Docker - 无法使用 docker buildx 构建多平台映像
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【中文标题】Docker - 无法使用 docker buildx 构建多平台映像【英文标题】：Docker - Cannot build multi-platform images with docker buildx 【发布时间】：2020-05-21 15:09:14 【问题描述】：我正在尝试使用 docker buildx 构建多平台（amd64、arm64 和 armv7）映像。由于我使用的是运行 Ubuntu 18.04 的 amd64 机器，因此我按照 Docker website 上的说明安装了 qemu 通过：
sudo apt install qemu-user
但是，当我执行上一个命令时，出现了一个奇怪的错误。更具体地说，binfmt-support 服务似乎存在问题。这是完整的日志：
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)
尽管如此，我还是尝试按照通常的程序进行，即：
docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx inspect --bootstrap
最后一条命令的输出在哪里：
[+] 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
如您所见，“linux/amd64”和“linux/386”被列为唯一可用的平台，但是我需要为“linux/arm64”和“linux/arm/v7”平台构建映像也是。 几个小时以来，我一直在寻找解决此问题的方法，但没有找到任何可行的方法
------------------------------------ 编辑 ---------- --------------------------
看起来我可以通过运行解决部分问题：
sudo apt purge --auto-remove qemu-user qemu-user-binfmt binfmt-support
然后重新安装它们。事实上，再次运行这个命令：
sudo apt install qemu-user
完全没有错误：
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) ...
同样，systemctl status binfmt-support.service 的输出也符合预期：
● 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.
但是，部分问题仍然存在，运行这三个命令后的输出：
docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx inspect --bootstrap
和之前一样，即：
[+] 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
这是为什么呢？为什么它向我显示 linux/amd64 和 linux/386 作为唯一可用的平台？
编辑#2（关于@LinPy 的评论）
docker context ls 的输出为：
NAME DESCRIPTION DOCKER ENDPOINT KUBERNETES ENDPOINT ORCHESTRATOR
default * Current DOCKER_HOST based configuration unix:///var/run/docker.sock swarm
我也尝试在 qemu 安装后重新启动 docker，但没有成功。另外，在 docker buildx 命令中指定目标平台：
docker buildx build -t <mytag> --platform linux/amd64,linux/arm64,linux/arm/v7 --load .
导致此错误：
[+] 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
顺便说一下，我的内核版本是4.15.0-76-generic
【问题讨论】：
【参考方案1】：首先运行多架构容器
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 --bootstrap你应该有你的替代架构。
【讨论】：
链接到 multiarch/qemu-user-static 存储库：github.com/multiarch/qemu-user-static【参考方案2】：标记此答案以响应第一个错误。命令已根据https://docs.docker.com/buildx/working-with-buildx/ 更新。
QEMU 是一个跨平台仿真器，负责为不同架构（通过 binfmt_misc 处理程序）获取二进制文件。
这将为一些人节省一些时间来首先使用此命令：
docker run --privileged --rm tonistiigi/binfmt --install all
【讨论】：
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