1. Docker technology introduction
DOCKER is a container engine built on top of LXC technology. It provides container resource isolation and security protection through kernel virtualization technology (namespace and cgroups). KVM is a virtualization technology implemented through hardware, which is implemented through the system. Resource isolation and security guarantee, occupying less system resources
Official website: https://www.docker.com/
Docker composition:
Client and server
Docker components:
Mirror image
container
warehouse
2.Comparison between Docker and Openstack
3. Advantages of Docker
1) Simplified procedure:
Docker allows developers to package their applications and dependent packages into a portable container, and then publish to any popular Linux machine, you can achieve virtualization. Docker has changed the way of virtualization. Under the processing of Docker containers, it only takes a few seconds to complete.
2) Diversity:
Docker helps you pack your entanglements! For example, Docker image; Docker image contains the operating environment and configuration, so Docker can simplify the deployment of multiple application instances. For example, Web applications, background applications, database applications, big data applications such as Hadoop clusters, message queues, etc. can all be packaged into a mirror deployment.3) Saving expenses: The
era of cloud computing has made developers no longer have to configure expensive hardware in pursuit of effects. Docker has changed the mindset that high performance is necessarily high in price. The combination of Docker and cloud makes cloud space more fully utilized. It not only solves the problem of hardware management, but also changes the way of virtualization.
1) The configuration needs to be simplified (the test environment is different from the production environment)
2) Code management (code upload and download)
3) Improve development efficiency (the installation of development environment configuration is the same as that of openstack kvm)
4) Application isolation
5) Server integration
6) Debug
7) Multi-terminal, multi-tenant
8) Need for rapid deployment and environmental consistency
Install Docker service
root@centos7 ~]# yum install docker -y
[root@centos7 ~]# systemctl start docker
Download the image file
[root@centos7 ~]# docker pull centos:latest
Trying to pull repository docker.io/library/centos ...
centos7: Pulling from docker.io/library/centos
93857f76ae30: Pull complete
Digest: sha256:4eda692c08e0a065ae91d74e82fff4af3da307b4341ad61fa61771cc4659af60
[root@centos7 ~]# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
docker.io/centos centos7 a8493f5f50ff 3 days ago 192.5 MB
Delete mirror
[root@centos7 ~]# docker rmi a8493f5f50ff ##容器ID
1) Create a container
method one:
[root@centos7 ~]# docker run centos /bin/echo "nihao" ##创建容器
nihao
[root@centos7 ~]# docker ps -a ##查看所有容器
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
3c113f9a4f1b centos "/bin/echo nihao" 43 seconds ago Exited (0) 41 seconds ago boring_liskov
The container name is not specified here, it is automatically named, and the status is automatic exit
Method 2: Create a custom-named container
[root@centos7 ~]# docker run --name mgg -t -i centos /bin/bash
名称 分配伪终端 -i 处于打开状态
[root@2db7f1389dbd /]# ps -ef
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 22:46 ? 00:00:00 /bin/bash
root 13 1 0 22:49 ? 00:00:00 ps -ef
[root@centos7 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2db7f1389dbd centos "/bin/bash" 4 minutes ago Up 4 minutes mgg
docker ps -a displays all containers including those that are not running (same as virsh list --all)
2) Enter, exit, and start the container
[root@2db7f1389dbd /]# exit ##退出容器
exit
[root@centos7 ~]# docker start 2db7f1389dbd ##启动容器
2db7f1389dbd
[root@centos7 ~]# docker attach 2db7f1389dbd ##进入容器（必须是启动状态下）
[root@2db7f1389dbd /]# hostname
2db7f1389dbd
This way of entering, the container will enter the Down state after exiting, as follows
[root@2db7f1389dbd /]# exit
exit
[root@centos7 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
3) Use the nsenter command to enter the container
[root@centos7 ~]# nsenter --help
Usage:
nsenter [options] <program> [<argument>...]
Run a program with namespaces of other processes.
Options:
-t, --target <pid> target process to get namespaces from
-m, --mount[=<file>] enter mount namespace
-u, --uts[=<file>] enter UTS namespace (hostname etc)
-i, --ipc[=<file>] enter System V IPC namespace
-n, --net[=<file>] enter network namespace
-p, --pid[=<file>] enter pid namespace
-U, --user[=<file>] enter user namespace
-S, --setuid <uid> set uid in entered namespace
-G, --setgid <gid> set gid in entered namespace
--preserve-credentials do not touch uids or gids
-r, --root[=<dir>] set the root directory
-w, --wd[=<dir>] set the working directory
-F, --no-fork do not fork before exec'ing <program>
-Z, --follow-context set SELinux context according to --target PID
-h, --help display this help and exit
-V, --version output version information and exit
Get the PID of the container
[root@centos7 ~]# docker inspect --format "{{.State.Pid}}" 2db7f1389dbd
4580
[root@centos7 ~]# nsenter -t 4580 -u -i -n -p
[root@2db7f1389dbd ~]# hostname
2db7f1389dbd
[root@2db7f1389dbd ~]# exit
logout
[root@centos7 ~]# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2db7f1389dbd centos "/bin/bash" 22 minutes ago Up 7 minutes mgg4) Delete the container
[root@centos7 ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2db7f1389dbd centos "/bin/bash" 31 minutes ago Up 16 minutes mgg
3c113f9a4f1b centos "/bin/echo nihao" 38 minutes ago Exited (0) 38 minutes ago boring_liskov
[root@centos7 ~]# docker rm 3c113f9a4f1b ##接名称也可以，删除一个停止的容器
3c113f9a4f1b
[root@centos7 ~]# docker rm -f 3c113f9a4f1b ##删除一个正在运行的容器
[root@centos7 ~]# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2db7f1389dbd centos "/bin/bash" 31 minutes ago Up 16 minutes mgg
[root@centos7 ~]# docker run --rm centos /bin/echo "hello" ##创建时自动删除，用于测试
[root@centos7 ~]#docker --kill $(docker ps -a -q) ##删除正在运行的容器Recommended reading
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