在docker中重定向命令输出 [英] Redirecting command output in docker
问题描述
我想为我的服务器做一些简单的日志记录,这是一个在Docker容器中运行的小型Flask应用程序。
这里是Dockerfile
#Dockerfile
从dreen / flask
MAINTAINER dreen
WORKDIR / srv
#获取源
运行mkdir -p / srv
COPY perfektimprezy.tar.gz /srv/perfektimprezy.tar.gz
运行tar x -f perfektimprezy.tar.gz
RUN rm perfektimprezy.tar.gz
#运行服务器
EXPOSE 80
CMD [python,index.py,1> server.log,2>服务器.log]
如最后一行所示,我将stderr和stdout重定向到一个文件。现在我运行这个容器和shell进入它
docker run -d -p 80:80 perfektimprezy
docker exec - 它...容器的id ...bash
并观察以下事项: p>
服务器正在运行,网站正常运行
没有 / srv / server。日志
ps aux | grep python
产生:
根1 1.6 3.2 54172 16240? Ss 13:43 0:00 python index.py 1> server.log 2> server.log
root 12 1.9 3.3 130388 16740? Sl 13:43 0:00 / usr / bin / python index.py 1> server.log 2> server.log
root 32 0.0 0.0 8860 388? R + 13:43 0:00 grep --color = auto python
但是没有日志..但是,如果我将 docker附加
到容器中,我可以在控制台中看到生成输出的应用程序。
当使用Docker时,是否正确将stdout / err重定向到文件?
当您将JSON列表指定为 CMD
在 Dockerfile
中,它不会在shell中执行,所以通常的shell函数,如stdout和stderr重定向,
从文档 :
exec表单被解析为JSON数组,这意味着您必须使用双引号(
)围绕单词不单引号(
'
)。
与外壳形式不同,exec表单不调用命令shell,这意味着正常的shell处理不会发生充足的
CMD [echo,$ HOME]
不会在$ HOME
上执行变量替换。如果你需要shell处理,那么可以使用shell窗体或直接执行shell,例如:CMD [sh,-c,echo,$ HOME]
您的命令实际上是执行 index.py
脚本并传递字符串1> server.log
和2> server.log
作为这个python脚本的命令行参数。
使用以下代码之一(两者都应该工作):
-
CMDpython index.py> server.log 2>& 1
-
CMD [/ bin / sh,-c,python index.py> server.log 2& 1]
li>
I want to do some simple logging for my server which is a small Flask app running in a Docker container.
Here is the Dockerfile
# Dockerfile
FROM dreen/flask
MAINTAINER dreen
WORKDIR /srv
# Get source
RUN mkdir -p /srv
COPY perfektimprezy.tar.gz /srv/perfektimprezy.tar.gz
RUN tar x -f perfektimprezy.tar.gz
RUN rm perfektimprezy.tar.gz
# Run server
EXPOSE 80
CMD ["python", "index.py", "1>server.log", "2>server.log"]
As you can see on the last line I redirect stderr and stdout to a file. Now I run this container and shell into it
docker run -d -p 80:80 perfektimprezy
docker exec -it "... id of container ..." bash
And observe the following things:
The server is running and the website working
There is no /srv/server.log
ps aux | grep python
yields:
root 1 1.6 3.2 54172 16240 ? Ss 13:43 0:00 python index.py 1>server.log 2>server.log
root 12 1.9 3.3 130388 16740 ? Sl 13:43 0:00 /usr/bin/python index.py 1>server.log 2>server.log
root 32 0.0 0.0 8860 388 ? R+ 13:43 0:00 grep --color=auto python
But there are no logs... HOWEVER, if I docker attach
to the container I can see the app generating output in the console.
How do I properly redirect stdout/err to a file when using Docker?
When you specify a JSON list as CMD
in a Dockerfile
, it will not be executed in a shell, so the usual shell functions, like stdout and stderr redirection, won't work.
From the documentation:
The exec form is parsed as a JSON array, which means that you must use double-quotes (
"
) around words not single-quotes ('
).Unlike the shell form, the exec form does not invoke a command shell. This means that normal shell processing does not happen. For example,
CMD [ "echo", "$HOME" ]
will not do variable substitution on$HOME
. If you want shell processing then either use the shell form or execute a shell directly, for example:CMD [ "sh", "-c", "echo", "$HOME" ]
.
What your command actually does is executing your index.py
script and passing the strings "1>server.log"
and "2>server.log"
as command-line arguments into that python script.
Use one of the following instead (both should work):
CMD "python index.py > server.log 2>&1"
CMD ["/bin/sh", "-c", "python index.py > server.log 2>&1"]
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