docker使用远程节点构建多平台镜像

当在x86或arm平台使用buildx构建多平台镜像时，会发现buildx在构建与docker所在宿主机异构平台镜像包时，构建速度慢的问题。
当你同时有x86和arm服务器的基础上，可以使用远程节点来构建多平台镜像包，使用远程节点构建多平台镜像的好处如下：
1.无兼容性问题：在x86平台构建arm或在arm平台构建x86镜像，有时会存在兼容性问题导致构建失败。
2.构建速度提升：在x86平台构建arm（或相反）使用的QEMU模拟技术，构建速度相对较慢。
实现过程如下：
环境：
x86: 192.168.1.1 # docker engine version >=20
arm: 192.168.1.2 # docker engine version >=20

在x86服务器执行：

# 配置免密登录
[root@www ~]# ssh-keygen -t rsa -b 4096
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):     # 回车
Enter passphrase (empty for no passphrase):                  # 回车
Enter same passphrase again:                                 # 回车
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:LtKq7W8+LlJWK8prpzLKT4RFEDZaqZhqvoOJkvEcjb0 root@www.dehuinet.com
The key's randomart image is:
+---[RSA 4096]----+
| =+o             |
|o.+              |
|oo .             |
|+ o   .          |
|.. = . .S        |
|o.+ *...         |
|=B *.oo .        |
|XoO.Eoo.         |
|+*BO+*+.         |
+----[SHA256]-----+
# 上述命令执行成功会在家目录的.ssh目录下生成"id_rsa"和"id_rsa.pub"两个文件

[root@www ~]# ssh-copy-id -i ~/.ssh/id_rsa.pub root@192.168.10.2
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
The authenticity of host '192.168.1.2 (192.168.1.2)' can't be established.
ECDSA key fingerprint is SHA256:g4eZZsXuQumekQE19vucvMA+oVNLTGC3WV+PMKSWIh0.
ECDSA key fingerprint is MD5:53:10:36:82:8f:68:6f:c2:08:a4:4d:8b:42:cc:a0:05.
Are you sure you want to continue connecting (yes/no)? yes
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@192.168.1.2's password:

Number of key(s) added: 1

Now try logging into the machine, with:   "ssh 'root@192.168.1.2'"
and check to make sure that only the key(s) you wanted were added.
# 执行上述命令成功后就可以在x86服务器免密登录arm服务器了。

# 创建builder
docker buildx create \
--name multi_arch_builder \
--node node_amd64 \
--platform linux/amd64

# 向builder中追加新节点（arm）
docker buildx create \
--name multi_arch_builder \
--append \
--node node_arm64 \
--platform linux/arm64,linux/arm64/v8,linux/arm/v7,linux/arm/v6,linux/arm/v5 \
ssh://root@192.168.1.2

# 启用新builder
docker buildx user multi_arch_builder
docker buildx inspect --bootstrap
[root@www ~]# docker buildx inspect --bootstrap
[+] Building 19.7s (1/2)
[+] Building 30.3s (2/2) FINISHED
 => [node_amd64 internal] booting buildkit                                                                                                          30.3s
 => => pulling image moby/buildkit:buildx-stable-1                                                                                                  27.8s
 => => creating container buildx_buildkit_node_amd64                                                                                                 2.5s
 => [node_arm64 internal] booting buildkit                                                                                                          11.4s
 => => pulling image moby/buildkit:buildx-stable-1                                                                                                   8.2s
 => => pulling failed, using local image moby/buildkit:buildx-stable-1                                                                               0.0s
 => => creating container buildx_buildkit_node_arm64                                                                                                 3.2s
Name:   remote
Driver: docker-container

Nodes:
Name:      node_amd64
Endpoint:  unix:///var/run/docker.sock
Status:    running
Platforms: linux/amd64*, linux/amd64/v2, linux/386

Name:      node_arm64
Endpoint:  ssh://root@192.168.1.2
Status:    running
Platforms: linux/arm64*, linux/arm/v7*, linux/arm/v6*, linux/arm/v5*
# 此时在arm服务器上执行docker ps命令会看到新增了一个容器
[root@localhost lib]# docker ps
CONTAINER ID   IMAGE                                                                       COMMAND                  CREATED         STATUS                          PORTS     NAMES
e67cf241b477   moby/buildkit:buildx-stable-1                                               "buildkitd"              3 minutes ago   Up 3 minutes                              buildx_buildkit_node_arm64

上述步骤后，就可以向之前一样使用buildx进行多平台镜像的构建了。