Hai semuanya, di materi kali ini kita akan membahas secara lebih mendalam tentang Dockerfile perintah FROM sebagai berikut:

The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructions. As such, a valid Dockerfile must start with a FROM instruction. Berikut adalah format penulisan FROM instrustion

FROM [--platform=<platform>] <image> [AS <name>]
FROM [--platform=<platform>] <image>[:<tag>] [AS <name>]
FROM [--platform=<platform>] <image>[@<digest>] [AS <name>]

The image can be any valid image – it is especially easy to start by pulling an image from the Public Repositories.

  1. ARG is the only instruction that may precede FROM in the Dockerfile. See Understand how ARG and FROM interact.
  2. FROM can appear multiple times within a single Dockerfile to create multiple images or use one build stage as a dependency for another. Simply make a note of the last image ID output by the commit before each new FROM instruction. Each FROM instruction clears any state created by previous instructions.
  3. Optionally a name can be given to a new build stage by adding AS name to the FROM instruction. The name can be used in subsequent FROM and COPY --from=<name> instructions to refer to the image built in this stage.
  4. The tag or digest values are optional. If you omit either of them, the builder assumes a latest tag by default. The builder returns an error if it cannot find the tag value.

Contoh penggunaanya seperti berikut:

Jika di jalankan maka hasilnya seperti berikut:

➜ 07-dockerfile  docker build -t dimmaryanto93/centos:0.1 .
[+] Building 0.1s (6/6) FINISHED
 => [internal] load build definition from Dockerfile                                          0.0s 
 => => transferring dockerfile: 31B                                                           0.0s 
 => [internal] load .dockerignore                                                             0.0s 
 => => transferring context: 2B                                                               0.0s 
 => [internal] load metadata for docker.io/library/centos:7                                   0.0s 
 => [1/2] FROM docker.io/library/centos:7                                                     0.0s 
 => CACHED [2/2] RUN echo "halo semuanya, ini adalah contoh text" > /var/halo.txt             0.0s 
 => exporting to image                                                                        0.0s 
 => => exporting layers                                                                       0.0s 
 => => writing image sha256:53126b30ada3ad85fb6215503e2022bd264f0ef1a7ceac213a6e08e19afdf191  0.0s 
 => => naming to docker.io/dimmaryanto93/centos:0.1

➜ 07-dockerfile  docker run --rm dimmaryanto93/centos:0.1
halo semuanya, ini adalah contoh text

Cleanup

Seperti biasa, setelah kita mencoba kita bersih-bersih dulu ya berikut perintahnya: