What is the purpose of this configuration and where will it be used?
root@d33cdc59f198:/home/openwrt# grep "CONFIG_TARGET_INIT_CMD" .config
--- Init configuration options
(/usr/sbin:/usr/bin:/sbin:/bin) PATH for regular boot
() Environment variables to set when starting init (start with none)
(/sbin/init) Init command ------->>>>>>>
[*] Suppress stderr messages of init
What is the difference between configured and unconfigured? I'm using initramfs, when I configure it to /init, it fails to boot. When it is necessary to customize the configuration of this option？
it's a binary, or a script, not a dir.
as it says in the link, it kicks off all the other daemons and processes, if you remove it, nothing will work
you shouldn't customize it, unless you have a fitting replacement in place.