Can I install /bin/bash on the Docker image?

[mrsimonemms]

Question / Where do you need Help?

I work at Gitpod and trying to use K3d as a simple way of getting self-hosted running fast and simply. One part of the installation process is an nsenter command which runs a bash script on the node

As far as I can make out, the Docker image does not have /bin/bash included. Is there a way I can get bash installed? I don't mind it being done at runtime, in fact I'd prefer that as means can rely on the official images. I'm writing this bootstrapper as a script, so don't mind doing docker exec commands

I've tried mounting /bin/bash from my host machine and renaming ash with bash and these haven't worked.

Scope of your Question

• Is your question related to a specific version of k3d (or k3s)? No, I've tried it with various versions of k3d and with different k3s images
  • Please paste the output of k3d version here

k3d version v5.2.2
k3s version v1.21.7-k3s1 (default)

[iwilltry42]

Hi @mrsimonemms , thanks for opening this discussion!
The image is built on K3s' side: https://github.com/k3s-io/k3s/blob/master/package/Dockerfile
It's FROM scratch with K3s, K3s dependencies and busybox included, so there's no package manager that you could use.
Actually, the script you mention will also call systemctl, which is also not included in the image 🤔

[mrsimonemms]

Thanks @iwilltry42.

I've "solved" the issue by creating a custom Dockerfile. It's a little rough-and-ready, but it seems to work fairly well for my needs. Strangely, trying it the other way round (eg, create an Alpine image, install bash and import into the k3s image) didn't work - the bash binary kept complaining. However, I'm happy enough with this approach

Thanks for pointing out systemctl - I imagine I'd have found that as an issue had I continued with Busybox.

# @link https://github.com/k3s-io/k3s/blob/master/package/Dockerfile
ARG K3S_VERSION=v1.21.7-k3s1
FROM rancher/k3s:${K3S_VERSION} AS k3s

FROM alpine
COPY --from=k3s / /
RUN apk add --no-cache bash
## This is as per-the parent image
RUN chmod 1777 /tmp
VOLUME /var/lib/kubelet
VOLUME /var/lib/rancher/k3s
VOLUME /var/lib/cni
VOLUME /var/log
ENV PATH="$PATH:/bin/aux"
ENV CRI_CONFIG_FILE="/var/lib/rancher/k3s/agent/etc/crictl.yaml"
ENTRYPOINT ["/bin/k3s"]
CMD ["agent"]