Set immutable file attribute

Prevent any user (incl. root) from modifying the file

chattr +i /etc/resolv.conf && lsattr /etc/resolv.conf

More linux commands

Show extended file attributes

lsattr -R /etc/ 2>/dev/null | grep -v '^\-\-\-\-'

List non-default extended attrs in /etc/
ACL: show permissions

getfacl /srv/shared

Show POSIX ACL entries including owner, group, and extra users
ACL: grant user access

setfacl -m u:alice:rwx /srv/shared

Grant alice full access without changing group ownership
Find SUID/SGID binaries

find / -perm /6000 -type f -ls 2>/dev/null

Locate setuid/setgid executables (security audit)
Find process by name

pgrep -la nginx

List PIDs and full command lines matching a name