结论：一个pod中的不同容器共享pod的网络名称空间。

测试用yaml文件

apiVersion: v1
kind: Pod
metadata:
name: pod-demo
namespace: default
spec:
containers:
- name: myapp
image: ikubernetes/myapp:v1
imagePullPolicy: IfNotPresent
- name: bbox
image: busybox:latest
imagePullPolicy: IfNotPresent
command:
- /bin/sh
- -c
- "sleep 86400"

共有两个容器，一个为nginx,另一个为busybox

1. 进入bbox容器,用到的命令与docker中的类似

kubectl exec pod-demo bbox -it -- /bin/sh  #-it 在前台运行终端 ； --后面需要有空格
#docker命令 docker exec web -it /bin/bash

1. 查看bbox的状态

/ # ps aux
PID   USER     TIME   COMMAND
1 root       0:00 nginx: master process nginx -g daemon off;
6 nginx      0:00 nginx: worker process
17 root       0:00 /bin/sh
22 root       0:00 ps aux
/ # netstat -tnl
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN
/ # wget -O - -q 127.0.0.1
Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>

bbox中并未安装对外的服务，但在查看网络状态时，可以发现80口被监听。因为bbox和myapp共用一个网络名称空间。

突发奇想的测试

结论：别光想结果会怎样，先考虑总体架构，再决定怎么写配置。
b站上看到一条弹幕说一个pod加2个ngx, 显示的内容不一样，最后去访问结果会怎样。其实我第一反应就是端口冲突。可还是想看看具体现象。
测试配置：

apiVersion: v1
kind: Pod
metadata:
name: pod-demo
namespace: default
spec:
containers:
- name: ngx   #ngx默认配置，端口80
image: nginx:latest
imagePullPolicy: IfNotPresent
- name: myapp # 端口也是80
image: ikubernetes/myapp:v1
imagePullPolicy: IfNotPresent
- name: bbox #乱入的bbox，可以忽略
image: busybox:latest
imagePullPolicy: IfNotPresent
command:
- /bin/sh
- -c
- "sleep 86400"

使用apply以后查看pod状态,此处看到一个 CrashLoopBackOff状态。 且3个容器有1个未在运行。

[root@test basic]# kubectl get pods
NAME       READY   STATUS             RESTARTS   AGE
pod-demo   2/3     CrashLoopBackOff   4          2m3s

看看log，典型的端口冲突提示。

[root@test basic]# kubectl logs pods/pod-demo ngx
2020/05/05 15:36:42 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
2020/05/05 15:36:42 [emerg] 1#1: bind() to 0.0.0.0:80 failed (98: Address already in use)
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)