Using a Single Windows Virtual Machine with Multiple Mac User Accounts

Because being able to run Windows is so useful, you'll probably want to allow everyone who uses your Mac to do so. There are two basic approaches to doing this.

You could create a VM under each Mac user account, install Windows on it, and then each user would have a separate VM under which they can run Windows. However, there are a number of problems with this approach. One is that each disk image will consume large amounts of disk space. Another is that you will have a separate Windows environment for each user, which means you have to install applications in each environment, perform updates to each, and so on. This would be a pain and could be expensive if you have license applications for each environment.

However, the biggest problem is that you will also have to activate Windows in each environment, which means that you'll have to pay for a Windows license for each Mac user account.

A better way to do this is to store the disk image for your Windows virtual machine in a location where all the people who use your Mac will be able to access it and thus everyone can run the same Windows environment. You can create Windows user accounts to provide each user with his own Windows account. This saves disk space, but more importantly, you'll only have to work with a single Windows environment.

By default, Parallels Desktop for Mac stores the disk image file in your Library folder within your Home folder. This means that the file is not accessible from other Mac user accounts and so other people who use your Mac with their own user accounts can't use the virtual machine you created.

To allow this, you'll need to move your disk image files to a public location and make sure the files' permissions allow everyone who uses your Mac to change them. Then, under each Mac user account, point Parallels Desktop for Mac to the virtual machine you want to use. Finally, create a Windows user account for each user.

First, move the disk image and point the VM to its new location:

1.	If it's running, quit Parallels Desktop for Mac.
2.	Move to the location in which you saved the disk image file for your VM. By default, this will be Home folder/Library/Parallels/winxp (see Figure 7.15). Figure 7.15. By default, your VM files are stored in your Library folder.
3.	Move the winxp folder to a location on your Mac that is accessible by everyone who uses it. The obvious choice is the Public folder in your Home folder that is shared with all user accounts. You could also move the folder to a different disk, such as an external hard drive (the environment's performance might be slower).
4.	Launch Parallels Desktop for Mac. You should see a sheet ask you to select the VM you want to use.
5.	Click Browse.
6.	Use the resulting Open dialog box to move to the winxp folder and then select the .pvs file it contains and click Open. You'll return to the previous sheet and will see the path to the VM in the VM Path box (see Figure 7.16). Figure 7.16. Here, I've selected the .pvs file that I moved to my Public folder.
7.	Click Open. The VM will be loaded and you can work with the OS.
8.	Quit Parallels Desktop for Mac (save changes if you are prompted to do so).

Tip

When you quit Parallels Desktop for Mac, choose the Power Off option in the close sheet to make sure all the files open in the Windows are properly closed before Parallels Desktop for Mac quits.

Now, you have to make sure everyone who uses your Mac can read and write to the VM files:

1.	In the Finder, move to the winxp folder.
2.	Select the .pvs file and press +I. The Info window will open.
3.	Expand the Ownership & Permissions section.
4.	Set all the permissions to Read & Write.
5.	Close the Info window.
6.	Repeat steps 15 for each file in the winxp folder. At the least, you'll have one .hdd file. If you've added more disk images, there might be more than one.
7.	Switch another user account on your Mac.
8.	Launch Parallels Desktop for Mac. You'll see the sheet shown in Figure 7.16 except there will be no previous VMs shown.
9.	Navigate to the location in which you stored the files for your VM. If you've stored them in your Public folder, the path will be Users/youruseraccountname/public/winxp.
10.	Select the .pvs file and click Open. You'll see a warning explaining the configuration can't be locked out. What this means is that there is no way Parallels Desktop for Mac can prevent another user from accessing the same file while you are using it. That would be bad because only one version of the file can be saved at a time and so changes that each user makes could be lost. Note Make sure that you always quit Parallels Desktop for Mac when you aren't using it or when someone else is going to use your Mac. That will ensure changes you make to the VM files aren't overwritten by changes another user makes to the same files.
11.	Click OK to clear the warning.
12.	Power up the virtual environment. Windows will start up just as it did under your Mac user account.
13.	Quit Parallels Desktop for Mac.
14.	Repeat steps 714 for each Mac user account that you want to be able to access the same VM.

If one user tries to open a VM that is already opened by another user, a warning dialog will appear (see Figure 7.17). If that happens, the user should choose not to open the VM by clicking No to make sure that the other users don't lose data. Move back into the user account that has the VM open and shut it down before using it under another user account.

Figure 7.17. When someone else is already using a VM, this warning sheet will appear when another user tries to open it.

After you've enabled access to each user, you can create a Windows user account for each person. This will keep each Windows environment within the VM personalized for everyone with whom you share the VM. You'll learn how to set up Windows user accounts in Chapter 8, "Running Windows in a Virtual Machine."