERAL OPENSLX OPTIONS

Being a part of OpenSLX, this script supports several other options
which can be used to overrule the OpenSLX settings:

    --db-name=<string>         name of database
    --db-spec=<string>         full DBI-specification of database
    --db-type=<string>         type of database to connect to
    --locale=<string>          locale to use for translations
    --log-level=<int>          level of logging verbosity (0-3)
    --logfile=<string>         file to write logging output to
    --private-path=<string>    path to private data
    --public-path=<string>     path to public (client-accesible) data
    --temp-path=<string>       path to temporary data

Please refer to the C<slxsettings>-manpage for a more detailed description
of these options.

=cut