初识Dockerfile

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Docker通过从 Dockerfile读取指令来自动编译images, Dockerfile包含生成一个image所需要的所有命令集合,它是一个文档,使用 docker build用户可以持续执行一些命令行指令.

The 

docker
build

 command builds an image from a

Dockerfile

 and
a context.

The
build’s context is the files at a specified location 

PATH

 or 

URL

.

 
--The 

PATH

 is
a directory on your local filesystem.

 
--The 

URL

 is
a the location of a Git repository.

Warning:
Do not use your root directory, 

/

,
as the

PATH

 as
it causes the build to transfer the entire contents of your hard drive to the Docker daemon.

the 

Dockerfile

 is called 

Dockerfile

and
located in the root of the context. You use the 

-f

flag
with 

docker build

 to point to
a Dockerfile anywhere in your file system.

$ docker build -f /path/to/a/Dockerfile .

Image在编译好后的保存操作

>指定一个
image的保存路径

You can specify a repository and tag at which to save the new image if the build succeeds:

$ docker build -t shykes/myapp .

>tag多个image

To tag the image into multiple repositories after the build, add multiple 

-t

 parameters
when you run the 

build

command:

$ docker build -t shykes/myapp:1.0.2 -t shykes/myapp:latest .

加速Docker编译
Whenever
possible, Docker will re-use the intermediate images (cache), to accelerate the 

docker
build

process significantly. This is indicated by the

Using
cache

 message in the console output. (For more information, see the Build
cache section) in the

Dockerfile

 best
practices guide:

Docker
runs the instructions in a 

Dockerfile

 in
order.The first instruction must be `FROM` in
order to specify the Base
Image from which you are building.

"#" 是注释符

转义符( \ ) :

Escaping is possible by adding a 

\

 before
the variable:

\$foo

 or 

\${foo}

,
for example, will translate to

$foo

 and 

${foo}

 literals
respectively.