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I'm trying to build a multi-platform (amd64, arm64 and armv7) image using docker buildx. Since I'm using an amd64 machine running Ubuntu 18.04, I followed the instructions on the Docker website and installed qemu via:
sudo apt install qemu-user
However, a weird error appears when I execute the previous command. More specifically, there seems to be an issue with the binfmt-support service. Here's the full log:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Starting pkgProblemResolver with broken count: 0
Starting 2 pkgProblemResolver with broken count: 0
Done
The following additional packages will be installed:
binfmt-support qemu-user-binfmt
The following NEW packages will be installed:
binfmt-support qemu-user qemu-user-binfmt
0 upgraded, 3 newly installed, 0 to remove and 1 not upgraded.
Need to get 0 B/7.409 kB of archives.
After this operation, 63,4 MB of additional disk space will be used.
Do you want to continue? [Y/n]
Selecting previously unselected package binfmt-support.
(Reading database ... 245278 files and directories currently installed.)
Preparing to unpack .../binfmt-support_2.1.8-2_amd64.deb ...
Unpacking binfmt-support (2.1.8-2) ...
Selecting previously unselected package qemu-user.
Preparing to unpack .../qemu-user_1%3a2.11+dfsg-1ubuntu7.21_amd64.deb ...
Unpacking qemu-user (1:2.11+dfsg-1ubuntu7.21) ...
Selecting previously unselected package qemu-user-binfmt.
Preparing to unpack .../qemu-user-binfmt_1%3a2.11+dfsg-1ubuntu7.21_amd64.deb ...
Unpacking qemu-user-binfmt (1:2.11+dfsg-1ubuntu7.21) ...
Setting up binfmt-support (2.1.8-2) ...
Job for binfmt-support.service failed because the control process exited with error code.
See "systemctl status binfmt-support.service" and "journalctl -xe" for details.
invoke-rc.d: initscript binfmt-support, action "start" failed.
● binfmt-support.service - Enable support for additional executable binary formats
Loaded: loaded (/lib/systemd/system/binfmt-support.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Wed 2020-02-05 17:20:29 CET; 4ms ago
Docs: man:update-binfmts(8)
Process: 7766 ExecStart=/usr/sbin/update-binfmts --enable (code=exited, status=2)
Main PID: 7766 (code=exited, status=2)
feb 05 17:20:29 XPS-15-9570 systemd[1]: Starting Enable support for additional executable binary formats...
feb 05 17:20:29 XPS-15-9570 update-binfmts[7766]: update-binfmts: warning: unable to close /proc/sys/fs/binfmt_misc/register: No such file or directory
feb 05 17:20:29 XPS-15-9570 update-binfmts[7766]: update-binfmts: exiting due to previous errors
feb 05 17:20:29 XPS-15-9570 systemd[1]: binfmt-support.service: Main process exited, code=exited, status=2/INVALIDARGUMENT
feb 05 17:20:29 XPS-15-9570 systemd[1]: binfmt-support.service: Failed with result 'exit-code'.
feb 05 17:20:29 XPS-15-9570 systemd[1]: Failed to start Enable support for additional executable binary formats.
Setting up qemu-user (1:2.11+dfsg-1ubuntu7.21) ...
Setting up qemu-user-binfmt (1:2.11+dfsg-1ubuntu7.21) ...
update-binfmts: warning: current package is qemu-user-binfmt, but binary format already installed by qemu-user-static
update-binfmts: exiting due to previous errors
dpkg: error processing package qemu-user-binfmt (--configure):
installed qemu-user-binfmt package post-installation script subprocess returned error exit status 2
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for ureadahead (0.100.0-21) ...
Processing triggers for neon-settings (0.0+p18.04+git20191212.1343) ...
Processing triggers for systemd (237-3ubuntu10.33) ...
Errors were encountered while processing:
qemu-user-binfmt
E: Sub-process /usr/bin/dpkg returned an error code (1)
Despite that, I tried to go on with the usual procedure, namely:
docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx inspect --bootstrap
Where the output of the last command is:
[+] Building 5.0s (1/1) FINISHED
=> [internal] booting buildkit 5.0s
=> => pulling image moby/buildkit:buildx-stable-1 4.3s
=> => creating container buildx_buildkit_mybuilder0 0.7s
Name: mybuilder
Driver: docker-container
Nodes:
Name: mybuilder0
Endpoint: unix:///var/run/docker.sock
Status: running
Platforms: linux/amd64, linux/386
As you can see, "linux/amd64" and "linux/386" are listed as the only available platforms, however I would need to build the image for "linux/arm64" and "linux/arm/v7" platforms as well. I've been looking for a solution to this problem for hours, though I didn't find anything that worked
Looks like I was able to solve part of the issue by running:
sudo apt purge --auto-remove qemu-user qemu-user-binfmt binfmt-support
And then reinstalling them. In fact, running again this command:
sudo apt install qemu-user
gives no error at all:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Starting pkgProblemResolver with broken count: 0
Starting 2 pkgProblemResolver with broken count: 0
Done
The following additional packages will be installed:
binfmt-support qemu-user-binfmt
The following NEW packages will be installed:
binfmt-support qemu-user qemu-user-binfmt
0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/7.409 kB of archives.
After this operation, 63,4 MB of additional disk space will be used.
Do you want to continue? [Y/n]
Selecting previously unselected package binfmt-support.
(Reading database ... 245437 files and directories currently installed.)
Preparing to unpack .../binfmt-support_2.1.8-2_amd64.deb ...
Unpacking binfmt-support (2.1.8-2) ...
Selecting previously unselected package qemu-user.
Preparing to unpack .../qemu-user_1%3a2.11+dfsg-1ubuntu7.21_amd64.deb ...
Unpacking qemu-user (1:2.11+dfsg-1ubuntu7.21) ...
Selecting previously unselected package qemu-user-binfmt.
Preparing to unpack .../qemu-user-binfmt_1%3a2.11+dfsg-1ubuntu7.21_amd64.deb ...
Unpacking qemu-user-binfmt (1:2.11+dfsg-1ubuntu7.21) ...
Setting up binfmt-support (2.1.8-2) ...
Created symlink /etc/systemd/system/multi-user.target.wants/binfmt-support.service → /lib/systemd/system/binfmt-support.service.
Setting up qemu-user (1:2.11+dfsg-1ubuntu7.21) ...
Setting up qemu-user-binfmt (1:2.11+dfsg-1ubuntu7.21) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Processing triggers for ureadahead (0.100.0-21) ...
Processing triggers for neon-settings (0.0+p18.04+git20191212.1343) ...
Processing triggers for systemd (237-3ubuntu10.38) ...
Similarly, the output of systemctl status binfmt-support.service is as expected:
● binfmt-support.service - Enable support for additional executable binary formats
Loaded: loaded (/lib/systemd/system/binfmt-support.service; enabled; vendor preset: enabled)
Active: active (exited) since Mon 2020-02-10 11:42:23 CET; 1min 11s ago
Docs: man:update-binfmts(8)
Main PID: 7161 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 4915)
CGroup: /system.slice/binfmt-support.service
feb 10 11:42:23 XPS-15-9570 systemd[1]: Starting Enable support for additional executable binary formats...
feb 10 11:42:23 XPS-15-9570 systemd[1]: Started Enable support for additional executable binary formats.
However, part of the issue is still there, as the output after running these three commands:
docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx inspect --bootstrap
is the same as before, namely:
[+] Building 2.6s (1/1) FINISHED
=> [internal] booting buildkit 2.6s
=> => pulling image moby/buildkit:buildx-stable-1 2.0s
=> => creating container buildx_buildkit_mybuilder0 0.6s
Name: mybuilder
Driver: docker-container
Nodes:
Name: mybuilder0
Endpoint: unix:///var/run/docker.sock
Status: running
Platforms: linux/amd64, linux/386
Why is that? Why is it showing me linux/amd64 and linux/386 as the only available platforms?
The output of docker context ls is:
NAME DESCRIPTION DOCKER ENDPOINT KUBERNETES ENDPOINT ORCHESTRATOR
default * Current DOCKER_HOST based configuration unix:///var/run/docker.sock swarm
I've also tried to restart docker after qemu's installation, but to no success. Also, specifying the target platforms in the docker buildx command:
docker buildx build -t <mytag> --platform linux/amd64,linux/arm64,linux/arm/v7 --load .
results in this error:
[+] Building 0.6s (5/20)
=> [internal] load .dockerignore 0.0s
=> => transferring context: 2B 0.0s
=> [internal] load build definition from Dockerfile 0.0s
=> => transferring dockerfile: 32B 0.0s
=> [linux/arm/v7 internal] load metadata for docker.io/alegeno92/opencv_python3:3.4.2 0.6s
=> CANCELED [linux/arm64 internal] load metadata for docker.io/alegeno92/opencv_python3:3.4.2 0.6s
=> CANCELED [linux/amd64 internal] load metadata for docker.io/alegeno92/opencv_python3:3.4.2 0.6s
failed to solve: rpc error: code = Unknown desc = failed to solve with frontend dockerfile.v0: failed to load LLB: runtime execution on platform linux/arm/v7 not supported
By the way, my version of the kernel is 4.15.0-76-generic
496
Docker Buildx is a CLI plugin that extends the docker command with the full support of the features provided by Moby BuildKit builder toolkit. It provides the same user experience as docker build with many new features like creating scoped builder instances and building against multiple nodes concurrently.
In a multistage build, you have a single Dockerfile, but can define multiple images inside it to help build the final image.
In later versions of Docker, it provides the use of multi-stage dockerfiles. Using multi-stage dockerfiles, you can use several base images as well as previous intermediate image layers to build a new image layer.
Docker has for some time supported multiplatform images where an image can have multiple different versions for different architectures and platforms. Pulling a multiplatform image will pull only the version for your current architecture.
Run the multiarch container first
docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
docker buildx rm builder
docker buildx create --name builder --driver docker-container --use
docker buildx inspect --bootstrapAnd you should have your alternate architectures.
187
Tagging on this answer in response to the first error. The commands have been updated per https://docs.docker.com/buildx/working-with-buildx/.
QEMU is a cross-platform emulator responsible for sourcing the binaries for different architectures (through the binfmt_misc handler).
Will save some people some time to start with this command first:
docker run --privileged --rm tonistiigi/binfmt --install all
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