dockerfile.md

   1 ---
   2 title: Dockerfile
   3 category: Devops
   4 layout: 2017/sheet
   5 prism_languages: [docker]
   6 updated: 2019-10-20
   7 ---
   8
   9 ## Reference
  10 {: .-three-column}
  11
  12 ### Inheritance
  13
  14 ```docker
  15 FROM ruby:2.2.2
  16 ```
  17
  18 ### Variables
  19
  20 ```docker
  21 ENV APP_HOME /myapp
  22 RUN mkdir $APP_HOME
  23 ```
  24
  25 ```docker
  26 ARG APP_HOME=""
  27 RUN mkdir $APP_HOME
  28 ```
  29
  30 ### Initialization
  31
  32 ```docker
  33 RUN bundle install
  34 ```
  35
  36 ```docker
  37 WORKDIR /myapp
  38 ```
  39
  40 ```docker
  41 VOLUME ["/data"]
  42 # Specification for mount point
  43 ```
  44
  45 ```docker
  46 ADD file.xyz /file.xyz
  47 COPY --chown=user:group host_file.xyz /path/container_file.xyz
  48 ```
  49
  50 ### Run commands in strict shell
  51
  52 ```docker
  53 ENV my_var
  54 SHELL ["/bin/bash", "-euo", "pipefail", "-c"]
  55
  56 # With strict mode:
  57 RUN false # fails build like using &&
  58 RUN echo "$myvar" # will throw error due to typo
  59 RUN true | false # will bail out of pipe
  60 ```
  61
  62 Using `shell` will turn on strict mode for shell commands.
  63
  64 ### Onbuild
  65
  66 ```docker
  67 ONBUILD RUN bundle install
  68 # when used with another file
  69 ```
  70
  71 ### Commands
  72
  73 ```docker
  74 EXPOSE 5900
  75 CMD    ["bundle", "exec", "rails", "server"]
  76 ```
  77
  78 ### Entrypoint
  79
  80 ```docker
  81 ENTRYPOINT ["executable", "param1", "param2"]
  82 ENTRYPOINT command param1 param2
  83 ```
  84
  85 Configures a container that will run as an executable.
  86
  87 ```docker
  88 ENTRYPOINT exec top -b
  89 ```
  90
  91 This will use shell processing to substitute shell variables, and will ignore any `CMD` or `docker run` command line arguments.
  92
  93 ### Metadata
  94
  95 ```docker
  96 LABEL version="1.0"
  97 ```
  98
  99 ```docker
 100 LABEL "com.example.vendor"="ACME Incorporated"
 101 LABEL com.example.label-with-value="foo"
 102 ```
 103
 104 ```docker
 105 LABEL description="This text illustrates \
 106 that label-values can span multiple lines."
 107 ```
 108
 109 ## See also
 110 {: .-one-column}
 111
 112 - <https://docs.docker.com/engine/reference/builder/>