12 Troubleshooting This chapter provides answers to commonly asked questions. In order to improve your user experience with VirtualBox, it is recommended to read this section to learn more about common pitfalls and get recommendations on how to use the product. 12.1 Procedures and tools 12.1.1 Categorizing and isolating problems More often than not, a virtualized guest behaves like a physical system. Any problems that a physical machine would encounter, a virtual machine will encounter as well. If, for example, Internet connectivity is lost due to external issues, virtual machines will be affected just as much as physical ones. If a true VirtualBox problem is encountered, it helps to categorize and isolate the problem first. Here are some of the questions that should be answered before reporting a problem: 1. Is the problem specific to a certain guest OS? Specific release of a guest OS? Especially with Linux guest related problems, the issue may be specific to a certain distribution and version of Linux. 2. Is the problem specific to a certain host OS? Problems are usually not host OS specific (because most of the VirtualBox code base is shared across all supported platforms), but especially in the areas of networking and USB support, there are significant differences between host platforms. Some GUI related issues are also host specific. 3. Is the problem specific to certain host hardware? This category of issues is typically related to the host CPU. Because of significant differences between VT-x and AMD-V, problems may be specific to one or the other technology. The exact CPU model may also make a difference (even for software virtualization) because different CPUs support different features, which may affect certain aspects of guest CPU operation. 4. Is the problem specific to a certain virtualization mode? Some problems may only occur in software virtualization mode, others may be specific to hardware virtualization. 5. Is the problem specific to guest SMP? That is, is it related to the number of virtual CPUs (VCPUs) in the guest? Using more than one CPU usually significantly affects the internal operation of a guest OS. 6. Is the problem specific to the Guest Additions? In some cases, this is a given (e.g., a shared folders problem), in other cases it may be less obvious (for example, display problems). And if the problem is Guest Additions specific, is it also specific to a certain version of the Additions? 7. Is the problem specific to a certain environment? Some problems are related to a particular environment external to the VM this usually involves network setup. Certain configura- tions of external servers such as DHCP or PXE may expose problems which do not occur with other, similar servers. 8. Is the problem a regression? Knowing that an issue is a regression usually makes it signifi- cantly easier to find the solution. In this case, it is crucial to know which version is affected and which is not. 164