linux - Docker - 无法使用 docker buildx 构建多平台镜像

Question

我正在尝试使用 docker buildx 构建多平台(amd64、arm64 和 armv7)镜像。由于我使用的是运行 Ubuntu 18.04 的 amd64 机器，因此我按照 Docker website 上的说明进行操作。并安装 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， 似乎存在问题。 binfmt-support 服务。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，我还是尝试继续执行通常的程序，即:

docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx inspect --bootstrap

最后一个命令的输出是:

[+] 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，但是我还需要为“linux/arm64”和“linux/arm/v7”平台构建镜像。
几个小时以来，我一直在寻找解决此问题的方法，但我没有找到任何有效的方法

- - - - - - - - - - - - - - - - - - 编辑 - - - - - - - -----------------------

看起来我能够通过运行来解决部分问题:

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

根本没有错误:

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的输出正如预期的那样:

● 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，作为运行这三个命令后的输出:

docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx inspect --bootstrap

和以前一样，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？为什么它显示我 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的输出是:

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。此外，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

Answer 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。