Every step in a Dockerfile generates a new intermediate image, or "layer", consisting of anything that changed on the filesystem from the previous layer. A docker image consists of a collection of layers that are applied one on top of another to create the final filesystem.
Dockerfile中的每一步都会生成一个新的中间图像或“图层”,由前一层文件系统上发生的任何变化组成。 docker镜像由一组图层组成,这些图层一个在另一个上面应用,以创建最终的文件系统。
If you have:
如果你有:
RUN adduser example -D -h /example -s /bin/sh
Then you are probably changing nothing other than a few files in /etc (/etc/passwd, /etc/group, and their shadow equivalents).
那你除了/ etc(/ etc / passwd,/ etc / group和它们的阴影等价物)中的一些文件之外什么都没有改变。
If you have:
如果你有:
RUN adduser example -D -h /example -s /bin/sh && \
chown -R example.example /lib
Then the list of things that have changed includes, recursively, everything in /lib, which is potentially larger. In fact, in my alpine:edge container, it looks like the contents of /lib is 3.4MB:
然后,已经更改的事物列表递归地包括/ lib中的所有内容,这可能更大。事实上,在我的alpine:edge容器中,/ lib的内容看起来像是3.4MB:
/ # du -sh /lib
3.4M /lib
Which exactly accounts for the change in image size in your example.
这恰恰说明了示例中图像大小的变化。
UPDATE
Using your actual Dockerfile, with the npm install ... line commented out, I don't see any difference in the final image size whether or not the adduser and chown commands are run. Given:
使用实际的Dockerfile,npm install ...行注释掉,无论是否运行adduser和chown命令,我都看不出最终图像大小有任何差异。鉴于:
RUN echo "http://nl.alpinelinux.org/alpine/edge/main" > /etc/apk/repositories && \
echo "http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories && \
apk add -U wget iojs && \
apk upgrade && \
wget -q --no-check-certificate https://ghost.org/zip/ghost-0.6.0.zip -O /tmp/ghost.zip && \
unzip -q /tmp/ghost.zip -d /ghost && \
cd /ghost && \
# npm install --production && \
sed 's/127.0.0.1/0.0.0.0/' /ghost/config.example.js > /ghost/config.js && \
sed -i 's/"iojs": "~1.2.0"/"iojs": "~1.6.4"/' package.json && \
# adduser ghost -D -h /ghost -s /bin/sh && \
# chown -R ghost.ghost * && \
npm cache clean && \
rm -rf /var/cache/apk/* /tmp/*
I get:
$ docker build -t sotest .
[...]
Successfully built 058d9f41988a
$ docker inspect -f '{{.VirtualSize}}' 058d9f41988a
31783340
Whereas given:
RUN echo "http://nl.alpinelinux.org/alpine/edge/main" > /etc/apk/repositories && \
echo "http://nl.alpinelinux.org/alpine/edge/testing" >> /etc/apk/repositories && \
apk add -U wget iojs && \
apk upgrade && \
wget -q --no-check-certificate https://ghost.org/zip/ghost-0.6.0.zip -O /tmp/ghost.zip && \
unzip -q /tmp/ghost.zip -d /ghost && \
cd /ghost && \
# npm install --production && \
sed 's/127.0.0.1/0.0.0.0/' /ghost/config.example.js > /ghost/config.js && \
sed -i 's/"iojs": "~1.2.0"/"iojs": "~1.6.4"/' package.json && \
adduser ghost -D -h /ghost -s /bin/sh && \
chown -R ghost.ghost * && \
npm cache clean && \
rm -rf /var/cache/apk/* /tmp/*
I get:
$ docker build -t sotest .
[...]
Successfully built 696b481c5790
$ docker inspect -f '{{.VirtualSize}}' 696b481c5790
31789262
That is, the two images are approximately the same size (the difference is around 5 Kb).
也就是说,两个图像的大小大致相同(差异大约为5 Kb)。
I would of course expect the resulting image to be larger if the npm install command could run successfully (because that would install additional files).
如果npm install命令可以成功运行(因为那会安装其他文件),我当然希望得到的图像更大。
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