This guide explains how to create and deploy a C app with debugging enabled. 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-c-debug directory:

   git clone https://github.com/unikraft-cloud/examples
   cd examples/httpserver-c-debug/

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

For extensive debug information with strace, add the USE_STRACE=1 environment variable to the deploy command:

Using the unikraft CLI (Recommended)

unikraft build . --output <my-org>/httpserver-c-debug:latest
unikraft run --metro fra \
  -m 256M \
  -p 443:8080/tls+http \
  -p 2222:2222/tls \
  --scale-to-zero policy=off \
  -e PUBKEY=.... \
  -e USE_STRACE=1 \
  --image <my-org>/httpserver-c-debug:latest

or

Using the legacy kraft CLI

kraft cloud deploy \
  -M 256Mi \
  -p 443:8080/tls+http \
  -p 2222:2222/tls \
  --scale-to-zero off \
  -e PUBKEY="...." \
  -e USE_STRACE=1 \
  .

The output shows the instance address and other details:

Using the unikraft CLI (Recommended)

metro:        fra
name:         httpserver-c-debug-5pvem
uuid:         08629a94-e2b1-466e-abb9-15ce46411b66
state:        starting
image:        <my-org>/httpserver-c-debug
resources:
  memory:     256MiB
  vcpus:      1
service:
  uuid:       2e016406-0c59-4d74-6deb-fdcb206fdb1e
  name:       patient-snow-zdzhdy8r
  domains:
  - fqdn:     patient-snow-zdzhdy8r.fra.unikraft.app
networks:
- uuid:       80a11393-8eca-ec11-3028-fb8908b21894
  private-ip: 10.0.0.109
  mac:        12:b0:45:b3:18:b2
timestamps:
  created:    just now

or

Using the legacy kraft CLI

[●] Deployed successfully!
 │
 ├───────── name: httpserver-c-debug-5pvem
 ├───────── uuid: 08629a94-e2b1-466e-abb9-15ce46411b66
 ├──────── metro: https://api.fra.unikraft.cloud/v1
 ├──────── state: starting
 ├─────── domain: https://patient-snow-zdzhdy8r.fra.unikraft.app
 ├──────── image: oci://unikraft.io/<my-org>/httpserver-c-debug@sha256:b24b95e236c8eff69615dd4f5d257beed5ee4047fd98d1b6fb200f89c63fa54c
 ├─────── memory: 256 MiB
 ├────── service: patient-snow-zdzhdy8r
 ├─ private fqdn: httpserver-c-debug-5pvem.internal
 └─── private ip: 10.0.0.109

In this case, the instance name is httpserver-c-debug-5pvem and the address is patient-snow-zdzhdy8r.fra.unikraft.app. They're different for each run.

Use curl to query the Unikraft Cloud instance:

curl https://patient-snow-zdzhdy8r.fra.unikraft.app

Hello, World!

For SSH, you need to set up a tunnel that handles the TLS connection to the Unikraft Cloud instance. This way, you have a non-TLS port that your SSH client can connect to:

socat TCP-LISTEN:2222,reuseaddr,fork OPENSSL:patient-snow-zdzhdy8r.fra.unikraft.app:2222,verify=0

Then connect to the instance via SSH using:

ssh -l root localhost -p 2222

You might see warnings like REMOTE HOST IDENTIFICATION HAS CHANGED. This is normal if you have set up tunnels to connect with SSH on localhost, so don't worry.

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-c-debug-5pvem  running  <my-org>/httpserver-c-debug        256MiB  1      patient-snow-zdzhdy8r.fra.unikraft.app  2 minutes ago

or

Using the legacy kraft CLI

kraft cloud instance list

NAME                      FQDN                                    STATE    STATUS       IMAGE                                                     MEMORY   VCPUS  ARGS  BOOT TIME
httpserver-c-debug-5pvem  patient-snow-zdzhdy8r.fra.unikraft.app  running  since 4mins  oci://unikraft.io/<my-org>/httpserver-c-debug@sha256:...  256 MiB  1            66.56 ms

When done, you can remove the instance:

Using the unikraft CLI (Recommended)

unikraft instances delete httpserver-c-debug-5pvem

or

Using the legacy kraft CLI

kraft cloud instance remove httpserver-c-debug-5pvem

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.