Docker 映像 jenkins/jenkins:lts-alpine DNS 问题

Question

我有一个基于 jenkins/jenkins:lts-alpine 的 docker 镜像。由于某种原因，它无法解析 DNS 名称，如下所示：

[root@inf-jenkins02-prd ~]# docker ps
CONTAINER ID        IMAGE                   COMMAND                  CREATED             STATUS              PORTS                 NAMES
716ceece2017        myjenkins/jenkins:latest   "/sbin/tini -- /us..."   12 minutes ago      Up 12 minutes       8080/tcp, 50000/tcp   jenkins_main.1.heaupued6g8eygrgrk6c8hlvy
[root@inf-jenkins02-prd ~]# docker exec -ti 716ceece2017 nslookup www.google.com
nslookup: can't resolve '(null)': Name does not resolve

nslookup: can't resolve 'www.google.com': Try again
[root@inf-jenkins02-prd ~]#

但是，按预期运行以下操作：

[root@inf-jenkins02-prd ~]# docker run myjenkins/jenkins:latest nslookup google.com
nslookup: can't resolve '(null)': Name does not resolve

Name:      google.com
Address 1: 216.58.204.142 par21s05-in-f142.1e100.net

这是用于构建映像的 Dockerfile：

FROM jenkins/jenkins:lts-alpine
ENV JAVA_OPTS="-Djenkins.install.runSetupWizard=false -Dhudson.DNSMultiCast.disabled=true -Dhudson.udp=-1"
USER jenkins
RUN ssh-keygen -q -t rsa -N '' -f /var/jenkins_home/.ssh/id_rsa
COPY security.groovy /usr/share/jenkins/ref/init.groovy.d/security.groovy
COPY xlocation.groovy /usr/share/jenkins/ref/init.groovy.d/xlocation.groovy
COPY znodes.groovy /usr/share/jenkins/ref/init.groovy.d/znodes.groovy
COPY plugins.txt /usr/share/jenkins/ref/plugins.txt
RUN /usr/local/bin/install-plugins.sh < /usr/share/jenkins/ref/plugins.txt

这是 docker-compose 文件：

version: "3.1"
services:
  main:
    container_name: jenkins-mine
    image: myjenkins/jenkins
    deploy:
      placement:
        constraints:
          - node.role == manager
    ports:
      - 8080:8080
      - 50000:50000
    volumes:
      - /home/jenkins:/var/jenkins_home/  
      - /var/run/docker.sock:/var/run/docker.sock

那么，我只是在做：

docker stack deploy -c /.../docker-compose.yml jenkins

一切似乎都还好：

[root@inf-jenkins02-prd ~]# docker service ls
ID            NAME          MODE        REPLICAS  IMAGE
71h4jrygqp7m  jenkins_main  replicated  1/1       myjenkins/jenkins
[root@inf-jenkins02-prd ~]# docker service ps 71h4jrygqp7m
ID            NAME            IMAGE           NODE               DESIRED STATE  CURRENT STATE           ERROR  PORTS
heaupued6g8e  jenkins_main.1  myjenkins/jenkins  inf-jenkins02-prd  Running        Running 23 minutes ago
[root@inf-jenkins02-prd ~]#

但 google.com 无法解决：

[root@inf-jenkins02-prd ~]# docker exec -ti 716ceece2017 nslookup www.google.conf
nslookup: can't resolve '(null)': Name does not resolve

nslookup: can't resolve 'www.google.conf': Try again
[root@inf-jenkins02-prd ~]# docker exec -ti 716ceece2017 cat /etc/resolv.conf
search ...
nameserver 127.0.0.11
options ndots:0
[root@inf-jenkins02-prd ~]#

知道这里发生了什么吗？非常感谢。

亲切的问候，

尼古拉斯

Answer 1

如果您看到消息nslookup: can't resolve '(null)': Name does not resolve，那是因为nslookup 正在查找您要将DNS 查询发送到的服务器的名称。既然你没有提供，那就是null。这是nslookup 中的一个已知问题（请参阅https://github.com/gliderlabs/docker-alpine/issues/476）。另请参阅this SO question 了解更多详情..

要检查的一件事是您正在查找正确的域。 在这里，您查找的是www.google.conf，而不是www.google.com。 www.google.conf 不存在，所以你得到的输出是预期的。

# docker exec -ti 716ceece2017 nslookup www.google.conf
nslookup: can't resolve '(null)': Name does not resolve

nslookup: can't resolve 'www.google.conf': Try again

要检查的另一件事是使用不同的 DNS 解析器尝试 nslookup。 例如：

docker exec -ti 716ceece2017 nslookup www.google.conf 8.8.8.8

然后您可以查看问题是 Internet 还是 DNS 服务器。