The hidepid mount option is applicable to /proc and is used to
control who can access the information in /proc/[pid] directories.
The option can have one of the following values:
0: Everybody may access all /proc/[pid] directories.
1: Users may not access files and subdirectories inside any /proc/[pid] directories
but their own. The /proc/[pid] directories themselves remain visible.
2: Same as for mode 1, but in addition the /proc/[pid] directories belonging to other
users become invisible.
For example, if you choose the value 2:
Add the hidepid=2 option to the fourth column of
/etc/fstab for the line which controls mounting of
/proc.