I. image structure and principle
1.1 Docker image principle
- Image is the template for creating containers, which contains the file system and contents required to start containers. Therefore, image is mainly used to create and start containers conveniently and quickly.
- The Docker image adopts a layered construction mechanism. The bottom layer is bootfs, followed by rootfs.
- bootfs is the file system used for system boot, including bootloader and kernel. After the container is started, it will be unloaded to save memory resources.
- Rootfs is on top of bootfs and is represented as the root file system of the docker container. In docker, rootfs is mounted in read-only mode by the kernel, and then an additional writable layer is mounted through joint mounting technology.
- Joint mount technology can mount several layers of directories together to form a virtual file system. The virtual file system structure is just like the directory structure of ordinary linux. The image provides a linux virtual environment through these files and the kernel of the host. Each layer of file system is called layer 1. The federated file system can set three permissions for each layer of file system, read only, read write and whiteout able. However, each layer of file system in the image is read-only. When constructing an image, we start with the most basic operating system. Each operation submitted by the construction is equivalent to making a layer of modification. A layer of file system is added and stacked up layer by layer. The modification of the upper layer will cover the visibility of the lower position. When using an image, we will only see a complete whole without knowing how many layers there are.
1.2 Docker image structure
II. Search image
Click to view the coderoot@ubuntu:~# docker search nginx NAME DESCRIPTION STARS OFFICIAL AUTOMATED nginx Official build of Nginx. 15725 [OK] jwilder/nginx-proxy Automated Nginx reverse proxy for docker con... 2088 [OK] richarvey/nginx-php-fpm Container running Nginx + PHP-FPM capable of... 818 [OK] jc21/nginx-proxy-manager Docker container for managing Nginx proxy ho... 266 linuxserver/nginx An Nginx container, brought to you by LinuxS... 159 tiangolo/nginx-rtmp Docker image with Nginx using the nginx-rtmp... 142 [OK] jlesage/nginx-proxy-manager Docker container for Nginx Proxy Manager 142 [OK] alfg/nginx-rtmp NGINX, nginx-rtmp-module and FFmpeg from sou... 110 [OK] jasonrivers/nginx-rtmp Docker images to host RTMP streams using NGI... 95 [OK] nginxdemos/hello NGINX webserver that serves a simple page co... 76 [OK] privatebin/nginx-fpm-alpine PrivateBin running on an Nginx, php-fpm & Al... 59 [OK] nginx/nginx-ingress NGINX and NGINX Plus Ingress Controllers fo... 55 nginxinc/nginx-unprivileged Unprivileged NGINX Dockerfiles 54 staticfloat/nginx-certbot Opinionated setup for automatic TLS certs lo... 25 [OK] nginxproxy/nginx-proxy Automated Nginx reverse proxy for docker con... 23 nginx/nginx-prometheus-exporter NGINX Prometheus Exporter for NGINX and NGIN... 21 schmunk42/nginx-redirect A very simple container to redirect HTTP tra... 19 [OK] centos/nginx-112-centos7 Platform for running nginx 1.12 or building ... 15 centos/nginx-18-centos7 Platform for running nginx 1.8 or building n... 13 raulr/nginx-wordpress Nginx front-end for the official wordpress:f... 13 [OK] flashspys/nginx-static Super Lightweight Nginx Image 11 [OK] mailu/nginx Mailu nginx frontend 9 [OK] sophos/nginx-vts-exporter Simple server that scrapes Nginx vts stats a... 7 [OK] ansibleplaybookbundle/nginx-apb An APB to deploy NGINX 2 [OK] wodby/nginx Generic nginx 1 [OK]
III. Download Image
root@ubuntu:~# docker pull warehouse server: port / project name / image name: tag root@ubuntu:~# docker pull nginx
IV. view local image
root@ubuntu:~# docker images REPOSITORY TAG IMAGE ID CREATED SIZE nginx latest 87a94228f133 2 weeks ago 133MB hello-world latest feb5d9fea6a5 5 weeks ago 13.3kB
V. image export
root@ubuntu:~# docker save nginx -o /opt/nginx.tar.gz root@ubuntu:~# ls -l /opt/nginx.tar.gz -rw------- 1 root root 137544192 Oct 29 17:48 /opt/nginx.tar.gz
Vi. image import
root@ubuntu:~# docker load < /opt/nginx.tar.gz e81bff2725db: Loading layer [==================================================>] 72.52MB/72.52MB 43f4e41372e4: Loading layer [==================================================>] 64.97MB/64.97MB 788e89a4d186: Loading layer [==================================================>] 3.072kB/3.072kB f8e880dfc4ef: Loading layer [==================================================>] 4.096kB/4.096kB f7e00b807643: Loading layer [==================================================>] 3.584kB/3.584kB 9959a332cf6e: Loading layer [==================================================>] 7.168kB/7.168kB Loaded image: nginx:latest
VII. Image renaming
root@ubuntu:~# docker tag nginx test_nginx:v1.0 root@ubuntu:~# docker images REPOSITORY TAG IMAGE ID CREATED SIZE nginx latest 87a94228f133 2 weeks ago 133MB test_nginx v1.0 87a94228f133 2 weeks ago 133MB hello-world latest feb5d9fea6a5 5 weeks ago 13.3kB
VIII. View the image hierarchy history
Click to view the coderoot@ubuntu:~# docker image history nginx IMAGE CREATED CREATED BY SIZE COMMENT 87a94228f133 2 weeks ago /bin/sh -c #(nop) CMD ["nginx" "-g" "daemon... 0B <missing> 2 weeks ago /bin/sh -c #(nop) STOPSIGNAL SIGQUIT 0B <missing> 2 weeks ago /bin/sh -c #(nop) EXPOSE 80 0B <missing> 2 weeks ago /bin/sh -c #(nop) ENTRYPOINT ["/docker-entr... 0B <missing> 2 weeks ago /bin/sh -c #(nop) COPY file:09a214a3e07c919a... 4.61kB <missing> 2 weeks ago /bin/sh -c #(nop) COPY file:0fd5fca330dcd6a7... 1.04kB <missing> 2 weeks ago /bin/sh -c #(nop) COPY file:0b866ff3fc1ef5b0... 1.96kB <missing> 2 weeks ago /bin/sh -c #(nop) COPY file:65504f71f5855ca0... 1.2kB <missing> 2 weeks ago /bin/sh -c set -x && addgroup --system -... 64MB <missing> 2 weeks ago /bin/sh -c #(nop) ENV PKG_RELEASE=1~buster 0B <missing> 2 weeks ago /bin/sh -c #(nop) ENV NJS_VERSION=0.6.2 0B <missing> 2 weeks ago /bin/sh -c #(nop) ENV NGINX_VERSION=1.21.3 0B <missing> 2 weeks ago /bin/sh -c #(nop) LABEL maintainer=NGINX Do... 0B <missing> 2 weeks ago /bin/sh -c #(nop) CMD ["bash"] 0B <missing> 2 weeks ago /bin/sh -c #(nop) ADD file:910392427fdf089bc... 69.3MB
IX. view image information
Click to view the coderoot@ubuntu:~# docker inspect nginx
[
{
"Id": "sha256:87a94228f133e2da99cb16d653cd1373c5b4e8689956386c1c12b60a20421a02",
"RepoTags": [
"nginx:latest",
"test_nginx:v1.0"
],
"RepoDigests": [],
"Parent": "",
"Comment": "",
"Created": "2021-10-12T02:03:40.360294686Z",
"Container": "21fd1c6cb532225ca7e04c77f6592e220574b919aec07021663576ef438e0fee",
"ContainerConfig": {
"Hostname": "21fd1c6cb532",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"ExposedPorts": {
"80/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"NGINX_VERSION=1.21.3",
"NJS_VERSION=0.6.2",
"PKG_RELEASE=1~buster"
],
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ",
"CMD [\"nginx\" \"-g\" \"daemon off;\"]"
],
"Image": "sha256:e30f1b92b2c67fbe72fb24af7353a945f6df4f48d9064d47bf0f51674311251e",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": [
"/docker-entrypoint.sh"
],
"OnBuild": null,
"Labels": {
"maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>"
},
"StopSignal": "SIGQUIT"
},
"DockerVersion": "20.10.7",
"Author": "",
"Config": {
"Hostname": "",
"Domainname": "",
"User": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"ExposedPorts": {
"80/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"NGINX_VERSION=1.21.3",
"NJS_VERSION=0.6.2",
"PKG_RELEASE=1~buster"
],
"Cmd": [
"nginx",
"-g",
"daemon off;"
],
"Image": "sha256:e30f1b92b2c67fbe72fb24af7353a945f6df4f48d9064d47bf0f51674311251e",
"Volumes": null,
"WorkingDir": "",
"Entrypoint": [
"/docker-entrypoint.sh"
],
"OnBuild": null,
"Labels": {
"maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>"
},
"StopSignal": "SIGQUIT"
},
"Architecture": "amd64",
"Os": "linux",
"Size": 133277153,
"VirtualSize": 133277153,
"GraphDriver": {
"Data": {
"LowerDir": "/var/lib/docker/overlay2/5936365e35391fb0cbd58837deca3071b3e184f4b379ea9083fbe92abb41d1a1/diff:/var/lib/docker/overlay2/283e87848d1aa658db2042ef4a4e5e647df5802730c329055a2a9125a9af6048/diff:/var/lib/docker/overlay2/cc6da890b6136654f4d247b48a783d065bbed8c0bcf36515ab7fbd15273280c1/diff:/var/lib/docker/overlay2/fe9766053b8733da341d4c5d868f7ea156025820b62d1028174902f3d5696168/diff:/var/lib/docker/overlay2/ade8e887e82afa5c813e45352bec310a0120dc546ea7039b226c2d3877216207/diff",
"MergedDir": "/var/lib/docker/overlay2/272f7a79a4072689772c4344bc17bd165c91922aaa3bfc259a3411e87ba25499/merged",
"UpperDir": "/var/lib/docker/overlay2/272f7a79a4072689772c4344bc17bd165c91922aaa3bfc259a3411e87ba25499/diff",
"WorkDir": "/var/lib/docker/overlay2/272f7a79a4072689772c4344bc17bd165c91922aaa3bfc259a3411e87ba25499/work"
},
"Name": "overlay2"
},
"RootFS": {
"Type": "layers",
"Layers": [
"sha256:e81bff2725dbc0bf2003db10272fef362e882eb96353055778a66cda430cf81b",
"sha256:43f4e41372e42dd32309f6a7bdce03cf2d65b3ca34b1036be946d53c35b503ab",
"sha256:788e89a4d186f3614bfa74254524bc2e2c6de103698aeb1cb044f8e8339a90bd",
"sha256:f8e880dfc4ef19e78853c3f132166a4760a220c5ad15b9ee03b22da9c490ae3b",
"sha256:f7e00b807643e512b85ef8c9f5244667c337c314fa29572206c1b0f3ae7bf122",
"sha256:9959a332cf6e41253a9cd0c715fa74b01db1621b4d16f98f4155a2ed5365da4a"
]
},
"Metadata": {
"LastTagTime": "2021-10-29T17:54:04.494435623+08:00"
}
}
]X. delete image
Click to view the coderoot@ubuntu:~# docker rmi nginx Untagged: nginx:latest Untagged: nginx@sha256:644a70516a26004c97d0d85c7fe1d0c3a67ea8ab7ddf4aff193d9f301670cf36 Deleted: sha256:87a94228f133e2da99cb16d653cd1373c5b4e8689956386c1c12b60a20421a02 Deleted: sha256:55b6972054b24c53054322a52748324df5797eefbb6dc374e41522a91d532dd5 Deleted: sha256:6b88aa6f4485486bfc779cccfbe4a7a47a502a7cff2cd70be89c59dcd0db12a8 Deleted: sha256:472c64059965c7b6b1b534ba07374c1d034b17c99acb3cf4534fe78abed41101 Deleted: sha256:788a5cf1e4599312b5923694f53e556ba0e2eb4a6bbb51958e0ec2b510345a49 Deleted: sha256:410f31f9ae37c62af85e8f9575c5f4d75542be1739ac1ca5982cf461be0b13bc Deleted: sha256:e81bff2725dbc0bf2003db10272fef362e882eb96353055778a66cda430cf81broot@ubuntu:~# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx latest 87a94228f133 2 weeks ago 133MB
hello-world latest feb5d9fea6a5 5 weeks ago 13.3kB