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This chapter has given you a broad overview of some of the more advanced features that CentOS makes available for disk management. You ve learned about the different types of RAID that are available and how to configure software RAID under CentOS. We ve also taken a brief look at LVM and how to set up a

constructors had not yet been called. Instead, the most derived function that is already constructed is called, which is usually the version of the virtual function in the class whose constructor is being executed, but could be a function closer to the root of the tree if the function isn t implemented at that level in the inheritance tree. In C++/CLI, virtual functions act as they always do: the most derived method is called. Given that, can you predict the output of Listing 8-15 Listing 8-15. Using Virtual Functions in a Constructor // native_managed_virtual.cpp class NativeBase { public: NativeBase() { f_virt(); } virtual void f_virt() { System::Console::WriteLine("NativeBase::f_virt"); } }; class NativeDerived : public NativeBase { public: NativeDerived() { f_virt(); } virtual void f_virt() { System::Console::WriteLine("NativeDerived::f_virt"); } }; ref class ManagedBase { public: ManagedBase() { f_virt();

volume group and create some logical volumes. This chapter s information is likely to be only the beginning of your storage-related journey but should be more than enough to give you a solid start. In the next chapter, we ll look at user management and how to use both graphical and text-based tools to get the job done.

} virtual void f_virt() { System::Console::WriteLine("ManagedBase::f_virt"); } }; ref class ManagedDerived : ManagedBase { public: ManagedDerived() { f_virt(); } virtual void f_virt() override { System::Console::WriteLine("ManagedDerived::f_virt"); } }; int main() { NativeDerived nd; ManagedDerived rd; } The output of Listing 8-15 is as follows: NativeBase::f_virt NativeDerived::f_virt ManagedDerived::f_virt ManagedDerived::f_virt Surprised For CLI types, virtual function dispatch is always deep, meaning that the most derived override is always called. In classic C++, it is shallow in the constructor, but deep everywhere else. In fact, you ve arrived at the explanation of the difference in constructor initialization order as well. Because the most derived virtual function gets called, functions can execute on objects that have not been fully constructed. Initializing the fields first at least means that fields will be valid objects when derived class virtual functions get called, although you still need to take care in calling virtual functions in constructors, and also when implementing virtual functions that are called by base class constructors, to remember that objects are in a partially constructed state. To override this behavior, specify the fully scoped base class function, like this:

During installation of CentOS, you were able to set the passwords for the administrator account known as root and for one regular user. In this chapter, you will learn how to add, edit, and delete users and groups and how to allocate resources to them. User accounts are essential in an operating system, as they provide real users disk space to store their data and allow access to operating system services, such as desktop systems, e-mail, the Web, and FTP accounts which services are provided to users is determined by the system administrator. Sadly, some users abuse the services provided to them, and if these users consume excess resources, there won t be any left for others, which will cause service disruptions. For example, if the server is set up as an e-mail system and users store large attachments in their accounts, in time the disk space in the server will be consumed, and other users won t be able to receive incoming mail. Fortunately, as a system administrator, you have the capability to thwart or limit the disruption through user management and resource allocation. Every person who needs access to the system should have a unique user account, which ensures security and accountability. The account is secure, because by default, only the user and system administrator have access to the user s data. Users are accountable, because through logs, the system administrator can determine if a user is abusing an account. In this chapter, we begin by adding a user, which you have already done in the previous chapter, so without further ado, let s get started.

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