System has not been booted with systemd as init system

skyer9@skyer9:/mnt/c/Users/skyer$ sudo shutdown -h now
System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down
System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down
Failed to talk to init daemon: Host is down

skyer9@skyer9:/mnt/c/Users/skyer$ pstree
init─┬─init───init───bash───pstree
     └─2*[{init}]

skyer9@skyer9:/mnt/c/Users/skyer$ exit
logout

PS C:\Users\skyer> wsl --update
설치 중: Linux용 Windows 하위 시스템
Linux용 Windows 하위 시스템이(가) 설치되었습니다.

PS C:\Users\skyer> wsl -d Ubuntu
skyer9@skyer9:/mnt/c/Users/skyer$ pstree
systemd─┬─2*[agetty]
        ├─containerd───9*[{containerd}]
        ├─cron
        ├─dbus-daemon
        ├─dockerd───9*[{dockerd}]
        ├─init-systemd(Ub─┬─SessionLeader───Relay(547)───bash───pstree
        │                 ├─init───2*[{init}]
        │                 ├─login───bash