I would like to install Kali Linux on my computer using dual booting. My computer has 8GB of RAM. Will that RAM be separated into 4GB for Kali Linux OS and 4GB for Windows if I use dual boot?
Others have already answered correctly that no, the RAM would not be split in this case, but I want to add an explanation of why that is the case.
I find a helpful analogy for the workings of a computer is a kitchen. The RAM is the counter space. It's a close-at-hand space for temporarily storing things you are working with. Like a kitchen counter getting cleaned when finished cooking, the RAM is wiped when the computer is powered off. The hard disk is the fridge and pantry, long-term, less easily accessed storage. The data is the ingredients, and programs are recipes. The chef is the operating system.
You are the owner of the house, and currently employ an English chef (Windows). You want to try some recipes from cookbooks that are written in French, but you can't find suitable translations. So you want to hire a chef who speaks French (Linux).
Since the chefs each have their own set of cookbooks and ingredients, they'll each need their own space in the pantry (hard disk) for as long as you employ them. Whether they need to split the counter space (RAM) depends on if they work at the same time. If only one chef is working at a time, they will have exclusive use of all the counter space. The other chef's things are off the counter and in storage. If however, you run two operating systems simultaneously, like telling the chefs to work together, one as Head Chef (host) and one as Sous Chef (virtual), then they will need to split everything. They will have to take turns with the appliances (CPU, GPU, etc) and will need to mark out separate working spaces on the counter to put their cookbooks and ingredients while working.
For dual booting, no... You'll either have one or the other running at one time.
If you want to have both running at once, then you could use a hypervisor.
You might be interested in one of the following:
Unfortunately, "dual booting" doesn't mean you can boot two systems on the same computer at the same time.
It does mean you can boot two systems on the same computer, but still only one at a time.
(It's not limited to two; you could configure a great many more, depending on the boot loader requirements they have. But for some reason two got popular first, so "dual boot" is waay more common than "multi boot".)
Since only one system runs at a time, the running system has full control of all of the RAM, as well as the CPU power and all of the other hardware.
The thing that does get split is disk space. Just how split depends on how cooperative the different systems are. At the very least, you need a separate boot volume for each, and systems that don't get along may be entirely unable to access eachothers filesystems. So that music collection you have in your Windows Media Player won't be so easy to access from Linux. (Generally speaking, different flavors and versions of Linux get along fairly well, and different versions and editions of Windows vary from uncooperative to hostile.)
Since the running system has full control of the hardware, it can do things like reformat the disks the other systems are installed on. That's is how you can add or remove one system while another is running, but as always keep backups of everything and doublecheck what you're doing before you erase or remove any partitions.
As others have said, it is possible to run multiple operating systems on the same computer at the same time, but they do not have equal access to the hardware.
- The one that boots first, initiated by the ROM BIOS, is the "Host OS", and has full control of the physical hardware, as described above
- Each additional "Guest OS" must run in a Virtual Machine, initiated by "hypervisor" software, and has as about as much access to the physical hardware as an ordinary application
- Much like an ordinary application, any memory allocated to a Guest OS is not available for other use by the Host OS while the Guest OS is running. This is the closest thing to splitting RAM between two systems, but isn't limited to two.
- Sharing data between Host and Guest OSs or multiple Guest OSs is also limited. The virtual hard drives are typically ordinary files in the Host's filesystem, but they contain a potentially incompatible filesystem, and accessing files on other filesystems stored in files may require jumping through more hoops than accessing files on other filesystems stored on physical disks. And, of course, if you get stuck where you can't read the Host's files, you've also lost the Guest's virtual disks.
Using virtual machines is fairly common today, but wasn't widely practical until nearly two decades after the term "dual boot" was well known to power users.
Of course, it's also possible to get two (or more) computers. If your main interest is in trying out more operating systems, and if you have access to a used computer reseller, you could likely get several used computers good enough for experimentation for the price of one shiney new computer that has enough power to run several virtual machines without choking.
It won't split your RAM in two, but what you should know is that it will most likely split your storage in two, e.g. if you have a 500GB hard disk, you'll have to use part of it for operating system A and part of it for operating system B, be it 250GB for each, 100GB for A and 400GB for B or any other proportion you like.
While you're in complete control over how much storage you dedicate to each operating system, you'll always have to compromise some of it in order to dual boot. Specially because each operating system usually has its own file system, which is often not compatible with other operating systems at all or at least non-trivial to be made compatible with.