Unikernel Linux (UKL)

Unikernel Linux (UKL) is a small patch to Linux and glibc which allows you to build many programs, unmodified, as unikernels. That means they are linked with the Linux kernel into a final vmlinuz and run in kernel space. You can boot these kernels on baremetal or inside a virtual machine. Almost all features and drivers in Linux are available for use by the unikernel.

Requirements

autoconf & automake
GCC or Clang
GNU make
GNU sed
supermin (https://github.com/libguestfs/supermin)
qemu, if you want to test boot in a virtual machine

Building the included programs

git clone https://github.com/unikernelLinux/ukl
cd ukl
git submodule update --init
autoreconf -i
./configure --with-program=hello
make -j`nproc`

To test it (requires qemu):

make boot

If the program requires incoming network connections, use this target instead. Note this runs qemu with sudo:

make boot-priv

hello is a simple hello world example. You can try one of the other programs (see subdirectories in the source) by adjusting ./configure --with-program=...

Currently you must make clean -C linux if you change the program. (This is a bug which we should fix.)

Configuration options

Some additional options are available to turn on and off features of UKL:

$ ./configure --help
...
  --enable-bypass         enable glibc bypass (UKL_BP) [default=no]
  --enable-same-stack     enable same stack (CONFIG_UKL_SAME_STACK)
                          [default=no]
  --enable-use-ret        use ret instead of iret (CONFIG_UKL_USE_RET)
                          [default=no]
  --enable-use-ist-pf     use IST for PF instead of DF (CONFIG_UKL_USE_IST_PF)
                          [default=no]
  --enable-afterspace     enable afterspace (CONFIG_UKL_CREATE_AFTERSPACE)
                          [default=no]

Building into a separate build directory

If you want to build different configurations of UKL from the same source tree, you can do this by creating separate build directories, eg:

mkdir build-hello
pushd build-hello
../configure --with-program=hello
make -j`nproc`
popd

mkdir build-redis
pushd build-redis
../configure --with-program=redis
make -j`nproc`
popd

Building your own program

We would strongly recommend looking at the example hello world program in the hello/ subdirectory.