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Add the simple way to use qemu-register from other projects. #9

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545c49d
Cleanup register.sh
urpylka Feb 10, 2020
9661bd0
Remove build.sh
urpylka Feb 11, 2020
1a5741a
Cleanup Dockerfile
urpylka Feb 11, 2020
089043c
Update README.md
urpylka Feb 11, 2020
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2 changes: 1 addition & 1 deletion .circleci/config.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,7 @@ jobs:
- run:
name: Build image
command: |
./build.sh
docker build -t hypriot/qemu-register .

- deploy:
name: Push image
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8 changes: 4 additions & 4 deletions Dockerfile
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@@ -1,4 +1,3 @@
# Fetch base image
FROM debian:stretch as qemu

ENV QEMU_VERSION 4.2.0
Expand Down Expand Up @@ -27,14 +26,15 @@ RUN curl -sSL https://github.com/resin-io/qemu/commit/db186a3f83454268c43fc793a4
# - resulting binaries are located in "/usr/local/bin/qemu-*"
ARG TARGET_ARCH=arm-linux-user,aarch64-linux-user,ppc64le-linux-user,riscv64-linux-user
RUN mkdir build \
&& cd build \
&& ../configure --static --target-list=$TARGET_ARCH \
&& make -j $(nproc) install
&& cd build \
&& ../configure --static --target-list=$TARGET_ARCH \
&& make -j $(nproc) install

FROM busybox
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@StefanScherer StefanScherer Feb 10, 2020

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Why did you remove the much smaller final stage?

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@urpylka urpylka Feb 11, 2020 •
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I was guided by idea of gap between qemu-register and user-implementation. And if you wanna build your own implementation you can use large or smaller base image (qemu-register) and later copy binary files & register.sh. It's just one docker-layer. And it can be did before (as in your solution) or later (as in mine).

You are right. busybox is smaller than debian. And if it does matter, I can fixed it in PR (return previous structure).

COPY --from=qemu /usr/local/bin/qemu-arm /qemu-arm
COPY --from=qemu /usr/local/bin/qemu-aarch64 /qemu-aarch64
COPY --from=qemu /usr/local/bin/qemu-ppc64le /qemu-ppc64le
COPY --from=qemu /usr/local/bin/qemu-riscv64 /qemu-riscv64

ADD register.sh /register.sh
CMD ["/register.sh", "--reset"]
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@StefanScherer StefanScherer Feb 10, 2020

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This would break the usage of this image if there is no CMD any more.

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@urpylka urpylka Feb 11, 2020 •
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Yeah, I think that is not necessary for users, for example I can't using busybox in my project. I need debian, or alpine, or smthn else w package manager. Therefore CMD operation should using in user-implementation as I documented in README.md.

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@urpylka urpylka Feb 11, 2020

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I think about that a bit more and I has concluded that it can useful for tests. I return it back

56 changes: 45 additions & 11 deletions README.md
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@@ -1,42 +1,76 @@
# qemu-register

[![Build Status](https://circleci.com/gh/hypriot/qemu-register.svg?style=svg)](https://circleci.com/gh/hypriot/qemu-register)

### Build Docker image
```
./build.sh
qemu-register – is the docker-image providing `qemu-static` binaries for your cross-platform projects.

A simple way to register `qemu` usermode emulation binaries for your kernel:

```docker
FROM hypriot/qemu-register as qemu

# Fetching your base image (you can select another one)
FROM alpine

# Coping compiled binaries to your image
COPY --from=qemu /qemu-aarch64 /qemu-arm
COPY --from=qemu /qemu-aarch64 /qemu-aarch64
COPY --from=qemu /qemu-aarch64 /qemu-ppc64le
COPY --from=qemu /qemu-aarch64 /qemu-riscv64

# Coping & executing script for registering qemu in the kernel
COPY --from=qemu /register.sh /register.sh
RUN /register.sh --reset

# PUT HERE YOUR INSTRUCTIONS!!!

```

## How this works

### Check Qemu binaries and versions
Starting with the Linux kernel 4.8, there's a mechanism in the kernel to load the interpreter specified in your `binfmt_misc` ahead of time (and make sure it stays in memory even if the interpreter file is deleted or moved). This is described in better detail in [this blog post by npmccallum](https://npmccallum.gitlab.io/post/foreign-architecture-docker/), [nmpccallum`s github](https://github.com/npmccallum/qemu-register) and in the [kernel binfmt_misc docs](https://www.kernel.org/doc/Documentation/admin-guide/binfmt-misc.rst).

### Build Docker image

If you wanna build your own qemu-register using next instruction:

```bash
git clone https://github.com/hypriot/qemu-register.git
cd qemu-register
docker build -t hypriot/qemu-register:local .
```
docker run --rm hypriot/qemu-register sh -c 'ls -al /qemu*'

### Check Qemu binaries and versions

```bash
$ docker run --rm hypriot/qemu-register sh -c 'ls -al /qemu*'
-rwxr-xr-x 1 root root 6192520 Apr 27 11:25 /qemu-aarch64
-rwxr-xr-x 1 root root 5606984 Apr 27 11:25 /qemu-arm
-rwxr-xr-x 1 root root 5987464 Apr 27 11:25 /qemu-ppc64le

docker run --rm hypriot/qemu-register /qemu-arm --version
$ docker run --rm hypriot/qemu-register /qemu-arm --version
qemu-arm version 4.2.0
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers

docker run --rm hypriot/qemu-register /qemu-aarch64 --version
$ docker run --rm hypriot/qemu-register /qemu-aarch64 --version
qemu-aarch64 version 4.2.0
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers

docker run --rm hypriot/qemu-register /qemu-ppc64le --version
$ docker run --rm hypriot/qemu-register /qemu-ppc64le --version
qemu-ppc64le version 4.2.0
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers

docker run --rm hypriot/qemu-register /qemu-riscv64 --version
$ docker run --rm hypriot/qemu-register /qemu-riscv64 --version
qemu-riscv64 version 4.2.0
Copyright (c) 2003-2019 Fabrice Bellard and the QEMU Project developers
```


### Run the resulting Docker image to register the Qemu interpreters

```
docker run --rm --privileged hypriot/qemu-register
```


### Buy us a beer!

This FLOSS software is funded by donations only. Please support us to maintain and further improve it!
Expand Down
4 changes: 0 additions & 4 deletions build.sh
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This file was deleted.

28 changes: 14 additions & 14 deletions register.sh
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Expand Up @@ -3,26 +3,26 @@ set -e

# Mount if neccessary
if [ ! -d /proc/sys/fs/binfmt_misc ]; then
echo "No binfmt support in the kernel."
echo " Try: '/sbin/modprobe binfmt_misc' from the host"
exit 1
echo "No binfmt support in the kernel."
echo " Try: '/sbin/modprobe binfmt_misc' from the host"
exit 1
fi
if [ ! -f /proc/sys/fs/binfmt_misc/register ]; then
mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc
mount binfmt_misc -t binfmt_misc /proc/sys/fs/binfmt_misc
fi

# Reset all pre-registered interpreters, if requested
if [ "$1" = "--reset" ]; then
(
cd /proc/sys/fs/binfmt_misc
for file in *; do
case "${file}" in
case "${file}" in
status|register)
;;
;;
*)
echo -1 > "${file}"
;;
esac
echo -1 > "${file}"
;;
esac
done
)
fi
Expand All @@ -43,11 +43,11 @@ cd /proc/sys/fs/binfmt_misc
for file in *; do
case "${file}" in
status|register)
;;
;;
*)
echo "Registered interpreter=${file}"
cat ${file}
echo "---"
;;
echo "Registered interpreter=${file}"
cat ${file}
echo "---"
;;
esac
done