Arch下直接：

$ sudo pacmna -S shairport-sync
$ sudo systemctl enable shairport-sync

如果直接启动，会发现没有声音。因为默认的配置文件里，有这样一行：

alsa =
{
	output_device = "default"; // the name of the alsa output device. Use "alsamixer" or "aplay" to find out the names of devices, mixers, etc.
	mixer_control_name = "default"; // the name of the mixer to use to adjust output volume. If not specified, volume in adjusted in software.
	mixer_device = "default"; // the mixer_device default is whatever the output_device is. Normally you wouldn't have to use this.
    ...
}

修改成 hw:0。具体是什么要用 aplay -l 查看，不过一般都是这个值。

alsa =
{
	output_device = "hw:0"; // the name of the alsa output device. Use "alsamixer" or "aplay" to find out the names of devices, mixers, etc.
	mixer_control_name = "PCM"; // the name of the mixer to use to adjust output volume. If not specified, volume in adjusted in software.
	mixer_device = "hw:0"; // the mixer_device default is whatever the output_device is. Normally you wouldn't have to use this.

然后启动服务，打开iOS设备，就可以在手机上点歌，笔记本上放歌了 :)

不过我重启之后，使用 hw:0 又不行了，改回 default 又可以了，奇怪。