一、前言

1、首先明确是否修改过配置文件，多数启动失败是修改过配置文件的原因（本文是修改过配置文件但未重启Docker服务，导致重启系统后Docker服务启动失败）

2、如果不明确是否修改过配置文件，可查询docker日志是否出现报错，日志路径是/var/log/messages

tail -f /var/log/messages

报错如下，提示/etc/docker/daemon.json文件有问题

Jun 26 10:17:48 hecs-366931 systemd: Starting Docker Application Container Engine...
Jun 26 10:17:48 hecs-366931 dockerd: unable to configure the Docker daemon with file /etc/docker/daemon.json: invalid character '}' looking for beginning of object key string

二、Docker启动失败，根据报错查看镜像源配置文件/etc/docker/daemon.json

检查配置文件，发现json语法错误，"]"后面需要加个","

{
    "storage-driver":"devicemapper",
    "storage-opts":[
    "dm.thinpooldev=/dev/mapper/vgpaas-thinpool",
    "dm.use_deferred_removal=true",
    "dm.fs=ext4",
    "dm.use_deferred_deletion=true",
    "dm.basesize=10G"
    ]
    "insecure-registries":["docker.codedev.top:88","registry.cn-hangzhou.aliyuncs.com"]
}

修改配置文件并保存，重启Docker服务正常，问题解决

{
    "storage-driver":"devicemapper",
    "storage-opts":[
    "dm.thinpooldev=/dev/mapper/vgpaas-thinpool",
    "dm.use_deferred_removal=true",
    "dm.fs=ext4",
    "dm.use_deferred_deletion=true",
    "dm.basesize=10G"
    ],
    "insecure-registries":["docker.codedev.top:88","registry.cn-hangzhou.aliyuncs.com"]
}