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Capstan is a tool for rapidly building and running your application on OSv. Capstan is as simple and fast as using Docker for creating containers, but the result is a complete virtual machine image that will run on any hypervisor with OSv support.


  • Run multiple VMs of an image as copy-on-write
  • Linux, FreeBSD, OS X, and Windows support
  • Hypervisors:
    • QEMU/KVM
    • VirtualBox
    • VMware Workstation and Fusion
  • Cloud providers:
    • Google Compute Engine


You can install Capstan either by downloading pre-built binaries or building it from sources.

Prerequisites: local

You need to have a hypervisor such as QEMU/KVM or VirtualBox installed on your machine to run local OSv VMs.

If you want to build your own OSv images, you need QEMU installed.

On Fedora:

$ sudo yum install qemu-system-x86 qemu-img

On OS X:

$ brew install qemu

On FreeBSD:

$ sudo pkg install qemu

Prerequisites: Google Compute Engine

To run your OSv images on Google Compute Engine, you will need the gcutil utility, which is part of the Google Cloud SDK. Installation instructions are on the gcutil home page.

Installing Binaries

To install the binaries, make sure $HOME/bin is part of the PATH environment variable and then download the capstan executable and place it in $HOME/bin.

$ curl | bash

Installing from Sources

You need a working Go environment installed. See Go install instructions for how to do that. Go version 1.1 or later is required.

Make sure you have the GOPATH environment variable set to point to a writable Go workspace such as $HOME/go.

To install Capstan, type:

$ go get

This installs a capstan executable to your Go workspace so make sure your PATH environment variable includes $GOPATH/bin.

For more detailed information, check out installation instructions on the wiki.

Updating from Sources

To update capstan to the latest version execute the following commands:

$ cd $GOPATH/src/
$ git pull
$ ./install


To run OSv on default hypervisor which is QEMU/KVM, type:

$ capstan run cloudius/osv

To run OSv on VirtualBox, type:

$ capstan run -p vbox cloudius/osv

To port-forwarding OSv port 22 to Host port 10022, type:

$ capstan run -f "10022:22" cloudius/osv

To bridging OSv vNIC to Host bridge interface, type:

On Linux:
$ capstan run -n bridge cloudius/osv

On OS X with VirtualBox:
$ capstan run -n bridge -b <physical NIC name> cloudius/osv

To show a list of available remote images, type:

$ capstan search

To show a list of locally installed images, type:

$ capstan images


Check out the following example projects to get you going:



Capstan is distributed under the 3-clause BSD license.