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

I. instructions from docker file

1. Instruction 1:FROM instruction

FROM must be the first non-annotated instruction

Used to specify the base image, which can be any image

When using the FROM instruction, docker daemon will automatically find the specified image on the local computer. If not, it will go to docker hub or other services to find the image.

Grammatical format of FROM

Format 1:FROM [: tag]

Format 2:FROM @

Note:

The first kind of mirroring refers to making a new mirror based on the name of the basic image, but there may be a loophole in doing so.

The second format is based on the hash code of the image, so that the image can avoid this problem.

Example: mirroring based on the latest version of busybox

FROM busybox:latest

2. Instruction 2:MAINTANIER instruction

Has been abandoned and replaced with LABEL

Used to describe the name of the producer

Optional option

Example:

MAINTAINER "zxhk"

3. Instruction 3:LABEL instruction

This is the instruction in the new version of docker.

This command is used to specify all kinds of metadata, and the specified method is in kye value format. In fact, the author information is just one of them.

Grammatical format

LABEL =.

4. Instruction 4:COPY instruction

Copy the files from the working directory in the host to the file system of the target mirror

Grammatical format

Copy a file: COPY

Copy multiple files: COPY [...]

Note:

Source file path, usually relative path

The destination file path, which is usually an absolute path

Use of wildcards is supported

Guidelines for file replication

Guidelines 1:src must be a directory or file in the working directory, not in the parent directory

Rule 2: if dest does not exist, it will be created passively and automatically

Rule 3: if src is a directory, then when copying, everything under src will be copied recursively, but src itself will not be copied.

Rule 4: if more than one src is specified or wildcards are used in the src, the dest must be a directory and end with /

Example: copy the index.html under the current working directory to the file system of the target container under / data/web/html

COPY index / data/web/html

[with these four instructions, you can make a mirror image]

Case; demonstrate the process of creating a docker file

Demand:

Create an index.html in the container

Prepare the configuration file for yum in the container

Realization process

Step 1: create a working directory

[root@host1 ~] # mkdir / img1 [root@host1 ~] # cd / img1/

Step 2: create a html file

[root@host1 img1] # echo "test page" > > index.html [root@host1 img1] # lsindex.html

Step 3: prepare the configuration file for yum

[root@host1 img1] # cp-a / etc/yum.repos.d/. / [root@host1 img1] # lsindex.html yum.repos.d

Step 4: write the docker file file

Specify the author, either MAINTAINER or LABEL

Put index.html under / data/

Put all files under yum.repos.d under / etc/yum.repos.d

[root@host1 img1] # vim Dockerfile#my first docker fileFROM busybox:latestMAINTAINER "zxhk" COPY index.html / data/COPY yum.repos.d/ etc/yum.repos.d/

The source directory only needs to specify the directory name, and the files under the directory will be copied.

The source directory with the same name will not be generated at the destination location, must be specified manually, and must end with /

Step 5: make a mirror image

[root@host1 img1] # docker build-t miniser:v1-1. / Sending build context to Docker daemon 20.99kBStep 1 b534869c81f0Step 4: FROM busybox:latest-- > b534869c81f0Step 2 zxhk 4: MAINTAINER "zxhk"-- > Running in 9f9f8d0793faRemoving intermediate container 9f9f8d0793fa-- > c928cd55b12cStep 3 COPY index.html 4: COPY index.html / data/-- > 5fe09215a0e2Step 4 data/ 4: COPY yum.repos.d/ etc/yum.repos.d/-- > 679710cab9bfSuccessfully built 679710cab9bfSuccessfully tagged miniser:v1-1

-t: is used to specify the label of the image

[root@host1 img1] # docker image ls | grep miniminiser v1-1 679710cab9bf 2 minutes ago 1.23MB

Step 6: start a container based on the image

[root@host1 img1] # docker run-- name T123\ >-- rm miniser:v1-1 ls / etc/yum.repos.dCentOS-Base.repoCentOS-CR.repoCentOS-Debuginfo.repoCentOS-Media.repoCentOS-Sources.repoCentOS-Vault.repoCentOS-fasttrack.repodocker.repo

The container executes a ls command, and when the ls is finished, the container stops.

The execution result of this container is to output a list of repo file names

5. Instruction 5:ADD instruction

Similar to COPY, the difference is that ADD supports the use of URL paths, that is, if your mirrored host can be connected to the network, you can download a file on the network locally and introduce it into your file.

Another function of ADD is that if the source file is a local file and the file is tar compressed and archived, then ADD can automatically extract and expand the file to your working directory. It is important to note that if the source file is a network file, the expansion cannot be extracted automatically.

Syntax format:

ADD ADD ["". "]

Demo: download nginx and put it in the mirror / var/usr/src

Step 1: find the nginx download address

Step 2: edit the docker file file

# my first docker fileFROM busybox:latestMAINTAINER "zxhk" COPY index.html / data/COPY yum.repos.d/ etc/yum.repos.d/ADD http://nginx.org/download/nginx-1.17.6.tar.gz / var/usr/src/

Step 3: build an image

[root@host1 img1] # docker build-t miniser:v1-2. / [root@host1 img1] # docker image ls | grep miniminiser v1-2 eaceb1156a52 2 minutes ago 2.27MBminiser v1-1 679710cab9bf 23 minutes ago 1.23MB

Note: you can also download the installation package of nginx locally, and then import it into the image

The content of Dockerfile file is as follows

ADD nginx-1.17.2.tar.gz / usr/local/src/

This is the time to extract the nginx to the / usr/local/src directory

6. Instruction 6:WORKDIR instruction

To set the working directory, for example, in the previous example, if we put nginx under / usr/loca/src, we can set this directory as the working directory, as follows

# my first docker fileFROM busybox:latestMAINTAINER "zxhk" COPY index.html / data/COPY yum.repos.d/ etc/yum.repos.d/WORKDIR / var/usr/src/ADD http://nginx.org/download/nginx-1.17.6.tar.gz. /

7. Instruction 7:VOLUME instruction

Used to create a mount point directory in the mirror to mount volumes on hosts or other containers

The volume created based on dockerfile cannot specify the directory of the host where the volume is located, and needs to be generated automatically.

Grammatical format

VOLUME

If there were previously files under the volume specified by docker, the files will appear in the container after the volume is mounted

Case: modify Dockerfile with / data/mysql as volume

Step 1: modify the Dockerfile file

# my first docker fileFROM busybox:latestMAINTAINER "zxhk" COPY index.html / data/COPY yum.repos.d/ etc/yum.repos.d/WORKDIR / var/usr/src/ADD http://nginx.org/download/nginx-1.17.6.tar.gz. / VOLUME / data/mysql/

Step 2: build an image

[root@host1 img1] # docker build-t miniser:v1-3. /

Step 3: start the container to check the mount

[root@host1 img1] # docker run-rm-it-name t100 miniser:v1-3/var/usr/src # / var/usr/src # mount | grep mysql/dev/mapper/centos-root on / data/mysql type xfs (rw,seclabel,relatime,attr2,inode64,noquota) / var/usr/src #

You can also execute docker inspect to view

8. Instruction 8:EXPOSE instruction

Open the listening port for the container to communicate with the external host

Syntax format:

EXPOSE [/]...

Protocol is the specified protocol, which can be tcp or udp, and the default tcp

Example: exposure of multiple ports

Example: EXPOSE 11211/udp 11211/tcp

Note:

The EXPOSE instruction written in the file only says that the port can be leaked, but it is not really exposed.

When port leaks are needed, you need to use the option-P when creating an image. This option automatically reads the EXPOSE settings to expose the necessary ports.

Case: making an image, exposing port 80

Step 1: make dockerfile

# my first docker fileFROM busybox:latestMAINTAINER "zxhk" COPY index.html / data/COPY yum.repos.d/ etc/yum.repos.d/WORKDIR / var/usr/src/ADD nginx-1.17.6.tar.gz. / VOLUME / data/mysql/EXPOSE 80/tcp 53/udp

The second step is to create an image file.

[root@host1 img1] # docker build-t miniser:v1-4. /

Step 2: start the container and run apache at startup

[root@host1 img1] # docker run-- name T100-it-- rm miniser:v1-4 httpd-f-h / data

Check the address.

[root@host1 img1] # docker inspect t100-f'{{.NetworkSettings.IPAddress}} '172.17.0.3

Direct access to the address of the container

[root@host1 img1] # curl 172.17.0.3test page

You can check whether the port is leaked at this time.

[root@host1 img1] # docker port t100 [root@host1 img1] #

There are no leaked ports.

Next, restart and run a container with the-p option

[root@host1 img1] # docker run-- name T101-p 80-it-- rm miniser:v1-4 httpd-f-h / data

Check the leaked port again

[root@host1 ~] # docker port t10180/tcp-> 0.0.0.0purl 32768

In fact, at this time, you can also use the-p option to expose those ports in the image that do not have to be specified.

9. Instruction 9:ENV instruction

Used to define the required environment variables for the mirror

Environment variables defined by ENV can be called by subsequent instructions, such as COPY ADD

ENV can nest ENV

Call variable format $var or ${var}

Define the format of the variable: ENV or ENV =

Add:

Define multiple variables, and when you need to continue, you can use\

If there is a space in the variable name, it needs to be enclosed in quotation marks

Case: modify Dockerfile environment variable

# my first docker fileFROM busybox:latestMAINTAINER "zxhk" ENV SOFT_NGX=nginx-1.17.6.tar.gz\ DOC_ROOT=/data/\ WORK_DIR=/var/usr/src/\ REPO_DIR=/etc/yum.repos.d/\ MYSQL_DIR=/data/mysql/COPY index.html ${DOC_ROOT:-/var/www/html/} COPY yum.repos.d $REPO_DIRWORKDIR $WORK_DIRADD $SOFT_NGX. / VOLUME $MYSQL_DIREXPOSE 80/tcp 53/udp

Make a mirror image

[root@host1 img1] # docker build-t miniser:v1-5. / [root@host1 img1] # docker run-- name t103-- rm miniser:v1-5 printenvPATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/binHOSTNAME=a93864cdbbceSOFT_NGX=nginx-1.17.6.tar.gzDOC_ROOT=/data/WORK_DIR=/var/usr/src/REPO_DIR=/etc/yum.repos.d/MYSQL_DIR=/data/mysql/HOME=/root

Let's be clear that variables are passed twice from building the image to starting the container, as follows

Variables can also be passed when building a container from an image, and these variables can be obtained directly from the Dockerfile

You can also pass in variables manually when you create a container

Case: pass variables when you start the container

[root@host1 img1] # docker run-- name t103-- rm\ >-- env DOC_ROOT=/data/html/\ > miniser:v1-5 printenvPATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/binHOSTNAME=d76460e0f8cdDOC_ROOT=/data/html/SOFT_NGX=nginx-1.17.6.tar.gzWORK_DIR=/var/usr/src/REPO_DIR=/etc/yum.repos.d/MYSQL_DIR=/data/mysql/HOME=/root

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