开始学习 Docker 的同学基本上都是按照官方的 guide 来安装，之后要测试是否已经安装成功，官方会让你 pull 一个 hello-world 示例镜像下来并运行，如下命令：
@www.linuxidc.com ⮀ ~ ⮀ docker pull hello-world 31cbccb51277: Pull complete e45a5af57b00: Pull complete 511136ea3c5a: Already exists hello-world:latest: The image you are pulling has been verified. Important: image verification is a tech preview feature and should not be relied on to provide security. Status: Downloaded newer image for hello-world:latest guohl@ghl-MBP ⮀ ~ ⮀ docker run hello-world Hello from Docker. This message shows that your installation appears to be working correctly. To generate this message, Docker took the following steps: 1. The Docker client contacted the Docker daemon. 2. The Docker daemon pulled the "hello-world" image from the Docker Hub. (Assuming it was not already locally available.) 3. The Docker daemon created a new container from that image which runs the executable that produces the output you are currently reading. 4. The Docker daemon streamed that output to the Docker client, which sent it to your terminal. To try something more ambitious, you can run an Ubuntu container with: $ docker run -it ubuntu bash For more examples and ideas, visit: http://docs.docker.com/userguide/出现上面的输出信息表示你 Docker 安装成功。使用下面命令查看该镜像的信息，发现大小只有 910B：
@www.linuxidc.com ⮀ ~ ⮀ docker images hello-world REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE hello-world latest e45a5af57b00 3 months ago 910 B那么该镜像运行怎么就输出上面这一串信息的呢？如果对 Docker 了解一点的话自然会去找该镜像的 Dockerfile，Dockerfile 详细描述了该镜像是如何建立的以及运行时执行的命令。从 Docker Hub 上 hello-world 的库简介 找到其 Dockerfile 在 github 上，简简单单的三条语句：
FROM scratch ADD hello / CMD ["/hello"]hello 是一个可执行的二进制文件，从文章的开头可以推测该文件执行输出那一堆提示信息，那该文件怎样生成的呢？从 hello-world 的库中可以看到还有两个文件，一个是汇编文件 hello.asm，还有一个 Makefile 文件，可以猜测 hello 就是事先通过 hello.asm 编译得到的，如 Makefile 文件所描述的编译过程：
hello: hello.asm nasm -o $@ $< chmod +x hello .PHONY: clean clean: -rm -vf hello该 Makefile 文件比较容易理解，主要是使用 nasm 汇编器将 hello.asm 编译生成可执行文件 hello。
最后再来看看 hello.asm 文件，这是一段 Intel x86 汇编：
; this is especially thanks to: ; http://blog.markloiseau.com/2012/05/tiny-64-bit-elf-executables/ BITS 64 org 0x00400000 ; Program load offset ; 64-bit ELF header ehdr: ; 1), 0 (ABI ver.) db 0x7F, "ELF", 2, 1, 1, 0 ; e_ident times 8 db 0 ; reserved (zeroes) dw 2 ; e_type: Executable file dw 0x3e ; e_machine: AMD64 dd 1 ; e_version: current version dq _start ; e_entry: program entry address (0x78) dq phdr - $$ ; e_phoff program header offset (0x40) dq 0 ; e_shoff no section headers dd 0 ; e_flags no flags dw ehdrsize ; e_ehsize: ELF header size (0x40) dw phdrsize ; e_phentsize: program header size (0x38) dw 1 ; e_phnum: one program header dw 0 ; e_shentsize dw 0 ; e_shnum dw 0 ; e_shstrndx ehdrsize equ $ - ehdr ; 64-bit ELF program header phdr: dd 1 ; p_type: loadable segment dd 5 ; p_flags read and execute dq 0 ; p_offset dq $$ ; p_vaddr: start of the current section dq $$ ; p_paddr: " " dq filesize ; p_filesz dq filesize ; p_memsz dq 0x200000 ; p_align: 2^11=200000 = section alignment ; program header size phdrsize equ $ - phdr ; Hello World!/your program here _start: ; sys_write(stdout, message, length) mov rax, 1 ; sys_write mov rdi, 1 ; stdout mov rsi, message ; message address mov rdx, length ; message string length syscall ; sys_exit(return_code) mov rax, 60 ; sys_exit mov rdi, 0 ; return 0 (success) syscall message: db 'Hello from Docker.', 0x0A db 'This message shows that your installation appears to be working correctly.', 0x0A db 0x0A db 'To generate this message, Docker took the following steps:', 0x0A db ' 1. The Docker client contacted the Docker daemon.', 0x0A db ' 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.', 0x0A db ' (Assuming it was not already locally available.)', 0x0A db ' 3. The Docker daemon created a new container from that image which runs the', 0x0A db ' executable that produces the output you are currently reading.', 0x0A db ' 4. The Docker daemon streamed that output to the Docker client, which sent it', 0x0A db ' to your terminal.', 0x0A db 0x0A db 'To try something more ambitious, you can run an Ubuntu container with:', 0x0A db ' $ docker run -it ubuntu bash', 0x0A db 0x0A db 'For more examples and ideas, visit:', 0x0A db ' ', 0x0A length: equ $-message ; message length calculation ; File size calculation filesize equ $ - $$也比较简单，就调用了两个系统调用，sys_write 向标准输出打印一段信息，sys_exit 退出程序。