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Resuming Virtual Machines Repeatedly from the Same Point

Resuming Virtual Machines Repeatedly from the Same Point

When you suspend a virtual machine in the usual way, by clicking the Suspend button on the toolbar, a file with a .vmss extension is created. This file contains the entire state of the virtual machine. When the virtual machine is resumed, its state is restored from the .vmss file. This means that, in normal operation, the .vmss file cannot be used to resume a virtual machine again from the original suspended state.

If you want to be able to resume a virtual machine in the same state repeatedly - for example, in a QA testing or classroom environment - then you can take advantage of repeatable resume. Every time you resume the virtual machine, it starts from the same point at which it was suspended using the same .vmss file. This feature works only with virtual disks in nonpersistent mode. For a discussion of disk modes, see Disk Modes: Persistent, Undoable and Nonpersistent.

Repeatable resume makes it easy to start a virtual machine again and again in the exact same state. However you cannot suspend this virtual machine; you can only power it off. After you power it off, you can resume the virtual machine to start it up again. The virtual machine starts at the point at which it was suspended.

If you need to reset a virtual machine that is set up to use repeatable resume, you should restart the guest operating system (using Start > Shut Down > Restart for Windows guests, shutdown -r now for Linux guests). Do not click the Reset button on the virtual machine's toolbar. Otherwise, any files you created or other changes made to the guest operating system are lost.

Restarting or resetting the guest operating system does not affect the suspended state. To return to your repeatable resume point, just power off the virtual machine, then resume it.

If you want to restrict the user interface of a virtual machine using repeatable resume, see Using Repeatable Resume with a Restricted User Interface.

Enabling Repeatable Resume on a Windows Host

Enabling Repeatable Resume on a Windows Host

  1. Make sure the virtual machine is powered off. You can enable the repeatable resume feature only when the virtual machine is powered off.

  2. Open the Configuration Editor. Choose Settings > Configuration Editor.

  3. All virtual disks associated with this virtual machine must be in nonpersistent mode before you can enable repeatable resume. In the Configuration Editor, on the Hardware tab, select the virtual disk. Under Mode, make sure the Nonpersistent radio button is selected.

  4. Click the Options tab.

  5. If you intend to copy this virtual machine to other PCs, VMware suggests that you specify that the redo log is to be located in the same directory as the virtual machine. Click Browse to find the virtual machine's directory and select it.

  6. Check the Enable Repeatable Resume check box.

  7. Click OK to save your changes and close the Configuration Editor.

Enabling Repeatable Resume on a Linux Host

Enabling Repeatable Resume on a Linux Host

  1. Make sure the virtual machine is powered off. You can enable the repeatable resume feature only when the virtual machine is powered off.

  2. Open the Configuration Editor. Choose Settings > Configuration Editor.

  3. The virtual disks associated with this virtual machine must be in nonpersistent mode before you can enable repeatable resume. In the Configuration Editor, under SCSI Devices or IDE Drives, select the virtual disks and make sure the Mode is set to Nonpersistent.

  4. Click Misc. The Misc panel appears.

  5. If you intend to copy this virtual machine to other PCs, VMware suggests that you specify that the redo log is to be located in the same directory as the virtual machine. Click Choose to find the virtual machine's directory and select it.

  6. Select Repeatable resume.

  7. Click OK to save your changes and close the Configuration Editor.

Issues to Consider

Issues to Consider

Caution: By default, the redo-log file for a disk in nonpersistent mode is located in your system's temp directory. If you intend to move this virtual machine to another host, VMware suggests that you place the redo log for a virtual machine using repeatable resume in a different location (outlined in the steps below), as some temp directories may be small (and the redo log could exceed this limit as it grows) or, on Linux hosts, the temp directory may be cleared by the operating system on a regular basis, and this would remove the redo log.

Caution: VMware does not recommend moving a suspended virtual machine containing disks in nonpersistent mode to another host. However, if you want to take advantage of the repeatable resume feature in a classroom environment, for example, and do not want to set the same repeatable resume point individually on every student's machine, be very careful and keep the following warnings in mind:

  • VMware does not support the use of repeatable resume with a virtual machine when its disks are located on a networked drive. However, if you place a disk in nonpersistent mode on a shared network drive, note that locating the redo log in a directory on a networked drive may affect the performance of your virtual machine.
  • Do not distribute the virtual disk (.vmdk) files. Place the virtual disks in a location on a shared network drive the whole class can access. Multiple users can run the same nonpersistent disk at one time.
  • Make sure all the machines in the classroom contain the same hardware as the machine on which the virtual disk resides. This reduces the chance of hardware inconsistencies when the student resumes the virtual machine.
  • Before you power on the virtual machine and create your repeatable resume point, put the redo log in the directory with the virtual machine's configuration file. Use the Configuration Editor (choose Settings > Configuration Editor, then select the Options tab for Windows hosts, Misc panel for Linux hosts) to specify the location of the redo log.
  • After you create your repeatable resume point, copy all the files from the directory containing the virtual machine's configuration file to each student's computer.
Disabling Repeatable Resume

Disabling Repeatable Resume

If you no longer want to resume the virtual machine from this repeatable resume point, do the following:

  1. Resume the virtual machine, if it is not running already. The virtual machine must be running for you to disable the repeatable resume feature.

  2. Open the Configuration Editor (Settings > Configuration Editor). Then do one of the following:

    • On a Windows host, click the Options tab, then clear the Enable repeatable resume check box.
    • On a Linux host, click Misc, then deselect Enable repeatable resume.
  3. Click OK to save your changes and close the Configuration Editor.

  4. Power off the virtual machine. This removes the suspend state (.vmss file) and allows you to suspend and resume the virtual machine normally again. All redo-log files for this virtual machine are removed.

    With the virtual machine powered off, you can enable the feature again so that the next time you power on, you can set the virtual machine into a different state and save that as a new repeatable resume point.

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