docker run，docker exec和日志 [英] docker run, docker exec and logs

问题描述

如果我这样做:

docker run --name nginx -d nginx:alpine /bin/sh -c 'echo "Hello stdout" > /dev/stdout'

当我这样做时，我可以看到"Hello stdout":

I can see "Hello stdout" when I do :

docker logs nginx

但是当容器运行时(docker run --name nginx -d nginx:alpine)，我这样做了:

But when the container is running (docker run --name nginx -d nginx:alpine) and I do :

docker exec nginx /bin/sh -c 'echo "Hello stdout" > /dev/stdout'

或当我将容器附加到:

docker exec -it nginx /bin/sh

然后:

echo "Hello stdout" > /dev/stdout

我在Docker日志中什么都看不到.而且由于我的Nginx访问日志已重定向到/dev/stdout，所以我也看不到它们.

I can't see anything in docker logs. And since my Nginx access logs are redirected to /dev/stdout, I can't see them as well.

此标准输出在这里发生了什么?

What is happening here with this stdout ?

推荐答案

当您 docker exec 时，您会看到有多个进程

When you docker exec you can see you have several process

/ # ps -ef
PID   USER     TIME   COMMAND
    1 root       0:00 nginx: master process nginx -g daemon off;
    6 nginx      0:00 nginx: worker process
    7 root       0:00 /bin/sh
   17 root       0:00 ps -ef
/ # 

在Linux中，每个进程在/proc/pid/fd中都有自己的stdin，stdout，stderr(和其他文件描述符)

and in Linux, each process has its own stdin, stdout, stderr (and other file descriptors), in /proc/pid/fd

，因此，使用您的 docker exec (pid 7)，您将在其中显示某些内容

and so, with your docker exec (pid 7) you display something in

/proc/7/fd/1

/proc/7/fd/1

如果执行 ls -ltr/proc/7/fd/1 ，则会显示类似/proc/4608/fd/1->/dev/pts/2 表示输出正在发送到终端

If you do ls -ltr /proc/7/fd/1, it displays something like /proc/4608/fd/1 -> /dev/pts/2 which means output is being sent to terminal

您的nginx进程(pid 1)在其中显示其输出

while your nginx process (pid 1) displays his output in

/proc/1/fd/1

/proc/1/fd/1

如果执行 ls -ltr/proc/1/fd/1 ，则显示类似/proc/1/fd/1->的内容.管道:[184442508] ，这意味着输出正在发送到Docker日志记录驱动程序

If you do ls -ltr /proc/1/fd/1, it displays something like /proc/1/fd/1 -> pipe:[184442508] which means output is being sent to docker logging driver

这篇关于docker run，docker exec和日志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！