Run a Bun app

In this guide we create and deploy a Bun app. To run this example, follow these steps:

1. Install the kraft CLI tool and a container runtime engine, e.g. Docker.

2. Clone the examples repository and cd into the examples/bun directory:

git clone https://github.com/kraftcloud/examples
cd examples/bun/

Make sure to log into Unikraft Cloud by setting your token and a metro close to you. We use fra0 (Frankfurt, 🇩🇪) in this guide:

# Set Unikraft Cloud access token
export UKC_TOKEN=token
# Set metro to Frankfurt, DE
export UKC_METRO=fra0

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

kraft cloud deploy -p 443:3000 -M 512 .

The output shows the instance URL and other details:

[●] Deployed successfully!
 │
 ├────────── name: bun-700mp
 ├────────── uuid: e467a880-075c-41e0-97ac-88e3e938523e
 ├───────── state: starting
 ├──────── domain: https://quiet-pond-ao44imcg.fra0.kraft.host
 ├───────── image: bun@sha256:dfcbee1efe0d8a1d43ab2dab70cf1cc5066bb1353aa1c528c745533d2cc33276
 ├──────── memory: 512 MiB
 ├─────── service: quiet-pond-ao44imcg
 ├── private fqdn: bun-700mp.internal
 ├──── private ip: 172.16.3.3
 └────────── args: /usr/bin/bun run /usr/src/server.ts

In this case, the instance name is bun-700mp and the URL is https://quiet-pond-ao44imcg.fra0.kraft.host. They are different for each run.

Use curl to query the Unikraft Cloud instance of the Bun instance:

curl https://quiet-pond-ao44imcg.fra0.kraft.host

Hello, World!

At any point in time, you can list information about the instance:

kraft cloud instance list

NAME               FQDN                                 STATE    STATUS                    IMAGE                               MEMORY   ARGS                                                   BOOT TIME
bun-700mp          quiet-pond-ao44imcg.fra0.kraft.host  running  since 3mins               bun@sha256:dfcbee1efe0d8a1d43ab...  512 MiB  /usr/bin/bun run /usr/src/server.ts                    289.03 ms

When done, you can remove the instance:

kraft cloud instance remove bun-700mp

Customize your Application

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

• Kraftfile: the Unikraft Cloud specification
• Dockerfile: the Docker-specified application filesystem
• server.ts: the Bun server implementation

Kraftfile

spec: v0.6

name: bun

runtime: base-compat:latest

rootfs: ./Dockerfile

cmd: ["/usr/bin/bun", "run", "/usr/src/server.ts"]

Dockerfile

FROM oven/bun:1 AS bun

RUN set -xe; \
mv /usr/local/bin/bun /usr/bin/bun; \
mkdir /self; \
ln -sfn /usr/bin/bun /self/exe

FROM alpine:3 AS sys

RUN set -xe; \
mkdir -p /target/etc; \
mkdir -p /blank; \
apk --no-cache add \
  ca-certificates \
  tzdata \
; \
update-ca-certificates; \
ln -sf /usr/share/zoneinfo/Etc/UTC /target/etc/localtime; \
echo "Etc/UTC" > /target/etc/timezone;

FROM scratch

COPY --from=bun /self /proc/self
COPY --from=bun /usr/bin/bun /usr/bin/bun

COPY --from=bun /lib/x86_64-linux-gnu/libc.so.6 /lib/x86_64-linux-gnu/libc.so.6
COPY --from=bun /lib/x86_64-linux-gnu/libdl.so.2 /lib/x86_64-linux-gnu/libdl.so.2
COPY --from=bun /lib/x86_64-linux-gnu/libm.so.6 /lib/x86_64-linux-gnu/libm.so.6
COPY --from=bun /lib/x86_64-linux-gnu/libpthread.so.0 /lib/x86_64-linux-gnu/libpthread.so.0
COPY --from=bun /lib64/ld-linux-x86-64.so.2 /lib64/ld-linux-x86-64.so.2

COPY --from=sys /target/etc /etc
COPY --from=sys /usr/share/zoneinfo/UTC /usr/share/zoneinfo/UTC
COPY --from=sys /usr/share/zoneinfo/Etc/UTC /usr/share/zoneinfo/Etc/UTC
COPY --from=sys /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
COPY --from=sys /blank /tmp

COPY ./server.ts /usr/src/server.ts

server.ts

const port = process.env.PORT || 3000;

console.log(
`Launching Bun HTTP server on port: ${port}, url: http://0.0.0.0:${port} 🚀`
);

Bun.serve({
port: port,
fetch(_request) {
return new Response("Hello, World!\n");
},
});

Lines in the Kraftfile have the following roles:

• spec: v0.6: The current Kraftfile specification version is 0.6.

• runtime: base-compat:latest: The kernel to use.

• rootfs: ./Dockerfile: Build the application root filesystem using the Dockerfile.

• cmd: ["/usr/bin/bun", "run", "/usr/src/server.ts"]: Use /usr/bin/bun run /usr/src/server.ts as the starting command of the instance.

Lines in the Dockerfile have the following roles:

• FROM scratch: Build the filesystem from the scratch container image, to create a base image.

• COPY ...: Copy required files to the application filesystem: the bun binary executable, libraries, configuration files, the /usr/src/server.ts implementation.

• RUN ...: Run specific commands to generate or to prepare the filesystem contents.

The following options are available for customizing the application:

• If only updating the implementation in the server.ts source file, no other change is required.

• If you want to add additional files, you need to copy them into the filesystem using the COPY command in the Dockerfile.

• If you want to replace server.ts with a different source file, update the cmd line in the Kraftfile and replace /usr/src/server.ts with the path to your new source file.

• More extensive changes may require extending the Dockerfile with additional Dockerfile commands.

Learn More

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

kraft cloud --help

Or visit the CLI Reference.