This guide explains how to create and deploy a simple Ruby-based HTTP web server. To run this example, follow these steps:

1. Install the CLI. Use the unikraft CLI or the legacy kraft CLI. You need a BuildKit builder. The easiest way to get one is via Docker. Alternatively, you can also directly set up and use BuildKit, see the quick start.

   Note: The unikraft CLI is the current standard, while kraft is the legacy version. Choose one of the CLIs below and only run the commands associated with it for the rest of this guide.

2. Clone the examples repository and cd into the examples/httpserver-ruby3.2/ directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-ruby3.2/

Make sure to log into Unikraft Cloud and pick a metro close to you. This guide uses fra (Frankfurt, 🇩🇪):

Using the unikraft CLI (Recommended)

unikraft login

or

Using the legacy kraft CLI

# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra

When done, invoke the following command to deploy this app on Unikraft Cloud:

Using the unikraft CLI (Recommended)

unikraft build . --output <my-org>/httpserver-ruby32:latest
unikraft run --metro fra \
  -m 256M \
  -p 443:8080/tls+http \
  --scale-to-zero policy=on,cooldown-time=1000 \
  --image <my-org>/httpserver-ruby32:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 256Mi \
  -p 443:8080/tls+http \
  --scale-to-zero on \
  --scale-to-zero-cooldown 1s \
  .

The output shows the instance address and other details:

Using the unikraft CLI (Recommended)

metro:        fra
name:         httpserver-ruby32-s6l8n
uuid:         b1ebbbc0-5efa-476c-adb6-99866773245c
state:        starting
image:        <my-org>/httpserver-ruby32
resources:
  memory:     256MiB
  vcpus:      1
service:
  uuid:       bcc07c7c-9289-11f4-6e3d-8f7fdde45256
  name:       silent-resonance-1jtz5c66
  domains:
  - fqdn:     silent-resonance-1jtz5c66.fra.unikraft.app
networks:
- uuid:       50203783-cf51-81d1-aa2d-615f939043af
  private-ip: 10.0.3.3
  mac:        12:b0:0a:4f:7a:84
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: httpserver-ruby32-s6l8n
 ├───────── uuid: b1ebbbc0-5efa-476c-adb6-99866773245c
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://silent-resonance-1jtz5c66.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-ruby32@sha256:4cf3b341898e6ebff18ff2b68353ef872dded650c9d16a6f005a8fbe8a7cbb3d
 ├─────── memory: 256 MiB
 ├────── service: silent-resonance-1jtz5c66
 ├─ private fqdn: httpserver-ruby32-s6l8n.internal
 └─── private ip: 10.0.3.3

In this case, the instance name is httpserver-ruby32-s6l8n and the address is https://silent-resonance-1jtz5c66.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance of the Ruby-based HTTP web server:

curl https://silent-resonance-1jtz5c66.fra.unikraft.app

Hello, World!

You can list information about the instance by running:

Using the unikraft CLI (Recommended)

unikraft instances list

METRO  NAME                     STATE    IMAGE                       ARGS  MEMORY  VCPUS  FQDN                                    CREATED
fra    httpserver-ruby32-s6l8n  running  <my-org>/httpserver-ruby32        256MiB  1      silent-resonance-1jtz5c66.fra.unikraf…  2 minutes ago

or

Using the legacy kraft CLI

kraft cloud instance list

NAME                     FQDN                                        STATE    STATUS          IMAGE                                                    MEMORY   VCPUS  ARGS  BOOT TIME
httpserver-ruby32-s6l8n  silent-resonance-1jtz5c66.fra.unikraft.app  running  12 minutes ago  oci://unikraft.io/<my-org>/httpserver-ruby32@sha256:...  256 MiB  1            71.19 ms

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-ruby32-s6l8n

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-ruby32-s6l8n

To customize the app, update the files in the repository, listed below:

• server.rb: the actual Ruby HTTP server
• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified app filesystem

The following options are available for customizing the app:

• If you only update the implementation in the server.rb source file, you don't need to make any other changes.

• If you create any new source files, copy them into the app filesystem by using the COPY command in the Dockerfile.

• More extensive changes may require extending the Dockerfile (see Dockerfile syntax reference).

Use the --help option for detailed information on using Unikraft Cloud:

Using the unikraft CLI (Recommended)

unikraft --help

or

Using the legacy kraft CLI

kraft cloud --help

Or visit the CLI Reference or the legacy CLI Reference.