On Alpine linuxLinux, adduser -S will create a system user whose user id is startingID starts from 100, and who can not be login:
kong:x:100:65533:Linux User,,,:/home/kong:/sbin/nologin
kong:x:100:65533:Linux User,,,:/home/kong:/sbin/nologin
but it is different without -S :
horward:x:1000:1000:Linux User,,,:/home/horward:/bin/ash
horward:x:1000:1000:Linux User,,,:/home/horward:/bin/ash