docker鏡像瘦身行動

時間  2020-01-15
標籤 docker 鏡像 瘦身 行動 欄目 Docker 简体版
原文   原文鏈接

背景

隨着微服務概念的深刻人心，隨着docker開發的持續進行，咱們在生產的過程當中將會產生大量的docker鏡像，這些鏡像會隨着版本迭代的過程當中，這些鏡像將會佔用大量的存儲空間，本文將分析影響鏡像大小的因素，隨後提供鏡像瘦身的思路。python

Dockerfile、Docker 鏡像和 Docker 容器的關係

不可避免地，咱們在docker學習的過程當中必定繞不開理解這三者的關係，從研發流程的角度來看來看，Dockerfile 是軟件的原材料，Docker 鏡像是軟件的交付品，而 Docker 容器則能夠認爲是軟件的運行的狀態。從應用軟件的角度來看，Dockerfile、Docker 鏡像與 Docker 容器分別表明軟件的三個不一樣階段，Dockerfile 面向開發，Docker 鏡像成爲交付標準，Docker 容器則涉及部署與運維，三者缺一不可，協力充當 Docker 體系的基石。
簡單來說，Dockerfile構建出Docker鏡像，經過Docker鏡像運行Docker容器。後續有機會再詳細分析這三者的關係linux

精簡鏡像

如下是咱們精簡鏡像的目的：git

  • 更快的構建速度
  • 更小的Docker鏡像大小
  • 更少的Docker鏡像層
  • 充分利用鏡像緩存
  • 增長Dockerfile可讀性
  • 讓Docker容器使用起來更簡單

原理

簡單來說就是：最基礎的鏡像+合併操做指令（減小操做指令）sql

瘦身行動

咱們即將經過一系列的dockerfile開發，對鏡像打包進行一次次的試驗，以盡最大努力的減少鏡像的大小
原始文件
這是一份很是糟糕的Dockerfile文件打包以後，僅做爲分析用例docker

FROM python:3.5.6-slim-stretch
RUN apt-get update
RUN echo python -V 
RUN mkdir /code 
RUN mkdir /code/db
ADD . /code/
WORKDIR /code
RUN pip install -r requirement

運行命令：docker build -t spidermax:test_01 .
將會對鏡像進行打包，docker相關程序會讀取該文件（Dockerfile），如下是鏡像層的部署過程django

Sending build context to Docker daemon 289.8kB
Step 1/9 : FROM python:3.5.6-slim-stretch
---> 86669b8e5771
Step 2/9 : RUN apt-get update
---> Using cache
---> 1b77542b82f4
Step 3/9 : RUN echo python -V
---> Using cache
---> de6cc0a916d7
Step 4/9 : RUN mkdir /code
---> Using cache
---> 996828abe04e
Step 5/9 : RUN mkdir /code/db
---> Using cache
---> 2db7c4dfb918
Step 6/9 : ADD . /code/
---> d9d92db45b29
Step 7/9 : WORKDIR /code
---> Running in 5ae405de28fc
Removing intermediate container 5ae405de28fc
---> a7e3696c6a5b
Step 8/9 : RUN pip install -U pip
---> Running in dcf5b22f6f33
Collecting pip
Downloading https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl (1.4MB)
Installing collected packages: pip
Found existing installation: pip 18.1
Uninstalling pip-18.1:
Successfully uninstalled pip-18.1
Successfully installed pip-19.0.3
Removing intermediate container dcf5b22f6f33
---> 949d89aabe2b
Step 9/9 : RUN pip install -r requirement
---> Running in 697c65e4161a
Collecting Django==2.1.7 (from -r requirement (line 1))
Downloading https://files.pythonhosted.org/packages/c7/87/fbd666c4f87591ae25b7bb374298e8629816e87193c4099d3608ef11fab9/Django-2.1.7-py3-none-any.whl (7.3MB)
Collecting EasyProcess==0.2.5 (from -r requirement (line 2))
Downloading https://files.pythonhosted.org/packages/45/3a/4eecc0c7995a13a64739bbedc0d3691fc574245b7e79cff81905aa0c2b38/EasyProcess-0.2.5.tar.gz
Collecting PyMySQL==0.9.3 (from -r requirement (line 3))
Downloading https://files.pythonhosted.org/packages/ed/39/15045ae46f2a123019aa968dfcba0396c161c20f855f11dea6796bcaae95/PyMySQL-0.9.3-py2.py3-none-any.whl (47kB)
Collecting pytz==2018.9 (from -r requirement (line 4))
Downloading https://files.pythonhosted.org/packages/61/28/1d3920e4d1d50b19bc5d24398a7cd85cc7b9a75a490570d5a30c57622d34/pytz-2018.9-py2.py3-none-any.whl (510kB)
Collecting selenium==3.141.0 (from -r requirement (line 5))
Downloading https://files.pythonhosted.org/packages/80/d6/4294f0b4bce4de0abf13e17190289f9d0613b0a44e5dd6a7f5ca98459853/selenium-3.141.0-py2.py3-none-any.whl (904kB)
Collecting urllib3==1.24.1 (from -r requirement (line 6))
Downloading https://files.pythonhosted.org/packages/62/00/ee1d7de624db8ba7090d1226aebefab96a2c71cd5cfa7629d6ad3f61b79e/urllib3-1.24.1-py2.py3-none-any.whl (118kB)
Building wheels for collected packages: EasyProcess
Building wheel for EasyProcess (setup.py): started
Building wheel for EasyProcess (setup.py): finished with status 'done'
Stored in directory: /root/.cache/pip/wheels/41/22/19/af15ef6264c58b625a82641ed7483ad05e258fbd8925505227
Successfully built EasyProcess
Installing collected packages: pytz, Django, EasyProcess, PyMySQL, urllib3, selenium
Successfully installed Django-2.1.7 EasyProcess-0.2.5 PyMySQL-0.9.3 pytz-2018.9 selenium-3.141.0 urllib3-1.24.1
Removing intermediate container 697c65e4161a
---> f59692faac28
Successfully built f59692faac28
Successfully tagged spidermax:test_01緩存

經過docker images查看鏡像大小
docker鏡像瘦身行動
經過docker history咱們來觀察鏡像層打包的過程
docker鏡像瘦身行動
這裏有若干個missing層，實際上是docker打包程序程序自動優化的過程。Docker爲了加快鏡像構建速度，也會將每個鏡像層緩存下來。利用這個特性，能夠提高工做效率，不過能用到這個特性倒是有點尷尬：安全

  • 上一個指令可以在上一層緩存中找到
  • 緩存中存在一個鏡像層，並且指令和即將打包的指令如出一轍，即便有空格也不行！
  • 若是有相似COPY或者ADD指令，若是他們引用的文件的元數據發生變化，緩存也無效

優化1

接下來咱們對相同屬性指令進行合併，好比RUN命令等運維

FROM python:3.5.6-slim-stretch
RUN apt-get update &&\
    echo python -V &&\
    mkdir /code &&\
    mkdir /code/db
ADD . /code/
WORKDIR /code
RUN pip install -U pip &&\
    pip install -r requirement

如下是編譯日誌ide

docker build -t spidermax:test_02 .
Sending build context to Docker daemon 289.8kB
Step 1/5 : FROM python:3.5.6-slim-stretch
---> 86669b8e5771
Step 2/5 : RUN apt-get update && echo python -V && mkdir /code && mkdir /code/db
---> Running in 2a879b85221f
Get:1 http://security.debian.org/debian-security stretch/updates InRelease [94.3 kB]
Get:2 http://security.debian.org/debian-security stretch/updates/main amd64 Packages [481 kB]
Ign:3 http://deb.debian.org/debian stretch InRelease
Get:4 http://deb.debian.org/debian stretch-updates InRelease [91.0 kB]
Get:5 http://deb.debian.org/debian stretch Release [118 kB]
Get:6 http://deb.debian.org/debian stretch-updates/main amd64 Packages [11.1 kB]
Get:7 http://deb.debian.org/debian stretch Release.gpg [2434 B]
Get:8 http://deb.debian.org/debian stretch/main amd64 Packages [7084 kB]
Fetched 7881 kB in 8s (966 kB/s)
Reading package lists...
python -V
Removing intermediate container 2a879b85221f
---> 5ce22d4611e9
Step 3/5 : ADD . /code/
---> af87134918ca
Step 4/5 : WORKDIR /code
---> Running in 2a5c72670be3
Removing intermediate container 2a5c72670be3
---> 0324df92356d
Step 5/5 : RUN pip install -U pip && pip install -r requirement
---> Running in 439cc1586076
Collecting pip
Downloading https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl (1.4MB)
Installing collected packages: pip
Found existing installation: pip 18.1
Uninstalling pip-18.1:
Successfully uninstalled pip-18.1
Successfully installed pip-19.0.3
Collecting Django==2.1.7 (from -r requirement (line 1))
Downloading https://files.pythonhosted.org/packages/c7/87/fbd666c4f87591ae25b7bb374298e8629816e87193c4099d3608ef11fab9/Django-2.1.7-py3-none-any.whl (7.3MB)
Collecting EasyProcess==0.2.5 (from -r requirement (line 2))
Downloading https://files.pythonhosted.org/packages/45/3a/4eecc0c7995a13a64739bbedc0d3691fc574245b7e79cff81905aa0c2b38/EasyProcess-0.2.5.tar.gz
Collecting PyMySQL==0.9.3 (from -r requirement (line 3))
Downloading https://files.pythonhosted.org/packages/ed/39/15045ae46f2a123019aa968dfcba0396c161c20f855f11dea6796bcaae95/PyMySQL-0.9.3-py2.py3-none-any.whl (47kB)
Collecting pytz==2018.9 (from -r requirement (line 4))
Downloading https://files.pythonhosted.org/packages/61/28/1d3920e4d1d50b19bc5d24398a7cd85cc7b9a75a490570d5a30c57622d34/pytz-2018.9-py2.py3-none-any.whl (510kB)
Collecting selenium==3.141.0 (from -r requirement (line 5))
Downloading https://files.pythonhosted.org/packages/80/d6/4294f0b4bce4de0abf13e17190289f9d0613b0a44e5dd6a7f5ca98459853/selenium-3.141.0-py2.py3-none-any.whl (904kB)
Collecting urllib3==1.24.1 (from -r requirement (line 6))
Downloading https://files.pythonhosted.org/packages/62/00/ee1d7de624db8ba7090d1226aebefab96a2c71cd5cfa7629d6ad3f61b79e/urllib3-1.24.1-py2.py3-none-any.whl (118kB)
Building wheels for collected packages: EasyProcess
Building wheel for EasyProcess (setup.py): started
Building wheel for EasyProcess (setup.py): finished with status 'done'
Stored in directory: /root/.cache/pip/wheels/41/22/19/af15ef6264c58b625a82641ed7483ad05e258fbd8925505227
Successfully built EasyProcess
Installing collected packages: pytz, Django, EasyProcess, PyMySQL, urllib3, selenium
Successfully installed Django-2.1.7 EasyProcess-0.2.5 PyMySQL-0.9.3 pytz-2018.9 selenium-3.141.0 urllib3-1.24.1
Removing intermediate container 439cc1586076
---> d767a8a2d9f2
Successfully built d767a8a2d9f2
Successfully tagged spidermax:test_02

雖然在大小和原來沒有啥區別
docker鏡像瘦身行動
可是在鏡像打包上，步驟上少了不少，這樣在必定程度上就縮短鏡像打包的時間，這一點從剛纔的打包日誌也有所體現，由於test01版本是須要9步，優化1版本是僅須要5步，打包效率提高將近1倍
docker鏡像瘦身行動

優化2

咱們所使用的基礎鏡像是python:3.5.6-slim-stretch，該基礎鏡像致使咱們每次打包都須要在其之上進行操做，這樣也致使咱們的獎項將會變得很是的大，畢竟基礎就已經達到135M之大，雖說咱們不該該重複造輪子，可是這樣的輪子咱們要不起啊
docker鏡像瘦身行動
咱們不妨從新反思一下咱們所使用的鏡像功能，無非就是python的編譯器、pip以及apt功能，至於說另外的django等文件，是咱們經過requirement來安裝的，編譯器自帶的若干依賴咱們沒怎麼用到（這麼描述，不是很嚴謹），那咱們爲何不乾脆本身部署一個python環境，只要有apt，還有什麼事情沒有不能作的？
這裏推薦使用apline這款鏡像，簡直是惡魔！居然只有4M左右
docker鏡像瘦身行動
Alpine 的意思是「高山的」，好比 Alpine plants高山植物，Alpine skiing高山滑雪、the alpine resort阿爾卑斯山勝地。
Alpine Linux 網站首頁註明「Small！Simple！Secure！Alpine Linux is a security-oriented, lightweight Linux distribution based on musl libc and busybox.」歸納瞭如下特色：

  1. 小巧：基於Musl libc和busybox，和busybox同樣小巧，最小的Docker鏡像只有4MB；
  2. 安全：面向安全的輕量發行版；
  3. 簡單：提供APK包管理工具，軟件的搜索、安裝、刪除、升級都很是方便。
  4. 適合容器使用：因爲小巧、功能完備，很是適合做爲容器的基礎鏡像。
    docker鏡像瘦身行動
    test03版本的dockerfile以下 
    FROM alpine:3.7
RUN apk update && apk upgrade &&\
apk add python3 &&\
apk add python3-dev &&\
python3 -m ensurepip &&\
if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi &&\
if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi &&\
mkdir /code &&  mkdir /code/db
ADD . /code/
WORKDIR /code
RUN pip install -U pip && pip install -r requirement

    由於安裝python3的時候默認會是pip3，爲了安裝方便咱們須要將pip3修改成pip，此外還有將python3修改成python，方便咱們對鏡像的啓動，如下是運行的日誌
    docker build -t spidermax:test_03 .
    Sending build context to Docker daemon 290.3kB
    Step 1/5 : FROM alpine:3.7
    ---> 6d1ef012b567
    Step 2/5 : RUN apk update && apk upgrade && apk add python3 && apk add python3-dev && python3 -m ensurepip && if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi && if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi && mkdir /code && mkdir /code/db
    ---> Running in ef033831c1a9
    fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
    fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
    v3.7.3-6-g3eacd5f9a6 [http://dl-cdn.alpinelinux.org/alpine/v3.7/main]
    v3.7.3-4-g7296a289a6 [http://dl-cdn.alpinelinux.org/alpine/v3.7/community]
    OK: 9049 distinct packages available
    OK: 4 MiB in 13 packages
    (1/11) Installing libbz2 (1.0.6-r6)
    (2/11) Installing expat (2.2.5-r0)
    (3/11) Installing libffi (3.2.1-r4)
    (4/11) Installing gdbm (1.13-r1)
    由於安裝python3的時候默認會是pip3，爲了安裝方便咱們須要將pip3修改成pip，此外還有將python3修改成python，方便咱們對鏡像的啓動，如下是運行的日誌

    docker build -t spidermax:test_03 .
    Sending build context to Docker daemon 290.3kB
    Step 1/5 : FROM alpine:3.7
    ---> 6d1ef012b567
    Step 2/5 : RUN apk update && apk upgrade && apk add python3 && apk add python3-dev && python3 -m ensurepip && if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi && if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi && mkdir /code && mkdir /code/db
    ---> Running in ef033831c1a9
    fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
    fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
    v3.7.3-6-g3eacd5f9a6 [http://dl-cdn.alpinelinux.org/alpine/v3.7/main]
    v3.7.3-4-g7296a289a6 http://dl-cdn.alpinelinux.org/alpine/v3.7/community Installing xz-libs (5.2.3-r1)
    (6/11) Installing ncurses-terminfo-base (6.0_p20171125-r1)
    (7/11) Installing ncurses-terminfo (6.0_p20171125-r1)
    (8/11) Installing ncurses-libs (6.0_p20171125-r1)
    (9/11) Installing readline (7.0.003-r0)
    (10/11) Installing sqlite-libs (3.25.3-r0)
    (11/11) Installing python3 (3.6.5-r0)
    Executing busybox-1.27.2-r11.trigger
    OK: 66 MiB in 24 packages
    (1/2) Installing pkgconf (1.3.10-r0)
    (2/2) Installing python3-dev (3.6.5-r0)
    Executing busybox-1.27.2-r11.trigger
    OK: 79 MiB in 26 packages
    Requirement already satisfied: setuptools in /usr/lib/python3.6/site-packages
    Requirement already satisfied: pip in /usr/lib/python3.6/site-packages
    Removing intermediate container ef033831c1a9
    ---> 4250724684eb
    Step 3/5 : ADD . /code/
    ---> 8f1a939f8ac1
    Step 4/5 : WORKDIR /code
    ---> Running in 137e7b42decb
    Removing intermediate container 137e7b42decb
    ---> 29586daada18
    Step 5/5 : RUN pip install -U pip && pip install -r requirement
    ---> Running in 36baec208714
    Collecting pip
    Downloading https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl (1.4MB)
    Installing collected packages: pip
    Found existing installation: pip 9.0.3
    Uninstalling pip-9.0.3:
    Successfully uninstalled pip-9.0.3
    Successfully installed pip-19.0.3
    Collecting Django==2.1.7 (from -r requirement (line 1))
    Downloading https://files.pythonhosted.org/packages/c7/87/fbd666c4f87591ae25b7bb374298e8629816e87193c4099d3608ef11fab9/Django-2.1.7-py3-none-any.whl (7.3MB)
    Collecting EasyProcess==0.2.5 (from -r requirement (line 2))
    Downloading https://files.pythonhosted.org/packages/45/3a/4eecc0c7995a13a64739bbedc0d3691fc574245b7e79cff81905aa0c2b38/EasyProcess-0.2.5.tar.gz
    Collecting PyMySQL==0.9.3 (from -r requirement (line 3))
    Downloading https://files.pythonhosted.org/packages/ed/39/15045ae46f2a123019aa968dfcba0396c161c20f855f11dea6796bcaae95/PyMySQL-0.9.3-py2.py3-none-any.whl (47kB)
    Collecting pytz==2018.9 (from -r requirement (line 4))
    Downloading https://files.pythonhosted.org/packages/61/28/1d3920e4d1d50b19bc5d24398a7cd85cc7b9a75a490570d5a30c57622d34/pytz-2018.9-py2.py3-none-any.whl (510kB)
    Collecting selenium==3.141.0 (from -r requirement (line 5))
    Downloading https://files.pythonhosted.org/packages/80/d6/4294f0b4bce4de0abf13e17190289f9d0613b0a44e5dd6a7f5ca98459853/selenium-3.141.0-py2.py3-none-any.whl (904kB)
    Collecting urllib3==1.24.1 (from -r requirement (line 6))
    Downloading https://files.pythonhosted.org/packages/62/00/ee1d7de624db8ba7090d1226aebefab96a2c71cd5cfa7629d6ad3f61b79e/urllib3-1.24.1-py2.py3-none-any.whl (118kB)
    Installing collected packages: pytz, Django, EasyProcess, PyMySQL, urllib3, selenium
    Running setup.py install for EasyProcess: started
    Running setup.py install for EasyProcess: finished with status 'done'
    Successfully installed Django-2.1.7 EasyProcess-0.2.5 PyMySQL-0.9.3 pytz-2018.9 selenium-3.141.0 urllib3-1.24.1
    Removing intermediate container 36baec208714
    ---> e59b7105697a
    Successfully built e59b7105697a
    Successfully tagged spidermax:test_03

檢查鏡像大小，會發現這個鏡像和原來相比咱們將其縮小了近一倍

docker鏡像瘦身行動
那這樣已經達到目的了嗎？不還不夠！做爲工程師，優化永不止步！

優化3

每一次的鏡像打包，docker都會去雲端請求，下載相關的軟件，並安裝，那安裝以後的安裝包會怎麼處理呢？——還算存留在鏡像中，也就是所謂的緩存，這些是相對應用層來講的，他們只會佔用咱們存儲空間，並無過多的用處，所以須要的就是將這個緩存的內容刪除，實現起來也很簡單的帶上--no-cache便可，如圖見apk操做詳情
docker鏡像瘦身行動
修改以後的腳本爲

FROM alpine:3.7
RUN apk update --no-cache && apk upgrade --update-cache --available &&\
    apk add --no-cache python3 &&\
    apk add --no-cache python3-dev &&\
    python3 -m ensurepip &&\
    if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi &&\
    if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi &&\
    rm -rf /var/lib/apk/* &&\
    mkdir /code &&  mkdir /code/db
ADD . /code/
WORKDIR /code
RUN pip install -U pip && pip install -r requirement

這樣的話，會致使一個問題，就是每次打包都須要一次又一次的從新下載資源，這個其實也是一個效率上的矛盾，一個互相博弈的過程，鏡像大小變化
docker鏡像瘦身行動
固然了，咱們可刪除apk的緩存固然能夠刪除pip的緩存啦，咱們能夠經過直接刪除pip的安裝包的形式來減少文件的大小，代碼以下：

FROM alpine:3.7
RUN apk update && apk upgrade --update-cache --available &&\
    apk add python3 &&\
    apk add python3-dev &&\
    python3 -m ensurepip &&\
    rm -r /usr/lib/python*/ensurepip &&\
    if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi &&\
    if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi &&\
    rm -rf /var/lib/apk/* &&\
    mkdir /code && mkdir /code/db
ADD . /code/
WORKDIR /code
RUN pip install -U pip && pip install -r requirement && rm -rf ~/.cache/pip

鏡像的變化以下：
docker鏡像瘦身行動
經過咱們的一次次優化以後，咱們將一個高達203M的鏡像進行了優化，縮小了將近一倍，在這一次次的編譯過程當中，也體會到了打包速度一次比一次的提升，這樣纔是優化思想的應用，一次又一次的超越本身

修改以後

最後給這個dockerfile標記維護者的信息，表示說這個鏡像是我提供的，若是有問題了須要幫忙解決能夠聯繫我，也表示我對這個鏡像擁有著做權，雖然我已經將這個鏡像開源了

FROM alpine:3.7
MAINTAINER yerikyu "yerik_shu@139.com"
RUN apk update && apk upgrade --update-cache --available &&\
    apk add python3 &&\
    apk add python3-dev &&\
    python3 -m ensurepip &&\
    rm -r /usr/lib/python*/ensurepip &&\
    if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi &&\
    if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi &&\
    rm -rf /var/lib/apk/* &&\
    mkdir /code && mkdir /code/db
ADD . /code/
WORKDIR /code
RUN pip install -U pip && pip install -r requirement && rm -rf ~/.cache/pip

打包結果以下：
docker鏡像瘦身行動

總結

  • 編寫.dockerignore文件（這個用來忽略某些不須要的緩存文件相似gitignore)
  • 容器只運行單個應用(微服務的一個體現）
  • 將多個RUN指令合併爲一個
  • 基礎鏡像的標籤不要用latest
  • 每一個RUN指令後刪除多餘文件
  • 選擇合適的基礎鏡像(alpine版本最好)
  • 設置WORKDIR和CMD
  • 使用ENTRYPOINT (可選)
  • 在entrypoint腳本中使用exec（本次實驗未體現）
  • COPY與ADD優先使用前者
  • 合理調整COPY與RUN的順序
  • 設置默認的環境變量，映射端口和數據卷（這個我是在docker-compose進行設置的，後面有機會再討論）

    參考資料

    docker鏡像層：http://blog.daocloud.io/principle-of-docker-image/
    alpine官方資料：https://alpinelinux.org/

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