Resizing NTFS partition on USB drive

I think, psusi gave you the right hint.

Your partition /dev/sdc1 is a container that holds an NTFS filesystem. That filesystem in turn is a container that holds the files stored therein.

So if you want to shrink the partition, you have to shrink the filesystem first. If you want to keep all files therein, it is clear that you can shrink it at maximum by the amount of free space in the filesystem, minus some rounding that depends on the filesystem granularity.

I am not familiar with gparted but I guess it does both shrinking steps—transparent for you—in one process.

If you are not daunted by the command line, you can use the program ntfsresize to check whether your NTFS partition is shrinkable at all

ntfsresize --check /dev/sdc1 

and by what maximum amount

ntfsresize --info /dev/sdc1 

The latter command gives you a bunch of additional information including the space that is used by the contents of the filesystem (files) and that is therefore not available for shrinking, and the minimum size of the filesystem that you can shrink it to.

Depending on the distribution you find this program in the ntfsprogs or ntfs-3g package—the latter applies to the current Arch distribution.

Both commands have to be issued with sufficient privileges, thus typically using sudo or, if necessary, as root (be careful here).

If it turns out that you can shrink, but not far enough, follow psusi's advice and move some files out of the NTFS filesystem to free a sufficient amount of space there.

If you are familiar with gparted, I recommend to stick to it for the actual shrinking—albeit you could do this also from the command line using the NTFS utilities in the package named above and fdisk or gdisk as appropriate.

But whatever way you choose, your first two steps should always be

1. Have a backup of the whole disk—a disk image would be best.
2. Verify that backup (image) against the disk.

Good luck.