有一个app 跑在pod里面，这个app 默认会输出自己的运行日志到syslogd，

请问如何让host主机上运行的syslogd日志收集器收集到上面app输出的运行日志呢？

/dev/log

答案：把 主机的 /dev/log目录挂载到 pod 里面的 /dev/log即可。

Some of these messages need to be brought to a system administrator’s attention immediately. And it may not be just any system administrator – there may be a particular system administrator who deals with a particular kind of message. Other messages just need to be recorded for future reference if there is a problem. Still others may need to have information extracted from them by an automated process that generates monthly reports.

To deal with these messages, most Unix systems have a facility called “Syslog.” It is generally based on a daemon called “Syslogd” Syslogd listens for messages on a Unix domain socket named /dev/log.

参考syslog overview

mountPath

具体来说就在 pod 的yaml 定义中，添加 hostPath volume，然后挂载到pod里：

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        - name: syslog
          mountPath: /dev/log

      volumes:
        - name: syslog
          hostPath: 
            path: /dev/log

在client-go等sdk中这样写即可：

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          apiv1.Volume{
                      Name: "syslog",
                      VolumeSource: apiv1.VolumeSource{
                          HostPath: &apiv1.HostPathVolumeSource{
                              Path: "/dev/log",
                          },
                      },
                  },
      },
Containers: []apiv1.Container{
    apiv1.Container{
        apiv1.VolumeMount{
            Name:      "syslog",
            MountPath: "/dev/log",
        },
        },
    },