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【云原生之kubernetes】kubernetes集群下初始化容器的使用方法
一、初始化容器介绍
1.初始化容器简介
Kubernetes 中 Init 容器，也叫做初始化容器，是 K8s 官方为我们提供的一个 可以用来判断我们的环境是否已经满足运行 Pod 应用前所需要的条件。
2.初始化容器特点
1.初始化容器用于帮助主容器执行初始化，它会先与主容器启动.
2.初始化容器可以有多个，这些初始化容器时顺序执行的，任意一个初始化容器执行失败，则整个pod退出。
3.初始化容器的任务不是长时任务，初始化容器任务执行完毕，且正常退出，主容器才会启动。
二、检查本地集群状态
1.检查工作节点状态
[root@k8s-master ~]# kubectl get nodes -owide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
k8s-master Ready control-plane,master 16d v1.23.1 192.168.3.201 <none> CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.6.6
k8s-node01 Ready <none> 16d v1.23.1 192.168.3.202 <none> CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.6.6
k8s-node02 Ready <none> 16d v1.23.1 192.168.3.203 <none> CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.6.6
2.检查系统pod状态
[root@k8s-master ~]# kubectl get pods -A
NAMESPACE NAME READY STATUS RESTARTS AGE
default nfs-client-provisioner-779b7f4dfd-tgmmc 1/1 Running 94 (5m4s ago) 30h
kube-system calico-kube-controllers-7bc6547ffb-2nf66 1/1 Running 2 (3d6h ago) 16d
kube-system calico-node-8c4pn 0/1 Running 2 (3d6h ago) 16d
kube-system calico-node-f28qq 1/1 Running 2 (3d6h ago) 16d
kube-system calico-node-wmc2j 1/1 Running 2 (3d6h ago) 16d
kube-system coredns-6d8c4cb4d-6gm4x 1/1 Running 2 (3d6h ago) 16d
kube-system coredns-6d8c4cb4d-7vxlz 1/1 Running 2 (3d6h ago) 16d
kube-system etcd-k8s-master 1/1 Running 2 (3d6h ago) 16d
kube-system kube-apiserver-k8s-master 1/1 Running 2 (3d6h ago) 16d
kube-system kube-controller-manager-k8s-master 1/1 Running 2 (3d6h ago) 16d
kube-system kube-proxy-8dfw8 1/1 Running 2 (3d6h ago) 16d
kube-system kube-proxy-ghzrv 1/1 Running 2 (3d6h ago) 16d
kube-system kube-proxy-j867z 1/1 Running 2 (3d6h ago) 16d
kube-system kube-scheduler-k8s-master 1/1 Running 2 (3d6h ago) 16d
三、运行一个初始化容器的pod
1.编辑web_init.yaml 文件
[root@k8s-master init]# cat web_init.yaml
apiVersion: v1
kind: Pod
metadata:
name: web01
spec:
restartPolicy: Always #容器重启策略，Always总是重启，这是默认策略，OnFailure当pod异常退出时，则自动重启；Never不要重启
dnsPolicy: Default
volumes:
- name: rootdir
# hostPath:
# path: /data/nginx
emptyDir:
- name: localtime
hostPath: #挂载宿主机本地目录
path: /etc/localtime
initContainers:
- name: busybox01
image: busybox:1.28
volumeMounts:
- name: rootdir
mountPath: /data/index/html
command:
- /bin/sh
- -c
- "echo 'hello world' > /data/index/html/index.html"
containers:
- name: busybox02
image: busybox:1.28
imagePullPolicy: IfNotPresent
volumeMounts:
# - name: rootdir
# mountPath: /usr/share/nginx/html
- name: localtime
mountPath: /etc/localtime
readOnly: true #只读挂载
env:
- name: test
value: "123"
command:
- /bin/sh
- -c
args: #向Cmd传递参数
- "sleep 3600"
- image: nginx:1.21
name: nginxtest
imagePullPolicy: IfNotPresent
env:
- name: MYSQL_HOST
value: "192.169.0.1"
- name: MYSQL_PORT
value: "3306"
volumeMounts:
- name: rootdir
mountPath: /usr/share/nginx/html
- name: localtime
mountPath: /etc/localtime
# command:
# - /bin/bash
# - -c
# args: #向Cmd传递参数
# - "sleep 3600"
ports: #容器端口情况
- name: http
protocol: TCP
containerPort: 80
hostPort: 8080
# dnsPolicy: Default
2.运行pod
[root@k8s-master init]# kubectl apply -f web_init.yaml
3.检查pod状态
[root@k8s-master init]# kubectl get pods
NAME READY STATUS RESTARTS AGE
web01 0/2 Init:0/1 0 11s
[root@k8s-master init]# kubectl get pods
NAME READY STATUS RESTARTS AGE
web01 2/2 Running 0 2m
四、测试初始化容器效果
1.查看pod的ip信息
[root@k8s-master ~]# kubectl get pods -owide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
busybox03 1/1 Running 0 3m53s 10.244.85.202 k8s-node01 <none> <none>
web01 2/2 Running 0 15m 10.244.58.209 k8s-node02 <none> <none>
2.访问web内容
[root@k8s-master init]# kubectl exec -it web01 -c nginxtest -- /bin/bash
root@web01:/# curl 10.244.58.209
hello world
五、查看pod详细信息
[root@k8s-master ~]# kubectl describe pod web01
Name: web01
Namespace: default
Priority: 0
Node: k8s-node02/192.168.3.203
Start Time: Tue, 19 Jul 2022 17:46:07 +0800
Labels: <none>
Annotations: cni.projectcalico.org/containerID: 732320f6a7ffe9c7039b2b27de69c8773ecee304d2a20f98a4e9d243dfb7c8fc
cni.projectcalico.org/podIP: 10.244.58.209/32
cni.projectcalico.org/podIPs: 10.244.58.209/32
Status: Running
IP: 10.244.58.209
IPs:
IP: 10.244.58.209
Init Containers:
busybox01:
Container ID: containerd://e6d9f1432c63a13271ce9d38f5d63c1fdefbadf0800fa1668c7059d9eaa7fc33
Image: busybox:1.28
Image ID: docker.io/library/busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47
Port: <none>
Host Port: <none>
Command:
/bin/sh
-c
echo 'hello world' > /data/index/html/index.html
State: Terminated
Reason: Completed
Exit Code: 0
Started: Tue, 19 Jul 2022 17:46:25 +0800
Finished: Tue, 19 Jul 2022 17:46:25 +0800
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/data/index/html from rootdir (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-wzw77 (ro)
Containers:
busybox02:
Container ID: containerd://104d483e7b9a3af176d7c9deb9c5c7da29215bd6a207317531f62f85fe5315bf
Image: busybox:1.28
Image ID: docker.io/library/busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47
Port: <none>
Host Port: <none>
Command:
/bin/sh
-c
Args:
sleep 3600
State: Running
Started: Tue, 19 Jul 2022 17:46:25 +0800
Ready: True
Restart Count: 0
Environment:
test: 123
Mounts:
/etc/localtime from localtime (ro)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-wzw77 (ro)
nginxtest:
Container ID: containerd://2315c27ba2e0676bbb1e7ca0db764e96ca40af3f573ec1b536994f577332c911
Image: nginx:1.21
Image ID: docker.io/library/nginx@sha256:0d17b565c37bcbd895e9d92315a05c1c3c9a29f762b011a10c54a66cd53c9b31
Port: 80/TCP
Host Port: 8080/TCP
State: Running
Started: Tue, 19 Jul 2022 17:46:36 +0800
Ready: True
Restart Count: 0
Environment:
MYSQL_HOST: 192.169.0.1
MYSQL_PORT: 3306
Mounts:
/etc/localtime from localtime (rw)
/usr/share/nginx/html from rootdir (rw)
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-wzw77 (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
rootdir:
Type: EmptyDir (a temporary directory that shares a pod's lifetime)
Medium:
SizeLimit: <unset>
localtime:
Type: HostPath (bare host directory volume)
Path: /etc/localtime
HostPathType:
kube-api-access-wzw77:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Pulling 53m kubelet Pulling image "busybox:1.28"
Normal Scheduled 53m default-scheduler Successfully assigned default/web01 to k8s-node02
Normal Pulled 53m kubelet Successfully pulled image "busybox:1.28" in 17.313491259s
Normal Created 53m kubelet Created container busybox01
Normal Started 53m kubelet Started container busybox01
Normal Pulled 53m kubelet Container image "busybox:1.28" already present on machine
Normal Created 53m kubelet Created container busybox02
Normal Started 53m kubelet Started container busybox02
Normal Pulling 53m kubelet Pulling image "nginx:1.21"
Normal Pulled 53m kubelet Successfully pulled image "nginx:1.21" in 10.067013987s
Normal Created 53m kubelet Created container nginxtest
Normal Started 53m kubelet Started container nginxtest
六、查看pod日志信息
[root@k8s-master ~]# kubectl logs web01 busybox01
[root@k8s-master ~]# kubectl logs web01 busybox02
[root@k8s-master ~]# kubectl logs web01 nginxtest
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2022/07/19 17:46:36 [notice] 1#1: using the "epoll" event method
2022/07/19 17:46:36 [notice] 1#1: nginx/1.21.5
2022/07/19 17:46:36 [notice] 1#1: built by gcc 10.2.1 20210110 (Debian 10.2.1-6)
2022/07/19 17:46:36 [notice] 1#1: OS: Linux 3.10.0-957.el7.x86_64
2022/07/19 17:46:36 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 65536:65536
2022/07/19 17:46:36 [notice] 1#1: start worker processes
2022/07/19 17:46:36 [notice] 1#1: start worker process 31
2022/07/19 17:46:36 [notice] 1#1: start worker process 32
10.244.58.209 - - [19/Jul/2022:18:09:17 +0800] "GET / HTTP/1.1" 200 12 "-" "curl/7.74.0" "-"
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