Proc file link to a pipe

Kernels & Hardware, configuring network, installing services

Proc file link to a pipe

Postby DucLetoAtreides » 2020-05-06 07:39

Hello

I'm investigating an Apache server running in a docker container.

Logs are written to /proc/self/fd/1

and when I ask detail about this file i have :
docker exec cloudweb_apache-qwfpgja_1 ls -l /proc/self/fd/1
l-wx------ 1 root root 64 May 6 10:21 /proc/self/fd/1 -> pipe:[99209576]


How is it called and how does-it work ?

Thanks for your help
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Re: Proc file link to a pipe

Postby pylkko » 2020-05-06 10:53

it's an open pipe of a process. the directory /proc is special, it is not on a disk or storage medium, it is a "virtual" thing.

https://www.geeksforgeeks.org/proc-file-system-linux/ wrote:proc file system in Linux
Proc file system (procfs) is virtual file system created on fly when system boots and is dissolved at time of system shut down.
It contains the useful information about the processes that are currently running, it is regarded as control and information centre for kernel.
The proc file system also provides communication medium between kernel space and user space.


There are these virual files that if you for example wrrite to them, it's like pushing a button that tells the kernel to do something. Or alternatively the kernel can write information that other programs need there. For example, there could be a file that contains the current temperature of a processor, so when a user space progam wants to know it, it only needs to read the virtual file.

a pipe is a way a program can reflow information to another. as root you can try
Code: Select all
 lsof | grep 99209576
to get information about the pipe and the users
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