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Example apps

SSH and HTTP Server with C and Debugging Tools

This guide explains how to create and deploy a C app with debugging enabled. To run this example, follow these steps:

1. Install the unikraft 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.

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

   Code
   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, 🇩🇪):

Code
unikraft login

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

Code
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

The output shows the instance address and other details:

Code
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

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:

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

Code
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:

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

Then connect to the instance via SSH using:

Code
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:

Code
unikraft instances list

Code
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

When done, you can remove the instance:

Code
unikraft instances delete httpserver-c-debug-5pvem

Learn more

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

Code
unikraft --help

Or visit the CLI Reference.