You can also use the snapcore/snapcraft image.
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not certain what that means.
Do you mean there is a docker snapcore/snapcraft image ?
I agree, I think this topic should be closed and point to the other one
Also, the other topic reads better on docs.snapcraft.io: https://docs.snapcraft.io/building-the-snap-on-docker/6757 reads better and is more consistent than https://docs.snapcraft.io/build-on-docker/4158, which also appears to suffer from some formatting issues converting from here
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Hello,
I think this doc should be superseded by https://docs.snapcraft.io/building-the-snap-on-docker/6757
First of all, it gives docker installation instruction which seems out of scope (and a moving target depending on version of ubuntu and docker).
Then it uses sudo to interact with docker, which is not needed if the user is in the docker group.
Finally, it forgets to mention the command to be run against the docker container, so:
$ sudo docker run -v "$PWD":/snapcraft_build \
-w /snapcraft_build snapcore/snapcraft
$ snapcraft
This doesn’t result in an interactive shell, so either it should be something like (-it was added to Keep STDIN open even if not attached and Allocate a pseudo-TTY; we could also add --rm to clean after the operation):
$ docker run -it -v "$PWD:/snapcraft_build" -w /snapcraft_build snapcore/snapcraft
# snapcraft // <-- this is being executed within the container
Or something like the other page suggests (different folder names don’t matter, but snapcraft at the end does).
$ docker run -v "$PWD":/build -w /build snapcore/snapcraft snapcraft
Another things is that we need more than just snapcraft, see Building the snap on Docker
I think this should be updated to mention that before running snapcraft from the container, apt update needs to be run, because as it is the snapcore/snapcraft docker image has out of date apt sources and as such snapcraft will fail to install/download packages when using apt because the sources/sites are out of date
What do you folks think?
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Thanks for the input on this important topic. And yes, we should have only a single doc for Docker - and make sure it works - I’ll look into merging the two together, or reverting to the newer version, as suggested.
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The docker command should probably read docker run --rm -v ... otherwise each run will leave a container behind.
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Great point - thanks! I’ll add it to the command.
The current format of a snapcraft.yaml allows values for “title” and “license”. But when using the “snapcore/snapcraft” Docker image, I get:
Issues while validating snapcraft.yaml: Additional properties are not allowed (‘title’, ‘license’ were unexpected)
Also, it’s confusing to have seemingly two official Docker Hub organizations, both with seemingly outdated images:
The first one looks to be “more official” because of the Ubuntu logo and link to the website, but the official snapcraft docs link to the second one.
@pans validation error is because default image, which is latest, contains outdated 2.43.1 version of snapcraft. I filled https://bugs.launchpad.net/snapcraft/+bug/1823519 to track this.
Is there a core18 version of Dockerfile?
Just changing from xenial to bionic does not cut it. It seems that line 12:
RUN curl -L $(curl -H ‘X-Ubuntu-Series: 16’ ‘https://api.snapcraft.io/api/v1/snaps/details/core’ | jq ‘.download_url’ -r) --output core.snap
should reference Series: 18 and have a different core downloaded.
Any thoughts?
. Check Thanks for the prompt reply! I got it working on my Mac with a few other changes. It’s slower than multipass to build, but at least I don’t have to shut down my Vbox instances to run it.
On https://snapcraft.io/docs/build-on-docker the example Dockerfile for building for core18 first references ubuntu:bionic, but then in the middle is based on ubuntu:xenial before the copy commands
The script postet by @kyrofa is more like I expected. This script additionally downloads the core18 snap, which the documentation does not do.
I propose the following changes to the documentation
FROM ubuntu:bionic as builder
# Grab dependencies
RUN apt-get update
RUN apt-get dist-upgrade --yes
RUN apt-get install --yes \
curl \
jq \
squashfs-tools
# Grab the core snap from the stable channel and unpack it in the proper place
RUN curl -L $(curl -H 'X-Ubuntu-Series: 16' 'https://api.snapcraft.io/api/v1/snaps/details/core' | jq '.download_url' -r) --output core.snap
RUN mkdir -p /snap/core
RUN unsquashfs -d /snap/core/current core.snap
+# Grab the core18 snap from the stable channel and unpack it in the proper place
+RUN curl -L $(curl -H 'X-Ubuntu-Series: 16' 'https://api.snapcraft.io/api/v1/snaps/details/core18' | jq '.download_url' -r) --output core18.snap
+RUN mkdir -p /snap/core18
+RUN unsquashfs -d /snap/core18/current core18.snap
+
# Grab the snapcraft snap from the stable channel and unpack it in the proper place
RUN curl -L $(curl -H 'X-Ubuntu-Series: 16' 'https://api.snapcraft.io/api/v1/snaps/details/snapcraft?channel=stable' | jq '.download_url' -r) --output snapcraft.snap
RUN mkdir -p /snap/snapcraft
RUN unsquashfs -d /snap/snapcraft/current snapcraft.snap
# Create a snapcraft runner (TODO: move version detection to the core of snapcraft)
RUN mkdir -p /snap/bin
RUN echo "#!/bin/sh" > /snap/bin/snapcraft
RUN snap_version="$(awk '/^version:/{print $2}' /snap/snapcraft/current/meta/snap.yaml)" && echo "export SNAP_VERSION=\"$snap_version\"" >> /snap/bin/snapcraft
RUN echo 'exec "$SNAP/usr/bin/python3" "$SNAP/bin/snapcraft" "$@"' >> /snap/bin/snapcraft
RUN chmod +x /snap/bin/snapcraft
# Multi-stage build, only need the snaps from the builder. Copy them one at a
# time so they can be cached.
-FROM ubuntu:xenial
+FROM ubuntu:bionic
COPY --from=builder /snap/core /snap/core
+COPY --from=builder /snap/core18 /snap/core18
COPY --from=builder /snap/snapcraft /snap/snapcraft
COPY --from=builder /snap/bin/snapcraft /snap/bin/snapcraft
# Generate locale
RUN apt-get update && apt-get dist-upgrade --yes && apt-get install --yes sudo locales && locale-gen en_US.UTF-8
# Set the proper environment
ENV LANG="en_US.UTF-8"
ENV LANGUAGE="en_US:en"
ENV LC_ALL="en_US.UTF-8"
ENV PATH="/snap/bin:$PATH"
ENV SNAP="/snap/snapcraft/current"
ENV SNAP_NAME="snapcraft"
ENV SNAP_ARCH="amd64"
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Thank you for proposing those changes! I’ve merged them into the documented script.
I also added snapd as a dependency because, while testing, the image build failed with A tool snapcraft depends on could not be found: ‘snap’. I believe snapcraft now requires snapd externally.
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After some internal discussion, I updated the sample Dockerfile to add Snap-CDN: none HTTP headers in order to work properly in the Launchpad build farm.
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Hi @degville & others,
Thanks for this helpful thread & info. I tried out the build in Docker and that absolutely works fine. However, the point raised by @kyrofa is still valid: There is a prebuilt Docker image on Dockerhub from the organisation “snapcraft”, which contains images that are hopelessly outdated: snapcraft’s Profile | Docker Hub
And there is a Dockerhub org “snapcore” which does seem to contain an up to date Docker image that matches the current Dockerfile from the snapcraft repo: snapcore’s Profile | Docker Hub
Is there a way we could improve this? Could we link from these docs directly to the correct Dockerhub? That would help save people wanting to use Docker some time.
Kind regards,
Brecht
FYI, an anecdote, but I’ve had to move away from docker entirely because snapcraft’s core plugins are making wider use of build-snaps, which don’t work on docker. Tread carefully.
Hi,
Thanks for the heads-up. This got me thinking: wouldn’t you agree that “limitations of using Docker for building snaps” would be an interesting paragraph to mention on a “Build on Docker” doc page too?
The explanation you wrote here: Reasoning behind the move to multipass - snapcraft - snapcraft.io is a great read, you explain it there very nicely.
Kind regards,
Brecht