Shulou(Shulou.com)06/02 Report--

There are two ways to create images in Docker:

1. Container-based mirroring:

docker commit …

2. Making mirror images based on Dockerfile;

docker build …

Dockerfile production steps:

1. Create a directory;

2. Create a capitalized file in the directory for docker build to identify;

3. Because the execution environment of Dockerfile is in the directory created, you can create a corresponding file for Dockerfile to use;

ex：

[root@master ~]# ls docimageDockerfile index.html [root@master ~]# cat docimage/DockerfileFROM busybox:latest LABEL maintainer="hevttc" ENV DOC_ROOT="/tmp/" \ VOLUME_ROOT="/data/mydata" \ ARGU="/usr/sbin/" COPY index.html /tmp/ VOLUME ${VOLUME_ROOT} RUN ifconfig -a && \ cat ${DOC_ROOT}index.html

Dockerfile format:

Dockerfile Format

The line beginning with "#" is a comment line (multiple lines, anywhere);

INSTRUCTION arguments

Instructions and corresponding parameters, it is recommended that instructions be capitalized, parameters be lowercase, default case can be;

Can be completed with one line of instructions, try not to use multiple lines of instructions;

The first executable instruction must be a FROM instruction;

Docker is to execute the contents of Dockerfile in sequence, pay attention to the writing order;

There are several important commands in Dockerfile:

1. FROM (specify base mirror)

FROM |: or

FROM @

: Specifies the name as the base image;

: label of base image, optional, default to latest when omitted;

2. LABEL (write creator information of current Dockerfile);

LABEL = = = …

3. COPY (copy host files to mirror);

COPY …or COPY ["",... "" ]

: The source file or directory to copy. Wildcards are supported.

: Target path, i.e. file system path of image being created; absolute path is recommended, otherwise, COPY specifies WORKDIR as its starting path;

Note: When there are white space characters in the path, the second format is usually used;

ADD (similar to COPY command, support TAR file and URL path);

ADD …or ADD ["",... "" ]

Note:

If URL does not end with "/", the specified file will be downloaded and created directly as; if URL ends with "/", the file specified by filename URL will be downloaded and saved as/;

If it is a tar file in compressed format on the local system, it will be expanded into a directory, which behaves like the "tar -x" command; however, tar files retrieved via URL will not be expanded automatically;

If there is more than one, or it uses wildcards indirectly or directly, it must be a directory path ending with "/"; if it does not end with "/", it is treated as a normal file and the contents of will be written directly to;

WORKDIR (used to specify the working directory for all RUN, CMD, ENTRYPOINT, COPY and ADD in Dockerfile;);

WORKDIR

WORKDIR can occur multiple times in a Dockerfile, and its path can be relative, but relative to the path specified by the previous WORKDIR directive;

In addition, WORKDIR can also call variables defined by ENV;

VOLUME (used to create a mount point directory in image, which can be used to mount volumes on Docker Host);

VOLUME or VOLUME ["mountpoint"]

Personally, it is not recommended to use: this is Docker daemon to create managed volumes, not binding mounts;

7. EXPOSE (open the port to be listened to for the container, and realize communication with the outside);

EXPOSE [/] [/] [/] …

Used to specify the transport layer protocol, which can be either TCP or UDP, and the default is TCP;

ENV (defines environment variables for mirroring, can be called by other instructions, build_time and run_time can be used);

ENV or ENV =...

Call format:

$variable_name or ${variable_name}

9. ARG (variable used in creating mirror is build_time, generally ARG is used to write version number and author);

ARG [=]

10.RUN (used to specify the program to run during Docker build);

RUN or

RUN ["","","",...] (json array)

CMD (similar to RUN command, executed at run_time);

CMD

CMD ["","","",...] or

CMD ["","",...] (Provides default parameters for ENTRYPOINT directive)

12. ENTRYPOINT (similar to CMD command)

ENTRYPOINT

ENTRYPOINT ["","","",...]

[root@master ~]# cat docimage1/entrypoint.sh#!/ bin/sh exec $@[root@master ~]# cat docimage1/DockerfileFROM nginx:1.14-alpine COPY entrypoint.sh ["/usr/local/nginx","-g","daemon off;"] ENTRYPOINT ["/bin/entrypoint.sh"][root@master ~]# ll docimage1/total usage 8-rw-r-r- 1 root 129 November 1 20:42 Dockerfile-rwxr-xr-x 1 root 19 November 1 20:16 entrypoint.sh

command execution diagram

Create a Dockerfile;

[root@www ~]# mkdir docimage[root@www ~]# vim docimage/Dockerfile[root@www ~]#[root@www ~]# vim docimage/test.txt[root@www ~]# cat docimage/DockerfileFROM nginx:1.14-alpine LABEL maintainer="liujingyu" ENV DOC_ROOT="/tmp" \ VOLUME_ROOT=/data/mydata COPY test.txt ${DOC_ROOT} VOLUME ${VOLUME_ROOT} RUN echo 123 > ${DOC_ROOT}/test.txt CMD cat ${DOC_ROOT}/test.txt[root@www ~]#[root@www ~]# cat docimage/test.txtTHIS is Docker TEST;

Creating Mirrors with Dockerfile:

[root@www ~]# docker build docimage/ -t ljymyy/nginx:v0.2Sending build context to Docker daemon 3.072kBStep 1/7 : FROM nginx:1.14-alpine ---> 77bae8d00654Step 2/7 : LABEL maintainer="liujingyu" ---> Using cache ---> a012ac4c6f51Step 3/7 : ENV DOC_ROOT="/tmp" VOLUME_ROOT=/data/mydata ---> Using cache ---> ee6ed363bfdeStep 4/7 : COPY test.txt ${DOC_ROOT} ---> Using cache ---> a416671fde2aStep 5/7 : VOLUME ${VOLUME_ROOT} ---> Using cache ---> 84bf38b22301Step 6/7 : RUN echo 123 > ${DOC_ROOT}/test.txt ---> Using cache ---> 756cd9857096Step 7/7 : CMD cat ${DOC_ROOT}/test.txt ---> Running in a2f99fcc5fbaRemoving intermediate container a2f99fcc5fba ---> dac468a636e0Successfully built dac468a636e0Successfully tagged ljymyy/nginx:v0.2[root@www ~]# docker image lsREPOSITORY TAG IMAGE ID CREATED SIZEljymyy/nginx v0.2 dac468a636e0 2 minutes ago 17.7MB

Run this image:

[root@www ~]# docker container run --rm --name ngx1 ljymyy/nginx:v0.2123

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