2 replies to this topic

[hillyu]

Hi I am extremely happy to find out there is already a built in method called shadow which is identical to the unionfs under linux system, at first I wanted to make a ro root and use uninonfs to attach a writable fs to it and make the system apears to be writable, but thanks to the shadow, all those processes are simplified dramatically.(besides I am not sure the unionfs is supported by osx)

why i want this is basiclly because I want to make my eeepc901(16g mlc ssd) more speedly, because the old 16g mlc has really bad performanc at 4k writing which lead to a laggy performanc. what I plan to do is to mount my root read-only first and then attach a ramdisk as a shadow to it, this will make all writing to the root extreamly fast due to the actrual writing is taken place on ram. later I can easily mount the /users to a built in 4g slc in normally readable mode  to store my personal data, if you want to protect the data, you can left the whole root read-only.

To achieve this I only need to twik the boot script a little bit, and I do not need a whole system img to load into my ram at all, I am not building a "live cd" but a "shadow system".

But there is a question left, i don't know if there is a default boot script by modify which I do not need to boot into single user first and using the command to initial my "netboot" script. or if there is a method to load this script automatically.

[hillyu]

I made a mistake, shadow can only apply to the disk images, not the real disk.

so I have to resort to the union fs method, but I think I can not simply create a overlay over the root, under llinux, I can change the initrd to control the root's mounting process, but I don't know where to find such a thing, After loading the kernel, what exactly happen following.I think this is a key problem.

[spartango]

You might also try making a shutdown script to save the shadow file to disk(make all the writes at once) and then restore that to RAM on bootup.