What is the idiomatic way to write a docker file for building against many different versions of the same compiler?
I have a project which tests against a wide-range of versions of different compilers like gcc and clang as part of a CI job. At some point, the agents for the CI tasks were updated/changed, resulting in newer jobs failing -- and so I've started looking into dockerizing these builds to try to guarantee better reliability and stability.
However, I'm having some difficulty understanding what a proper and idiomatic approach is to producing build images like this without causing a large amount of duplication caused by layers.
For example, let's say I want to build using the following toolset:
gcc 4.8, 4.9, 5.1, ... (various versions)
cmake (latest)
ninja-build
I could write something like:
# syntax=docker/dockerfile:1.3-labs
# Parameterizing here possible, but would cause bloat from duplicated
# layers defined after this
FROM gcc:4.8
ENV DEBIAN_FRONTEND noninteractive
# Set the work directory
WORKDIR /home/dev
COPY . /home/dev/
# Install tools (cmake, ninja, etc)
# this will cause bloat if the FROM layer changes
RUN <<EOF
apt update
apt install -y cmake ninja-build
rm -rf /var/lib/apt/lists/*
EOF
# Default command is to use CMak
CMD ["cmake"]
However, the installation of tools like ninja-build and cmake occur after the base image, which changes per compiler version. Since these layers are built off of a different parent layer, this would (as far as I'm aware) result in layer duplication for each different compiler version that is used.
One alternative to avoid this duplication could hypothetically be using a smaller base image like alpine with separate installations of the compiler instead. The tools could be installed first so the layers remain shared, and only the compiler changes as the last layer -- however this presents its own difficulties, since it's often the case that certain compiler versions may require custom steps, such as installing certain keyrings.
What is the idiomatic way of accomplishing this? Would this typically be done through multiple docker files, or a single docker file with parameters? Any examples would be greatly appreciated.
I would separate the parts of preparing the compiler and doing the calculation, so the source doesn't become part of the docker container.
Prepare Compiler
For preparing the compiler I would take the ARG approach but without copying the data into the container. In case you wanna fast retry while having enough resources you could spin up multiple instances the same time.
ARG COMPILER=gcc:4.8
FROM ${COMPILER}
ENV DEBIAN_FRONTEND noninteractive
# Install tools (cmake, ninja, etc)
# this will cause bloat if the FROM layer changes
RUN <<EOF
apt update
apt install -y cmake ninja-build
rm -rf /var/lib/apt/lists/*
EOF
# Set the work directory
VOLUME /src
WORKDIR /src
CMD ["cmake"]
Build it
Here you have few options. You could either prepare a volume with the sources or use bind mounts together with docker exec like this:
#bash style
for compiler in gcc:4.9 gcc:4.8 gcc:5.1
do
docker build -t mytag-${compiler} --build-arg COMPILER=${compiler} .
# place to clean the target folder
docker run -v $(pwd)/src:/src mytag-${compiler}
done
And because the source is not part of the docker image you don't have bloat. You can also have two mounts, one for a readonly source tree and one for the output files.
Note: If you remove the CMake command you could also spin up the docker containers in parallel and use docker exec to start the build. The downside of this is that you have to take care of out of source builds to avoid clashes on the output folder.
put an ARG before the FROM and then invoke the ARG as the FROM
so:
ARG COMPILER=gcc:4.8
FROM ${COMPILER}
# rest goes here
then you
docker build . -t test/clang-8 --build-args COMPILER=clang-8
or similar.
If you want to automate just make a list of compilers and a bash script looping over the lines in your file, and paste the lines as inputs to the tag and COMPILER build args.
As for Cmake, I'd just do:
RUN wget -qO- "https://cmake.org/files/v3.23/cmake-3.23.1-linux-"$(uname -m)".tar.gz" | tar --strip-components=1 -xz -C /usr/local
When copying, I find it cleaner to do
WORKDIR /app/build
COPY . .
edit: formatting
As far as I know, there is no way to do that easily and safely. You could use a RUN --mount=type=cache, but the documentation clearly says that:
Contents of the cache directories persist between builder invocations without invalidating the instruction cache. Cache mounts should only be used for better performance. Your build should work with any contents of the cache directory as another build may overwrite the files or GC may clean it if more storage space is needed.
I have not tried it but I guess the layers are duplicated anyway, you just save time, assuming the cache is not emptied.
The other possible solution you have is similar to the one you mention in the question: starting with the tools installation and then customizing it with the gcc image. Instead of starting with an alpine image, you could start FROM scratch. scratch is basically the empty image, you could COPY the files generated by
RUN <<EOF
apt update
apt install -y cmake ninja-build
rm -rf /var/lib/apt/lists/*
EOF
Then you COPY the entire gcc filesystem. However, I am not sure it will work because the order of the initial layers is now reversed. This means that some files that were in the upper layer (coming from tools) now are in the lower layer and could be overwritten. In the comments, I asked you for a working Dockerfile because I wanted to try this out before answering. If you want, you can try this method and let us know. Anyway, the first step is extracting the files created from the tools layer.
How to extract changes from a layer?
Let's consider this Dockerfile and build it with docker build -t test .:
FROM debian:10
RUN apt update && apt install -y cmake && ( echo "test" > test.txt )
RUN echo "new test" > test.txt
Now that we have built the test image, we should find 3 new layers. You mainly have 2 ways to extract the changes from each layer:
the first is docker inspecting the image and then find the ids of the layers in the /var/lib/docker folder, assuming you are on Linux. Each layer has a diff subfolder containing the changes. Actually, I think it is more complex than this, that is why I would opt for...
skopeo: you can install it with apt install skopeo and it is a very useful tool to operate on docker images. The command you are interested in is copy, that extracts the layers of an image and export them as .tar:
skopeo copy docker-daemon:{image_name}:latest "dir:/home/test_img"
where image_name is test in this case.
Extracting layer content with Skopeo
In the specified folder, you should find some tar files and a configuration file (look at the skopeo copy command output and you will know which one is that). Then extract each {layer}.tar in a different folder and you are done.
Note: to find the layer containing your tools just open the configuration file (maybe using jq because it is json) and take the diff_id that corresponds to the RUN instruction you find in the history property. You should understand it once you open the JSON configuration. This is unnecessary if you have a small image that has, for example, debian as parent image and a single RUN instruction containing the tools you want to install.
Get GCC image content
Now that we have the tool layer content, we need to extract the gcc filesystem. we don't need skopeo for this one, but docker export is enough:
create a container from gcc (with the tag you need):
docker create --name gcc4.8 gcc:4.8
export it as tar:
docker export -o gcc4.8.tar gcc4.8
finally extract the tar file.
Putting all together
The final Dockerfile could be something like:
FROM scratch
COPY ./tools_layer/ /
COPY ./gcc_4.x/ /
In this way, the tools layer is always reused (unless you change the content of that folder, of course), but you can parameterize the gcc_4.x with the ARG instruction for example.
Read carefully: all of this is not tested but you might encounter 2 issues:
the gcc image overwrites some files you have changed in the tools layer. You could check if this happens by computing the diff between the gcc layer folder and the tools layer folder. If it happens, you can only keep track of that file/s and add it/them in the dockerfile after the COPY ./gcc ... with another COPY.
When in the upper layer a file is removed, docker marks that file with a .wh extension (not sure if it is different with skopeo). If in the tools layer you delete a file that exists in the gcc layer, then that file will not be deleted using the above Dockerfile (the COPY ./gcc ... instruction would overwrite the .wh). In this case too, you would need to add an additional RUN rm ... instruction.
This is probably not the correct approach if you have a more complex image that the one you are showing us. In my opinion, you could give this a try and just see if this works out with a single Dockerfile. Obviously, if you have many compilers, each one having its own tools set, the maintainability of this approach could be a real burden. Instead, if the Dockerfile is more or less linear for all the compilers, this might be good (after all, you do not do this every day).
Now the question is: is avoiding layer replication so important that you are willing to complicate the image-building process this much?
How do I make my COPY command work for absolute paths on Windows? I tried git-bash, cmd and powershell consoles to build with docker build -t custom-maven-image .
# Dockerfile
FROM maven:3-openjdk-11-slim
# these are three versions of copy command I tried
COPY C:/Users/myuser/.m2 /root/.m2
COPY /C/Users/myuser/.m2 /root/.m2
COPY /c/Users/myuser/.m2 /root/.m2
What I get is an error:
...
#5 ERROR: "/C/Users/myuser/.m2" not found: not found
UPDATE:
Thx #Jeremy for bugs references and now I see that docs clearly says:
COPY obeys the following rules:
The path must be inside the context of the build; you cannot
COPY ../something /something, because the first step of a docker build
is to send the context directory (and subdirectories) to the docker
daemon.
All the resources need to be in the dir that you run the build, i.e. where your Dockerfile is. You cant use an absolute path from elsewhere, think of it from the build perspective - where is the build happening - in the Dockerfile? It can run commands but those resources need to be public.
https://github.com/moby/moby/issues/4592
https://github.com/docker/compose/issues/4857
I want to use variables across multi-stage docker builds. Similar to This question (unanswered at the time of writing.)
My specific use case is to build my Go project in a builder stage and save the directory this is done in in a variable and use the same variable in the next stage(s): The BUILD_DIR variable.
My Dockerfile is (The example in the commented lines doesn't work.):
FROM golang:1.11.5 as builder
WORKDIR /project-name
# What I want to do:
#ENV BUILD_DIR /project-name
#WORKDIR ${BUILD_DIR}
# Vendored dependencies of my project:
COPY ./vendor ./vendor
COPY ./*.go ./
# Source code:
COPY ./go.* ./
RUN GOFLAGS=-mod=vendor GOOS=linux go build .
FROM something-else:some-version
WORKDIR some-folder
# Executable from previous stage:
COPY --from=builder /project-name/executable-name .
# Config files:
COPY ./conf ./conf
# What I want to do to copy the executable:
#COPY --from=builder /${BUILD_DIR}/executable-name .
ENTRYPOINT ["./executable-name"]
To send variable we can use "ARG" solution, the "base" solution, and "file" solution.
ARG version_default=v1
FROM alpine:latest as base1
ARG version_default
ENV version=$version_default
RUN echo ${version}
RUN echo ${version_default}
FROM alpine:latest as base2
ARG version_default
RUN echo ${version_default}
another way is to use base container for multiple stages:
FROM alpine:latest as base
ARG version_default
ENV version=$version_default
FROM base
RUN echo ${version}
FROM base
RUN echo ${version}
You can find more details here: https://github.com/moby/moby/issues/37345
Also you could save the hash into a file in the first stage, and copy the file in the second stage and then read it and use it there.
From what I understand you want to copy the built program into the new docker for multistage build that the output size is smaller.
Basically you do not need to send a variable you need to know were you built it in the first image and copy it from there
FROM golang:alpine as gobuilder
RUN apk update && apk add git
COPY sources/src/ $GOPATH/src/folder/
WORKDIR $GOPATH/src/folder/
#get dependencies
RUN go get -d -v
#build the binary
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -installsuffix cgo -ldflags="-w -s" -o /go/bin/myGoProgram myGoSource.go
FROM alpine:latest
COPY --from=gobuilder /go/bin/myGoProgram /usr/local/bin/myGoProgram
ENTRYPOINT ["myGoProgram"] # or ENTRYPOINT ["/usr/local/bin/myGoProgram"]
I'm working on a github repo which I just cloned. I have a new virtual environment and I'd like to add all of the packages from the requirements.txt file to the virtual env.
For some reason it is not finding my requirements.txt file.
Edit the first line of /Users/byrd/Desktop/Github Repositories/herokusite/venv/bin/pip file to correct the path to python. You can obtain this path by calling which python. I think it should be:
#!/Users/byrd/Desktop/Github\ Repositories/herokusite/venv/bin/python
EDIT: Seems like it is a known bug in unixes - you can't use spaces in shebang line.
Also try this workaround, it may help you.
Do not use spaces in any component of the path where your virtual environment is stored.
It causes problems for the bootstrapping process.
Create a new blank environment, in a directory that has no spaces in its path:
$ cd # this takes you to your home directory, in OSX its is /Users/yourlogin
$ cd Desktop
$ virtualenv myvenv
$ source myvenv/bin/activate
(myvenv) $ pip install -r /path/to/requirements.txt
first, execute which pip after activating the environment if you found a space between any of the folders like
as seen in this link
you must have noticed a space between the folder name
2nd july
next, delete the new virualenv (in my case envname) and rename the folder with space between its name
then create a new virual environment and then install the requirements through
pip install -r requirements.txt
on the folder location with the requirements file
I´m trying to build my gradle projects from other locations than the project folder itself, but it always says it couldn´t find build task.
What I´ve tried so far:
sudo ./myprojects/myapp/gradlew build
sudo ./myprojects/myapp/gradlew ./myprojects/myapp/build
How can I execute a gradle build task from any location?
Various people have written (and published) scripts to execute gradlew from any subproject directory (in a multi-project build). To reliably execute Gradle from any subdirectory, it is necessary to set the "current project directory" via -p. It would be nice to have this restriction lifted (this would make a good feature request).
You may try this script, which is 90-lines long: https://github.com/dougborg/gdub
Or use this straightforward one-liner I use myself:
function lookupgradle() {
find . .. ../.. ../../.. ../../../.. ../../../../.. ../../../../../.. -maxdepth 1 -name 'gradlew' -executable -print -quit
}
alias g='$(lookupgradle)'
If you'll find out that it is still required to specify project directory, add -p .:
alias g='$(lookupgradle) -p .'
./usmobile-microservice/gradlew -p ./usmobile-microservice clean buildUI
./project_directory/gradlew -p ./project_directory clean build
worked for me