为什么chown会增加docker映像的大小？ [英] Why does chown increase size of docker image?
问题描述
我不明白为什么'chown'命令应该增加我的docker镜像的大小？
以下Dockerfile创建了一个大小5.3MB的图片：
FROM alpine：edge
RUN adduser example -D -h / example -s / bin / sh
此示例创建的图像大小为8.7MB：
FROM alpine：edge
RUN adduser示例-D -h / example -s / bin / sh& cho
chown -R example.example / lib
为什么？
注意：我实际的dockerfile当然比该示例更长，因此图像大小的增加也很大。这就是我什至关心的原因。
Dockerfile中的每个步骤都会生成一个新的中间映像或层，由与上一层相比，文件系统上发生的任何更改。 docker映像由一组图层组成，这些图层相互叠加以创建最终的文件系统。
如果您有：
RUN adduser示例-D -h / example -s / bin / sh
然后，您可能只更改了 / etc （ / etc / passwd ， / etc / group 及其影子等效项）。
如果您有：
RUN adduser example -D -h / example -s / bin / sh&& cho
chown -R example.example / lib
然后列出具有以下内容的事物递归更改包括 / lib 中的所有内容，这可能更大。实际上，在我的 alpine：edge 容器中， / lib 的内容看起来是3.4MB：
/＃du -sh / lib
3.4M / lib
在您的示例中确切说明了图像大小的变化。
更新
使用实际的Dockerfile，并在 npm install ... 行中注释掉，我没有无论是否运行 adduser 和 chown 命令，都可以看到最终图像大小的任何差异。给出：
RUN echo http://nl.alpinelinux.org/alpine/edge/main> / etc / apk / repositories&& \
echo http://nl.alpinelinux.org/alpine/edge/testing>> / etc / apk / repositories&& b
apk添加-U wget iojs&& b
apk升级&& \
wget -q --no-check-certificate https://ghost.org/zip/ghost-0.6.0.zip -O /tmp/ghost.zip&& \
解压缩-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缓存清理&& \
rm -rf / var / cache / apk / * / tmp / *
我得到：
$ docker build -t sotest。
[...]
成功构建058d9f41988a
$ docker inspect -f'{{.VirtualSize}}'058d9f41988a
31783340
给出的地方：
RUN echo http： //nl.alpinelinux.org/alpine/edge/main> / etc / apk / repositories&& \
echo http://nl.alpinelinux.org/alpine/edge/testing>> / etc / apk / repositories&& b
apk添加-U wget iojs&& b
apk升级&& \
wget -q --no-check-certificate https://ghost.org/zip/ghost-0.6.0.zip -O /tmp/ghost.zip&& \
解压缩-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&& cho
chown -R ghost.ghost *&& \
npm缓存清理&& \
rm -rf / var / cache / apk / * / tmp / *
我得到：
$ docker build -t sotest。
[...]
成功构建了696b481c5790
$ docker inspect -f'{{.VirtualSize}}'696b481c5790
31789262
也就是说，两个图像的大小大致相同（
的差约为5 Kb）。
如果 npm install 命令可以成功运行（因为这会安装其他文件），我当然希望生成的图像更大。 p>
I can't understand why the 'chown' command should increase the size of my docker image?
The following Dockerfile creates an image of size 5.3MB:
FROM alpine:edge
RUN adduser example -D -h /example -s /bin/sh
This example however creates an image of size 8.7MB:
FROM alpine:edge
RUN adduser example -D -h /example -s /bin/sh && \
chown -R example.example /lib
Why?
Note: My actual dockerfile is of course much longer than this example and therefore the increase in image size is also quite larger. That's why I even care..
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.
If you have:
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).
If you have:
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:
/ # du -sh /lib
3.4M /lib
Which exactly accounts for the change in image size in your example.
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:
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).
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).
这篇关于为什么chown会增加docker映像的大小？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
