#! /usr/bin/perl -w

# getXenMounts.pl
# Author: R. W. Rodolico (http://www.dailydata.net)
# Date: 20121121
# Description:
# Script that uses xenstore to read all attached block devices on all domU's
# in running DOM0. Output is a tab delimited file designed for easy parsing
# 
# Field 1: domu name
# Field 2: domu number
# Field 3: drive number (vbd number)
# Field 4: drive name on DOMU
# Field 5: drive number on DOM0
# 
# designed to allow you easily determine what to use for xm block-attach and
# xm block-detach, for example if a drive needs to be detached from a DOMU to
# resize or replace.
#
# Simple usage example:
# determine which drive is mounted as /home on virtual named book:
#    1. Log into book. Issue command 'mount' to see what device name is. umount that drive.
#       Assume it was xvda3
#    2. Log into DOM0. Issue command getXenMounts.pl | grep book | grep xvda3
#       output similar to 'book 26 51715 xvda3 /dev/virtuals/book.dailydata.net-home'
#    3. Detach the drive with command 'xm block-detach book 51715' (or, 'xm block-detach 26 51715')
#       'book' is the name, 26 is the domain number, and they are interchangable
#    4. Perform the work you need to do on /dev/virtuals/book.dailydata.net-home (resize, replace, whatever)
#    5. Re-attach to domain with command 'xm block-attach book phy:/dev/virtuals/book.dailydata.net-home xvda3 w'
#       Again, book and 26 are interchangable as long as you have not changed the domain id in the process
#    6. Log back into the server and remount drive.

# Deficiencies:
#    Probably would be nice to accept a couple of parameters denoting domain ID and device on domain, then get a single value returned
#    Subject to change of xenstore database format. This works on xenstore v4.0.1

# Copyright 2012, R. W. Rodolico
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see .

# Revisions:
# 20130813 - fixed bug where domu name was not printing correctly
# 20121121 - Initial release


# get a list of running virtuals, return as an array
sub getRunningVirtuals {
   my @virtuals = ´xenstore-list /local/domain/0/backend/vbd´;
   chomp @virtuals;
   return @virtuals;
}

# find all drives for a given virtual, then retrieve the device name on the virtual (dev)
# and the device name on DOM0 (params)
# return a hash reference
sub getDrivesForVirtual {
   my $virnum = shift;
   my %output;
   my @drives = ´xenstore-list /local/domain/0/backend/vbd/$virnum´; # get all attached vbd's
   chomp @drives;
   foreach my $thisDrive ( @drives ) { # go through the list of drives
      # find the name on the virtual (sans /dev/, which is assumed)
      $output{$thisDrive}{'DomU'} = ´xenstore-read /local/domain/0/backend/vbd/$virnum/$thisDrive/dev´;
      chomp $output{$thisDrive}{'DomU'};
      # and, find the name on DOM0 that provides this
      $output{$thisDrive}{'Dom0'} = ´xenstore-read /local/domain/0/backend/vbd/$virnum/$thisDrive/params´;
      chomp $output{$thisDrive}{'Dom0'};
   }
   return \%output;
}

# helper sub that simply determines the "human" name of a given DomU and returns it
sub getDOMUName {
   my $virtnum = shift;
   my $virtname = ´xenstore-read /local/domain/$virtnum/name´;
   chomp $virtname;
   return $virtname;
}   


my %output; # hash for output

my @virtuals = &getRunningVirtuals(); # store dom-id (integer) in array for all running DOMU's

foreach my $thisVirt ( @virtuals ) { # for each of them
   # create a hash entry and attach the drive information for it
   $output{$thisVirt} = &getDrivesForVirtual( $thisVirt );
}

# print them out.
print "domu\tdomu\tdrive\tdomu\tdom0\n";
print "name\tid\tid\tdevice\tdevice\n";
print "====\t====\t=====\t====\t====\n";
foreach my $virtual ( keys %output ) {
   my $driveList = $output{$virtual};
   foreach my $drive ( keys %$driveList ) {
      print &getDOMUName($virtual) . "\t$virtual\t$drive\t$$driveList{$drive}{'DomU'}\t$$driveList{$drive}{'Dom0'}\n";
   }
}

1;