Easily create a RAM-disk in Linux

This command creates a 2GB RAM-disk and mounts it to /tmp/space.

$ mkdir /tmp/space
$ sudo mount -t tmpfs tmpfs /tmp/space -o size=2G,nr_inodes=200k,mode=01777

You should now have an extra 2GB storage device.

 $ df -h | grep space
$ tmpfs                 2.0G     0  2.0G   0% /tmp/space

You access the temporarily device by it's mountpoint /tmp/space. Needless to say, once you unmount this volume (for instance, with a reboot), the data on it will be gone. Use with care! :) Tested on Ubuntu, should work with any 2.4 or 2.6 kernel...

KQemu on Ubuntu Gutsy Gibbon

QEMU is an open source processor emulator in which you can run Virtual Machines. It comes with a kernel module called KQemu which accelerates the VM's to 'near native' speeds. Due to some licensing issues KQemu is not distributed and installed with QEMU, though it is easily available in Ubuntu and a lot of other operating systems. This message appears when starting QEMU while KQemu is not loaded:

Could not open '/dev/kqemu' - QEMU acceleration layer not activated

This howto shows how to get KQemu running on Ubuntu 7.10 (Gutsy Gibbon) First install the following packages:

sudo apt-get install kqemu-source kqemu-common build-essential

Then run the following commands:

sudo module-assistant prepare kqemu sudo module-assistant auto-install kqemu

If everything went right (so no errors occurred) you can load the module with this command:

sudo modprobe kqemu

Now check if the module is loaded correctly. If you get a line of output starting with the word kqemu it means the module is loaded properly:

lsmod | grep qemu

To use this module as a user the right permission need to be set:

sudo chmod a+rw /dev/kqemu

You QEMU VM's should now run without the warning above and run a whole lot faster!