Introduction to Docker in operation and maintenance practice

What is Docker

In short:

Docker in IT software refers to container technology, which is used to support the creation and use of docker containers
With Docker, containers can be used as lightweight, modular virtual machines At the same time, you will also gain a high degree of flexibility, so as to realize the efficient creation, deployment and replication of containers, and smoothly migrate them from one environment to another, which will help you optimize your applications for the cloud
Docker uses Google's Go language Development and implementation, based on Linux kernel cgroup，namespace , and OverlayFS Class Union FS And other technologies to encapsulate and isolate the process Virtualization technology at the operating system level . Because the isolated process is independent of the host and other isolated processes, it is also called a container.

Differences from traditional virtualization

Compared with traditional virtualization

Containers do not need to simulate the hardware layer. Traditional virtualization must have a virtualized operating system layer
Share the kernel of the same host

Install Docker

For Docker, you need to know the following in advance

Docker creates containers through images, which are stored in the warehouse

The container contains its own contents and settings, and port mapping is required for external interaction

##Installation dependency
yum install -y container-selinux-2.77-1.el7.noarch.rpm containerd.io-1.4.4-3.1.el7.x86_64.rpm 
##Install docker CE
yum install -y docker-ce-19.03.15-3.el7.x86_64.rpm docker-ce-cli-19.03.15-3.el7.x86_64.rpm 

##Enable service
systemctl start docker.service 
##View Docker information
docker info

This step is specially listed here for explanation

[root@Server1 docker-ce]# docker info
Client:
 Debug Mode: false

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 19.03.15
 Storage Driver: overlay2
  Backing Filesystem: xfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05f951a3781f4f2c1911b05e61c160e9c30eaa8e
 runc version: 12644e614e25b05da6fd08a38ffa0cfe1903fdec
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 3.10.0-957.el7.x86_64
 Operating System: Red Hat Enterprise Linux Server 7.6 (Maipo)
 OSType: linux
 Architecture: x86_64
 CPUs: 2
 Total Memory: 991MiB
 Name: Server1
 ID: BTTL:NBTO:2QFW:6AI3:6MAG:7XRR:MMZV:7RMH:W4WA:Z7JC:WIAQ:U5TX
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled

You can see that there are two lines of warning messages at the end

WARNING: bridge-nf-call-iptables is disabled
WARNING: bridge-nf-call-ip6tables is disabled

This is because the implementation of Docker service needs the help of network bridge, and these two settings may not be turned on by default

[root@Server1 sysctl.d]# sysctl -a | grep bridge-nf-call-iptables
net.bridge.bridge-nf-call-iptables = 0
sysctl: reading key "net.ipv6.conf.all.stable_secret"
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.docker0.stable_secret"
sysctl: reading key "net.ipv6.conf.eth0.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
[root@Server1 docker-ce]# sysctl net.bridge.bridge-nf-call-iptables
net.bridge.bridge-nf-call-iptables = 0

[root@Server1 docker-ce]# sysctl -a | grep bridge-nf-call-ip6tables
net.bridge.bridge-nf-call-ip6tables = 0
sysctl: reading key "net.ipv6.conf.all.stable_secret"
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.docker0.stable_secret"
sysctl: reading key "net.ipv6.conf.eth0.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
[root@Server1 docker-ce]# sysctl net.bridge.bridge-nf-call-ip6tables
net.bridge.bridge-nf-call-ip6tables = 0

Change the setting of sysctl by modifying its configuration

Usually we don't change sysctl directly The content of conf is to add a new configuration file to its configuration directory for easy management

[root@Server1 docker-ce]# cd /etc/sysctl.d/
[root@Server1 sysctl.d]# ls
99-sysctl.conf
[root@Server1 sysctl.d]# vim docker.conf

net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1

##Refresh the configuration to see it take effect
[root@Server1 sysctl.d]# sysctl --system
* Applying /usr/lib/sysctl.d/00-system.conf ...
net.bridge.bridge-nf-call-ip6tables = 0
net.bridge.bridge-nf-call-iptables = 0
net.bridge.bridge-nf-call-arptables = 0
* Applying /usr/lib/sysctl.d/10-default-yama-scope.conf ...
kernel.yama.ptrace_scope = 0
* Applying /usr/lib/sysctl.d/50-default.conf ...
kernel.sysrq = 16
kernel.core_uses_pid = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.promote_secondaries = 1
net.ipv4.conf.all.promote_secondaries = 1
fs.protected_hardlinks = 1
fs.protected_symlinks = 1
* Applying /etc/sysctl.d/99-sysctl.conf ...
* Applying /etc/sysctl.d/docker.conf ...
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
* Applying /etc/sysctl.conf ...

##Check the information again and the warning disappears
[root@Server1 sysctl.d]# docker info
Client:
 Debug Mode: false

Server:
 Containers: 0
  Running: 0
  Paused: 0
  Stopped: 0
 Images: 0
 Server Version: 19.03.15
 Storage Driver: overlay2
  Backing Filesystem: xfs
  Supports d_type: true
  Native Overlay Diff: true
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05f951a3781f4f2c1911b05e61c160e9c30eaa8e
 runc version: 12644e614e25b05da6fd08a38ffa0cfe1903fdec
 init version: fec3683
 Security Options:
  seccomp
   Profile: default
 Kernel Version: 3.10.0-957.el7.x86_64
 Operating System: Red Hat Enterprise Linux Server 7.6 (Maipo)
 OSType: linux
 Architecture: x86_64
 CPUs: 2
 Total Memory: 991MiB
 Name: Server1
 ID: BTTL:NBTO:2QFW:6AI3:6MAG:7XRR:MMZV:7RMH:W4WA:Z7JC:WIAQ:U5TX
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 Registry: https://index.docker.io/v1/
 Labels:
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

Simple introduction

##Search the official warehouse for images for simple contacts
[root@Server1 sysctl.d]# docker search yakexi007

NAME                 DESCRIPTION         STARS               OFFICIAL            AUTOMATED
yakexi007/game2048                       0                                       
yakexi007/mario                          0                                       
yakexi007/nginx                          0    

##Download the image of 2048 games
[root@Server1 sysctl.d]# docker pull yakexi007/game2048

Using default tag: latest
latest: Pulling from yakexi007/game2048
534e72e7cedc: Pull complete 
f62e2f6dfeef: Pull complete 
fe7db6293242: Pull complete 
3f120f6a2bf8: Pull complete 
4ba4e6930ea5: Pull complete 
Digest: sha256:8a34fb9cb168c420604b6e5d32ca6d412cb0d533a826b313b190535c03fe9390
Status: Downloaded newer image for yakexi007/game2048:latest
docker.io/yakexi007/game2048:latest

##View local image list
[root@Server1 sysctl.d]# docker images
REPOSITORY           TAG                 IMAGE ID            CREATED             SIZE
yakexi007/game2048   latest              19299002fdbe        4 years ago         55.5MB

##Building containers by mirroring
[root@Server1 sysctl.d]# docker run -d --name 2048 -p 80:80 yakexi007/game2048
2f6310c4fba15bf9c95ec50918c5ff2bc18d4309dd5fe8cec198470af4b21710

About the parameters of this command

-d		Background run container,And return to the container ID
--name	Specify container name
-p		Specify port mapping,Format as host(host)port:Container port

Last is the specified image

Check after completion

##Check the port usage. You can see that docker proxy appears on port 80
[root@Server1 sysctl.d]# netstat -antlp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      3215/sshd           
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      3404/master         
tcp        0      0 172.25.5.1:22           172.25.5.250:45152      ESTABLISHED 3499/sshd: root@pts 
tcp6       0      0 :::80                   :::*                    LISTEN      4520/docker-proxy   
tcp6       0      0 :::22                   :::*                    LISTEN      3215/sshd           
tcp6       0      0 ::1:25                  :::*                    LISTEN      3404/master  

##List containers in operation
[root@Server1 sysctl.d]# docker ps
CONTAINER ID        IMAGE                COMMAND                  CREATED             STATUS              PORTS                         NAMES
2f6310c4fba1        yakexi007/game2048   "/bin/sh -c 'sed -i ..."   20 seconds ago      Up 20 seconds       0.0.0.0:80->80/tcp, 443/tcp   2048

##List all containers, including those that are not running
[root@Server1 sysctl.d]# docker ps -a
CONTAINER ID        IMAGE                COMMAND                  CREATED             STATUS              PORTS                         NAMES
2f6310c4fba1        yakexi007/game2048   "/bin/sh -c 'sed -i ..."   24 seconds ago      Up 23 seconds       0.0.0.0:80->80/tcp, 443/tcp   2048

Keywords: Docker

Added by Muses on Sat, 19 Feb 2022 04:27:59 +0200

Programming VIP

Introduction to Docker in operation and maintenance practice

What is Docker

Differences from traditional virtualization

Install Docker

Simple introduction

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