在 mkfs.ext4 /dev/sda2 格式化硬盘空间时，可能出现这样的错误。
had this situation at office where I was told to re-partition an already existing partition. The situation was to get the below schema
/dev/sdb1 1 3040 24418768+ 83 Linux
/dev/sdb2 3041 6080 24418800 83 Linux
/dev/sdb3 6081 30515 196274137+ 83 Linux
to
/dev/sdb1 1 3040 24418768+ 83 Linux
/dev/sdb2 3041 6080 24418800 83 Linux
/dev/sdb3 6081 30515 196274137+ 5 Extended
/dev/sdb5 6081 18239 97667136 83 Linux
/dev/sdb6 18240 30515 98606938+ 83 Linux
Alright, now the partition /dev/sdb2 was in use and cannot be unmounted. So what happens when you finish the partitioning with fdisk ?
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.
This happends, if you are using/mounted any partitions of the HDD which you just re-partitioned. Normally we do reboot the machine to get this right. But this is not always the easy way out, when you have something running on the machine/multiple users are
on the machine working etc. So there comes the “parted” for rescue.
The package “parted” provides a tool called “partprobe“. This will do the magic for you, you just type in the command (see the man page for more info on partprobe) and this will give the information needed about your newly created partition to your kernel.
解决方法：执行下partprobe
命令
partprobe包含在parted的rpm软件包中。partprobe可以修改kernel中分区表，使kernel重新读取分区表。
因此，使用该命令就可以创建分区并且在不重新启动机器的情况下系统能够识别这些分区。
查看是否安装该命令：
[[email protected] dev]# rpm -q parted
parted-1.8.1-23.el5
我们执行一下该命令：
[[email protected] dev]# partprobe
Warning: Unable to open /dev/hdc read-write (Read-only file system). /dev/hdc has been opened read-only.
如果还有错误，可以从错误中看出来，需要reboot重启然后再mkfs格式化硬盘空间就可以了。