是什么导致码头工人卷被填充? [英] what causes a docker volume to be populated?

问题描述

我正在运行以下命令:

docker run --name wiki --link wiki-mdb:mysql -p 9081:80 -v/var/data/wikimedia/apache2:/etc/apache2 -v/var/data/wikimedia/wiki:/var/www/html -d synctree/mediawiki

容器死了，因为apache2在/etc/apach2中找不到其配置文件...

and the container dies because apache2 cant find its config file in /etc/apach2 ...

好的，所以我再次运行命令，而没有使用apache2卷:

ok, so I run the command again without the apache2 volume as:

docker run --name wiki --link wiki-mdb:mysql -p 9081:80 -v/var/data/wikimedia/wiki:/var/www/html -d synctree/mediawiki

不仅有效，而且/var/data/wikimedia/wiki以空开始，并填充了所需的所有php文件.

and not only does it work ... but /var/data/wikimedia/wiki which started out as empty is populated with all the php files needed.

那有什么区别?为什么某些卷中填充了容器中的内容，而另一些卷则更喜欢将空白文件夹安装在容器内部配置之上?

so what is the difference? Why are some volumes populated with content from container while other volumes will prefer to mount the blank folder over top of a containers internal configuration?

我最终通过运行 sudo docker cp 9f9ba217a2ec:/etc/apache2 ./来生成默认的apache2文件夹来解决我的问题...但是似乎应该有押韵或理由为什么在卷中生成内容?

I ended up solving my issue by running sudo docker cp 9f9ba217a2ec:/etc/apache2 ./ to generate a default apache2 folder ... however it seems like there should be some rhyme or reason to why content is generated in the volume or not.

我认为这可能与 Dockerfile 有关，但没有任何一条路径的具体引用.

I thought it might have something to do with the Dockerfile, but it does not have any specific reference to either path.

推荐答案

从 -v/var/data/wikimedia/apache2:/etc/apache2 开始，链接您的本地/var/容器中包含/etc/apache2 的data/wikimedia/apache2 .这将掩盖在生成时创建的容器文件夹.因为/etc/apache2 是apache寻找配置的地方，所以将没有配置的/var/data/wikimedia/apache2 链接到/etc/apache2 导致服务器找不到配置并且无法启动.

Starting with -v /var/data/wikimedia/apache2:/etc/apache2 links your local /var/data/wikimedia/apache2 with /etc/apache2 within the container. This masks the container folder created at the build time. Because /etc/apache2 is where apache is looking for its configuration, linking /var/data/wikimedia/apache2 without configuration into /etc/apache2 results in server finding no configuration and failing to start.

将此卷保留为不会掩盖在构建时创建的容器中已经存在的/etc/apache2 文件夹，从而将配置文件保留在此处<在构建时完整执行code> Dockerfile 脚本.服务器找到合适的配置并按预期启动.

Leaving this volume out does not mask the already present /etc/apache2 folder within the container created at the build time, thus keeping configuration files placed by there the Dockerfile script at the build time intact. The server finds a suitable configuration and starts as expected.

我不是php方面的专家，尤其是在什么时候生成的文件，但是我怀疑在服务器正常启动时，php文件已被填充到/var/www/html (显然)在容器中.因为后者只是到本地/var/data/wikimedia/wiki 的链接，所以您还可以在主机系统上看到这些文件.

I am not a pro in php and in particular at which point which files are generated if at all, but I suspect that as the server starts normally php files are being populated into /var/www/html in the container (apparently). Because the latter is just a link to your local /var/data/wikimedia/wiki you can also see those files on your host system.

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