Bug 216584

Summary: Undocumented mount option subset=pid for proc
Product: Documentation Reporter: Philipp Wendler (linux)
Component: man-pagesAssignee: documentation_man-pages (documentation_man-pages)
Status: NEW ---    
Severity: normal    
Priority: P1    
Hardware: All   
OS: Linux   
Kernel Version: Subsystem:
Regression: No Bisected commit-id:

Description Philipp Wendler 2022-10-14 05:55:07 UTC 
Since Linux 5.8, proc can be mounted with options subset=pids to hide all non-task-related information. This is missing from proc(5).

Original patch:
https://lore.kernel.org/all/20200423200316.164518-6-gladkov.alexey@gmail.com/

The kernel documentation shows the option:
https://www.kernel.org/doc/html/latest/filesystems/proc.html#mount-options

This option is useful when mounting proc for a container nested for example in a Docker container that hides certain parts of /proc, otherwise one is not allowed to mount /proc (https://lkml.kernel.org/lkml/cover.1597931457.git.gladkov.alexey@gmail.com/). It might be useful to add a note about this as well.
Comment 1 Philipp Wendler 2022-10-14 06:15:12 UTC 
Actually, skip my last paragraph, it seems this patch did not get merged yet. Last iteration I found is at https://lore.kernel.org/all/cover.1626432185.git.legion@kernel.org/. But the mount option does exist.