6.5.1

Table Of Contents
Limit Informational Messages From Virtual Machines to
VMX Files
Limit informational messages from the virtual machine to the VMX file to avoid filling the datastore and
causing a Denial of Service (DoS). A DoS can occur when you do not control the size of a virtual
machine's VMX file and the amount of information exceeds datastore capacity.
The virtual machine configuration file (VMX file) limit is 1 MB by default. This capacity is usually sufficient,
but you can change this value if necessary. For example, you might increase the limit if you store large
amounts of custom information in the file.
Note Consider carefully how much information you require. If the amount of information exceeds
datastore capacity, a DoS can result.
The default limit of 1 MB is applied even when the tools.setInfo.sizeLimit parameter is not listed in
the advanced options.
Procedure
1 Log in to a vCenter Server system using the vSphere Web Client and find the virtual machine.
a In the Navigator, select VMs and Templates.
b Find the virtual machine in the hierarchy.
2 Right-click the virtual machine and click Edit Settings.
3 Select VM Options.
4 Click Advanced and click Edit Configuration.
5 Add or edit the tools.setInfo.sizeLimit parameter.
Prevent Virtual Disk Shrinking
Nonadministrative users in the guest operating system can shrink virtual disks. Shrinking a virtual disk
reclaims the disk's unused space. However, if you shrink a virtual disk repeatedly, the disk can become
unavailable and cause a denial of service. To prevent this, disable the ability to shrink virtual disks.
Prerequisites
n
Turn off the virtual machine.
n
Verify that you have root or administrator privileges on the virtual machine.
Procedure
1 Log in to a vCenter Server system using the vSphere Web Client and find the virtual machine.
a In the Navigator, select VMs and Templates.
b Find the virtual machine in the hierarchy.
vSphere Security
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