Versions of the files below may be downloaded here. This post is probably still useful as documentation.
This isn’t specific to BackupPC by any means, but I’ll preface this with a brief explanation: BackupPC is a “set it and forget it” backup system driven from the server, that allows you to back up the entire network of *nix and Windows PCs. It doesn’t require any software on the systems it backs up at all, since it relies upon rsync and smbclient, and optionally ssh.
For *nix, this works beautifully. For Windows, this also works beautifully, except that “open files” can’t be backed up at all. This problem isn’t unique to BackupPC, any attempt to back up or copy these files will fail, so most commercial backup systems have special “open file” clients to cope with it.
The official Windows solution for XP and later is something called a “volume shadow copy.” It’s probably far more complex than it possibly needs to be, but essentially, it creates a pseudo-volume for any actual volume, with the difference being that you can actually back up files on it. So, this can be handily used for rsync in order to make full backups, including every single file… in theory, anyway.
My goals in getting this working:
- The solution should work with off-the-shelf components (i.e., no binaries or code)
- Installation and footprint should be minimal
- It should “just work” — if it’s too delicate, it’s not all that useful as a backup solution
It took quite a bit of trial-and-error, so I’ll skip what didn’t work, and get straight to what actually does work. There are a few required components:
- winexe, a *nix program for remotely executing commands on Windows systems
- vshadow, a Windows program that creates and manages shadow copies
- dosdev, a Windows program that maps drive letters to volumes
- cwrsync, a Windows version of rsync (the “server” isn’t necessary)
Once all the pieces are assembled, I created a C:\BackupPC directory on the Windows box with all the necessary files. Note that rsync does not need to be installed as a service, it actually gets loaded on-the-fly. (Note that this directory is hard-coded in a lot of the files.) Here’s a listing of that directory:
Directory of C:\BackupPC 08/08/2008 07:11 PM 65 backuppc.cmd 08/10/2008 12:56 PM 1,928 cwrsync.cmd 07/22/2008 04:30 PM 1,082,368 cygcrypto-0.9.8.dll 04/11/2008 07:03 AM 999,424 cygiconv-2.dll 04/11/2008 07:03 AM 31,744 cygintl-3.dll 04/11/2008 07:03 AM 20,480 cygminires.dll 07/22/2008 04:30 PM 1,872,884 cygwin1.dll 04/11/2008 07:03 AM 66,048 cygz.dll 09/28/2004 02:07 PM 6,656 dosdev.exe 08/11/2008 11:08 PM 1,000 pre-cmd.vbs 08/11/2008 11:05 PM 44 pre-exec.cmd 07/22/2008 02:26 PM 348,160 rsync.exe 08/11/2008 10:12 PM 161 rsyncd.conf 08/11/2008 10:12 PM 22 rsyncd.secrets 08/11/2008 11:26 PM 1,177 sleep.vbs 06/08/2005 03:17 PM 294,912 vshadow.exe 08/11/2008 10:09 PM 581 vsrsync.cmd 08/11/2008 11:33 PM 308 vss-setvar.cmd
So, here’s how it works. Before each backup, BackupPC has an option to call a local script first, waiting for that script to finish. Here’s the execution chain:
- preusercmd.sh launches “pre-exec.cmd” on the Windows box
- preexec.cmd launches “pre-cmd.vbs”
- pre-cmd.vbs cleans up some files, launches “sleep.vbs” in the background (more on this later) and then launches “backuppc.cmd” in the background, and waits for the pid file to appear that signals that rsyncd has been launched
- backuppc.cmd launches vshadow, and tells it to execute vsrsync.cmd
- vsrsync.cmd maps the shadow volume to B:, and launches rsyncd — it sits and waits here, leaving vshadow and rsync open while the backup or rsync process runs — on the shadow copy on B:
Once the backup is completed, another local script is run — here’s its execution chain:
- postusercmd.sh puts a file called “wake.up” in the C:\BackupPC directory
- sleep.vbs wakes up, sees this file, reads rsyncd.pid, and kills the rsyncd process
- vsrsync.cmd now continues, since the rsync process is dead. It unmaps the B: drive. Once this script completes, vshadow automatically deletes the shadow volume.
Sure, it seems simple, but a lot of work went into that, since there are a lot of nuances to sort out. Here are the file listings:
#!/bin/bash WINEXE=/usr/bin/winexe UNAME="Administrator" PWD="admin.password" WRKGRP="WORKGROUP" BOX=$1 $WINEXE --interactive=0 -U $UNAME -W $WRKGRP --password=$PWD //$BOX 'cmd /c c:\backuppc\pre-exec.cmd' sleep 5 echo "Rsync and shadow copy loaded" kill $$ # The script needs to be killed, otherwise, winexe waits for input
cd \backuppc @echo off cscript pre-cmd.vbs
Const Flag = "C:\BackupPC\rsyncd.pid" ' ' Pid file shouldn't be there already ' If DoesFileExist(Flag)=0 Then Set fso = CreateObject("Scripting.FileSystemObject") Set aFile = fso.GetFile(Flag) aFile.Delete End If ' ' Nor should "wake.up" ' If DoesFileExist("C:\BackupPC\wake.up")=0 Then Set fso = CreateObject("Scripting.FileSystemObject") Set aFile = fso.GetFile("C:\BackupPC\wake.up") aFile.Delete End If ' Set objShell = CreateObject("WScript.Shell") objShell.Exec "cscript C:\BackupPC\sleep.vbs" ' Set objShell = CreateObject("WScript.Shell") objShell.Exec "C:\BackupPC\backuppc.cmd > C:\BackupPC\file.out" ' ' Just sleep until the file "rsyncd.pid" appears ' While DoesFileExist(Flag) wscript.sleep 10000 Wend ' ' functions ' function DoesFileExist(FilePath) Dim fso Set fso = CreateObject("Scripting.FileSystemObject") if not fso.FileExists(FilePath) then DoesFileExist = -1 else DoesFileExist = 0 end if Set fso = Nothing end function
Const Rsync = "C:\BackupPC\rsyncd.pid" Const Flag = "C:\BackupPC\wake.up" ' ' Just sleep until the file "rsyncd.pid" appears ' While DoesFileExist(Rsync) wscript.sleep 10000 Wend ' ' Now sleep until the file "wake.up" appears ' While DoesFileExist(Flag) wscript.sleep 10000 Wend ' Set fso = CreateObject("Scripting.FileSystemObject") Set aFile = fso.GetFile(Flag) aFile.Delete ' ' It's time to kill Rsync ' Set fso = CreateObject("Scripting.FileSystemObject") Set aReadFile = fso.OpenTextFile(Rsync, 1) strContents = aReadFile.ReadLine aReadFile.Close ' Set objShell = CreateObject("WScript.Shell") objShell.Run "taskkill /f /pid " & strContents, 0, true ' ' Wait for Rsync to let go ' wscript.sleep 5000 ' ' Delete PID file ' If DoesFileExist(Rsync)=0 Then Set objShell = CreateObject("WScript.Shell") objShell.Run "cmd /c del C:\BackupPC\rsyncd.pid", 0, true End If ' ' functions ' function DoesFileExist(FilePath) Dim fso Set fso = CreateObject("Scripting.FileSystemObject") if not fso.FileExists(FilePath) then DoesFileExist = -1 else DoesFileExist = 0 end if Set fso = Nothing end function
cd \backuppc vshadow -script=vss-setvar.cmd -exec=vsrsync.cmd c:
REM @ECHO OFF call vss-setvar.cmd cd \BackupPC SET CWRSYNCHOME=\BACKUPPC SET CYGWIN=nontsec SET CWOLDPATH=%PATH% SET PATH=\BACKUPPC;%PATH% dosdev B: %SHADOW_DEVICE_1% REM Go into daemon mode, we'll kill it once we're done rsync -v -v --daemon --config=rsyncd.conf --no-detach --log-file=diagnostic.txt dosdev -r -d B:
use chroot = false strict modes = false pid file = rsyncd.pid [C] path = /cygdrive/B/ auth users = Administrator secrets file = rsyncd.secrets
#!/bin/bash WINEXE=/usr/bin/winexe UNAME="Administrator" PWD="admin.password" WRKGRP="WORKGROUP" BOX=$1 PID=$($WINEXE -U $UNAME -W $WRKGRP --password=$PWD //$BOX 'cmd /c echo '1' > c:\backuppc\wake.up') echo "Rsync and shadow copy unloaded"