If su/sudo cannot work, especially in termux, please try remounting the filesystem without suid:
mount -o remount,nosuid /datacat /etc/resolv.confIf there is no valid nameserver, please add one, for example:
rm -f /etc/resolv.conf
echo "nameserver 1.1.1.1" >> /etc/resolv.confTry running fixup.sh in container. Or see #13
Rurima does not provide network isolation support, a possible implementation is at net_wrapper.sh