Mirari

Mirari is a tool to create and deploy applications with Mirage. There are several diverse backends in Mirage that require rather specialised build steps (from Javascript to Xen microkernels), and this compexity is wrapped up in Mirari.

There are three stages to using Mirari:

• a configuration phase where OPAM package dependencies are satisfied.

• a build phase where the compiler and any support scripts are run.

• a run phase where Mirari spawns and tracks the progress of the deployment (e.g. as a UNIX process or a Xen kernel).

Configuration files

Mirari currently uses a configuration file to build a Mirage unikernel. Support for command line arguments should be available soon.

An example of an app.conf:

# IP configuration

# This will use DHCP for configuring the unikernel's network interfaces

ip-use-dhcp: true

# This will manually set an IPv4 to the unikernel's network
# interfaces. For now, this technique only works when a unikernel has
# only one network interface.

# ip-address: 10.0.0.2
# ip-netmask: 255.255.255.0
# ip-gateway: 10.0.0.1

# Filesystem configuration. Directories can be specified here, and
# they will be compiled into a "filesystem" where each file will be
# presented to the unikernel via a key value interface. For example
# here, there will be two databases, named respectively "static" and
# "template", presenting the content of dir "../files" and "../templ"
# respectively.

fs-static: ../files
fs-template: ../tmpl

# HTTP configuration
http-port: 80
http-address: *

# Main function

# If your main is a Dispatch function for cohttp
main-http: Dispatch.main

# If Ping.min has signature Net.Manager.t -> Net.Manager.interface -> Net.Manager.id -> 'a Lwt.t
# main-ip: Ping.min

# Noip.main must have signature unit -> 'a Lwt.t (do not use networking)
# main-noip: Noip.main

# Dependencies

depends: cohttp.syntax, uri, re, cow.syntax
packages: mirage-net, cow

# Target (Select a target compiler: takes precedence over --xen or
# --unix switch on the command line)

compiler: 4.01.0dev+mirage-xen

# XL parameters. They will be used for creating the xl config file
# when doing a `mirari run --xen`.

xl-memory: 32
xl-on_crash: preserve
xl-vif: [ 'mac=00:16:3E:74:34:32' ]

• depends is a list of ocamlfind libraries
• packages is a list of OPAM packages (which contains the depends libraries)
• compiler is a OPAM compiler selector (see opam switch)

We do understand there is replication between depends and packages at the moment, but this will eventually converge as OPAM understands ocamlfind better.

Configuring Mirage Applications

Provided that one and only one file of name <foo>.conf (where <foo> can be any string) is present in the current working directory, the command:

$ mirari configure

will configure your project. It will:

• generate main.ml
• generate main.obuild
• call the right OPAM commands to satisfy dependencies.
• call obuild configure

To build for the unix-direct target (using tap interfaces), do:

$ mirari configure --unix

To build for the xen target, do:

$ mirari configure --xen

Building Mirage Applications

The command:

$ mirari build

will build your project. Likewise, you can use the --unix or --xen switches to build for a particular target.

Running Mirage Applications

The command:

$ mirari run (--unix or --xen)

will run the unikernel on the selected backend.

• Under the unix-socket backend, it just executes the unikernel.

• Under the unix-direct backend (--unix), mirari sets up a virtual interface (tap) is passes its fd to the unikernel that will use it to perform networking operations.

• Under the xen backend (--xen), mirari creates a xl configuration file and uses xl to run the unikernel locally. Xen has to be installed and running on the machine.

Compiling to Xen and deploying to the cloud

In order to deploy a Mirage unikernel to Amazon EC2, you need to install the AWS tools on your machine, build a unikernel with the --xen option and then use the ec2.sh script (in directory script) in order to register you kernel with AWS. Then you can start your kernel with the web interface to AWS or any other mean AWS provides to start EC2 instances.