Compose from arbitrary folder with files in build context and Dockerfile folder

Compose from arbitrary folder with files in build context and Dockerfile folder - docker

I'd like to compose a service while keeping the file structure of my project neat. But Docker appears to have issues with paths outside the build context. I'm creating a package and would like to keep all Docker related stuff in a folder under the project root. But I can't find a way to reference the project files from docker-compose and Dockerfile. When creating the containers files from the project must be copied.
Here's my current project structure:
root/
docker/
docker-compose.yml
Dockerfile
docker_resource.txt
config
src/
project-files.whatever
root-files.txt
Now if I $cd docker and $docker-compose up, there are two possibilities that I've tried. Either my Dockerfile copies the files with COPY .. /path/in/container or the compose file has build instructions like:
x-build: &my-build
context: ..
dockerfile: docker/Dockerfile
The first approach doesn't work. Apparently Dockerfile cannot reference anything outside the build context. The second approach appears to work, but only after I edit my copy command from docker_resource.txt to docker/docker_resource.txt. Ideally I'd like to retain the ability to docker build from ./docker and keep the things clean - not having to worry about the composing context in the Dockerfile. Is this possible?
Minimally I'm after a way to have docker related files in an arbitrary folder and to be able to specify the build context in the compose file without additional changes.

You need to treat src/project-files.whatever like a self-sufficient minimal build. I would put a Dockerfile inside src. It should be treated as part of the project, and should be specific to it. You would still need to edit your copy command though.
root/
docker/
docker-compose.yml
docker_resource.txt
config
src/
project-files.whatever
Dockerfile
root-files.txt
You want to separate your compose and Dockerfile and resources anyway. Depending on what is inside docker_resourceyou may want to move it into src. Think the image as the program itself, with no configuration. I suggest putting resource / config stuff in a volume so that you wouldn't have to rebuild from scratch with every change.
Another way to do it is to put Dockerfile one level above and allow your root to be the build context. Your structure would be something like this in that case:
/root
Dockerfile
docker-compose.yml
docker_resource.txt
config
src/
project-files.whatever
root-Files/
root-files.txt
Not sure if you like that.

Related

Copy the files from other folder in docker container using docker compose [duplicate]

How can I include files from outside of Docker's build context using the "ADD" command in the Docker file?
From the Docker documentation:
The path must be inside the context of the build; you cannot ADD
../something/something, because the first step of a docker build is to
send the context directory (and subdirectories) to the docker daemon.
I do not want to restructure my whole project just to accommodate Docker in this matter. I want to keep all my Docker files in the same sub-directory.
Also, it appears Docker does not yet (and may not ever) support symlinks: Dockerfile ADD command does not follow symlinks on host #1676.
The only other thing I can think of is to include a pre-build step to copy the files into the Docker build context (and configure my version control to ignore those files). Is there a better workaround for than that?

The best way to work around this is to specify the Dockerfile independently of the build context, using -f.
For instance, this command will give the ADD command access to anything in your current directory.
docker build -f docker-files/Dockerfile .
Update: Docker now allows having the Dockerfile outside the build context (fixed in 18.03.0-ce). So you can also do something like
docker build -f ../Dockerfile .

I often find myself utilizing the --build-arg option for this purpose. For example after putting the following in the Dockerfile:
ARG SSH_KEY
RUN echo "$SSH_KEY" > /root/.ssh/id_rsa
You can just do:
docker build -t some-app --build-arg SSH_KEY="$(cat ~/file/outside/build/context/id_rsa)" .
But note the following warning from the Docker documentation:
Warning: It is not recommended to use build-time variables for passing secrets like github keys, user credentials etc. Build-time variable values are visible to any user of the image with the docker history command.

I spent a good time trying to figure out a good pattern and how to better explain what's going on with this feature support. I realized that the best way to explain it was as follows...
Dockerfile: Will only see files under its own relative path
Context: a place in "space" where the files you want to share and your Dockerfile will be copied to
So, with that said, here's an example of the Dockerfile that needs to reuse a file called start.sh
Dockerfile
It will always load from its relative path, having the current directory of itself as the local reference to the paths you specify.
COPY start.sh /runtime/start.sh
Files
Considering this idea, we can think of having multiple copies for the Dockerfiles building specific things, but they all need access to the start.sh.
./all-services/
/start.sh
/service-X/Dockerfile
/service-Y/Dockerfile
/service-Z/Dockerfile
./docker-compose.yaml
Considering this structure and the files above, here's a docker-compose.yml
docker-compose.yaml
In this example, your shared context directory is the runtime directory.
Same mental model here, think that all the files under this directory are moved over to the so-called context.
Similarly, just specify the Dockerfile that you want to copy to that same directory. You can specify that using dockerfile.
The directory where your main content is located is the actual context to be set.
The docker-compose.yml is as follows
version: "3.3"
services:
service-A
build:
context: ./all-service
dockerfile: ./service-A/Dockerfile
service-B
build:
context: ./all-service
dockerfile: ./service-B/Dockerfile
service-C
build:
context: ./all-service
dockerfile: ./service-C/Dockerfile
all-service is set as the context, the shared file start.sh is copied there as well the Dockerfile specified by each dockerfile.
Each gets to be built their own way, sharing the start file!

On Linux you can mount other directories instead of symlinking them
mount --bind olddir newdir
See https://superuser.com/questions/842642 for more details.
I don't know if something similar is available for other OSes.
I also tried using Samba to share a folder and remount it into the Docker context which worked as well.

If you read the discussion in the issue 2745 not only docker may never support symlinks they may never support adding files outside your context. Seems to be a design philosophy that files that go into docker build should explicitly be part of its context or be from a URL where it is presumably deployed too with a fixed version so that the build is repeatable with well known URLs or files shipped with the docker container.
I prefer to build from a version controlled source - ie docker build
-t stuff http://my.git.org/repo - otherwise I'm building from some random place with random files.
fundamentally, no.... -- SvenDowideit, Docker Inc
Just my opinion but I think you should restructure to separate out the code and docker repositories. That way the containers can be generic and pull in any version of the code at run time rather than build time.
Alternatively, use docker as your fundamental code deployment artifact and then you put the dockerfile in the root of the code repository. if you go this route probably makes sense to have a parent docker container for more general system level details and a child container for setup specific to your code.

I believe the simpler workaround would be to change the 'context' itself.
So, for example, instead of giving:
docker build -t hello-demo-app .
which sets the current directory as the context, let's say you wanted the parent directory as the context, just use:
docker build -t hello-demo-app ..

You can also create a tarball of what the image needs first and use that as your context.
https://docs.docker.com/engine/reference/commandline/build/#/tarball-contexts

This behavior is given by the context directory that the docker or podman uses to present the files to the build process.
A nice trick here is by changing the context dir during the building instruction to the full path of the directory, that you want to expose to the daemon.
e.g:
docker build -t imageName:tag -f /path/to/the/Dockerfile /mysrc/path
using /mysrc/path instead of .(current directory), you'll be using that directory as a context, so any files under it can be seen by the build process.
This example you'll be exposing the entire /mysrc/path tree to the docker daemon.
When using this with docker the user ID who triggered the build must have recursively read permissions to any single directory or file from the context dir.
This can be useful in cases where you have the /home/user/myCoolProject/Dockerfile but want to bring to this container build context, files that aren't in the same directory.
Here is an example of building using context dir, but this time using podman instead of docker.
Lets take as example, having inside your Dockerfile a COPY or ADDinstruction which is copying files from a directory outside of your project, like:
FROM myImage:tag
...
...
COPY /opt/externalFile ./
ADD /home/user/AnotherProject/anotherExternalFile ./
...
In order to build this, with a container file located in the /home/user/myCoolProject/Dockerfile, just do something like:
cd /home/user/myCoolProject
podman build -t imageName:tag -f Dockefile /
Some known use cases to change the context dir, is when using a container as a toolchain for building your souce code.
e.g:
podman build --platform linux/s390x -t myimage:mytag -f ./Dockerfile /tmp/mysrc
or it can be a path relative, like:
podman build --platform linux/s390x -t myimage:mytag -f ./Dockerfile ../../
Another example using this time a global path:
FROM myImage:tag
...
...
COPY externalFile ./
ADD AnotherProject ./
...
Notice that now the full global path for the COPY and ADD is omitted in the Dockerfile command layers.
In this case the contex dir must be relative to where the files are, if both externalFile and AnotherProject are in /opt directory then the context dir for building it must be:
podman build -t imageName:tag -f ./Dockerfile /opt
Note when using COPY or ADD with context dir in docker:
The docker daemon will try to "stream" all the files visible on the context dir tree to the daemon, which can slowdown the build. And requires the user to have recursively permission from the context dir.
This behavior can be more costly specially when using the build through the API. However,with podman the build happens instantaneously, without needing recursively permissions, that's because podman does not enumerate the entire context dir, and doesn't use a client/server architecture as well.
The build for such cases can be way more interesting to use podman instead of docker, when you face such issues using a different context dir.
Some references:
https://docs.docker.com/engine/reference/commandline/build/
https://docs.podman.io/en/latest/markdown/podman-build.1.html

As is described in this GitHub issue the build actually happens in /tmp/docker-12345, so a relative path like ../relative-add/some-file is relative to /tmp/docker-12345. It would thus search for /tmp/relative-add/some-file, which is also shown in the error message.*
It is not allowed to include files from outside the build directory, so this results in the "Forbidden path" message."

Using docker-compose, I accomplished this by creating a service that mounts the volumes that I need and committing the image of the container. Then, in the subsequent service, I rely on the previously committed image, which has all of the data stored at mounted locations. You will then have have to copy these files to their ultimate destination, as host mounted directories do not get committed when running a docker commit command
You don't have to use docker-compose to accomplish this, but it makes life a bit easier
# docker-compose.yml
version: '3'
services:
stage:
image: alpine
volumes:
- /host/machine/path:/tmp/container/path
command: bash -c "cp -r /tmp/container/path /final/container/path"
setup:
image: stage
# setup.sh
# Start "stage" service
docker-compose up stage
# Commit changes to an image named "stage"
docker commit $(docker-compose ps -q stage) stage
# Start setup service off of stage image
docker-compose up setup

Create a wrapper docker build shell script that grabs the file then calls docker build then removes the file.
a simple solution not mentioned anywhere here from my quick skim:
have a wrapper script called docker_build.sh
have it create tarballs, copy large files to the current working directory
call docker build
clean up the tarballs, large files, etc
this solution is good because (1.) it doesn't have the security hole from copying in your SSH private key (2.) another solution uses sudo bind so that has another security hole there because it requires root permission to do bind.

I think as of earlier this year a feature was added in buildx to do just this.
If you have dockerfile 1.4+ and buildx 0.8+ you can do something like this
docker buildx build --build-context othersource= ../something/something .
Then in your docker file you can use the from command to add the context
ADD –from=othersource . /stuff
See this related post https://www.docker.com/blog/dockerfiles-now-support-multiple-build-contexts/

Workaround with links:
ln path/to/file/outside/context/file_to_copy ./file_to_copy
On Dockerfile, simply:
COPY file_to_copy /path/to/file

I was personally confused by some answers, so decided to explain it simply.
You should pass the context, you have specified in Dockerfile, to docker when
want to create image.
I always select root of project as the context in Dockerfile.
so for example if you use COPY command like COPY . .
first dot(.) is the context and second dot(.) is container working directory
Assuming the context is project root, dot(.) , and code structure is like this
sample-project/
docker/
Dockerfile
If you want to build image
and your path (the path you run the docker build command) is /full-path/sample-project/,
you should do this
docker build -f docker/Dockerfile .
and if your path is /full-path/sample-project/docker/,
you should do this
docker build -f Dockerfile ../

An easy workaround might be to simply mount the volume (using the -v or --mount flag) to the container when you run it and access the files that way.
example:
docker run -v /path/to/file/on/host:/desired/path/to/file/in/container/ image_name
for more see: https://docs.docker.com/storage/volumes/

I had this same issue with a project and some data files that I wasn't able to move inside the repo context for HIPAA reasons. I ended up using 2 Dockerfiles. One builds the main application without the stuff I needed outside the container and publishes that to internal repo. Then a second dockerfile pulls that image and adds the data and creates a new image which is then deployed and never stored anywhere. Not ideal, but it worked for my purposes of keeping sensitive information out of the repo.

In my case, my Dockerfile is written like a template containing placeholders which I'm replacing with real value using my configuration file.
So I couldn't specify this file directly but pipe it into the docker build like this:
sed "s/%email_address%/$EMAIL_ADDRESS/;" ./Dockerfile | docker build -t katzda/bookings:latest . -f -;
But because of the pipe, the COPY command didn't work. But the above way solves it by -f - (explicitly saying file not provided). Doing only - without the -f flag, the context AND the Dockerfile are not provided which is a caveat.

How to share typescript code between two Dockerfiles
I had this same problem, but for sharing files between two typescript projects. Some of the other answers didn't work for me because I needed to preserve the relative import paths between the shared code. I solved it by organizing my code like this:
api/
Dockerfile
src/
models/
index.ts
frontend/
Dockerfile
src/
models/
index.ts
shared/
model1.ts
model2.ts
index.ts
.dockerignore
Note: After extracting the shared code into that top folder, I avoided needing to update the import paths because I updated api/models/index.ts and frontend/models/index.ts to export from shared: (eg export * from '../../../shared)
Since the build context is now one directory higher, I had to make a few additional changes:
Update the build command to use the new context:
docker build -f Dockerfile .. (two dots instead of one)
Use a single .dockerignore at the top level to exclude all node_modules. (eg **/node_modules/**)
Prefix the Dockerfile COPY commands with api/ or frontend/
Copy shared (in addition to api/src or frontend/src)
WORKDIR /usr/src/app
COPY api/package*.json ./ <---- Prefix with api/
RUN npm ci
COPY api/src api/ts*.json ./ <---- Prefix with api/
COPY shared usr/src/shared <---- ADDED
RUN npm run build
This was the easiest way I could send everything to docker, while preserving the relative import paths in both projects. The tricky (annoying) part was all the changes/consequences caused by the build context being up one directory.

One quick and dirty way is to set the build context up as many levels as you need - but this can have consequences.
If you're working in a microservices architecture that looks like this:
./Code/Repo1
./Code/Repo2
...
You can set the build context to the parent Code directory and then access everything, but it turns out that with a large number of repositories, this can result in the build taking a long time.
An example situation could be that another team maintains a database schema in Repo1 and your team's code in Repo2 depends on this. You want to dockerise this dependency with some of your own seed data without worrying about schema changes or polluting the other team's repository (depending on what the changes are you may still have to change your seed data scripts of course)
The second approach is hacky but gets around the issue of long builds:
Create a sh (or ps1) script in ./Code/Repo2 to copy the files you need and invoke the docker commands you want, for example:
#!/bin/bash
rm -r ./db/schema
mkdir ./db/schema
cp -r ../Repo1/db/schema ./db/schema
docker-compose -f docker-compose.yml down
docker container prune -f
docker-compose -f docker-compose.yml up --build
In the docker-compose file, simply set the context as Repo2 root and use the content of the ./db/schema directory in your dockerfile without worrying about the path.
Bear in mind that you will run the risk of accidentally committing this directory to source control, but scripting cleanup actions should be easy enough.

Creating my first container in Docker and need a little assistance

I've just installed docker and I'm following the ‘[Getting started tutorial][1]’
[1]: http://localhost/tutorial/our-application/ which is packaged within the Docker install. At the beginning of the tutorial it says...
In order to build the application, we need to use a Dockerfile. A
Dockerfile is simply a text-based script of instructions that is used
to create a container image. Create a file named Dockerfile with the
following contents.....
So far so good, but before issuing the 'Build' command it doesn't specify where I'm supposed to put/save the dockerfile??

You can save your Dockerfile anywhere. You can specify the path to your Dockerfile when running docker build by using flag --file.

A basic Docker folder structure would look something like this:
myapp/
- src/
- Dockerfile
- docker-compose.yml (optional: If you want to use docker-compose)
And the folder structure if you are using multiple services using docker-compose would be:
myapp/
- app1/
- src/
- Dockerfile
- app2/
- src/
- Dockerfile
- docker-compose.yml
But, in these case, you cannot access the files outside the folder containing Dockerfile. In those cases, as mentioned by #Nguyễn you can use a --file flag along with docker build.

problem with Dockerfile copy folder error with absolute or relative path [duplicate]

How can I include files from outside of Docker's build context using the "ADD" command in the Docker file?
From the Docker documentation:
The path must be inside the context of the build; you cannot ADD
../something/something, because the first step of a docker build is to
send the context directory (and subdirectories) to the docker daemon.
I do not want to restructure my whole project just to accommodate Docker in this matter. I want to keep all my Docker files in the same sub-directory.
Also, it appears Docker does not yet (and may not ever) support symlinks: Dockerfile ADD command does not follow symlinks on host #1676.
The only other thing I can think of is to include a pre-build step to copy the files into the Docker build context (and configure my version control to ignore those files). Is there a better workaround for than that?

The best way to work around this is to specify the Dockerfile independently of the build context, using -f.
For instance, this command will give the ADD command access to anything in your current directory.
docker build -f docker-files/Dockerfile .
Update: Docker now allows having the Dockerfile outside the build context (fixed in 18.03.0-ce). So you can also do something like
docker build -f ../Dockerfile .

I often find myself utilizing the --build-arg option for this purpose. For example after putting the following in the Dockerfile:
ARG SSH_KEY
RUN echo "$SSH_KEY" > /root/.ssh/id_rsa
You can just do:
docker build -t some-app --build-arg SSH_KEY="$(cat ~/file/outside/build/context/id_rsa)" .
But note the following warning from the Docker documentation:
Warning: It is not recommended to use build-time variables for passing secrets like github keys, user credentials etc. Build-time variable values are visible to any user of the image with the docker history command.

On Linux you can mount other directories instead of symlinking them
mount --bind olddir newdir
See https://superuser.com/questions/842642 for more details.
I don't know if something similar is available for other OSes.
I also tried using Samba to share a folder and remount it into the Docker context which worked as well.

If you read the discussion in the issue 2745 not only docker may never support symlinks they may never support adding files outside your context. Seems to be a design philosophy that files that go into docker build should explicitly be part of its context or be from a URL where it is presumably deployed too with a fixed version so that the build is repeatable with well known URLs or files shipped with the docker container.
I prefer to build from a version controlled source - ie docker build
-t stuff http://my.git.org/repo - otherwise I'm building from some random place with random files.
fundamentally, no.... -- SvenDowideit, Docker Inc
Just my opinion but I think you should restructure to separate out the code and docker repositories. That way the containers can be generic and pull in any version of the code at run time rather than build time.
Alternatively, use docker as your fundamental code deployment artifact and then you put the dockerfile in the root of the code repository. if you go this route probably makes sense to have a parent docker container for more general system level details and a child container for setup specific to your code.

I believe the simpler workaround would be to change the 'context' itself.
So, for example, instead of giving:
docker build -t hello-demo-app .
which sets the current directory as the context, let's say you wanted the parent directory as the context, just use:
docker build -t hello-demo-app ..

You can also create a tarball of what the image needs first and use that as your context.
https://docs.docker.com/engine/reference/commandline/build/#/tarball-contexts

As is described in this GitHub issue the build actually happens in /tmp/docker-12345, so a relative path like ../relative-add/some-file is relative to /tmp/docker-12345. It would thus search for /tmp/relative-add/some-file, which is also shown in the error message.*
It is not allowed to include files from outside the build directory, so this results in the "Forbidden path" message."

Using docker-compose, I accomplished this by creating a service that mounts the volumes that I need and committing the image of the container. Then, in the subsequent service, I rely on the previously committed image, which has all of the data stored at mounted locations. You will then have have to copy these files to their ultimate destination, as host mounted directories do not get committed when running a docker commit command
You don't have to use docker-compose to accomplish this, but it makes life a bit easier
# docker-compose.yml
version: '3'
services:
stage:
image: alpine
volumes:
- /host/machine/path:/tmp/container/path
command: bash -c "cp -r /tmp/container/path /final/container/path"
setup:
image: stage
# setup.sh
# Start "stage" service
docker-compose up stage
# Commit changes to an image named "stage"
docker commit $(docker-compose ps -q stage) stage
# Start setup service off of stage image
docker-compose up setup

Create a wrapper docker build shell script that grabs the file then calls docker build then removes the file.
a simple solution not mentioned anywhere here from my quick skim:
have a wrapper script called docker_build.sh
have it create tarballs, copy large files to the current working directory
call docker build
clean up the tarballs, large files, etc
this solution is good because (1.) it doesn't have the security hole from copying in your SSH private key (2.) another solution uses sudo bind so that has another security hole there because it requires root permission to do bind.

I think as of earlier this year a feature was added in buildx to do just this.
If you have dockerfile 1.4+ and buildx 0.8+ you can do something like this
docker buildx build --build-context othersource= ../something/something .
Then in your docker file you can use the from command to add the context
ADD –from=othersource . /stuff
See this related post https://www.docker.com/blog/dockerfiles-now-support-multiple-build-contexts/

Workaround with links:
ln path/to/file/outside/context/file_to_copy ./file_to_copy
On Dockerfile, simply:
COPY file_to_copy /path/to/file

I was personally confused by some answers, so decided to explain it simply.
You should pass the context, you have specified in Dockerfile, to docker when
want to create image.
I always select root of project as the context in Dockerfile.
so for example if you use COPY command like COPY . .
first dot(.) is the context and second dot(.) is container working directory
Assuming the context is project root, dot(.) , and code structure is like this
sample-project/
docker/
Dockerfile
If you want to build image
and your path (the path you run the docker build command) is /full-path/sample-project/,
you should do this
docker build -f docker/Dockerfile .
and if your path is /full-path/sample-project/docker/,
you should do this
docker build -f Dockerfile ../

An easy workaround might be to simply mount the volume (using the -v or --mount flag) to the container when you run it and access the files that way.
example:
docker run -v /path/to/file/on/host:/desired/path/to/file/in/container/ image_name
for more see: https://docs.docker.com/storage/volumes/

I had this same issue with a project and some data files that I wasn't able to move inside the repo context for HIPAA reasons. I ended up using 2 Dockerfiles. One builds the main application without the stuff I needed outside the container and publishes that to internal repo. Then a second dockerfile pulls that image and adds the data and creates a new image which is then deployed and never stored anywhere. Not ideal, but it worked for my purposes of keeping sensitive information out of the repo.

In my case, my Dockerfile is written like a template containing placeholders which I'm replacing with real value using my configuration file.
So I couldn't specify this file directly but pipe it into the docker build like this:
sed "s/%email_address%/$EMAIL_ADDRESS/;" ./Dockerfile | docker build -t katzda/bookings:latest . -f -;
But because of the pipe, the COPY command didn't work. But the above way solves it by -f - (explicitly saying file not provided). Doing only - without the -f flag, the context AND the Dockerfile are not provided which is a caveat.

How to share typescript code between two Dockerfiles
I had this same problem, but for sharing files between two typescript projects. Some of the other answers didn't work for me because I needed to preserve the relative import paths between the shared code. I solved it by organizing my code like this:
api/
Dockerfile
src/
models/
index.ts
frontend/
Dockerfile
src/
models/
index.ts
shared/
model1.ts
model2.ts
index.ts
.dockerignore
Note: After extracting the shared code into that top folder, I avoided needing to update the import paths because I updated api/models/index.ts and frontend/models/index.ts to export from shared: (eg export * from '../../../shared)
Since the build context is now one directory higher, I had to make a few additional changes:
Update the build command to use the new context:
docker build -f Dockerfile .. (two dots instead of one)
Use a single .dockerignore at the top level to exclude all node_modules. (eg **/node_modules/**)
Prefix the Dockerfile COPY commands with api/ or frontend/
Copy shared (in addition to api/src or frontend/src)
WORKDIR /usr/src/app
COPY api/package*.json ./ <---- Prefix with api/
RUN npm ci
COPY api/src api/ts*.json ./ <---- Prefix with api/
COPY shared usr/src/shared <---- ADDED
RUN npm run build
This was the easiest way I could send everything to docker, while preserving the relative import paths in both projects. The tricky (annoying) part was all the changes/consequences caused by the build context being up one directory.

One quick and dirty way is to set the build context up as many levels as you need - but this can have consequences.
If you're working in a microservices architecture that looks like this:
./Code/Repo1
./Code/Repo2
...
You can set the build context to the parent Code directory and then access everything, but it turns out that with a large number of repositories, this can result in the build taking a long time.
An example situation could be that another team maintains a database schema in Repo1 and your team's code in Repo2 depends on this. You want to dockerise this dependency with some of your own seed data without worrying about schema changes or polluting the other team's repository (depending on what the changes are you may still have to change your seed data scripts of course)
The second approach is hacky but gets around the issue of long builds:
Create a sh (or ps1) script in ./Code/Repo2 to copy the files you need and invoke the docker commands you want, for example:
#!/bin/bash
rm -r ./db/schema
mkdir ./db/schema
cp -r ../Repo1/db/schema ./db/schema
docker-compose -f docker-compose.yml down
docker container prune -f
docker-compose -f docker-compose.yml up --build
In the docker-compose file, simply set the context as Repo2 root and use the content of the ./db/schema directory in your dockerfile without worrying about the path.
Bear in mind that you will run the risk of accidentally committing this directory to source control, but scripting cleanup actions should be easy enough.

Move docker setup into folder

I have a docker-compose setup something like:
/
- sources/
- docker-compose.yml
- Dockerfile
- .dockerignore
- many more files
The Dockerfile contains instructions including a COPY command of the sources.
Because of all the different tools, including multiple docker setups, I'd like to organise it a bit, by either moving all files to a folder:
/
- sources/
- docker/
- many more files
or leaving just the docker-compose.yml file outside of this folder:
/
- sources/
- docker/
- many more files
I'd like to do this because:
It cleans up the project folder
I currently have multiple docker setups in the project folder, moving them to seperate folders allows for a more clear and/or precise setup (e.g. multiple dockerignore files)
Currently I am running into some issues which do make sense, such as:
COPY failed: Forbidden path outside the build context: ../sources/
Is it possible to achieve this setup? Thanks!

Inside the Dockerfile, you cannot access files that are outside the build context. In your case the build context is the directory containing the Dockerfile.
You can change the build context inside the composefile.
Below is an example where the composefile is at the root and Dockerfile is under docker folder:
version: '3'
services:
test:
build:
context: .
dockerfile: docker/Dockerfile
In this case, inside the Dockerfile the file paths should be set relative to the context.
COPY sources sources
For dockerignore:
As specified in the docs for .dockerignore file:
Before the docker CLI sends the context to the docker daemon, it looks for a file named .dockerignore in the root directory of the context
Thus you need to add the dockerignore file to the root of the context.

You can't use that within the Dockerfile however you should be able to make it work using a .env file and pulling it in from there.
https://docs.docker.com/compose/env-file/
You could try something like:
.env
SOURCE_PATH=../sources/
Dockerfile
COPY ${SOURCE_PATH}/myfile /some/destination

How to include files outside of Docker's build context?

How can I include files from outside of Docker's build context using the "ADD" command in the Docker file?
From the Docker documentation:
The path must be inside the context of the build; you cannot ADD
../something/something, because the first step of a docker build is to
send the context directory (and subdirectories) to the docker daemon.
I do not want to restructure my whole project just to accommodate Docker in this matter. I want to keep all my Docker files in the same sub-directory.
Also, it appears Docker does not yet (and may not ever) support symlinks: Dockerfile ADD command does not follow symlinks on host #1676.
The only other thing I can think of is to include a pre-build step to copy the files into the Docker build context (and configure my version control to ignore those files). Is there a better workaround for than that?

The best way to work around this is to specify the Dockerfile independently of the build context, using -f.
For instance, this command will give the ADD command access to anything in your current directory.
docker build -f docker-files/Dockerfile .
Update: Docker now allows having the Dockerfile outside the build context (fixed in 18.03.0-ce). So you can also do something like
docker build -f ../Dockerfile .

I often find myself utilizing the --build-arg option for this purpose. For example after putting the following in the Dockerfile:
ARG SSH_KEY
RUN echo "$SSH_KEY" > /root/.ssh/id_rsa
You can just do:
docker build -t some-app --build-arg SSH_KEY="$(cat ~/file/outside/build/context/id_rsa)" .
But note the following warning from the Docker documentation:
Warning: It is not recommended to use build-time variables for passing secrets like github keys, user credentials etc. Build-time variable values are visible to any user of the image with the docker history command.

On Linux you can mount other directories instead of symlinking them
mount --bind olddir newdir
See https://superuser.com/questions/842642 for more details.
I don't know if something similar is available for other OSes.
I also tried using Samba to share a folder and remount it into the Docker context which worked as well.

If you read the discussion in the issue 2745 not only docker may never support symlinks they may never support adding files outside your context. Seems to be a design philosophy that files that go into docker build should explicitly be part of its context or be from a URL where it is presumably deployed too with a fixed version so that the build is repeatable with well known URLs or files shipped with the docker container.
I prefer to build from a version controlled source - ie docker build
-t stuff http://my.git.org/repo - otherwise I'm building from some random place with random files.
fundamentally, no.... -- SvenDowideit, Docker Inc
Just my opinion but I think you should restructure to separate out the code and docker repositories. That way the containers can be generic and pull in any version of the code at run time rather than build time.
Alternatively, use docker as your fundamental code deployment artifact and then you put the dockerfile in the root of the code repository. if you go this route probably makes sense to have a parent docker container for more general system level details and a child container for setup specific to your code.

I believe the simpler workaround would be to change the 'context' itself.
So, for example, instead of giving:
docker build -t hello-demo-app .
which sets the current directory as the context, let's say you wanted the parent directory as the context, just use:
docker build -t hello-demo-app ..

You can also create a tarball of what the image needs first and use that as your context.
https://docs.docker.com/engine/reference/commandline/build/#/tarball-contexts

As is described in this GitHub issue the build actually happens in /tmp/docker-12345, so a relative path like ../relative-add/some-file is relative to /tmp/docker-12345. It would thus search for /tmp/relative-add/some-file, which is also shown in the error message.*
It is not allowed to include files from outside the build directory, so this results in the "Forbidden path" message."

Using docker-compose, I accomplished this by creating a service that mounts the volumes that I need and committing the image of the container. Then, in the subsequent service, I rely on the previously committed image, which has all of the data stored at mounted locations. You will then have have to copy these files to their ultimate destination, as host mounted directories do not get committed when running a docker commit command
You don't have to use docker-compose to accomplish this, but it makes life a bit easier
# docker-compose.yml
version: '3'
services:
stage:
image: alpine
volumes:
- /host/machine/path:/tmp/container/path
command: bash -c "cp -r /tmp/container/path /final/container/path"
setup:
image: stage
# setup.sh
# Start "stage" service
docker-compose up stage
# Commit changes to an image named "stage"
docker commit $(docker-compose ps -q stage) stage
# Start setup service off of stage image
docker-compose up setup

Create a wrapper docker build shell script that grabs the file then calls docker build then removes the file.
a simple solution not mentioned anywhere here from my quick skim:
have a wrapper script called docker_build.sh
have it create tarballs, copy large files to the current working directory
call docker build
clean up the tarballs, large files, etc
this solution is good because (1.) it doesn't have the security hole from copying in your SSH private key (2.) another solution uses sudo bind so that has another security hole there because it requires root permission to do bind.

I think as of earlier this year a feature was added in buildx to do just this.
If you have dockerfile 1.4+ and buildx 0.8+ you can do something like this
docker buildx build --build-context othersource= ../something/something .
Then in your docker file you can use the from command to add the context
ADD –from=othersource . /stuff
See this related post https://www.docker.com/blog/dockerfiles-now-support-multiple-build-contexts/

Workaround with links:
ln path/to/file/outside/context/file_to_copy ./file_to_copy
On Dockerfile, simply:
COPY file_to_copy /path/to/file

I was personally confused by some answers, so decided to explain it simply.
You should pass the context, you have specified in Dockerfile, to docker when
want to create image.
I always select root of project as the context in Dockerfile.
so for example if you use COPY command like COPY . .
first dot(.) is the context and second dot(.) is container working directory
Assuming the context is project root, dot(.) , and code structure is like this
sample-project/
docker/
Dockerfile
If you want to build image
and your path (the path you run the docker build command) is /full-path/sample-project/,
you should do this
docker build -f docker/Dockerfile .
and if your path is /full-path/sample-project/docker/,
you should do this
docker build -f Dockerfile ../

An easy workaround might be to simply mount the volume (using the -v or --mount flag) to the container when you run it and access the files that way.
example:
docker run -v /path/to/file/on/host:/desired/path/to/file/in/container/ image_name
for more see: https://docs.docker.com/storage/volumes/

I had this same issue with a project and some data files that I wasn't able to move inside the repo context for HIPAA reasons. I ended up using 2 Dockerfiles. One builds the main application without the stuff I needed outside the container and publishes that to internal repo. Then a second dockerfile pulls that image and adds the data and creates a new image which is then deployed and never stored anywhere. Not ideal, but it worked for my purposes of keeping sensitive information out of the repo.

In my case, my Dockerfile is written like a template containing placeholders which I'm replacing with real value using my configuration file.
So I couldn't specify this file directly but pipe it into the docker build like this:
sed "s/%email_address%/$EMAIL_ADDRESS/;" ./Dockerfile | docker build -t katzda/bookings:latest . -f -;
But because of the pipe, the COPY command didn't work. But the above way solves it by -f - (explicitly saying file not provided). Doing only - without the -f flag, the context AND the Dockerfile are not provided which is a caveat.

How to share typescript code between two Dockerfiles
I had this same problem, but for sharing files between two typescript projects. Some of the other answers didn't work for me because I needed to preserve the relative import paths between the shared code. I solved it by organizing my code like this:
api/
Dockerfile
src/
models/
index.ts
frontend/
Dockerfile
src/
models/
index.ts
shared/
model1.ts
model2.ts
index.ts
.dockerignore
Note: After extracting the shared code into that top folder, I avoided needing to update the import paths because I updated api/models/index.ts and frontend/models/index.ts to export from shared: (eg export * from '../../../shared)
Since the build context is now one directory higher, I had to make a few additional changes:
Update the build command to use the new context:
docker build -f Dockerfile .. (two dots instead of one)
Use a single .dockerignore at the top level to exclude all node_modules. (eg **/node_modules/**)
Prefix the Dockerfile COPY commands with api/ or frontend/
Copy shared (in addition to api/src or frontend/src)
WORKDIR /usr/src/app
COPY api/package*.json ./ <---- Prefix with api/
RUN npm ci
COPY api/src api/ts*.json ./ <---- Prefix with api/
COPY shared usr/src/shared <---- ADDED
RUN npm run build
This was the easiest way I could send everything to docker, while preserving the relative import paths in both projects. The tricky (annoying) part was all the changes/consequences caused by the build context being up one directory.

One quick and dirty way is to set the build context up as many levels as you need - but this can have consequences.
If you're working in a microservices architecture that looks like this:
./Code/Repo1
./Code/Repo2
...
You can set the build context to the parent Code directory and then access everything, but it turns out that with a large number of repositories, this can result in the build taking a long time.
An example situation could be that another team maintains a database schema in Repo1 and your team's code in Repo2 depends on this. You want to dockerise this dependency with some of your own seed data without worrying about schema changes or polluting the other team's repository (depending on what the changes are you may still have to change your seed data scripts of course)
The second approach is hacky but gets around the issue of long builds:
Create a sh (or ps1) script in ./Code/Repo2 to copy the files you need and invoke the docker commands you want, for example:
#!/bin/bash
rm -r ./db/schema
mkdir ./db/schema
cp -r ../Repo1/db/schema ./db/schema
docker-compose -f docker-compose.yml down
docker container prune -f
docker-compose -f docker-compose.yml up --build
In the docker-compose file, simply set the context as Repo2 root and use the content of the ./db/schema directory in your dockerfile without worrying about the path.
Bear in mind that you will run the risk of accidentally committing this directory to source control, but scripting cleanup actions should be easy enough.

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