I have 2 operating systems: 1st windows xp 2nd UBUNTU
and I have 512 X 2 of RAM.
I want to Install more 2g of RAM so after I install it do I have to reinstall my OSes.

In the linux case my swap drive = 2g because I heard from some linux books that the swap drive must be twice the RAM size so when I install more RAM my overall RAM will be = 3g Do I have to make the swap drive = 6g? or 2g swap drive ok for 3g RAM?

No need to reinstall. 2GB swap should be more than enough. 2xRAM size is a bit outdated except for servers and for people who use suspend-to-swap.

You'll be within 3G; that will be fine for any *nix-style OS that I can think of; had you gone abvove 4, you may have needed a new kernel, but it isn't necessarily a complete re-install.

Unless you are buying RAM because you have suddenly started doing things that use a lot more memory than the things that you used to do (have you just started doing CAE?, CAD? running big databases?), there is no case whatsoever for saying that because you have more ram you will need more swap, in normal usage.

In fact, apart from the suspend case mentioned earlier, more ram will equal less need for swap. Unless you are very short of disk space, I wouldn't advise you to decrease the size of swap from where you are, though; there just isn't any advantage.

First!!!! Oh, well. Don't know much about this XP thing that you mention, but you may run into the degrading business of having to beg from the supplier of some kind of activation code to run the software that you thought that you had already paid for the right to run. You probably don't have to do this if you haven't been changing other hardware. (Or is this just Vista that is so anti-customer?)

About the windows Xp in the manual of my MOBO they stated that if you use windows xp 32 bit it is not advice able to use more than 2 GB of
RAM

You might have to install a new kernel if the kernel you are using was not compiled with the hugemem flag set.

Just to make one more point that hasn't been made yet, if you do need more swap space, you can always make a swap FILE and use it instead of resizing your swap partition. You are not limited to only one swap space. If you find that your system is running out of swap often (which I would highly doubt unless you are running some very memory intensive apps) search Google for "linux swap file" and you can find instructions on how to set it up. With the 2.6 kernel, swap files are just as fast as swap partitions anyway.

HTH

Forrest

I actually will install more ram for the VMware because I may open more than one vm at a time, with 1G RAM I cant use more than 2 vm and give every one 128mg of RAM each and when I open more VMs or give the VM more RAM the system hangs and didnt respond. (I use vm on ubuntu 8.10)
So do I have to resize the space of the swap and make it bigger in the case of using the VMs?

I didnt mean First in use, I only use XP for games only and all my work is on ubnutu.

Well, you most certainly do not want to use swap for a vm - ever. When the host OS needs to use swap, it gets slow; but it is nothing compared to a vm accessing swap. So, yes, you could create more swap space in case your vms need it but if they do, it will not be fun.

Thanks ay73 for answering me but I didnt got the answer,
Do I have to make my swap drive more bigger or not?
sorry I think I am stupid

by the way almost all my VMs guests will be windows XP and vista and small linux systems like xubuntu, I think you will not need this to answer me but maybe it will help you got what I want.

I have other question please:
How to know that I need more swap?

Type "free -m" and look at the result. It will tell you whether you are using swap or not. You say you have 2GB of swap space already. I can't imagine a situation where more swap space would result in a better performing system. 2GB is already a lot. If the "free -m" command shows that you have a lot of swap in use, then the answer would be to add more RAM, not more swap.

No, I don't think you need more swap. My virtual machines never use any (but then I assign at least 1GB of RAM to each so that is not so surprising).
Of course, it also depends on how your virtual machines are used. For example, if you install some heavy applications in them, that will cause your vms to eat a lot more RAM; and if things get out of hand, you may actually reach a point where swap becomes vital.

I would not worry for now; you can always add more swap if you discover that your physical RAM is not sufficient.

free -m, as pointed out. Keep an eye on it because if you run out of swap, your virtual machine is likely to crash.