ACL: grant user access

Grant alice full access without changing group ownership

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

More linux commands

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
Kill process tree

kill -TERM -$(pgrep -f 'my-app')

Send SIGTERM to the entire process group
Change process priority

renice -n 10 -p <pid>

Lower priority (nice +10) of a running process
Limit process resources (cgroup)

systemd-run --scope -p MemoryMax=512M -p CPUQuota=50% -- ./heavy.sh

Run a command in a transient systemd scope with resource limits