现在 Docker 重启容器之后为什么修改过的东西还在？

去年中的时候玩过一段时间的 Docker，后来感觉对我没啥用就没完了。

这几天想复习下，就又开始玩了。

然后创建了一个容器：

docker container run -it --name=test centos

在里面创建一个空白文件：

touch 111

然后按 Ctrl+D 关闭容器。

再开启容器：

docker container start -a test

然后查看文件：

ls 111

会发现这个文件还在……

为什么会这样，我记得以前我一重启容器里面的文件都会丢失的。

附上 inspect，好像里面也没使用数据卷。

[
    {
        "Id": "f149e9ffd626dcffc86f3c8325abf0a7c3ddbd62e1834f4db652aae58a992dd4",
        "Created": "2018-04-02T08:01:58.043257934Z",
        "Path": "/bin/bash",
        "Args": [],
        "State": {
            "Status": "exited",
            "Running": false,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 0,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2018-04-02T08:04:00.805282255Z",
            "FinishedAt": "2018-04-02T08:05:40.914734517Z"
        },
        "Image": "sha256:2d194b392dd16955847a14f969b2dd319251471ffa6356be6d8f16c5bf53db9b",
        "ResolvConfPath": "/mnt/sda1/var/lib/docker/containers/f149e9ffd626dcffc86f3c8325abf0a7c3ddbd62e1834f4db652aae58a992dd4/resolv.conf",
        "HostnamePath": "/mnt/sda1/var/lib/docker/containers/f149e9ffd626dcffc86f3c8325abf0a7c3ddbd62e1834f4db652aae58a992dd4/hostname",
        "HostsPath": "/mnt/sda1/var/lib/docker/containers/f149e9ffd626dcffc86f3c8325abf0a7c3ddbd62e1834f4db652aae58a992dd4/hosts",
        "LogPath": "/mnt/sda1/var/lib/docker/containers/f149e9ffd626dcffc86f3c8325abf0a7c3ddbd62e1834f4db652aae58a992dd4/f149e9ffd626dcffc86f3c8325abf0a7c3ddbd62e1834f4db652aae58a992dd4-json.log",
        "Name": "/test",
        "RestartCount": 0,
        "Driver": "overlay2",
        "Platform": "linux",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "",
        "ExecIDs": null,
        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "default",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "CapAdd": null,
            "CapDrop": null,
            "Dns": [],
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": null,
            "GroupAdd": null,
            "IpcMode": "shareable",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": null,
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "ConsoleSize": [
                0,
                0
            ],
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": [],
            "BlkioDeviceReadBps": null,
            "BlkioDeviceWriteBps": null,
            "BlkioDeviceReadIOps": null,
            "BlkioDeviceWriteIOps": null,
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DiskQuota": 0,
            "KernelMemory": 0,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": null,
            "OomKillDisable": false,
            "PidsLimit": 0,
            "Ulimits": null,
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0
        },
        "GraphDriver": {
            "Data": {
                "LowerDir": "/mnt/sda1/var/lib/docker/overlay2/3435bb5d5dbb430fcb6a9af122d0c5200de27131d5234aac3fc336c8d7070efd-init/diff:/mnt/sda1/var/lib/docker/overlay2/933b109e2e6219526f5393e8bca8dcadc22f592b41a5fcb8eadb52221eaf4838/diff",
                "MergedDir": "/mnt/sda1/var/lib/docker/overlay2/3435bb5d5dbb430fcb6a9af122d0c5200de27131d5234aac3fc336c8d7070efd/merged",
                "UpperDir": "/mnt/sda1/var/lib/docker/overlay2/3435bb5d5dbb430fcb6a9af122d0c5200de27131d5234aac3fc336c8d7070efd/diff",
                "WorkDir": "/mnt/sda1/var/lib/docker/overlay2/3435bb5d5dbb430fcb6a9af122d0c5200de27131d5234aac3fc336c8d7070efd/work"
            },
            "Name": "overlay2"
        },
        "Mounts": [],
        "Config": {
            "Hostname": "f149e9ffd626",
            "Domainname": "",
            "User": "",
            "AttachStdin": true,
            "AttachStdout": true,
            "AttachStderr": true,
            "Tty": true,
            "OpenStdin": true,
            "StdinOnce": true,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/bash"
            ],
            "ArgsEscaped": true,
            "Image": "centos",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {
                "build-date": "20180302",
                "license": "GPLv2",
                "name": "CentOS Base Image",
                "vendor": "CentOS"
            }
        },
        "NetworkSettings": {
            "Bridge": "",
            "SandboxID": "25cdd513903dff03fd8adfa4f8ebd1a61f75532eb23e493e23cb2350bda3de07",
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
            "Ports": {},
            "SandboxKey": "/var/run/docker/netns/25cdd513903d",
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "",
            "Gateway": "",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "",
            "IPPrefixLen": 0,
            "IPv6Gateway": "",
            "MacAddress": "",
            "Networks": {
                "bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "a34d1f55d960138eedeaac53eb341429a1b69444abdeec387afe999c0c96b4f9",
                    "EndpointID": "",
                    "Gateway": "",
                    "IPAddress": "",
                    "IPPrefixLen": 0,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "",
                    "DriverOpts": null
                }
            }
        }
    }
]