Centos7 Docker基本特性入门实践-3

续CentOS 7 Docker基本特性入门实践-1

续CentOS 7 Docker基本特性入门实践-2

• 断开Container网络

可以断开一个Container的网络，来将一个Container从一个Docker网络中移除，只需要指定网络名称和Container名称即可（或者Container的ID），命令如下所示：

1	docker network disconnect bridge pgdb

2

或

3	docker network disconnect bridge 5ab157767bbd991401c351cfb452d663f5cd93dd1edc56767372095a5c2e7f73

• 连通处于两个子网中的Docker Container

下面，运行一个Web application，默认使用bridge网络：

1	docker run -d --name myweb training/webapp python app.py

通过命令：

1	docker inspect --format='{{json .NetworkSettings.Networks}}'  myweb

可以查看该应用连接网络的状况，如下所示（结果格式化过）：

01

{

02	"bridge": {

03	"IPAMConfig": null,

04	"Links": null,

05	"Aliases": null,

06	"NetworkID": "2872de41fddddc22420eecad253107e09a305f3512ade31d4172d3b80723d8b6",

07	"EndpointID": "a4e66b540e632c346f345c7972617ccdfaa4ef36eefbdc3a298d524b5cf13897",

08	"Gateway": "172.17.0.1",

09	"IPAddress": "172.17.0.4",

10	"IPPrefixLen": 16,

11	"IPv6Gateway": "",

12	"GlobalIPv6Address": "",

13	"GlobalIPv6PrefixLen": 0,

14	"MacAddress": "02:42:ac:11:00:04"

15

}

16

}

或者，获取直接Container的IP地址，执行命令：

1	docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' myweb

结果如下：

1	172.17.0.4

接着，我们再在my-bridge-network网络中启动一个Container，名称为mydb，执行如下命令：

1	docker run -d --name mydb --network my-bridge-network training/postgres

查看mydb应用连接网络的状态（结果格式化过）：

01

{

02	"my-bridge-network": {

03	"IPAMConfig": null,

04	"Links": null,

05	"Aliases": [

06	"fbfbad9e0bd3"

07

],

08	"NetworkID": "fc19452525e5d2f5f1fc109656f0385bf2f268b47788353c3d9ee672da31b33a",

09	"EndpointID": "49c7afbf24be165b98ea29dbfd7b1e2c0eecd9c1ef16a7efde00ab92d0563985",

10	"Gateway": "172.18.0.1",

11	"IPAddress": "172.18.0.2",

12	"IPPrefixLen": 16,

13	"IPv6Gateway": "",

14	"GlobalIPv6Address": "",

15	"GlobalIPv6PrefixLen": 0,

16	"MacAddress": "02:42:ac:12:00:02"

17

}

18

}

应用mydb所在网络为my-bridge-network，IP地址为172.18.0.2。
下面，测试从我们的mydb应用所在Container，连接到myweb应用所在的Container（，实际是跨了2个子网，即从my-bridge-network网络连接到bridge网络）。执行如下命令，使得可以在默认的bridge网络中的Container连接到my-bridge-network中的Container，执行如下命令：

1	docker network connect my-bridge-network myweb

这样，就可以进入到在my-bridge-network网络中的mydb应用所在Container中，通过ping命令，来ping另一个默认bridge网络中myweb应用：

01	[root@localhost mydockerbuild]# docker exec -it mydb bash

02	root@fbfbad9e0bd3:/# ifconfig

03	eth0      Link encap:Ethernet  HWaddr 02:42:ac:12:00:02

04	inet addr:172.18.0.2  Bcast:0.0.0.0  Mask:255.255.0.0

05	inet6 addr: fe80::42:acff:fe12:2/64 Scope:Link

06	UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

07	RX packets:36 errors:0 dropped:0 overruns:0 frame:0

08	TX packets:14 errors:0 dropped:0 overruns:0 carrier:0

09	collisions:0 txqueuelen:0

10	RX bytes:3530 (3.5 KB)  TX bytes:1124 (1.1 KB)

11

12	lo        Link encap:Local Loopback

13	inet addr:127.0.0.1  Mask:255.0.0.0

14	inet6 addr: ::1/128 Scope:Host

15	UP LOOPBACK RUNNING  MTU:65536  Metric:1

16	RX packets:26 errors:0 dropped:0 overruns:0 frame:0

17	TX packets:26 errors:0 dropped:0 overruns:0 carrier:0

18	collisions:0 txqueuelen:1

19	RX bytes:2274 (2.2 KB)  TX bytes:2274 (2.2 KB)

20	root@fbfbad9e0bd3:/# ping myweb

21	PING myweb (172.18.0.3) 56(84) bytes of data.

22	64 bytes from myweb.my-bridge-network (172.18.0.3): icmp_seq=1 ttl=64 time=0.318 ms

23	64 bytes from myweb.my-bridge-network (172.18.0.3): icmp_seq=2 ttl=64 time=2.06 ms

24	64 bytes from myweb.my-bridge-network (172.18.0.3): icmp_seq=3 ttl=64 time=0.506 ms

25	64 bytes from myweb.my-bridge-network (172.18.0.3): icmp_seq=4 ttl=64 time=0.404 ms

26

^C

27	--- myweb ping statistics ---

28	4 packets transmitted, 4 received, 0% packet loss, time 3003ms

29	rtt min/avg/max/mdev = 0.318/0.822/2.061/0.718 ms

可见，在不同Docker网络的两个Container之间的网络是连通的。

Docker Data Volumes

一个Data Volume是在一个或多个Container里面的特定的目录，它能够绕过Union Filesystem，提供持久化或共享数据的特性。
添加一个Data Volume，执行如下命令：

1	docker run -d -P --name vweb -v /webapp training/webapp python app.py

添加一个Data Volume，使用-v选项，目录名为/webapp，该目录是在Container内部的目录，可以通过执行命令docker inspect vweb查看当前Container中对应的信息，如下所示：

001

[

002

{

003	"Id": "fcea99542d4d2838102fc4b627c68a201b868d85f229722325d83968b32c8b33",

004	"Created": "2017-03-05T16:53:12.614318467Z",

005	"Path": "python",

006

"Args": [

007

"app.py"

008

],

009	"State": {

010	"Status": "running",

011	"Running": true,

012	"Paused": false,

013	"Restarting": false,

014	"OOMKilled": false,

015	"Dead": false,

016	"Pid": 7555,

017	"ExitCode": 0,

018	"Error": "",

019	"StartedAt": "2017-03-05T16:53:13.380982103Z",

020	"FinishedAt": "0001-01-01T00:00:00Z"

021

},

022	"Image": "sha256:6fae60ef344644649a39240b94d73b8ba9c67f898ede85cf8e947a887b3e6557",

023	"ResolvConfPath": "/var/lib/docker/containers/fcea99542d4d2838102fc4b627c68a201b868d85f229722325d83968b32c8b33/resolv.conf",

024	"HostnamePath": "/var/lib/docker/containers/fcea99542d4d2838102fc4b627c68a201b868d85f229722325d83968b32c8b33/hostname",

025	"HostsPath": "/var/lib/docker/containers/fcea99542d4d2838102fc4b627c68a201b868d85f229722325d83968b32c8b33/hosts",

026	"LogPath": "/var/lib/docker/containers/fcea99542d4d2838102fc4b627c68a201b868d85f229722325d83968b32c8b33/fcea99542d4d2838102fc4b627c68a201b868d85f229722325d83968b32c8b33-json.log",

027	"Name": "/vweb",

028	"RestartCount": 0,

029	"Driver": "overlay",

030	"MountLabel": "",

031	"ProcessLabel": "",

032	"AppArmorProfile": "",

033	"ExecIDs": null,

034	"HostConfig": {

035	"Binds": null,

036	"ContainerIDFile": "",

037	"LogConfig": {

038	"Type": "json-file",

039	"Config": {}

040

},

041	"NetworkMode": "default",

042	"PortBindings": {},

043	"RestartPolicy": {

044	"Name": "no",

045	"MaximumRetryCount": 0

046

},

047	"AutoRemove": false,

048	"VolumeDriver": "",

049	"VolumesFrom": null,

050	"CapAdd": null,

051	"CapDrop": null,

052	"Dns": [],

053	"DnsOptions": [],

054	"DnsSearch": [],

055	"ExtraHosts": null,

056	"GroupAdd": null,

057	"IpcMode": "",

058	"Cgroup": "",

059	"Links": null,

060	"OomScoreAdj": 0,

061	"PidMode": "",

062	"Privileged": false,

063	"PublishAllPorts": true,

064	"ReadonlyRootfs": false,

065	"SecurityOpt": null,

066	"UTSMode": "",

067	"UsernsMode": "",

068	"ShmSize": 67108864,

069	"Runtime": "runc",

070	"ConsoleSize": [

071

0,

072

0

073

],

074	"Isolation": "",

075	"CpuShares": 0,

076	"Memory": 0,

077	"NanoCpus": 0,

078	"CgroupParent": "",

079	"BlkioWeight": 0,

080	"BlkioWeightDevice": null,

081	"BlkioDeviceReadBps": null,

082	"BlkioDeviceWriteBps": null,

083	"BlkioDeviceReadIOps": null,

084	"BlkioDeviceWriteIOps": null,

085	"CpuPeriod": 0,

086	"CpuQuota": 0,

087	"CpuRealtimePeriod": 0,

088	"CpuRealtimeRuntime": 0,

089	"CpusetCpus": "",

090	"CpusetMems": "",

091	"Devices": [],

092	"DiskQuota": 0,

093	"KernelMemory": 0,

094	"MemoryReservation": 0,

095	"MemorySwap": 0,

096	"MemorySwappiness": -1,

097	"OomKillDisable": false,

098	"PidsLimit": 0,

099	"Ulimits": null,

100	"CpuCount": 0,

101	"CpuPercent": 0,

102	"IOMaximumIOps": 0,

103	"IOMaximumBandwidth": 0

104

},

105	"GraphDriver": {

106	"Name": "overlay",

107

"Data": {

108	"LowerDir": "/var/lib/docker/overlay/59f20340fa5232f5b13300a715b6d422acc32d21385f48336cead00c3227c63a/root",

109	"MergedDir": "/var/lib/docker/overlay/9c602e4263c42984824b7f1e3c62416cb6056332e6447e65c3d08de7c1f50cd6/merged",

110	"UpperDir": "/var/lib/docker/overlay/9c602e4263c42984824b7f1e3c62416cb6056332e6447e65c3d08de7c1f50cd6/upper",

111	"WorkDir": "/var/lib/docker/overlay/9c602e4263c42984824b7f1e3c62416cb6056332e6447e65c3d08de7c1f50cd6/work"

112

}

113

},

114	"Mounts": [

115

{

116	"Type": "volume",

117	"Name": "228bc2018d65523797450822a068550fb8afbdf6ca2e4010a32cbb36961e3d5f",

118	"Source": "/var/lib/docker/volumes/228bc2018d65523797450822a068550fb8afbdf6ca2e4010a32cbb36961e3d5f/_data",

119	"Destination": "/webapp",

120	"Driver": "local",

121	"Mode": "",

122	"RW": true,

123	"Propagation": ""

124

}

125

],

126	"Config": {

127	"Hostname": "fcea99542d4d",

128	"Domainname": "",

129	"User": "",

130	"AttachStdin": false,

131	"AttachStdout": false,

132	"AttachStderr": false,

133	"ExposedPorts": {

134	"5000/tcp": {}

135

},

136	"Tty": false,

137	"OpenStdin": false,

138	"StdinOnce": false,

139

"Env": [

140	"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"

141

],

142

"Cmd": [

143

"python",

144

"app.py"

145

],

146	"Image": "training/webapp",

147	"Volumes": {

148	"/webapp": {}

149

},

150	"WorkingDir": "/opt/webapp",

151	"Entrypoint": null,

152	"OnBuild": null,

153	"Labels": {}

154

},

155	"NetworkSettings": {

156	"Bridge": "",

157	"SandboxID": "3f2f86ae96ec76c08e8841c7b8eb75e586000397a8acef9a0098ddf02f2c7da7",

158	"HairpinMode": false,

159	"LinkLocalIPv6Address": "",

160	"LinkLocalIPv6PrefixLen": 0,

161	"Ports": {

162	"5000/tcp": [

163

{

164	"HostIp": "0.0.0.0",

165	"HostPort": "32768"

166

}

167

]

168

},

169	"SandboxKey": "/var/run/docker/netns/3f2f86ae96ec",

170	"SecondaryIPAddresses": null,

171	"SecondaryIPv6Addresses": null,

172	"EndpointID": "39693d7b104dab973e7ed27d16bb71b290be39aa83cce5e78f8b80de35309c5a",

173	"Gateway": "172.17.0.1",

174	"GlobalIPv6Address": "",

175	"GlobalIPv6PrefixLen": 0,

176	"IPAddress": "172.17.0.5",

177	"IPPrefixLen": 16,

178	"IPv6Gateway": "",

179	"MacAddress": "02:42:ac:11:00:05",

180	"Networks": {

181	"bridge": {

182	"IPAMConfig": null,

183	"Links": null,

184	"Aliases": null,

185	"NetworkID": "2872de41fddddc22420eecad253107e09a305f3512ade31d4172d3b80723d8b6",

186	"EndpointID": "39693d7b104dab973e7ed27d16bb71b290be39aa83cce5e78f8b80de35309c5a",

187	"Gateway": "172.17.0.1",

188	"IPAddress": "172.17.0.5",

189	"IPPrefixLen": 16,

190	"IPv6Gateway": "",

191	"GlobalIPv6Address": "",

192	"GlobalIPv6PrefixLen": 0,

193	"MacAddress": "02:42:ac:11:00:05"

194

}

195

}

196

}

197

}

198

]

从上面可以看到，在应用vweb所在Container内部的Data Volume为/webapp。
也可以mount一个宿主机的目录，作为Docker Container的Data Volume：

1	docker run -d -P --name vvweb -v /src/webapp:/webapp training/webapp python app.py

上面命令行中，-v选项的值通过冒号分隔，前半部分是宿主机的目录，而后半部分是Container中的相对目录，并且要求宿主机的目录一定包含Container中的Data Volume的路径。
Docker的Data Volume默认是read-write模式，可以手动指定为只读模型，执行如下命令：

1	docker run -d -P --name web -v /src/webapp:/webapp:ro training/webapp python app.py

另外，也可以创建一个用来存储的Data Volume Container，便于多个Container中的应用共享数据。例如创建一个用来存储数据库数据的Data Volume Container，执行如下命令：

1	docker create -v /dbdata --name dbstore training/postgres /bin/true

创建了一个名称为dbstore的Container。如果其他应用想要共享我们创建的用于存储的Data Volume Container，可以在启动应用Container的时候指定Data Volume，例如启动下面两个Container使用我们创建的dbstore作为共享Data Volume：

1	docker run -d --volumes-from dbstore --name db1 training/postgres

2	docker run -d --volumes-from dbstore --name db2 training/postgres

db1和db2这两个Container共享我们创建的dbstore Data Volume Container，查看这两个Container对应的Volume信息，执行如下命令行：

1	docker inspect db1

2	docker inspect db2

结果分别取出两个Container的Mounts信息，对比发现内容是相同的，如下所示：

01	"Mounts": [

02

{

03	"Name": "741950cc3ef8d901dc6cfdbebf8450082a0d22b07957f43bd0de73d05447b365",

04	"Source": "/var/lib/docker/volumes/741950cc3ef8d901dc6cfdbebf8450082a0d22b07957f43bd0de73d05447b365/_data",

05	"Destination": "/dbdata",

06	"Driver": "local",

07	"Mode": "",

08	"RW": true,

09	"Propagation": ""

10

}

11

]

可见，只能作为Data Volume使用的Container，可以被其他多个应用所共享。