Changing a MyBook usb3 drive from NTFS to ext3 using RT-N66U

[DSwit]

Hello all

I am trying to convert the filesystem on a WD 2TB MyBook usb 3 drive from NTFS to ext3 using the utilities that come with the RT-N66U/RMerlin 374.43 the drive is plugged in to.

fdisk is able to delete the existing partitions but is unable to write the new (single partition) partition data.

The error returned from fdisk:

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table
fdisk: WARNING: rereading partition table failed, kernel still uses old table: Invalid argument

and from mkfs.ext3:

admin@RT-N66U-6338:/# mkfs.ext3 /dev/sdc1
mke2fs 1.42.8 (20-Jun-2013)
/dev/sdc1 is mounted; will not make a filesystem here!


I'm obviously missing a step in the process.
Could someone point me at a guide or posting that would provide some enlightenment on this issue?

TIA

 

[sinshiva]

umount /dev/sdc1

 

[YasharF]

For anyone with this problem, with fdisk issues:

If it is fdisk: "WARNING: rereading partition table failed, kernel still uses old table: Invalid argument", you might be pointing fdisk to the partition instead of the device. For example for /dev/sdc, don't run fdisk like "fdisk /dev/sdc1", run it for the device as "fdisk /dev/sdc"

That fixed the issue for me on my /dev/sda, usb stick repartition