怎么样使命令在后台执行

1.比如拷贝一个镜像
df -hT 查看磁盘
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root ext4 45G 2.7G 41G 7% /
tmpfs tmpfs 1.9G 200K 1.9G 1% /dev/shm
/dev/sda1 ext4 45G 2.7G 41G 7% /boot
/dev/sr0 iso9660 4.2G 4.2G 0 100% /media/cdrom

2.[root@localhost ~]#cp -r /media/cdrom/Packages/ /boot/ & 在后面加一个&

3.查看进程
[root@localhost ~]# ps -ef | grep cp
root 24 2 0 10:45 ? 00:00:00 [kacpid]
root 25 2 0 10:45 ? 00:00:00 [kacpi_notify]
root 26 2 0 10:45 ? 00:00:00 [kacpi_hotplug]
root 1512 1480 84 10:49 pts/0 00:00:06 cp -i -r /media/cdrom/Packages/ /boot/
root 1514 1480 0 10:49 pts/0 00:00:00 grep cp