我有一个外置硬盘 TOSHIBA 1TB USB 3，权限始终为只读。
fdisk -l（输出）：
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xf2198b37
Device Boot Start End Blocks Id System
/dev/sda1 * 2046 362369023 181183489 5 Extended
/dev/sda3 362371072 976771071 307200000 7 HPFS/NTFS/exFAT
/dev/sda5 2048 976895 487424 83 Linux
/dev/sda6 978944 362369023 …