µOSv is merged into OSv. Please check upstream.
This repository is not maintained anymore.

µOSv is lightweight edition of OSv, which uses mruby interpreter instead of Java VM for its system language.
Here's a movie how µOSv looks like: http://www.youtube.com/watch?v=hSK_VZkwmxI

It's cloud OS which specialized for running mruby script, works on both KVM and Xen, and some IaaS/VPS services.
Able to run very few memory amount(>90MB for now), very small disk image size(26MB for now), very fast boot-up speed(less than 2sec).
Original OSv is great OS to run Java application, but it's too huge in some usecases. µOSv offers much smaller / simpler enviroment for developers who loves scripting language.

KVM on Ubuntu 13.10/x86_64

Copy and paste following commands on your shell.

wget https://dl.dropboxusercontent.com/u/648670/uosv_20131219.img
sudo qemu-system-x86_64 -m 128m -drive file=uosv_20131219.img,if=virtio,cache=none \
-netdev user,id=un0,net=192.168.122.0/24,host=192.168.122.1 \
-device virtio-net-pci,netdev=un0 -enable-kvm -cpu host,+x2apic \
-chardev stdio,mux=on,id=stdio -mon chardev=stdio,mode=readline,default \
-device isa-serial,chardev=stdio -nographic

There are prerequisite packages before start building.

Ubuntu

sudo apt-get install openjdk-7-jdk autotools-dev libltdl-dev libtool autoconf autopoint libboost-all-dev \
genromfs zfs-fuse autoconf ant libffi-dev ruby bison gyp git build-essential qemu-utils qemu-system-x86 \
bridge-utils libvirt0 libvirt-bin

wget https://launchpad.net/ubuntu/+archive/primary/+files/libuv-dev_0.10.18-1_amd64.deb
wget https://launchpad.net/ubuntu/+archive/primary/+files/libuv0.10-dbg_0.10.18-1_amd64.deb
wget https://launchpad.net/ubuntu/+archive/primary/+files/libuv0.10_0.10.18-1_amd64.deb
sudo dpkg -i libuv*.deb

To start building, execute following command:

git clone https://github.com/syuu1228/uosv.git
cd uosv
./build.sh

If you want to enable GPL mrbgems, use

./build_gpl.sh

To run µOSv, execute following command:

./run.sh

You also can specify VM memory size like this:

./run.sh 90m

Add files under userdata/, then execute following command:

./update.sh

OSv related products are almost under BSDL.
mruby related products are almost under MIT.
mruby-vedis is under Sleepycat License.

These modules are lisenced under copyleft license, disabled by default.

• libuv is ported, but very unstable for now.
• µOSv disables OSv's ZFS, so you only have ramfs for now.
  You can write files on ramfs, but you'll lost all you written data beyond shutdown/reboot.