[bug] In docker , already be root , but cannot execute!

[djerryz]

# docker exec -it ubuntu23 /bin/bash

# whoami
> root

#  ls -alh /usr/bin/arp-scan
> -rwxr-xr-x 1 root root 4.6M Feb 26 14:55 /usr/bin/arp-scan

# arp-scan
>   Should run this binary as root or use --help for options

# su - root -c "arpscan"
> Selected interface ens33 with IP 192.168.1.19/24 (everything is fine)