Kuberbetes的DaemonSet

DaemonSet确保全部（或者一些）Node上运行一个Pod的副本。当有Node加入集群时，也会为他们新增一个Pod，当有Node从集群移除时，这些Pod也会被回收，删除DaemonSet将会删除他创建的所有Pod

使用daemonSet的一些典型用法：

• 运行集群存储Daemon，例如在每个Node上运行glusterd、ceph
• 在每个Node上运行日志收集daemon，例如fluentd、logstash
• 在每个Node上运行监控daemon，例如Prometheus Node Exporter、collectd、datadog代理、new relic代理或者Ganglia gmond

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: ds-test
  labels:
    app: filebeat
spec:
  selector:
    matchLabels:
      app: filebeat
  template:
    metadata:
      labels:
        app: filebeat
    spec:
      containers:
      - name: logs
        image: nginx
        ports:
        - containerPort: 80
        volumeMounts:
        - name: varlog
          mountPath: /tmp/log
      volumes:
      - name: varlog
        hostPath:
          path: /var/log

执行并查看日志

[root@test yaml]# kubectl apply -f ds.yaml 
daemonset.apps/ds-test created
[root@test yaml]# kubectl get pods
NAME                   READY   STATUS    RESTARTS   AGE
ds-test-gs6z5          1/1     Running   0          10s
ds-test-xfjgt          1/1     Running   0          10s
web-586db47859-6vpfr   1/1     Running   0          23h
web-586db47859-8hmxs   1/1     Running   0          23h
web-586db47859-wspl7   1/1     Running   0          23h
[root@test yaml]# kubectl exec -it ds-test-gs6z5 bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
root@ds-test-gs6z5:/# ls
bin  boot  dev    docker-entrypoint.d  docker-entrypoint.sh  etc    home  lib  lib64  media  mnt  opt  proc  root  run  sbin  srv  sys  tmp  usr  var
root@ds-test-gs6z5:/# ls tmp/log/
audit           btmp-20201201  cron-20201206       kube-apiserver    maillog-20201206   ntpstats  secure-20201115   spooler-20201129  zabbix
boot.log       chrony      dmesg              kubernetes    messages       pods      secure-20201122   spooler-20201206
boot.log-20200821  containers      dmesg.old          lastlog        messages-20201115  qemu-ga   secure-20201129   tallylog
boot.log-20200825  cron          elasticsearch       maillog        messages-20201122  redis     secure-20201206   tuned
boot.log-20200915  cron-20201115  firewalld          maillog-20201115    messages-20201129  rhsm      spooler           wtmp
boot.log-20201107  cron-20201122  grubby          maillog-20201122    messages-20201206  sa         spooler-20201115  yum.log
btmp           cron-20201129  grubby_prune_debug  maillog-20201129    mongodb           secure    spooler-20201122  yum.log-20201120
root@ds-test-gs6z5:/# exit
exit