GPT-Disk-On-Ram

Linux block device driver that builds a virtual disk in RAM using the GPT partitioning scheme. This project aims to let the user spawn a disk in RAM that the operating system recognizes as a disk drive that it can perform operations on as it could on a normal drive.

The disk that spawns when loading dor.ko has 1 partition of 2MB, but theoretically supports up to 128 partitions on the disk. This disk is fully operable, and can be edited with your favorite disk partitoning program such as Gparted.

Compiling the driver

First make sure that you have your current kernel's latest module-header files. As we are not invoking the kernels build system, we need to have our own headers.

-- Install the lastest kernel headers

In Arch based systems this can be done by installing the meta-package and then selecting your kernel's headers by typing

$ sudo pacman -Sy linux-headers

In Debian based systems this can be similiarly done with

$ sudo apt-get install linux-headers-$(uname -r)

-- Compile the driver

Enter the GPT-Disk-On-Ram directory and type

$ make

If it complains that it cannot find the directory /lib/modules/$(KERNEL_VERSION) then you need to install the latest kernel headers for your currently running kernel. If all is well you should see a dor.ko file.

Running the driver

With the dor.ko file, we will now load the module. The great thing about Linux kernel modules is that we can add new kernel code without having to re-compile the kernel. Neat!

-- Loading the driver

To load the driver type

$ sudo insmod dor.ko

This will load the driver. If it does not let you, make sure that your kernel headers match the currently running kernel. If all is well, the module should now be loaded and running.

-- Testing the driver

To see if the module was successfully loaded type

$ dmesg | grep "dor"

There should be a status message saying that the driver was loaded or an error message telling you why it did not load. If all is well the kernel should have registered the disk as being active and usable. Type

$ sudo fdisk -l

To see a list of disk, our kernel driver should be one of them with the name "/dev/dor" and a partition named "/dev/dor1" The disk should now be accessible and ready to use.

Using the driver

Now with the driver loaded the virtual disk operates like a regular disk and can be manipulated and used just as you could any disk. An example of how to use it would be to format the disk with a file system (ext2, ext3, fat32, etc.) and use it as you normally would any filesystem. This is especially useful for testing things in a filesystem environment that you wouldn't want in your own environment.

-- Examples

Here is an example of formating and mounting your drive using the first partition of the disk.

$ sudo mkfs.ext2 /dev/dor1
$ sudo mount /dev/dor1 /mnt
$ cd /mnt

You now have your own disk environment to play in! Remember that this is stored on RAM and will not persist after reboot.

Unloading the driver

To unload the driver one could simply reboot and the OS will do all the proper unmounting and shutting down of the driver. To unload the driver manually we need to take a few extra steps. First make sure to cease all uses of the drive and in particular unmount the drive if you mounted it.

$ sudo umount /mnt

Next we remove the device driver

$ sudo rmmod dor

Everything should be removed and the device driver should no longer be active.

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