1. 背景

该环境是在一个VM虚拟中进行的docker测试

DOCKERFILE文档

FROM golang:1.9 as builder
RUN mkdir -p /go/src/test
WORKDIR /go/src/test
COPY main.go .
RUN CGO_ENABLED=0 GOOS=linux go build -o app .

FROM alpine:latest
RUN apk add --no-cache ca-certificates
WORKDIR /root/
COPY --from=builder /go/src/test/app .
CMD ["./app"]

创建命令

docker build -t lqliw/test02:V1 .

运行报错如下

[+] Building 12.3s (12/14)                                                                                                                                                                                                                                                    
 => [internal] load build definition from Dockerfile                                                                                                                                                                                                                     0.0s
 => => transferring dockerfile: 302B                                                                                                                                                                                                                                     0.0s
 => [internal] load .dockerignore                                                                                                                                                                                                                                        0.0s
 => => transferring context: 2B                                                                                                                                                                                                                                          0.0s
 => [internal] load metadata for docker.io/library/golang:1.9                                                                                                                                                                                                            1.9s
 => [internal] load metadata for docker.io/library/alpine:latest                                                                                                                                                                                                         0.0s
 => CACHED [builder 1/5] FROM docker.io/library/golang:1.9@sha256:8b5968585131604a92af02f5690713efadf029cc8dad53f79280b87a80eb1354                                                                                                                                       0.0s
 => [internal] load build context                                                                                                                                                                                                                                        0.0s
 => => transferring context: 28B                                                                                                                                                                                                                                         0.0s
 => CACHED [stage-1 1/4] FROM docker.io/library/alpine:latest                                                                                                                                                                                                            0.0s
 => ERROR [stage-1 2/4] RUN apk add --no-cache ca-certificates                                                                                                                                                                                                          10.3s
 => [builder 2/5] RUN mkdir -p /go/src/test                                                                                                                                                                                                                              0.4s
 => [builder 3/5] WORKDIR /go/src/test                                                                                                                                                                                                                                   0.0s
 => [builder 4/5] COPY main.go .                                                                                                                                                                                                                                         0.0s
 => [builder 5/5] RUN CGO_ENABLED=0 GOOS=linux go build -o app .                                                                                                                                                                                                         0.5s
------                                                                                                                                                                                                                                                                        
 > [stage-1 2/4] RUN apk add --no-cache ca-certificates:                                                                                                                                                                                                                      
#0 0.291 fetch https://dl-cdn.alpinelinux.org/alpine/v3.17/main/x86_64/APKINDEX.tar.gz                                                                                                                                                                                        
#0 5.296 WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.17/main: temporary error (try again later)
#0 5.296 fetch https://dl-cdn.alpinelinux.org/alpine/v3.17/community/x86_64/APKINDEX.tar.gz
#0 10.30 WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.17/community: temporary error (try again later)
#0 10.30 ERROR: unable to select packages:
#0 10.30   ca-certificates (no such package):
#0 10.30     required by: world[ca-certificates]
------
Dockerfile:8
--------------------
   6 |     
   7 |     FROM alpine:latest
   8 | >>> RUN apk add --no-cache ca-certificates
   9 |     WORKDIR /root/
  10 |     COPY --from=builder /go/src/test/app .
--------------------
ERROR: failed to solve: process "/bin/sh -c apk add --no-cache ca-certificates" did not complete successfully: exit code: 1

2、解决过程

1. 刚开始想的是ca-certificates证书安装失败，原因是读取不到文件，想了一下应该是网上下载的，所以修改为国内APT阿里源和清华源，结果还是报错

#更新Alpine的软件源为阿里云
RUN echo http://mirrors.aliyun.com/alpine/v3.10/main/ > /etc/apk/repositories && \
    echo http://mirrors.aliyun.com/alpine/v3.10/community/ >> /etc/apk/repositories
RUN apk update && upgrade

2. 使用alpine直接建一个容器，进入直接使用命令操作。一样的报错

[root@localhost dockertest2]# docker run -itd alpine
/ # apk add --no-cache ca-certificates
fetch https://dl-cdn.alpinelinux.org/alpine/v3.17/main/x86_64/APKINDEX.tar.gz
WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.17/main: temporary error (try again later)
fetch https://dl-cdn.alpinelinux.org/alpine/v3.17/community/x86_64/APKINDEX.tar.gz
WARNING: Ignoring https://dl-cdn.alpinelinux.org/alpine/v3.17/community: temporary error (try again later)
ERROR: unable to select packages:
  ca-certificates (no such package):
    required by: world[ca-certificates]

3. 更换为阿里源、清华源也一样

/ # echo http://mirrors.aliyun.com/alpine/v3.10/main/ > /etc/apk/repositories && \
>     echo http://mirrors.aliyun.com/alpine/v3.10/community/ >> /etc/apk/repositories
/ # apk update && apk upgrade
fetch http://mirrors.aliyun.com/alpine/v3.10/main/x86_64/APKINDEX.tar.gz
ERROR: http://mirrors.aliyun.com/alpine/v3.10/main/: temporary error (try again later)
WARNING: Ignoring http://mirrors.aliyun.com/alpine/v3.10/main/: No such file or directory
fetch http://mirrors.aliyun.com/alpine/v3.10/community/x86_64/APKINDEX.tar.gz
ERROR: http://mirrors.aliyun.com/alpine/v3.10/community/: temporary error (try again later)
WARNING: Ignoring http://mirrors.aliyun.com/alpine/v3.10/community/: No such file or directory
2 errors; 15 distinct packages available

4. 后来发现网络不通！？

/ # ping g.cn
^C
/ # ping 61.139.2.69
PING 61.139.2.69 (61.139.2.69): 56 data bytes
^C
--- 61.139.2.69 ping statistics ---
5 packets transmitted, 0 packets received, 100% packet loss

5. 问题找到了，来源：https://www.ngui.cc/el/3157056.html

原因：docker run默认的容器网络运行模式是桥接模式即bridge模式，该模式下应该也可以访问外网，但是能力不够没有研究出来应该怎样配置，不管怎么配置仍然无法连接外网。在host模式下，docker容器与宿主机共享网络，即可以访问外网和使用apt-get等操作。

运行容器时更改docker网络连接模式来解决这个问题，即在docker run 指令后加参数 --network=host，host模式的含义是使docker的网络连接模式与宿主机的网络连接模式一致。命令如下所示：

docker run --network=host -i -t ubuntu /bin/bash

同样如果想使用Dockerfile和docker bulid来构建docker镜像，如果Dockerfile中有apt-get等网络下载指令并且由于不能连接网络导致构建失败，同样也可以使用–network=host参数。代码如下所示：

docker build --network=host  -t="test/static_web:first" .

3、解决办法

在build时增加--network=host参数，如下

docker build --network=host -t lqliw/test01:V1 .

最后：写这么细的原因是，看到的朋友可以避坑。花了1小时才解决。