Introduction to docker 1: docker installation, basic commands and redis operation examples

Environmental Science:

  • centos8.2 minimize installation
  • docker

1, docker concept

Official website:
Github Docker source code:

Docker is an open source application container engine, which is based on Go language and complies with Apache 2.0 0 protocol is open source.

Docker allows developers to package their applications and dependency packages into a lightweight and portable container, and then publish them to any popular Linux machine. It can also realize virtualization.

The container uses the sandbox mechanism completely, and there will be no interface between them (similar to iPhone app). More importantly, the performance overhead of the container is very low.

After version 17.0 three, Docker is divided into CE (Community Edition) and EE (Enterprise Edition). We can use the Community Edition.

reference: Docker tutorial

2, docker installation

2.1 installation dependency

First, install GCC and gcc-c + +:

yum -y install gcc
yum -y install gcc-c++

Then, install other dependencies:

yum install -y yum-utils device-mapper-persistent-data lvm2

2.2 installing docker

First, configure the docker warehouse address:

yum-config-manager --add-repo

Then, before installing, we can search the docker package:

[root@bogon ~]# yum list docker-ce.x86_64  --showduplicates | sort -r 
docker-ce.x86_64                3:20.10.6-3.el8                 docker-ce-stable
docker-ce.x86_64                3:20.10.5-3.el8                 docker-ce-stable
docker-ce.x86_64                3:20.10.4-3.el8                 docker-ce-stable
docker-ce.x86_64                3:20.10.3-3.el8                 docker-ce-stable
docker-ce.x86_64                3:20.10.2-3.el8                 docker-ce-stable
docker-ce.x86_64                3:20.10.1-3.el8                 docker-ce-stable
docker-ce.x86_64                3:20.10.0-3.el8                 docker-ce-stable
docker-ce.x86_64                3:19.03.15-3.el8                docker-ce-stable
docker-ce.x86_64                3:19.03.14-3.el8                docker-ce-stable
docker-ce.x86_64                3:19.03.13-3.el8                docker-ce-stable
Docker CE Stable - x86_64                       2.8 kB/s |  12 kB     00:04    
Last metadata expiration check: 0:00:02 Before, it was implemented at 08:38:18 on Wednesday, May 12, 2021.
Installable packages
[root@bogon ~]# 

Finally, install the latest docker CE directly: Yum - y install docker CE

[root@bogon ~]# yum -y install docker-ce
 Last metadata expiration check: 0:01:08 Before, it was implemented at 08:38:18 on Wednesday, May 12, 2021.
Dependency resolution.
 software package                                             framework                         edition                                                           Warehouse                                    size
 docker-ce                                          x86_64                       3:20.10.6-3.el8                                                docker-ce-stable                        27 M
 libsemanage                                        x86_64                       2.9-3.el8                                                      BaseOS                                 165 k
 Install dependencies:
 checkpolicy                                        x86_64                       2.9-1.el8                                                      BaseOS                                 348 k
 tar                                                x86_64                       2:1.30-5.el8                                                   BaseOS                                 838 k
 Enable module flow:
 container-tools                                                                 rhel8                                                                                                      

Transaction summary
Install 20 packages
 Upgrade 1 package

Total Download: 112 M
 Download package:
(1/21): container-selinux-2.155.0-1.module_el8.3.0+699+d61d9c41.noarch.rpm                                                                                   208 kB/s |  51 kB     00:00    
total                                                                                                                                                         3.1 MB/s | 112 MB     00:36     
Warning:/var/cache/dnf/docker-ce-stable-fa9dc42ab4cec2f4/packages/ head V4 RSA/SHA512 Signature, secret key ID 621e9f35: NOKEY
Docker CE Stable - x86_64                                                                                                                                    2.6 kB/s | 1.6 kB     00:00    
Import GPG Public key 0 x621E9F35:
 Userid: "Docker Release (CE rpm) <>"
 fingerprint: 060A 61C5 1B55 8A7F 742B 77AA C52F EB6B 621E 9F35
 come from:
 Import public key succeeded
 Run transaction check
 Transaction check succeeded.
Run transaction test
 Transaction test succeeded.
Run transaction
  In preparation  :                                                                                                                                                                              1/1 
  install    : docker-scan-plugin-0.7.0-3.el8.x86_64   


already installed:
  checkpolicy-2.9-1.el8.x86_64                              container-selinux-2:2.155.0-1.module_el8.3.0+699+d61d9c41.noarch                          
  docker-ce-3:20.10.6-3.el8.x86_64                          docker-ce-cli-1:20.10.6-3.el8.x86_64                                docker-ce-rootless-extras-20.10.6-3.el8.x86_64              
  docker-scan-plugin-0.7.0-3.el8.x86_64                     fuse-common-3.2.1-12.el8.x86_64                                     fuse-overlayfs-1.3.0-2.module_el8.3.0+699+d61d9c41.x86_64   
  fuse3-3.2.1-12.el8.x86_64                                 fuse3-libs-3.2.1-12.el8.x86_64                                      libcgroup-0.41-19.el8.x86_64                                
  libslirp-4.3.1-1.module_el8.3.0+475+c50ce30b.x86_64       policycoreutils-python-utils-2.9-9.el8.noarch                       python3-audit-3.0-0.17.20191104git1c2f876.el8.x86_64        
  python3-libsemanage-2.9-3.el8.x86_64                      python3-policycoreutils-2.9-9.el8.noarch                            python3-setools-4.3.0-2.el8.x86_64                          
  slirp4netns-1.1.8-1.module_el8.3.0+699+d61d9c41.x86_64    tar-2:1.30-5.el8.x86_64                                            

[root@bogon ~]# 

2.3 start docker

systemctl start docker

Note: if you run the docker command without starting docker, you may be prompted: Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?

2.4 check the installed version of docker:

[root@bogon ~]# clear
[root@bogon ~]# docker --version
Docker version 20.10.6, build 370c289
[root@bogon ~]# docker version
Client: Docker Engine - Community
 Version:           20.10.6
 API version:       1.41
 Go version:        go1.13.15
 Git commit:        370c289
 Built:             Fri Apr  9 22:44:36 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
  Version:          20.10.6
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.13.15
  Git commit:       8728dd2
  Built:            Fri Apr  9 22:43:02 2021
  OS/Arch:          linux/amd64
  Experimental:     false
  Version:          1.4.4
  GitCommit:        05f951a3781f4f2c1911b05e61c160e9c30eaa8e
  Version:          1.0.0-rc93
  GitCommit:        12644e614e25b05da6fd08a38ffa0cfe1903fdec
  Version:          0.19.0
  GitCommit:        de40ad0
[root@bogon ~]# 

3, Docker image, container and warehouse

DockerHub address:

  • Image: similar to the software installed in the operating system (existing in the hard disk and not running).

  • Container: similar to the process in the operating system (running from the installed software).

    Note: it is a virtual sandbox. If a redis is running in the container, we need to manually expose the external interface of redis so that it can be accessed from the outside. Also, for each container, it has its own localhost and, so be careful when it comes to ip addresses.

  • Warehouse: docker has created a hub for sharing packaged images, which is similar to maven in java and npm in js net.

    We can not only pull the packaged images of others from it, but also register our own account and upload them.
    Of course, we can only package the image locally for our own use without uploading it to the hub, and the image pulled from the hub will be cached locally.

Version control of image:
Each image has a tag to identify the version of the image, so that we can specify a special version of the image during installation. Unfortunately, however, the tag is not displayed in the search results of docker (I will write my own script later).

Take redis as an example to illustrate the use of docker command:

3.1 search available Redis images from DockerHub: docker search redis

[root@bogon ~]# docker search redis
NAME                             DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED
redis                            Redis is an open source key-value store that...   9417      [OK]       
bitnami/redis                    Bitnami Redis Docker Image                      178                  [OK]
sameersbn/redis                                                                  83                   [OK]
grokzen/redis-cluster            Redis cluster 3.0, 3.2, 4.0, 5.0, 6.0, 6.2      78                   
rediscommander/redis-commander   Alpine image for redis-commander - Redis man...   58                   [OK]
redislabs/redisearch             Redis With the RedisSearch module pre-loaded...   34                   
redislabs/redisinsight           RedisInsight - The GUI for Redis                30                   
redislabs/redis                  Clustered in-memory database engine compatib...   29                   
oliver006/redis_exporter          Prometheus Exporter for Redis Metrics. Supp...   25                   
redislabs/rejson                 RedisJSON - Enhanced JSON data type processi...   23                   
arm32v7/redis                    Redis is an open source key-value store that...   23                   
bitnami/redis-sentinel           Bitnami Docker Image for Redis Sentinel         21                   [OK]
redislabs/redisgraph             A graph database module for Redis               15                   [OK]
redislabs/redismod               An automated build of redismod - latest Redi...   12                   [OK]
arm64v8/redis                    Redis is an open source key-value store that...   12                   
webhippie/redis                  Docker images for Redis                         11                   [OK]
insready/redis-stat              Docker image for the real-time Redis monitor...   10                   [OK]
s7anley/redis-sentinel-docker    Redis Sentinel                                  10                   [OK]
circleci/redis                   CircleCI images for Redis                       7                    [OK]
centos/redis-32-centos7          Redis in-memory data structure store, used a...   5                    
clearlinux/redis                 Redis key-value data structure server with t...   3                    
tiredofit/redis                  Redis Server w/ Zabbix monitoring and S6 Ove...   1                    [OK]
wodby/redis                      Redis container image with orchestration        1                    [OK]
runnable/redis-stunnel           stunnel to redis provided by linking contain...   1                    [OK]
xetamus/redis-resource           forked redis-resource                           0                    [OK]
[root@bogon ~]# 

3.2 view the version of the official redis image

There is an official image in the above search results: "redis", but the tag list is not displayed. We will make our own script to realize it:

  • Create the file docker search show tag in the directory / bin SH, as follows:
    # Simple script that will display docker repository tags.
    # Usage:
    #   $ ubuntu centos
    for Repo in $* ; do
      curl -s -S "$Repo/tags/" | \
        sed -e 's/,/,\n/g' -e 's/\[/\[\n/g' | \
        grep '"name"' | \
        awk -F\" '{print $4;}' | \
        sort -fu | \
        sed -e "s/^/${Repo}:/"
  • Give the script executable permission: Chmod 744 / bin / docker search show tag sh
    [root@bogon ~]# chmod 744 /bin/

Use the above script to show all versions of image redis:

[root@bogon ~]# redis
[root@bogon ~]# 

Many tags (versions) are listed above. Note: there is a latest in it. Literally, this version should represent the latest. In fact, this tag is also an ordinary tag, but the name is a little special (Note: once downloaded locally, it belongs to the local and will not be automatically updated from the remote every time it runs...).
In addition, we all agree that the image of this version should always be kept up-to-date, so we can pull and manually update this version to keep our program up-to-date;

3.3 install redis image & view the existing local image

Install the latest redis image: docker pull redis
Install the image of the specified version: docker pull redis:6.0

When installing the latest redis image:

[root@bogon ~]# docker pull redis
Using default tag: latest

latest: Pulling from library/redis
f7ec5a41d630: Pull complete 
a36224ca8bbd: Pull complete 
7630ad34dcb2: Pull complete 
e74b2f747260: Pull complete 
ebc61c7bf222: Pull complete 
1aafd9c07208: Pull complete 
Digest: sha256:6cddb3822e19f09a6a369c35680562ddd2e44bd3bfd6fe25ec6456c42f45728b
Status: Downloaded newer image for redis:latest
[root@bogon ~]# 

You can see that since there is no tag specified for installation, docker cli will have a confirmation process and just enter.

After installation, run docker images to view the local image list:

[root@bogon ~]# docker images
redis        latest    ccee4cdf984f   8 days ago   105MB
[root@bogon ~]#

The above shows that we have installed the latest version of redis, but which version of redis is this version? We can use the following command:

[root@bogon ~]# docker image inspect redis:latest | grep -i version
        "DockerVersion": "19.03.12",
[root@bogon ~]# 

We can know that the latest version of redis downloaded at present is actually version 6.2.3.

Of course, we can manually specify the image version when downloading:

[root@bogon ~]# docker pull redis:6.0
6.0: Pulling from library/redis
f7ec5a41d630: Already exists 
a36224ca8bbd: Already exists 
7630ad34dcb2: Already exists 
b794377c17d4: Pull complete 
a134ee7a12b3: Pull complete 
ab302c2d25fc: Pull complete 
Digest: sha256:dee031783fcbe8b5d9056303091043f1023853d73dfd3a83c7802c5038ad6f84
Status: Downloaded newer image for redis:6.0
[root@bogon ~]# docker images
redis        6.0       3038fc9615f1   8 days ago   104MB
redis        latest    ccee4cdf984f   8 days ago   105MB
[root@bogon ~]#

3.4 running redis container

Execute the following command to run redis: docker run -it --name="redis6.0" -p 6379:6379 redis:6.0

After running, we can access it from the outside (linux is the virtual machine, and the local physical machine is windows10):

The above command allows us to run redis in blocking mode, but more often we want to run redis in background mode and re run the following command:

[root@bogon ~]# docker run -d --name="redistest2" -p 16379:6379 redis:6.0
[root@bogon ~]# 

After the above command is executed, the redis container id is returned.

We use redis client to connect:

3.5 start and stop of redis container & view redis container

View the running container command: docker ps

[root@bogon ~]# docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                                         NAMES
2420c44f4576   redis:6.0   "docker-entrypoint.s..."   3 minutes ago   Up 3 minutes>6379/tcp, :::16379->6379/tcp   redistest2
d7fa06746181   redis:6.0   "docker-entrypoint.s..."   9 minutes ago   Up 9 minutes>6379/tcp, :::6379->6379/tcp     redistest
[root@bogon ~]#

If you want to pause a container (redistest), you can use the following command:

[root@bogon ~]# docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                                         NAMES
2420c44f4576   redis:6.0   "docker-entrypoint.s..."   3 minutes ago   Up 3 minutes>6379/tcp, :::16379->6379/tcp   redistest2
d7fa06746181   redis:6.0   "docker-entrypoint.s..."   9 minutes ago   Up 9 minutes>6379/tcp, :::6379->6379/tcp     redistest
[root@bogon ~]# docker stop redistest
[root@bogon ~]# docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED         STATUS         PORTS                                         NAMES
2420c44f4576   redis:6.0   "docker-entrypoint.s..."   5 minutes ago   Up 5 minutes>6379/tcp, :::16379->6379/tcp   redistest2
[root@bogon ~]# 

If we want to stop all the containers (including the ones below):

[root@bogon ~]# docker ps -a
CONTAINER ID   IMAGE       COMMAND                  CREATED          STATUS                          PORTS                                         NAMES
2420c44f4576   redis:6.0   "docker-entrypoint.s..."   6 minutes ago    Up 6 minutes          >6379/tcp, :::16379->6379/tcp   redistest2
d7fa06746181   redis:6.0   "docker-entrypoint.s..."   12 minutes ago   Exited (0) About a minute ago                                                 redistest
[root@bogon ~]# 

The existing (0) about a minute ago shown above indicates that the redistest container has stopped running 1 minute ago.

We can rerun it with the following command:

[root@bogon ~]# docker start redistest
[root@bogon ~]# docker ps
CONTAINER ID   IMAGE       COMMAND                  CREATED          STATUS         PORTS                                         NAMES
2420c44f4576   redis:6.0   "docker-entrypoint.s..."   8 minutes ago    Up 8 minutes>6379/tcp, :::16379->6379/tcp   redistest2
d7fa06746181   redis:6.0   "docker-entrypoint.s..."   14 minutes ago   Up 2 seconds>6379/tcp, :::6379->6379/tcp     redistest
[root@bogon ~]# 

About docker run command:
Common parameters of the docker run command above
-it: means to run the container interactively (temporarily, generally in the background);

-d: Indicates that the container has been run in background mode;

--Name: name of the running container,

For example: docker run -it --name="redistest" -p 6379:6379 redis indicates that the container name after running is redistest.

-p: Indicates the exposed interface,

For example: docker run -it --name="redistest" -p 16379:6379 redis means that after the container runs, the 6379 port of the internal program is provided externally as 16379.
If there are more than one port, it is as follows: - p 16379:6379 -p 80:80.
If you want to expose continuous ports, as follows: -p 9600-9700:9600-9700, refer to:

-e: Represents the environment variable of the container,

For example, run ASP Net core program, if we want to specify the running environment as Development, we can use the following command:
docker -e "ASPNETCORE_ENVIRONMENT=FatA" -d --name="coreweb" -p 5000:5000 coreweb
If there are multiple environment variables, see the following:
docker -e "ASPNETCORE_ENVIRONMENT=FatA" -e "env_test=tag" -d --name="coreweb" -p 5000:5000 coreweb

-v: Mount the storage volume to the container and mount it to a directory of the container,

For example, we can use this parameter to manually specify the time zone in the docker container, as follows:
docker -e "ASPNETCORE_ENVIRONMENT=FatA" -v /etc/localtime:/etc/localtime -d --name="coreweb" -p 5000:5000 coreweb
In the above command, we specify that the time zone in the docker container uses the time zone setting of the linux machine.

3.6 removing mirrors and containers

  • Remove image: docker rmi redis:6.0

    First of all, we must remove all the containers that are running (including all the ones that have been removed).

  • Remove container: docker rmi redistest

    We must stop this container before removing it.

  • Remove containers that have been stopped: docker container prune

Keywords: Linux Docker

Added by azul85 on Thu, 10 Feb 2022 02:19:14 +0200