k8s实践(八)：ConfigMap and Secret

loong576 • 2023-01-03 • 云技术社区 • 274 阅读

环境说明：

主机名

操作系统版本

ip

docker version

kubelet version

配置

备注

master

Centos 7.6.1810

172.27.9.131

Docker 18.09.6

V1.14.2

2C2G

master主机

node01

Centos 7.6.1810

172.27.9.135

Docker 18.09.6

V1.14.2

2C2G

node节点

node02

Centos 7.6.1810

172.27.9.136

Docker 18.09.6

V1.14.2

2C2G

node节点

k8s集群部署详见：Centos7.6部署k8s(v1.14.2)集群

k8s学习资料详见：基本概念、kubectl命令和资料分享

一、概述

1. ConfigMap

  在实际的应用部署中， 经常需要为各种应用／中间件配置各种参数， 如数据库地址、 用户名、 密码等， 而且大多数生产环境中的应用程序配置较为复杂， 可能是多个 Config 文件、 命令行参数和环境变量的组合。 要完成这样的任务有很多种方案， 比如：

1.可以直接在打包镜像的时候写在应用配置文件里面，但这种方式的坏处显而易见，因为在应用部署中往往需要修改这些配置参数，或者说制作镜像时并不知道具体的参数配置，一旦打包到镜像中将无法更改配置。另外，部分配置信息涉及安全信息（如用户名、 密码等），打包人镜像容易导致安全隐患;
2.可以在配置文件里面通过ENV环境变量传入，但是如若修改ENV就意味着要修改yaml文件，而且需要重启所有的容器才行;
3.可以在应用启动时在数据库或者某个特定的地方取配置文件。

显然，前两种方案不是最佳方案，而第三种方案实现起来又比较麻烦。为了解决这个难题,kubernetes引入ConfigMap这个API资源来满足这一需求。

2. 为什么需要ConfigMap和Secret

  ConfigMap和Secret是Kubernetes系统上两种特殊类型的存储卷，ConfigMap象用于为容器中的应用提供配置数据以定制程序的行为，不过敏感的配置信息，例如密钥、证书等通常由Secret对象来进行配置。它们将相应的配置信息保存于对象中，而后在Pod资源上以存储卷的形式将其挂载并获取相关的配置，以实现配置与镜像文件的解耦。

3. ConfigMap作用

  • 向容器传递命令行参数
  • 为每个容器设置自定义环境变量
  • 通过特殊类型的卷将配置文件挂载到容器中

二、准备工作

  制作基础镜像loong576/date-random，创建pod date-random-configmap，pod中包含容器centos-date和nginx-server，其中容器centos-date由镜像loong576/date-random创建，通过访问容器nginx-server验证参数是否生效。

1. 制作镜像

制作镜像loong576/date-random并上传dockerhub

[root@master loong576]# more Dockerfile 
FROM centos:centos7.6.1810 

ADD date-random.sh /usr/bin/date-random

ENTRYPOINT /usr/bin/date-random
[root@master loong576]# more date-random.sh 
#!/bin/bash
mkdir /var/htdocs

while : 
do
  /usr/bin/echo "date is : " `date` >> /var/htdocs/index.html
  /usr/bin/echo "RANDOM is : " `echo $RANDOM` >> /var/htdocs/index.html
  sleep 5
done
[root@master loong576]# docker build -t loong576/date-random .
Sending build context to Docker daemon  4.096kB
Step 1/3 : FROM centos:centos7.6.1810
 ---> f1cb7c7d58b7
Step 2/3 : ADD date-random.sh /usr/bin/date-random
 ---> 58296331ae70
Step 3/3 : ENTRYPOINT /usr/bin/date-random
 ---> Running in e9a3184518e7
Removing intermediate container e9a3184518e7
 ---> 07db2452d706
Successfully built 07db2452d706
Successfully tagged loong576/date-random:latest
[root@master loong576]# docker images |grep loong576/date-random
loong576/date-random                 latest              07db2452d706        24 seconds ago      202MB

基础镜像为centos:centos7.6.1810，向其中写入脚本date-random.sh并执行，该脚本运行date和echo $RANDOM命令，前者输出当前时间，后者输出0~32767之间的随机数，脚本循环时间为5秒。

2. 上传dockerhub

[root@master loong576]# docker push loong576/date-random
The push refers to repository [docker.io/loong576/date-random]
ec4ecb05d6b3: Pushed 
89169d87dbe2: Layer already exists 
latest: digest: sha256:a680438f09b92f40b38f3da5f9ea34e4b3561c540f1093d9cbcc2385c0184551 size: 736

上传至dockerhub前需执行登录操作docker login

3. 验证镜像

[root@master loong576]# more date-random-configmap.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: date-random-configmap 
spec:
  containers:
  - image: loong576/date-random
    name: centos-date 
    volumeMounts:
    - name: html
      mountPath: /var/htdocs
  - image: nginx
    name: nginx-server
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html
      readOnly: true
  volumes:
  - name: html
    emptyDir: {}
[root@master loong576]# kubectl apply -f date-random-configmap.yaml 
pod/date-random-configmap created
[root@master loong576]# kubectl get po -o wide                              
NAME                    READY   STATUS    RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
date-random-configmap   2/2     Running   0          14s   10.244.1.203   node01   <none>           <none>
[root@master loong576]# curl 10.244.1.203
date is :  Mon Sep 16 02:51:21 UTC 2019
RANDOM is :  17563
date is :  Mon Sep 16 02:51:26 UTC 2019
RANDOM is :  434
date is :  Mon Sep 16 02:51:31 UTC 2019
RANDOM is :  18246
date is :  Mon Sep 16 02:51:36 UTC 2019
RANDOM is :  2225

运行date-random-configmap.yaml并访问容器nginx-server（nginx默认端口为80），发现每5秒输出date和随机数，符合预期。

三、容器中的配置数据传递

1. 容器的ENTRYPOINT和CMD

Dockerfile中的两种指令分别定义命令与参数这两个部分：

  • ENTRYPOINT定义容器启动时运行的命令。
  • CMD指定传递给ENTRYPOINT的参数。

CMD也可以执行命令，一般为默认的启动命令。

k8s中与ENTRYPOINT和CMD对应的如下：

Docker

Kubernetes

说明

ENTRYPOINT

command

在容器中执行可执行程序

CMD

args

传递给可执行程序的参数

pod中指定自定义命令和参数

[root@master loong576]# more nginx.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx 
    name: nginx
    command: ["/bin/echo"]
    args: ["hello","world"]
[root@master loong576]# kubectl apply -f nginx.yaml 
pod/nginx created
[root@master loong576]# kubectl logs nginx 
hello world

可以查看日志可以看到pod nginx的输出为'hello world'，与pod里面command和args中的定义一致。

2. 向容器传递命令行参数

2.1 循环间隔参数化

[root@master loong576]# more date-random.sh 
#!/bin/bash
mkdir /var/htdocs
INTERVAL=$1
while : 
do
  /usr/bin/echo "date is : " `date` >> /var/htdocs/index.html
  /usr/bin/echo "RANDOM is : " `echo $RANDOM` >> /var/htdocs/index.html
  sleep $INTERVAL 
done
[root@master loong576]# more Dockerfile 
FROM centos:centos7.6.1810 

ADD date-random.sh /usr/bin/date-random

ENTRYPOINT ["/usr/bin/date-random"]

CMD ["10"]
[root@master loong576]# docker build -t loong576/date-random:args .
Sending build context to Docker daemon   5.12kB
Step 1/4 : FROM centos:centos7.6.1810
 ---> f1cb7c7d58b7
Step 2/4 : ADD date-random.sh /usr/bin/date-random
 ---> 307e2f66dfa4
Step 3/4 : ENTRYPOINT ["/usr/bin/date-random"]
 ---> Running in ab41b93f6b28
Removing intermediate container ab41b93f6b28
 ---> 5f536f70da1f
Step 4/4 : CMD ["10"]
 ---> Running in 90f5d58c68fb
Removing intermediate container 90f5d58c68fb
 ---> 8bf9ce828481
Successfully built 8bf9ce828481
Successfully tagged loong576/date-random:args
[root@master loong576]# docker push loong576/date-random:args 
The push refers to repository [docker.io/loong576/date-random]
200d475bbffa: Pushed 
89169d87dbe2: Layer already exists 
args: digest: sha256:08e4c791dc9d6b71ce45b13768ab09194cc11ecd4856b52f2719372d912ee9c1 size: 736

将之前的循环间隔5秒修改为参数INTERVAL，在Dockerfile中传递该参数值为10秒，上传dockerhub。Dockerfile中ENTRYPOINT和CMD后面的[]表明执行格式为Exec，区别于之前的Shell格式。

2.2 Docker运行带参数镜像

[root@master loong576]# docker run -itd --name centos-args loong576/date-random:args 
159e3204dad64516adc4681e9d7b1fe9f4d11a178e3cca7e9a9f13fd10252a43
[root@master loong576]# docker run -d --name centos-args loong576/date-random:args   
ee938a39167afb52fe72f9367ad23d9e8b2985037320ad1ccc6ec7e3f9bc9255
[root@master loong576]# docker exec -it centos-args sh
sh-4.2# [root@master loong576]# 
[root@master loong576]# 
[root@master loong576]# 
[root@master loong576]# docker run -it --name centos-args loong576/date-random:args  


[root@master loong576]# docker run -itd --name centos-args loong576/date-random:args  
2a25e91a0f5b54c1c568ce089d879d50cd9a12513be5d365dc5743d74f2ac737
[root@master loong576]# docker ps |grep centos
2a25e91a0f5b        loong576/date-random:args   "/usr/bin/date-rando…"   18 seconds ago      Up 16 seconds                           centos-args
[root@master loong576]# docker exec -it centos-args sh
sh-4.2# cd /var/htdocs/
sh-4.2# ls -alrt
total 4
drwxr-xr-x 1 root root  20 Sep 16 07:24 ..
drwxr-xr-x 2 root root  24 Sep 16 07:24 .
-rw-r--r-- 1 root root 234 Sep 16 07:25 index.html
sh-4.2# tail -f index.html 
date is :  Mon Sep 16 07:24:31 UTC 2019
RANDOM is :  26700
date is :  Mon Sep 16 07:24:41 UTC 2019
RANDOM is :  13556
date is :  Mon Sep 16 07:24:51 UTC 2019
RANDOM is :  7320
date is :  Mon Sep 16 07:25:01 UTC 2019
RANDOM is :  6041
date is :  Mon Sep 16 07:25:11 UTC 2019
RANDOM is :  23591
^C
sh-4.2#

index.html输出的巡检间隔为10秒，证明Dockerfile设置生效。

2.3 Docker直接指定参数运行镜像

指定循环间隔为3秒

[root@master loong576]# docker run -itd --name centos-args2 loong576/date-random:args 3
498e48dabb0b2eb15366286d7cfd317774cf993a98c19310e3b3fe2aad9d8d6a
[root@master loong576]# docker ps |grep centos
498e48dabb0b        loong576/date-random:args   "/usr/bin/date-rando…"   7 seconds ago       Up 5 seconds                            centos-args2
2a25e91a0f5b        loong576/date-random:args   "/usr/bin/date-rando…"   6 minutes ago       Up 6 minutes                            centos-args
[root@master loong576]# docker exec -it centos-args2 sh                                
sh-4.2# tail -f /var/htdocs/index.html 
date is :  Mon Sep 16 07:31:24 UTC 2019
RANDOM is :  17156
date is :  Mon Sep 16 07:31:27 UTC 2019
RANDOM is :  30995
date is :  Mon Sep 16 07:31:30 UTC 2019
RANDOM is :  24714
date is :  Mon Sep 16 07:31:33 UTC 2019
RANDOM is :  11670
date is :  Mon Sep 16 07:31:36 UTC 2019
RANDOM is :  32253
date is :  Mon Sep 16 07:31:39 UTC 2019
RANDOM is :  18917
^C
sh-4.2#

可以看到index.html的输出间隔时间为3秒

2.4 pod中定义传递的参数值

定义pod date-random-configmap-args，设置传递容器的参数值为4.

[root@master loong576]# more date-random-configmap-args.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: date-random-configmap-args 
spec:
  containers:
  - image: loong576/date-random:args
    args: ["4"]
    name: centos-date 
    volumeMounts:
    - name: html
      mountPath: /var/htdocs
  - image: nginx
    name: nginx-server
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html
      readOnly: true
  volumes:
  - name: html
    emptyDir: {}
[root@master loong576]# kubectl apply -f date-random-configmap-args.yaml 
pod/date-random-configmap-args created
[root@master loong576]# kubectl get po -o wide
NAME                         READY   STATUS             RESTARTS   AGE    IP             NODE     NOMINATED NODE   READINESS GATES
date-random-configmap        2/2     Running            0          5h2m   10.244.1.203   node01   <none>           <none>
date-random-configmap-args   2/2     Running            0          100s   10.244.2.209   node02   <none>           <none>
nginx                        0/1     CrashLoopBackOff   20         81m    10.244.1.205   node01   <none>           <none>
[root@master loong576]# curl 10.244.2.209
date is :  Mon Sep 16 07:52:37 UTC 2019
RANDOM is :  5067
date is :  Mon Sep 16 07:52:41 UTC 2019
RANDOM is :  1512
date is :  Mon Sep 16 07:52:45 UTC 2019
RANDOM is :  30707
date is :  Mon Sep 16 07:52:49 UTC 2019
RANDOM is :  9853
date is :  Mon Sep 16 07:52:53 UTC 2019
RANDOM is :  4578
date is :  Mon Sep 16 07:52:57 UTC 2019
RANDOM is :  22461
date is :  Mon Sep 16 07:53:01 UTC 2019
RANDOM is :  23571
date is :  Mon Sep 16 07:53:05 UTC 2019
RANDOM is :  27206
date is :  Mon Sep 16 07:53:09 UTC 2019
RANDOM is :  5840
date is :  Mon Sep 16 07:53:13 UTC 2019
RANDOM is :  16860
date is :  Mon Sep 16 07:53:17 UTC 2019
RANDOM is :  3697
date is :  Mon Sep 16 07:53:21 UTC 2019
RANDOM is :  24393
date is :  Mon Sep 16 07:53:25 UTC 2019
RANDOM is :  6753

index.html的输出时间间隔为4秒，与pod的args设置的值一致。

3. 为容器设置环境变量

3.1 生成镜像loong576/date-random:env

[root@master loong576]# more date-random.sh                           
#!/bin/bash
mkdir /var/htdocs
#INTERVAL=$1
while : 
do
  /usr/bin/echo "date is : " `date` >> /var/htdocs/index.html
  /usr/bin/echo "RANDOM is : " `echo $RANDOM` >> /var/htdocs/index.html
  sleep $INTERVAL 
done
[root@master loong576]# more Dockerfile                           
FROM centos:centos7.6.1810 

ADD date-random.sh /usr/bin/date-random

ENTRYPOINT ["/usr/bin/date-random"]

#CMD ["10"]
[root@master loong576]# docker build -t loong576/date-random:env .
Sending build context to Docker daemon  6.144kB
Step 1/3 : FROM centos:centos7.6.1810
 ---> f1cb7c7d58b7
Step 2/3 : ADD date-random.sh /usr/bin/date-random
 ---> 1ddb8d15b11d
Step 3/3 : ENTRYPOINT ["/usr/bin/date-random"]
 ---> Running in e34374da108a
Removing intermediate container e34374da108a
 ---> b5daa0cf4479
Successfully built b5daa0cf4479
Successfully tagged loong576/date-random:env
[root@master loong576]# docker push loong576/date-random:env  
The push refers to repository [docker.io/loong576/date-random]
5a389d8a01f4: Pushed 
89169d87dbe2: Layer already exists 
env: digest: sha256:f51c0831235a559e589ede54226d9f387966bea45435026acafad5416eba5e69 size: 736

生成镜像loong576/date-random:env，该镜像相比loong576/date-random:args主要是注释脚本中的参数传递'INTERVAL=$1'和Dockerfile中指定的参数值'CMD "10"'

3.2 pod中指定环境变量

新建pod date-random-configmap-env并指定环境变量INTERVAL，赋值为6

[root@master loong576]# more date-random-configmap-env.yaml             
apiVersion: v1
kind: Pod
metadata:
  name: date-random-configmap-env
spec:
  containers:
  - image: loong576/date-random:env
    env:
    - name: INTERVAL
      value: "6"
    name: centos-date 
    volumeMounts:
    - name: html
      mountPath: /var/htdocs
  - image: nginx
    name: nginx-server
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html
      readOnly: true
  volumes:
  - name: html
    emptyDir: {}
[root@master loong576]# kubectl apply -f date-random-configmap-env.yaml 
pod/date-random-configmap-env created
[root@master loong576]# kubectl get po -o wide
NAME                         READY   STATUS             RESTARTS   AGE     IP             NODE     NOMINATED NODE   READINESS GATES
date-random-configmap        2/2     Running            0          5h29m   10.244.1.203   node01   <none>           <none>
date-random-configmap-args   2/2     Running            0          29m     10.244.2.209   node02   <none>           <none>
date-random-configmap-env    2/2     Running            0          4m20s   10.244.1.208   node01   <none>           <none>
nginx                        0/1     CrashLoopBackOff   8          18m     10.244.1.206   node01   <none>           <none>
[root@master loong576]# curl 10.244.1.208
date is :  Mon Sep 16 08:16:50 UTC 2019
RANDOM is :  30120
date is :  Mon Sep 16 08:16:56 UTC 2019
RANDOM is :  8149
date is :  Mon Sep 16 08:17:02 UTC 2019
RANDOM is :  2752
date is :  Mon Sep 16 08:17:08 UTC 2019
RANDOM is :  20276
date is :  Mon Sep 16 08:17:14 UTC 2019
RANDOM is :  19299
date is :  Mon Sep 16 08:17:21 UTC 2019
RANDOM is :  20116
date is :  Mon Sep 16 08:17:27 UTC 2019
RANDOM is :  22331
date is :  Mon Sep 16 08:17:33 UTC 2019
RANDOM is :  3626
date is :  Mon Sep 16 08:17:39 UTC 2019
RANDOM is :  28190
date is :  Mon Sep 16 08:17:45 UTC 2019
RANDOM is :  3241
date is :  Mon Sep 16 08:17:51 UTC 2019
RANDOM is :  27762
date is :  Mon Sep 16 08:17:57 UTC 2019
RANDOM is :  26519
date is :  Mon Sep 16 08:18:03 UTC 2019
RANDOM is :  28403
date is :  Mon Sep 16 08:18:09 UTC 2019
RANDOM is :  27219

index.html的输出时间间隔为6秒，与pod的env设置的值一致。

四、ConfigMap

  通过'三、容器中的配置数据传递'，可以将要传递给容器的参数直接定义在镜像中或者pod中通过定义参数值和环境变量方式传递参数给容器，这些方式有如下弊端：

  • 1.pod配置不能复用，生产和开发环境需定义两套；
  • 2.参数变更时需重启容器；
  • 3.镜像中的参数变更需新建镜像；
  • 4.不适合分布式环境；

这时就需要ConfigMap，通过Volume的形式被mount到Pod或者环境变量的方式传递参数给容器。

1. 创建configmap

1.1 --from-file指定文件方式

[root@master loong576]# more file1.txt 
file1:abc
file1:123
[root@master loong576]# more file2.txt 
file2:abcd
file2:1234
[root@master loong576]# kubectl create cm my-config-file --from-file=file1.txt --from-file=test2=file2.txt
configmap/my-config-file created
[root@master loong576]# kubectl get cm
NAME             DATA   AGE
my-config-file   2      5s
[root@master loong576]# kubectl describe cm my-config-file 
Name:         my-config-file
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
file1.txt:
----
file1:abc
file1:123

test2:
----
file2:abcd
file2:1234

Events:  <none>

创建configmap my-config-file，指定文件为file1.txt和file2.txt，key值分别为默认的file1.txt和指定的test2。

1.2 --from-file指定目录方式

[root@master configmap]# kubectl create configmap my-config-dir --from-file=/root/loong576/configmap/
configmap/my-config-dir created
[root@master configmap]# kubectl get cm
NAME             DATA   AGE
my-config-dir    2      6s
my-config-file   2      16h

创建configmap my-config-dir,指定目录为/root/loong576/configmap/,该目录下有文件my-nginx-config.conf和sleep-interval,一个为nginx配置,一个为脚本循环时间设置，后面的configmap会用到。

1.3 --from-literal字面量方式

[root@master loong576]# kubectl create cm  my-config-literal --from-literal=username=admin --from-literal=password=123456                    
configmap/my-config-literal created
[root@master loong576]# kubectl get cm
NAME                DATA   AGE
my-config-dir       2      18m
my-config-file      2      16h
my-config-literal   2      4s

创建configmap my-config-literal,key分别为admin和password

1.4 --from-env-file键值对方式

[root@master loong576]# more bar.env 
a=1
b=2
c=3
d=4
e
f=
gggg
h='8'
#i = '9'
j="10"
[root@master loong576]# kubectl create configmap my-config-env --from-env-file=./bar.env 
configmap/my-config-env created
[root@master loong576]# kubectl get cm
NAME                DATA   AGE
my-config-dir       2      23m
my-config-env       9      3s
my-config-file      2      16h
my-config-literal   2      5m35s

键值对方式对格式有一定要求：有效的环境变量名必须由字母字符、数字、''-'或'.'组成，并且不能以数字开头（例如，'.my.env name'，或'.my'.env.name'，或'.myenvname1'，用于验证的regex是'-.'-z a-z*'）

1.5 yaml文件方式

[root@master loong576]# more configmap.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: my-config-yaml
data:
  sleep-interval: "15"
[root@master loong576]# kubectl apply -f configmap.yaml 
configmap/my-config-yaml created
[root@master loong576]# kubectl get cm
NAME                DATA   AGE
my-config-dir       2      34m
my-config-env       9      11m
my-config-file      2      16h
my-config-literal   2      16m
my-config-yaml      1      3s
[root@master loong576]# kubectl describe cm my-config-yaml 
Name:         my-config-yaml
Namespace:    default
Labels:       <none>
Annotations:  kubectl.kubernetes.io/last-applied-configuration:
                {"apiVersion":"v1","data":{"sleep-interval":"15"},"kind":"ConfigMap","metadata":{"annotations":{},"name":"my-config-yaml","namespace":"def...

Data
====
sleep-interval:
----
15
Events:  <none>

创建configmap my-config-yaml,指定key值sleep-interval为15

2. 使用configmap

2.1 新建pod date-random-configmap-volume

创建pod date-random-configmap-volume,给容器centos-date传递ConfigMap条目sleep-interval作为环境变量；将ConfigMap作为卷挂载至容器nginx-server作为nginx配置文件

[root@master loong576]# more date-random-configmap-volume.yaml             
apiVersion: v1
kind: Pod
metadata:
  name: date-random-configmap-volume
spec:
  containers:
  - image: loong576/date-random:env    #容器centos-date使用的镜像，tag为env
    env:
    - name: INTERVAL                   #环境变量名为INTERVAL，与脚本date-random.sh中定义的保持一致
      valueFrom:
        configMapKeyRef:               #使用ConfigMap初始化
          name: my-config-dir          #ConfigMap名称
          key: sleep-interval          #环境变量的值被设置为ConfigMap下sleep-interval对应的值
    name: centos-date 
    volumeMounts:
    - name: html
      mountPath: /var/htdocs           #挂载emptyDir卷的位置
  - image: nginx
    name: nginx-server 
    volumeMounts:
    - name: html
      mountPath: /usr/share/nginx/html #挂载emptyDir卷的位置
      readOnly: true
    - name: config
      mountPath: /etc/nginx/conf.d     #挂载ConfigMap卷的位置
      readOnly: true
  volumes:
  - name: html
    emptyDir: {}
  - name: config
    configMap:
      name: my-config-dir              #定义卷类型为ConfigMap，名字为my-config-dir
      items:                           #选择包含在卷中的条目
      - key: my-nginx-config.conf      #被挂载的条目为my-nginx-config.conf 
        path: nginx-port.conf          #挂载至容器的文件名
[root@master loong576]# kubectl apply -f date-random-configmap-volume.yaml 
pod/date-random-configmap-volume created
[root@master loong576]# kubectl get po -o wide
NAME                           READY   STATUS             RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
date-random-configmap          2/2     Running            2          29h   10.244.1.211   node01   <none>           <none>
date-random-configmap-args     2/2     Running            2          24h   10.244.2.210   node02   <none>           <none>
date-random-configmap-env      2/2     Running            2          24h   10.244.1.209   node01   <none>           <none>
date-random-configmap-volume   2/2     Running            0          20s   10.244.1.216   node01   <none>           <none>
nginx                          0/1     CrashLoopBackOff   113        24h   10.244.1.212   node01   <none>           <none>

通过挂载ConfigMap更新nginx配置原理：Nginx需读取配置文件/etc/nginx/nginx.conf, 默认配置文件会自动嵌入子文件夹/etc/nginx/conf.d/下的所有conf文件， 因此只需要将你的配置文件置于该子文件夹中即可

2.2 访问测试

[root@master loong576]# curl 10.244.1.216:81
date is :  Tue Sep 17 08:27:34 UTC 2019
RANDOM is :  9389
date is :  Tue Sep 17 08:27:42 UTC 2019
RANDOM is :  22109
date is :  Tue Sep 17 08:27:50 UTC 2019
RANDOM is :  13043

访问pod，nginx端口为81，date输出的间隔为8秒

[root@master loong576]# kubectl exec  -it date-random-configmap-volume -c nginx-server sh
# cd /etc/nginx/conf.d
# ls
nginx-port.conf
# more nginx-port.conf
server {
    listen              81;
    server_name         localhost;

    gzip on;
    gzip_types text/plain application/xml;

    location / {
        root   /usr/share/nginx/html;
        index  index.html index.htm;
    }

}

进入容器nginx-server，/etc/nginx/conf.d下发现作为卷挂载的ConfigMap条目nginx-port.conf

3. 更新应用配置

3.1 更新ConfigMap

[root@master loong576]# kubectl edit cm my-config-dir

更新my-config-dir,将条目my-nginx-config.conf的nginx监听端口由81更改为82

3.2 nginx加载配置

# nginx -s reload

由于nginx不会自动加载配置，故需重新加载

3.3 再次访问nginx

[root@master loong576]# curl 10.244.1.216:82
date is :  Tue Sep 17 08:27:34 UTC 2019
RANDOM is :  9389
date is :  Tue Sep 17 08:27:42 UTC 2019
RANDOM is :  22109
date is :  Tue Sep 17 08:27:50 UTC 2019
RANDOM is :  13043

再次访问nginx，端口变为82.

使用ConfigMap更新配置文件可避免pod重启或容器重建。

五、Secret

为了存储与分发此类信息，Kubemetes提供了一种称为Secret的单独资源对象。Secret结构与ConfigMap类似，均是键／值对的映射。

Secret作用:

  • 将 Secret 条目作为环境变量传递给容器
  • 将 Secret 条目暴露为卷中的文件

1. 创建Secret

和ConfigMap类似，Secret也有5中创建方式

使用文件、目录和字面量方式：

[root@master loong576]# kubectl create secret generic mysecret --from-file=./username.txt --from-file=mypassword=./password.txt --from-literal=loong=576  --from-file=./secret-dir/ 
secret/mysecret created
[root@master loong576]# kubectl get secrets mysecret 
NAME       TYPE     DATA   AGE
mysecret   Opaque   5      15s

secret有三种类型：

  • docker-registry 创建一个给Docker registry使用的secret
  • generic 从本地file, directory或者literal value创建一个secret
  • tls 创建一个TLS secret

这里使用的是generic方式，后面还会用到docker-registry方式。

键值对方式：

[root@master loong576]# kubectl create secret generic mysecret-env --from-env-file=secret-env.txt
secret/mysecret-env created
[root@master loong576]# kubectl get secrets 
NAME                  TYPE                                  DATA   AGE
default-token-gwhj2   kubernetes.io/service-account-token   3      2m29s
mysecret              Opaque                                5      103s
mysecret-env          Opaque                                3      7s

yaml方式：

[root@master loong576]# echo loong|base64                              
bG9vbmcK
[root@master loong576]# echo 576|base64                
NTc2Cg==
[root@master loong576]# more secret-yaml.yaml 
apiVersion: v1
kind: Secret
metadata:
  name: mysecret-yaml
data:
  username: bG9vbmcK 
  password: NTc2Cg== 
[root@master loong576]# kubectl apply -f secret-yaml.yaml 
secret/mysecret-yaml created
[root@master loong576]# kubectl get secrets 
NAME                  TYPE                                  DATA   AGE
default-token-gwhj2   kubernetes.io/service-account-token   3      31m
mysecret              Opaque                                5      30m
mysecret-env          Opaque                                3      29m
mysecret-yaml         Opaque                                2      5s

注意，yaml方式中条目对应的key值对应的value需base64编码，直接写明文会报错。

2. 查看Secret

[root@master loong576]# kubectl get secrets              
NAME                  TYPE                                  DATA   AGE
default-token-gwhj2   kubernetes.io/service-account-token   3      36m
mysecret              Opaque                                5      35m
mysecret-env          Opaque                                3      33m
mysecret-yaml         Opaque                                2      4m53s
[root@master loong576]# kubectl describe secrets mysecret
Name:         mysecret
Namespace:    default
Labels:       <none>
Annotations:  <none>

Type:  Opaque

Data
====
dir1.txt:      8 bytes
dir2.txt:      8 bytes
loong:         3 bytes
mypassword:    7 bytes
username.txt:  6 bytes
[root@master loong576]# kubectl get secrets mysecret -o yaml
apiVersion: v1
data:
  dir1.txt: dGVzdDAwMQo=
  dir2.txt: dGVzdDAwMgo=
  loong: NTc2
  mypassword: YWJjMTIzCg==
  username.txt: YWRtaW4K
kind: Secret
metadata:
  creationTimestamp: "2019-09-18T01:55:47Z"
  name: mysecret
  namespace: default
  resourceVersion: "2643256"
  selfLink: /api/v1/namespaces/default/secrets/mysecret
  uid: 6ebdc96c-d9b7-11e9-863b-000c29d99ba3
type: Opaque
[root@master loong576]# echo dGVzdDAwMQo=|base64 --decode   
test001

通过'kubectl get secrets'查看所有secret，通过'kubectl describe secrets mysecret'查看条目key值，通过'kubectl get secrets mysecret -o yaml'可查看条目的value值，不过需要base64解码。

3. 使用Secret

本文以使用Secret拉取私有镜像为例介绍Secret的用法。

3.1 创建secret docker-registry

[root@master loong576]# kubectl create secret docker-registry loong576-secret --docker-username=loong576 --docker-password=xxxxxxxxxx  --docker-email=xxxxxxxxx@126.com
secret/loong576-secret created
[root@master loong576]# kubectl get secrets loong576-secret 
NAME              TYPE                             DATA   AGE
loong576-secret   kubernetes.io/dockerconfigjson   1      16s
[root@master loong576]#

创建secret docker-registry：loong576-secret，dockerhub的用户名密码和邮箱根据个人的实际情况填写。

3.2 创建私有镜像loong576/test

在dockerhub上创建私有镜像loong576/test

3.3 创建pod private-pod-secret

[root@master loong576]# more private-image-secret-volume.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: private-pod-secret
spec:
  imagePullSecrets:
  - name: loong576-secret                    #引用创建的docker-registry secret:loong576-secret
  containers:
  - image: loong576/test                     #拉取私有镜像 
    name: busybox576 
    args: ["/bin/sh","-c","sleep 600000"]
    volumeMounts:
    - name: vol-secret
      mountPath: /etc/loong576               #将卷挂载至容器的路径
      readOnly: true 
  volumes:
  - name: vol-secret                         #将secret作为卷挂载，卷名为vol-secret
    secret:
      secretName: mysecret-yaml              #引用之前创建的secret mysecret-yaml 
[root@master loong576]# kubectl apply -f private-image-secret-volume.yaml 
pod/private-pod-secret created
[root@master loong576]# kubectl get po -o wide
NAME                           READY   STATUS             RESTARTS   AGE   IP             NODE     NOMINATED NODE   READINESS GATES
date-random-configmap          2/2     Running            4          2d    10.244.1.217   node01   <none>           <none>
date-random-configmap-args     2/2     Running            4          43h   10.244.2.213   node02   <none>           <none>
date-random-configmap-env      2/2     Running            4          42h   10.244.1.220   node01   <none>           <none>
date-random-configmap-volume   2/2     Running            2          18h   10.244.1.221   node01   <none>           <none>
nginx                          0/1     CrashLoopBackOff   156        43h   10.244.1.218   node01   <none>           <none>
private-pod-secret             1/1     Running            0          45s   10.244.2.218   node02   <none>           <none>

创建pod private-pod-secret，使用secret loong576-secret拉取私有镜像，将secret mysecret-yaml作为卷挂载至容器。

3.4 pod中查看secret

[root@master loong576]# kubectl exec -it private-pod-secret sh
/ # df -h
Filesystem                Size      Used Available Use% Mounted on
overlay                   5.0G      3.5G      1.5G  70% /
tmpfs                    64.0M         0     64.0M   0% /dev
tmpfs                   909.8M         0    909.8M   0% /sys/fs/cgroup
tmpfs                   909.8M      8.0K    909.8M   0% /etc/loong576
/dev/mapper/root--vg-var
                          5.0G      3.5G      1.5G  70% /dev/termination-log
/dev/mapper/root--vg-var
                          5.0G      3.5G      1.5G  70% /etc/resolv.conf
/dev/mapper/root--vg-var
                          5.0G      3.5G      1.5G  70% /etc/hostname
/dev/mapper/root--vg-var
                          5.0G      3.5G      1.5G  70% /etc/hosts
shm                      64.0M         0     64.0M   0% /dev/shm
tmpfs                   909.8M     12.0K    909.8M   0% /var/run/secrets/kubernetes.io/serviceaccount
tmpfs                   909.8M         0    909.8M   0% /proc/acpi
tmpfs                    64.0M         0     64.0M   0% /proc/kcore
tmpfs                    64.0M         0     64.0M   0% /proc/keys
tmpfs                    64.0M         0     64.0M   0% /proc/timer_list
tmpfs                    64.0M         0     64.0M   0% /proc/timer_stats
tmpfs                    64.0M         0     64.0M   0% /proc/sched_debug
tmpfs                   909.8M         0    909.8M   0% /proc/scsi
tmpfs                   909.8M         0    909.8M   0% /sys/firmware
/ # cd /etc/loong576/
/etc/loong576 # ls -l
total 0
lrwxrwxrwx    1 root     root            15 Sep 18 03:15 password -> ..data/password
lrwxrwxrwx    1 root     root            15 Sep 18 03:15 username -> ..data/username
/etc/loong576 # more username 
loong
/etc/loong576 # more password 
576

进入容器查看secret，发现/etc/loong576下作为卷挂载的secret；/etc/loong576文件系统类型为tmpfs，说明secret卷采用内存文件系统挂载，secret数据不会写入磁盘，保证数据安全。

4. 更新Secret

[root@master loong576]# echo loong-update|base64
bG9vbmctdXBkYXRlCg==
[root@master loong576]# echo 576-update|base64
NTc2LXVwZGF0ZQo=
[root@master loong576]# kubectl edit secret mysecret-yaml 
secret/mysecret-yaml edited

更新mysecret-yaml，发现容器中挂载的内容同时被更新。

本文所有脚本和配置文件已上传：k8s实践(八)：ConfigMap and Secret

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k8s实践(八)：ConfigMap and Secret
  在实际的应用部署中， 经常需要为各种应用／中间件配置各种参数， 如数据库地址、 用户名、 密码等， 而且大多数生产环境中的应用程序配置较为复杂， 可能是多个...
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