Pod镜像拉取策略
我们在创建pod的时候,他都需要一个镜像,他需要这个镜像的时候我们呢怎么拉取这个镜像,有个策略
#下载策略有三个
[root@k8s-master1 ~]# kubectl explain pod.spec.containers.imagePullPolicy
KIND: Pod
VERSION: v1
FIELD: imagePullPolicy <string>
#这也是个字符串
DESCRIPTION:
Image pull policy. One of Always, Never, IfNotPresent. Defaults to Always
#三个下载策略一个叫Always 一个Never 一个叫IfNotPresent
#镜像下载策略分两种情况,本地有没有,就是你把pod已经通过调度器已经绑定到一个node节点上了,
#那么这个node节点有没有这个镜像呢,有镜像和没有镜像是两种情况,如果有,还要不要下载,
#Always是有没有都要下载
#Never不管有没有都不下载
#IfNotPresent根据你镜像版本号(tag)如果是latest(最新的)(比如(nginx:latest)
#他就永远都会去时使用Always(不管你本地有没有都会去拉取)如果你镜像不是latest(比如nginx:1.22.1)
#如果你本地有他就不拉取
if :latest tag is specified, or IfNotPresent otherwise. Cannot be updated.
More info:
https://kubernetes.io/docs/concepts/containers/images#updating-images
Possible enum values:
- `"Always"` means that kubelet always attempts to pull the latest image.
Container will fail If the pull fails.
- `"IfNotPresent"` means that kubelet pulls if the image isn't present on
disk. Container will fail if the image isn't present and the pull fails.
- `"Never"` means that kubelet never pulls an image, but only uses a local
image. Container will fail if the image isn't present镜像拉取策略有三个:
Always:总是拉取，当镜像 tag 为 latest 时，且 imagePullPolicy 未配置，默认为Always
Never:不管是否存在都不会拉取
IfNotPresent : 镜像不存在时拉取镜像，如果tag 为非 latest，且 imagePullPolicy 未配置，默认为 IfNotPresent
操作方式 |
说明 |
Always |
总是拉取,当镜像tag为latest时,且imagePullPolicy未配置默认为Always |
Never |
不管是否存在都不会拉取 |
IfNotPresent |
镜像不存在时拉取镜像,如果tag为非lasest,且imagePullPolicy,未配置,默认为IfNotPresent |
Pod重启策略
可以使用spec.restartPolicy指定容器的重启策略
重启肯定就是你的pod停止了,pod down了 容器down了,宕机以后会不会把我们这个容器进行重启呢?
restartPolicy比上面讲的级别要高,他不是在容器里面的,他是在spec里面的
他的级别也有三个
[root@k8s-master1 ~]# kubectl explain pod.spec.restartPolicy
KIND: Pod
VERSION: v1
FIELD: restartPolicy <string>
DESCRIPTION:
Restart policy for all containers within the pod. One of Always, OnFailure,
Never. Default to Always. More info:
https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy
Possible enum values:
- `"Always"`
#不管什么原因造成的pod退出,都给你pod进行重启,默认是Always
- `"Never"`
#不管什么原因造成的都不重启
- `"OnFailure"`
#如果容器退出不是以0状态退出,非0状态退出容器,他会自动重启,如果不是非0的就不重启
操作方式 |
说明 |
Always |
默认策略,容器失效时,自动重启该容器 |
Never |
无论何种状态都不重启 |
Onfailure |
容器以不为0的状态码中止,自动重启该容器 |
-o yaml 以yaml格式打印出来
[root@k8s-master1 ~]# kubectl get pods nginx-5 -o yaml
apiVersion: v1
#版本v1 自己写的
kind: Pod
#类型pod自己写的
metadata:
annotations:
#给加的资源注解自动加的
cni.projectcalico.org/containerID: a0d92f4cecd6d9987c4e3b89f35b16780d4dca64fd8922f2f95bb3ed420eead0
cni.projectcalico.org/podIP: 192.28.252.231/32
cni.projectcalico.org/podIPs: 192.28.252.231/32
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"app":"nginx","linux":"ubuntu"},"name":"nginx-5","namespace":"default"},"spec":{"containers":[{"image":"images.guoguo.com/apps/ubuntu-nginx:1.22.1","name":"nginx","ports":[{"containerPort":80}]}],"nodeName":"k8s-node2.guoguo.com"}}
creationTimestamp: "2023-08-09T02:35:08Z"
#创建的时间戳自动加的
labels:
#标签自己写的
app: nginx
linux: ubuntu
name: nginx-5
#pod名称自己写的
namespace: default
#名称空间自己写的
resourceVersion: "116336"
#版本自动加的
uid: c3082ae6-0952-44e0-bfb9-f89b9fa3013a
spec:
containers:
- image: images.guoguo.com/apps/ubuntu-nginx:1.22.1
#镜像路径自己写的
imagePullPolicy: IfNotPresent
#镜像下载策略因为我们写的tag版本不是latest,本地如果有就不下载了
name: nginx
#容器名字自己写的
ports:
- containerPort: 80
#容器端口号自己写的
protocol: TCP
resources: {}
#资源限制没写,为空
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: kube-api-access-cfg9z
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
nodeName: k8s-node2.guoguo.com
preemptionPolicy: PreemptLowerPriority
priority: 0
restartPolicy: Always
#pod重启策略,Always 默认就是这个
schedulerName: default-scheduler
#调度器的名称
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- name: kube-api-access-cfg9z
projected:
defaultMode: 420
sources:
- serviceAccountToken:
expirationSeconds: 3607
path: token
- configMap:
items:
- key: ca.crt
path: ca.crt
name: kube-root-ca.crt
- downwardAPI:
items:
- fieldRef:
apiVersion: v1
fieldPath: metadata.namespace
path: namespace
status:
#第五种状态,我们有五大状态,1是apiVersion,2是kind,3是spec,4是metadata,前四种是需要写在yaml文件里面的,
#第五种是status不需要我们呢自己手动写,自动加上的
conditions:
- lastProbeTime: null
lastTransitionTime: "2023-08-09T02:35:08Z"
status: "True"
type: Initialized
- lastProbeTime: null
lastTransitionTime: "2023-08-09T02:38:19Z"
status: "True"
type: Ready
- lastProbeTime: null
lastTransitionTime: "2023-08-09T02:38:19Z"
status: "True"
type: ContainersReady
- lastProbeTime: null
lastTransitionTime: "2023-08-09T02:35:08Z"
status: "True"
type: PodScheduled
containerStatuses:
- containerID: containerd://0c57c25f874d8dc4810c5f45604c0926e285111adc9674473304f041a0684f6e
image: images.guoguo.com/apps/ubuntu-nginx:1.22.1
imageID: images.guoguo.com/apps/ubuntu-nginx@sha256:5d90159fb7d3c4076eabbe2fefe74dafe262e5a16d40a64fd685dbb4f14926d9
lastState: {}
name: nginx
ready: true
restartCount: 0
started: true
state:
running:
startedAt: "2023-08-09T02:38:19Z"
hostIP: 172.17.8.12
phase: Running
podIP: 192.28.252.231
podIPs:
- ip: 192.28.252.231
qosClass: BestEffort
startTime: "2023-08-09T02:35:08Z"以上这些在我们文件里可以进行修改
vim nginx-pod.yamlapiVersion: v1
kind: Pod
metadata:
name: nginx-5
namespace: default
labels:
app: nginx
linux: ubuntu
spec:
nodeName: k8s-node2.guoguo.com
containers:
name: nginx
ports:
- containerPort: 80
image: images.guoguo.com/apps/ubuntu-nginx:1.20.1
apiVersion: v1
kind: Pod
metadata:
name: nginx-5
namespace: default
labels:
app: nginx
linux: ubuntu
spec:
restartPolicy: Never #pod重启策略,默认是Always,改为Nerser 不重启
containers:
- name: nginx
imagePullPolicy: Never #新加的镜像下载策略默认是Always,我们改为Nerser 不管有没有都不下载
ports:
- containerPort: 80
image: images.guoguo.com/apps/ubuntu-nginx:1.24.0 #改为一个仓库没有的镜像[root@k8s-master1 ~]# kubectl delete -f nginx-pod.yml
#删除原来的pod从新创建
[root@k8s-master1 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-5 0/1 ErrImageNeverPull 0 4s
#镜像下载失败
[root@k8s-master1 ~]# kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE
nginx-5 0/1 ErrImageNeverPull 0 59s 192.17.65.215 k8s-node3.guoguo.com
#已经绑定了node节点了describe看下
[root@k8s-master1 ~]# kubectl describe pods nginx-5
#前面省略
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 105s default-scheduler Successfully assigned default/nginx-5 to k8s-node3.guoguo.com
Warning ErrImageNeverPull 11s (x10 over 105s) kubelet Container image "images.guoguo.com/apps/ubuntu-nginx:1.24.0" is not present with pull policy of Never
#容器镜像 1.29.1 不存在 #下载策略为Nerser
Warning Failed 11s (x10 over 105s) kubelet Error: ErrImageNeverPull因为node3没有nginx1.24.1镜像所以不能生成,我们去node3下载一个镜像
切换到node3 下载一个1.24.0镜像
然后再看pod状态
[root@k8s-master1 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-5 1/1 Running 0 4m39s
#已经Running了
[root@k8s-master1 ~]# kubectl describe pods nginx-5
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 7m41s default-scheduler Successfully assigned default/nginx-5 to k8s-node3.guoguo.com
Warning ErrImageNeverPull 5m40s (x12 over 7m40s) kubelet Container image "images.guoguo.com/apps/ubuntu-nginx:1.24.0" is not present with pull policy of Never
Warning Failed 5m40s (x12 over 7m40s) kubelet Error: ErrImageNeverPull
Normal Pulled 5m25s kubelet Container image "images.guoguo.com/apps/ubuntu-nginx:1.24.0" already present on machine
#已经发现镜像存在主机里面 正常拉取到了
继续关注 restartPolicy: Never #pod重启策略,默认是Always,改为Nerser 不重启
restartPolicy设置的是Nerver,不重启
我们进入容器里面然后关闭nginx服务,这样容器就会退出,看看给不给重启
可以去dashboard 的ui界面去操作
也可以命令行kubectl exec 进入容器里面
[root@k8s-master1 ~]# kubectl exec -it nginx-5 /bin/bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
root@nginx-5:/# nginx -s stop
#关闭nginx
root@nginx-5:/# command terminated with exit code 137
[root@k8s-master1 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-5 0/1 Completed 0 82m
#状态为Completed如果我们关闭了容器的进程,那么容器会关闭,因为我们设置了容器的重启策略为Nerver
删掉这容器
[root@k8s-master1 ~]# kubectl delete -f nginx-pod.yml
pod "nginx-5" deleted我们将restartPolicy的状态改为Always,不管啥情况都重启
vim nginx-pod.ymlapiVersion: v1
kind: Pod
metadata:
name: nginx-5
namespace: default
labels:
app: nginx
linux: ubuntu
spec:
restartPolicy: Always #改为Always
containers:
- name: nginx
imagePullPolicy: Never
ports:
- containerPort: 80
image: images.guoguo.com/apps/ubuntu-nginx:1.24.0[root@k8s-master1 ~]# kubectl apply -f nginx-pod.yml
pod/nginx-5 created
[root@k8s-master1 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-5 1/1 Running 1 (7s ago) 80s
[root@k8s-master1 ~]# kubectl exec -it nginx-5 /bin/bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
root@nginx-5:/# nginx -s stop
root@nginx-5:/# command terminated with exit code 137
[root@k8s-master1 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-5 0/1 Completed 1 (43s ago) 116s
#稍等片刻再查询
[root@k8s-master1 ~]# kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-5 1/1 Running 2 (32s ago) 2m24s[root@k8s-master1 ~]# kubectl describe pods nginx-5
#前面省略
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 2m51s default-scheduler Successfully assigned default/nginx-5 to k8s-node3.guoguo.com
Warning BackOff 58s kubelet Back-off restarting failed container nginx in pod nginx-5_default(bf17257e-c091-4ef5-bc06-25d6bf392802)
Normal Pulled 44s (x3 over 2m51s) kubelet Container image "images.guoguo.com/apps/ubuntu-nginx:1.24.0" already present on machine
Normal Created 44s (x3 over 2m51s) kubelet Created container nginx
Normal Started 44s (x3 over 2m51s) kubelet Started container nginx