Docker Contrast VM

Docker's Network Model

Dokcer provides communication between containers by using Linux bridges. Docker has four network modes

They are the following four modes

• Host mode, specified using -- net=host.
• Container mode, specified using -- net=container:NAMEorID.
• None mode, specified using -- net=none.
• Bridge mode, specified with -- net=bridge, default configuration

host mode
If the container uses host mode, the container will not get a separate Network Namespace, but share a Network Namespace with the host. Containers will not virtualize their own network cards and configure IP, etc., but use the host's IP and ports. It's the same as running directly in the host. But the container's file system, process list, etc. are still isolated from the host.

container mode
This pattern specifies that the newly created container and an existing container share a Network Namespace rather than the host. The newly created container does not create its own network card and configure IP, but shares IP, port range, etc. with a specified container. Similarly, the two containers are still isolated except for the network.

none mode
This pattern is different from the first two. The Docker container has its own Network Namespace, but the Docker container has no network configuration. Instead, we need to manually add network cards, configure IP, etc. to the Docker container.

bridge mode
This mode is the default network setting for Docker, which assigns Network Namespace to each container and connects a Docker container on a host to a virtual bridge.

Running container

[root@centos7 ~]# docker run -d -P nginx  #- d Start to Background
6135db66a7d7c1237901a79974f88f1079b3d467c14ce83fc46bc6b4eb8b3240
[root@centos7 ~]# docker ps
CONTAINER ID  IMAGE  COMMAND    CREATED   STATUS   PORTS   NAMES
6135db66a7d7   nginx   "nginx -g 'daemon off"   33 seconds ago  Up 31 seconds   0.0.0.0:32769->80/tcp, 0.0.0.0:32768->443/tcp   gigantic_meitner

Random one port to automatically map 80

Parameter description

• Docker-P random port mapping
• Docker-p Specified Port Mapping
• -p hostport:containerport
• -p ip:hostport:containerport

Example illustrate

[root@centos7 ~]# docker run -d -p 81:80 nginx
3ca9f847bebec3684952b0f2c081d31f84b9489de50b635246d9a592cc06d46c
[root@centos7 ~]# docker ps
CONTAINER ID   IMAGE   COMMAND  CREATED   STATUS   PORTS   NAMES
3ca9f847bebe  nginx  "nginx -g 'daemon off"  8 seconds ago   Up 6 seconds  443/tcp, 0.0.0

Start container services can be accessed through specified ports

Docker Data Storage

docker manages data in two ways:

• Data volume
• Data Volume Container

Data volume

A data volume is a directory or containers specifically designated to bypass Union File System to provide some useful functionality for persistence or data sharing:

• Data volumes can be shared and reused between containers
• Data volume data changes are directly modified
• Volume data changes will not be included in the container
• Data volumes are persistent until no container uses them

Parameter description

• - v/data mounts the data directory directly into the container/data directory
• - v src:dst mounts physical machine directory to container directory

Example operation

[root@centos7 ~]# docker run -it --name test-001 -v /data centos
[root@4578675314b9 /]# ls -l /data/
total 0
[root@centos7 ~]# docker ps
CONTAINER ID   IMAGE  COMMAND  CREATED  STATUS  PORTS   NAMES
4578675314b9  centos  "/bin/bash"  2 minutes ago Up 2 minutes test-001
[root@centos7 ~]# docker inspect 4578675314b9
"Mounts": [
            {
                "Name": "ab2f85f900a68813c4fdbf3b0fe88242247e7e8320bb75035b1367ab82804115",
                "Source": "/var/lib/docker/volumes/ab2f85f900a68813c4fdbf3b0fe88242247e7e8320bb75035b1367ab82804115/_data",
              "Destination": "/data", ##You can see that the storage directory in the container is mounted to / data
                "Driver": "local",
                "Mode": "",
                "RW": true,
                "Propagation": ""
            }
        ],
[root@centos7 ~]# cd /var/lib/docker/volumes/ab2f85f900a68813c4fdbf3b0fe88242247e7e8320bb75035b1367ab82804115/_data  ###This is the catalogue of physical machines.
[root@centos7 _data]# ll
total 0
[root@centos7 _data]# mkdir test

View data in containers

[root@4578675314b9 /]# cd /data/  ###This is the catalogue in the container.
[root@4578675314b9 data]# ll
total 0
drwxr-xr-x 2 root root 6 Apr 10 08:54 test

You can see that there is also a test directory just created by the physical machine under the container's data directory.

You can also mount it using the following methods

docker run -it -v /data1:/mnt centos         

The former is the physical machine directory (which is automatically created on the physical machine after mounting) and the latter is the container directory.

[root@centos7 ~]# docker run -it -v /data1:/mnt centos
[root@425569ce9eef /]# cd /mnt/
[root@425569ce9eef mnt]# ll
total 0
[root@centos7 ~]# cd /data1/
[root@centos7 data1]# echo "hello">test.txt
[root@centos7 data1]# ll
total 4
-rw-r--r-- 1 root root 6 Apr 10 17:09 test.txt
[root@centos7 data1]# cat test.txt
hello

Check whether the container directory has files and contents

[root@425569ce9eef mnt]# ll
total 4
-rw-r--r-- 1 root root 6 Apr 10 09:09 test.txt
[root@425569ce9eef mnt]# cat test.txt 
hello
[root@425569ce9eef mnt]# pwd
/mnt
[root@425569ce9eef mnt]# hostname
425569ce9eef

This method is suitable for developing code management. The code directory is mounted directly into the container and can be accessed by modifying the WEB site directory.

docker run -it -v /data2:/opt:ro centos

#Specify read-only permissions for mounting

docker run -it -v /data2:/opt:rw centos 

#Specify read and write permissions to mount

docker run -it -v /root/file1:file1 centos

#Mount a single file to the container directory

The Way of Container Volume

--volumes-from # directory for using other containers

[root@centos7 ~]# docker run -d --name mydocker -v /data centos  
4f243ada709ee87d8f1e50bf13ab225c8dfd6b38f7dad97fa84ab0cb3d7d517b
[root@centos7 ~]# docker run -it --name mynfs --volumes-from mydocker centos
[root@82a489adb07a /]# ll /data/
total 0

At this point, enter the mydocker container / data directory to write data for testing

[root@centos7~]# cd /var/lib/docker/volumes/8421a48b58337a30ac4750c06748e01a3f328bdc2fa3b945d7f9737d9bc1b002/_data
[root@centos7 _data]# ls
[root@centos7 _data]# echo "welcome to here">file
[root@centos7 _data]# ll
total 4
-rw-r--r-- 1 root root 16 Apr 10 17:34 file

Check to see if there is any data in the container just now.

[root@82a489adb07a /]# hostname
82a489adb07a
[root@82a489adb07a /]# cd /data/
[root@82a489adb07a data]# ll
total 4
-rw-r--r-- 1 root root 16 Apr 10 09:34 file
[root@82a489adb07a data]# cat file 
welcome to here