I’ve got a long running, daemonized Python process that uses subprocess to spawn new child processes when certain events occur. The long running process is started by a user with super user privileges. I need the child processes it spawns to run as a different user (e.g., “nobody”) while retaining the super user privileges for the parent process.
When you fork a process, the child inherits its parent’s file descriptors. I understand that when this happens, the child receives a copy of the parent’s file descriptor table with the pointers in each pointing to the same open file description. Is this the same thing as a file table, as in http://en.wikipedia.org/wiki/File_descriptor, or something else?
In Unix whenever we want to create a new process, we fork the current process, creating a new child process which is exactly the same as the parent process; then we do an exec system call to replace all the data from the parent process with that for the new process.
I have been studying the Linux kernel behaviour for quite some time now, and it’s always been clear to me that:
In Program 1 Hello world gets printed just once, but when I remove n and run it (Program 2), the output gets printed 8 times. Can someone please explain me the significance of n here and how it affects the fork()?
I’m currently developping a systemd daemon. The problem I’m facing is that the daemon is killed 1m30s after beeing launched because the forking is not detected.
I am running a docker server on Arch Linux (kernel 4.3.3-2) with several containers. Since my last reboot, both the docker server and random programs within the containers crash with a message about not being able to create a thread, or (less often) to fork. The specific error message is different depending on the program, but most of them seem to mention the specific error Resource temporarily unavailable. See at the end of this post for some example error messages.
First this question is related but definitely not the same as this very nice question:
I’ve a very specific question about fork system call. I’ve this piece of code:
When running the fork call to create a new process, if it succeed it returns either 0 (the child) or the parent.