後來又查了一下。
https://bbs.archlinux.org/viewtopic.php?id=147964

Static units are those which cannot be enabled/disabled, but it doesn't mean they are always executed. They will only if another unit depends on them, or if they are manually started.

Actually, static units are simply those without an [Install] section. As enabling units means just creating a symlink to wherever [Install] mandates, those units without [Install] section cannot be enabled, as systemctl doesn't know where to place the symlink.

Of course, you can still manually create a symlink from a static unit to (for instance) /etc/systemd/system/multi-user.target.wants/, and it will be executed as any other enabled unit. But I suppose static units are not intended to be enabled in that way, and most probably you shouldn't need to do it

http://linux.vbird.org/linux_basic/0560daemons.php
看起來應該可以自己修改。讓他可以enable。

在底下加了這行
[Install]
WantedBy=multi-user.target

enable 是可以了
但一樣沒執行

放錯地方了, 不能放在rc.local. 要放在rc.local.bak 就會動了. 不然就是自己寫個service 也可以