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Full Discussion: Process existence or/and permission
Top Forums Shell Programming and Scripting Process existence or/and permission Post 302999920 by chebarbudo on Friday 30th of June 2017 04:28:23 AM
Old 06-30-2017
When I don't know how to undo something, I often search how to DO it. It worked today with linux hide processes from other users - Recherche Google.
So if hidepid allows you to hide processes, it should do the opposite if deactivated.
Apparently hidepid is not in use though and I can only see 4 processes wether I use ls /proc or ps:
Code:
santiago@alphard:~$ sudo mount | grep proc
proc on /proc type proc (rw,relatime)
santiago@alphard:~$ ls -ld /proc/{0..9}* 2> /dev/null | wc -l
4
santiago@alphard:~$ ps x -o pid= | wc -l
4

But I'm still going to try to tweak hidepid and indeed I can see more processes with ls /proc but not with ps:
Code:
santiago@alphard:~$ sudo mount -o remount,hidepid=1 /proc
santiago@alphard:~$ sudo mount | grep proc
proc on /proc type proc (rw,relatime,hidepid=1)
santiago@alphard:~$ ls -ld /proc/{0..9}* 2> /dev/null | wc -l
202
santiago@alphard:~$ ps x -o pid= | wc -l
4

Surprisingly, hidepid level 1 gives me more permission but levels 0 and 2 are exactly the same:
Code:
santiago@alphard:~$ (echo -e "mount opt\tls /proc\tps" | sed 'p;s/[^\t]/-/g'; for h in 0 1 2; do echo -e "hidepid=$h\t$(sudo mount -o remount,hidepid=$h /proc; ls -ld /proc/{0..9}* 2> /dev/null | wc -l)\t$(ps x -o pid= | wc -l)"; done) | column -tns$'\t'
mount opt  ls /proc  ps
---------  --------  --
hidepid=0  7         7
hidepid=1  201       7
hidepid=2  7         7

I'm still investigating but level 0 should give me all permissions like in old behavior.
 

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LEARN ABOUT FREEBSD

linprocfs

LINPROCFS(5)						      BSD File Formats Manual						      LINPROCFS(5)

NAME

     linprocfs -- Linux process file system

SYNOPSIS

     linproc	     /compat/linux/proc      linprocfs	     rw 0 0

DESCRIPTION

     The Linux process file system, or linprocfs, emulates a subset of Linux' process file system and is required for the complete operation of
     some Linux binaries.

     The linprocfs provides a two-level view of process space.	At the highest level, processes themselves are named, according to their process
     ids in decimal, with no leading zeros.  There is also a special node called self which always refers to the process making the lookup
     request.

     Each node is a directory containing several files:

     exe     A reference to the vnode from which the process text was read.  This can be used to gain access to the process' symbol table, or to
	     start another copy of the process.

     mem     The complete virtual memory image of the process.	Only those addresses which exist in the process can be accessed.  Reads and writes
	     to this file modify the process.  Writes to the text segment remain private to the process.

     Each node is owned by the process's user, and belongs to that user's primary group, except for the mem node, which belongs to the kmem group.

FILES

     /compat/linux/proc 	      The normal mount point for the linprocfs.
     /compat/linux/proc/cpuinfo       CPU vendor and model information in human-readable form.
     /compat/linux/proc/meminfo       System memory information in human-readable form.
     /compat/linux/proc/pid	      A directory containing process information for process pid.
     /compat/linux/proc/self	      A directory containing process information for the current process.
     /compat/linux/proc/self/exe      The executable image for the current process.
     /compat/linux/proc/self/mem      The complete virtual address space of the current process.

EXAMPLES

     To mount a linprocfs file system on /compat/linux/proc:

	   mount -t linprocfs linproc /compat/linux/proc

SEE ALSO

     mount(2), unmount(2), procfs(5), pseudofs(9)

HISTORY

     The linprocfs first appeared in FreeBSD 4.0.

AUTHORS

     The linprocfs was derived from procfs by Pierre Beyssac.  This manual page was written by Dag-Erling Smorgrav, based on the procfs(5) manual
     page by Garrett Wollman.

BSD
								  August 10, 1994							       BSD
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