Docker学习笔记・03
这篇讲讲docker的各种文件在Fedora中的位置。
以下是docker这个包的核心文件：
$ rpm -ql docker | grep -v man | grep -v share
/etc/docker
/etc/docker/certs.d
/etc/docker/certs.d/redhat.com
/etc/docker/certs.d/redhat.com/redhat-ca.crt
/etc/docker/certs.d/redhat.io
/etc/docker/certs.d/redhat.io/redhat-ca.crt
/etc/sysconfig/docker-network
/etc/sysconfig/docker-storage
/etc/sysconfig/docker-storage-setup
/usr/bin/docker-current
/usr/bin/docker-storage-setup
/usr/bin/dockerd-current
/usr/lib/docker-storage-setup
/usr/lib/docker-storage-setup/docker-storage-setup
/usr/lib/docker-storage-setup/dss-child-read-write
/usr/lib/docker-storage-setup/libdss.sh
/usr/lib/systemd/system/docker-containerd.service
/usr/lib/systemd/system/docker-storage-setup.service
/usr/lib/systemd/system/docker.service
/usr/lib/udev/rules.d/80-docker.rules
/usr/libexec/docker/docker-containerd-current
/usr/libexec/docker/docker-containerd-shim-current
/usr/libexec/docker/docker-ctr-current
/usr/libexec/docker/docker-proxy-current
/usr/libexec/docker/docker-runc-current
/var/lib/docker
docker的默认存储位置位于/var/lib/docker：
$ pwd
/var/lib/docker
$ ls -l
total 32
drwx------ 10 root root 4096 Jan 5 22:44 containers
drwx------ 5 root root 4096 Jan 5 21:19 devicemapper
drwx------ 3 root root 4096 Jan 4 00:08 image
drwxr-x--- 3 root root 4096 Jan 4 00:08 network
drwx------ 2 root root 4096 Jan 4 00:08 swarm
drwx------ 2 root root 4096 Jan 5 21:29 tmp
drwx------ 2 root root 4096 Jan 4 00:08 trust
drwx------ 2 root root 4096 Jan 4 00:08 volumes
其中「containers」里面包含了容器的信息：
$ pwd
/var/lib/docker/containers
$ ls -l
total 32
drwx------ 4 root root 4096 Jan 5 21:46 0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b
drwx------ 4 root root 4096 Jan 5 22:42 1df9c3cd8f95d35373813d4d62149e46723c7f9e2133285d1720da54560b5648
drwx------ 4 root root 4096 Jan 5 21:31 3107159e0fabad4b4af9076f135ae74d3834b6568909d252d489a862a4638419
drwx------ 4 root root 4096 Jan 5 21:47 3125d511be3a675c9a7ca8ca17f0be386fb56072a2074c43ce8c61ea31d85970
drwx------ 4 root root 4096 Jan 5 21:19 33b17fbc6ffcc17da91ed3039e713351fec101c8f6150b3a665731c14e658b32
drwx------ 4 root root 4096 Jan 5 21:31 8f993b7308b2913789ee797f1ee2023d2646fb09d37d840ac1bc28d03902b313
drwx------ 4 root root 4096 Jan 5 22:44 c17ce8cb0de3f05d10eee83672a03c14963befb60379585cbcd6572e8df9e528
drwx------ 4 root root 4096 Jan 5 21:45 caedccb3c1b09f7f7c85a041e751b67d2fac9b785eb90173256507224d3cb253
$
可以看看其中一个容器里面的内容：
$ ls 0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b
config.v2.json hostconfig.json hostname hosts resolv.conf resolv.conf.hash secrets shm
如上所示，每一个容器里面有这个容器的一些配置文件。主要看config.v2.json这个文件的内容：
{
"StreamConfig": {},
"State": {
"Running": false,
"Paused": false,
"Restarting": false,
"OOMKilled": false,
"RemovalInProgress": false,
"Dead": false,
"Pid": 0,
"ExitCode": 127,
"Error": "invalid header field value \"oci runtime error: container_linux.go:247: starting container process caused \\\"exec: \\\\\\\"bash\\\\\\\": executable file not found in $PATH\\\"\\n\"",
"StartedAt": "0001-01-01T00:00:00Z",
"FinishedAt": "0001-01-01T00:00:00Z",
"Health": null
},
"ID": "0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b",
"Created": "2018-01-05T13:46:49.695891865Z",
"Managed": false,
"Path": "bash",
"Args": [],
"Config": {
"Hostname": "0036e9d07882",
"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": [
"bash"
],
"Image": "hello-world",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": null,
"OnBuild": null,
"Labels": {}
},
"Image": "sha256:f2a91732366c0332ccd7afd2a5c4ff2b9af81f549370f7a19acd460f87686bc7",
"NetworkSettings": {
"Bridge": "",
"SandboxID": "a56b00fc2d904a2bcacb6e2e84adbf4d90c2f9c1c8ce1808eb5f1d8a42aff944",
"HairpinMode": false,
"LinkLocalIPv6Address": "",
"LinkLocalIPv6PrefixLen": 0,
"Networks": {
"bridge": {
"IPAMConfig": null,
"Links": null,
"Aliases": null,
"NetworkID": "2429ef9d3c2b11cc55f64658a217809810ea164b8ece01629e4102eaa22d32f9",
"EndpointID": "996aa17d758445e1e1043702c02355c7f79c720ad1d7e59d6aa6c74296c37614",
"Gateway": "172.17.0.1",
"IPAddress": "172.17.0.2",
"IPPrefixLen": 16,
"IPv6Gateway": "",
"GlobalIPv6Address": "",
"GlobalIPv6PrefixLen": 0,
"MacAddress": "02:42:ac:11:00:02"
}
},
"Service": null,
"Ports": {},
"SandboxKey": "/var/run/docker/netns/a56b00fc2d90",
"SecondaryIPAddresses": null,
"SecondaryIPv6Addresses": null,
"IsAnonymousEndpoint": true
},
"LogPath": "",
"Name": "/compassionate_bohr",
"Driver": "devicemapper",
"MountLabel": "",
"ProcessLabel": "",
"RestartCount": 0,
"HasBeenStartedBefore": false,
"HasBeenManuallyStopped": false,
"MountPoints": {},
"AppArmorProfile": "",
"HostnamePath": "/var/lib/docker/containers/0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b/hostname",
"HostsPath": "/var/lib/docker/containers/0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b/hosts",
"ShmPath": "/var/lib/docker/containers/0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b/shm",
"ResolvConfPath": "/var/lib/docker/containers/0036e9d0788249562268287f4bda5351d36b4dca62e1936a9b1e3eefd537d80b/resolv.conf",
"SeccompProfile": "",
"NoNewPrivileges": false
}
上面的配置文件里面包含了容器的核心信息。比如告诉了我们容器对应的image id：
"Image": "sha256:f2a91732366c0332ccd7afd2a5c4ff2b9af81f549370f7a19acd460f87686bc7"
我们可以在「/var/lib/docker/」里面搜索这个id：
[root@f64 docker]# find . | grep f2a91732366c0332ccd7afd2a5c4ff2b9af81f549370f7a19acd460f87686bc7
./image/devicemapper/imagedb/content/sha256/f2a91732366c0332ccd7afd2a5c4ff2b9af81f549370f7a19acd460f87686bc7
可以看到容器对应的image文件录是：
/var/lib/docker/image/devicemapper/imagedb/content/sha256/f2a91732366c0332ccd7afd2a5c4ff2b9af81f549370f7a19acd460f87686bc7
注意保存image所使用的文件系统是devicemapper。docker支持多种文件系统1，而「devicemapper」是其中之一。
关于device mapper，可以查看wikipedia的相关文档2。
以下是「IO_stack_of_the_Linux_kernel」3：
