sudo systemctl start docker
System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down如果是一般的Linux操作系统，可能是因为Linux中没有使用systemd，想用systemd命令来管理Linux上的服务，因此会报错，很可能是使用的是经典的SysV init（sysvinit）系统。
但我这个是window11下WSL的Ubuntu，就会使SysV init而不是systemd。
解决方法：
更换命令，用SysV init的命令代替systemd的,对应关系如下:
| Systemd command | Sysvinit command |
| systemctl start service_name | service service_name start |
| systemctl stop service_name | service service_name stop |
| systemctl restart service_name | service service_name restart |
| systemctl status service_name | service service_name status |
| systemctl enable service_name | chkconfig service_name on |
| systemctl disable service_name | chkconfig service_name off |
sudo service docker start
启动成功