systemctl管理系统配置、服务

systemctl daemon-reload \
&& systemctl enable docker \
&& systemctl start docker \
&& systemctl restart docker \

查看服务状态
systemctl status docker

调试服务：（以kubelet为例）

查看service的启动命令
查看启动配置
修改启动配置
重新启动

查看命令的执行日志
查看系统日志

vagrant@ubuntu-xenial:/vagrant$ systemctl status kubelet
● kubelet.service - Kubernetes Kubelet Server
   Loaded: loaded (/etc/systemd/system/kubelet.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat -- :: UTC; 1h 23min ago
     Docs: https://github.com/GoogleCloudPlatform/kubernetes
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
  Process:  ExecStartPre=/bin//SUCCESS)
 Main PID:  (kubelet)
    Tasks:
   Memory: 87.2M
      CPU: 13min .454s
   CGroup: /system.slice/kubelet.service
           └─ /usr/bin/kubelet --v= --address=0.0.0.0 --hostname-override=10.0.2.15 --kubeconfig=/etc/kubernetes/kubelet.kubeconfig --pod-manifest-path=/etc/kubernetes/manifests --log-dir=/root/info/logs/k8s -
lines -/ (END)

ctrl+c退出
查看命令脚本：
vagrant@ubuntu-xenial:/vagrant$ cat /etc/systemd/system/kubelet.service
[Unit]
Description=Kubernetes Kubelet Server
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=docker.service
Requires=docker.service

[Service]
WorkingDirectory=/var/lib/kubelet
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/cpuset/system.slice
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/perf_event/system.slice
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/net_cls,net_prio/system.slice
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/freezer/system.slice
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/hugetlb/system.slice
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/pids/system.slice
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/pids/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/blkio/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/cpu,cpuacct/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/systemd/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/net_cls,net_prio/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/freezer/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/memory/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/cpuset/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/perf_event/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/devices/kubelet.service
ExecStartPre=/bin/mkdir -p /sys/fs/cgroup/hugetlb/kubelet.service
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/kubelet
ExecStart=/usr/bin/kubelet \
            $KUBE_LOGTOSTDERR \
            $KUBE_LOG_LEVEL \
            $KUBELET_API_SERVER \
            $KUBELET_ADDRESS \
            $KUBELET_PORT \
            $KUBELET_HOSTNAME \
            $KUBE_ALLOW_PRIV \
            $KUBELET_ARGS
Restart=always
RestartSec=

[Install]
WantedBy=multi-user.target

vagrant@ubuntu-xenial:/vagrant$ cat /etc/kubernetes/kubelet.kubeconfig
apiVersion: v1
kind: Config
current-context: kubelet-to-cluster.local
preferences: {}
clusters:
- cluster:
    certificate-authority: /etc/kubernetes/certs/ca.crt
    server: https://10.0.2.15:6443
  name: cluster.local
contexts:
- context:
    cluster: cluster.local
    user: kubelet
  name: kubelet-to-cluster.local
users:
- name: kubelet
  user:
    token: lHiWR3ogjcdq691yX4QxMq06SRmv1DfF
此处可以修改kubelet服务地址，比如：此时虚机网络设置为private-network, ip=192.168.33.10， 可以将server地址改为192.168.33.10，外面就可以通过小网192.168.33.10访问。

vagrant@ubuntu-xenial:/vagrant$ cat /etc/kubernetes/config
###
# kubernetes system config
#
# The following values are used to configure various aspects of all
# kubernetes services, including
#
#   kube-apiserver.service
#   kube-controller-manager.service
#   kube-scheduler.service
#   kubelet.service
#   kube-proxy.service

# journal verbosity level, the higher is the more verbose
KUBE_LOG_LEVEL="--v=0"

# How the replication controller, scheduler, and proxy
KUBE_MASTER="--master=https://10.0.2.15:6443"

vagrant@ubuntu-xenial:/vagrant$ systemctl restart kubelet