[问题]格式化U盘时出现的一个问题

[ley1982]

我在U盘上用fdisk /dev/sda创建了两个分区
lienyu@lienyu:~$ fdisk -l
显示如下：
Disk /dev/sda: 266 MB, 266600448 bytes
9 heads, 57 sectors/track, 1015 cylinders
Units = cylinders of 513 * 512 = 262656 bytes

Device Boot Start End Blocks Id System
/dev/sda1 1 77 19722 83 Linux
/dev/sda2 78 1015 240597 5 Extended
然后我进行格式化
lienyu@lienyu:~$ mkfs.ext2 /dev/sda1
系统提示
mke2fs 1.40-WIP (14-Nov-2006)
Could not stat /dev/sda1 --- No such file or directory

The device apparently does not exist; did you specify it correctly?
说找不到 设备，这是怎么回事呢？