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#1 2013-11-10 19:02:55

jthompson333
Member
Registered: 2013-11-10
Posts: 15

Mounting FAT32 USB stick or drive with ntfs-3g installed

I am unable to mount a FAT32 usb stick or drive.
I have dosfstools installed.

The kernel seems to pick up the drive:

fdisk -l

Disk /dev/sdc: 7.8 GiB, 8370782208 bytes, 16349184 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
Disklabel type: dos
Disk identifier: 0x00000000

Device    Boot Start       End  Blocks  Id System
/dev/sdc1         63  16338104 8169021   b W95 FAT32

However when I try to mount the drive manually I get the following:

mount -t vfat /dev/sdc1 /mnt/usb
mount: special device /dev/sdc1 does not exist
dmesg | grep sdc

[ 1096.871256] sd 8:0:0:0: [sdc] READ CAPACITY failed
[ 1096.871261] sd 8:0:0:0: [sdc]  
[ 1096.871265] sd 8:0:0:0: [sdc]  
[ 1096.871270] sd 8:0:0:0: [sdc]  
[ 1097.591319] sd 8:0:0:0: [sdc] Test WP failed, assume Write Enabled
[ 1098.288625] sd 8:0:0:0: [sdc] Asking for cache data failed
[ 1098.288630] sd 8:0:0:0: [sdc] Assuming drive cache: write through
[ 1098.493001] sd 8:0:0:0: [sdc] 16349184 512-byte logical blocks: (8.37 GB/7.79 GiB)
[ 1098.497508] sd 8:0:0:0: [sdc] No Caching mode page found
[ 1098.497514] sd 8:0:0:0: [sdc] Assuming drive cache: write through
[ 1098.497519] sd 8:0:0:0: [sdc] Attached SCSI removable disk

The irony here is that I can mount ntfs drives or CD's just fine.

I have ntfs-3g installed. 

I'm also not that familiar with systemd, so I'm not sure where to get system logs for this...
Long time Linux users, but, a fairly new Arch user...

Any ideas?

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#2 2013-11-10 19:16:18

srs5694
Member
From: Woonsocket, RI
Registered: 2012-11-06
Posts: 719
Website

Re: Mounting FAT32 USB stick or drive with ntfs-3g installed

First, the fdisk command you provided proves nothing about the kernel, beyond the fact that it can read the /dev/sdc device -- and even that conclusion comes with caveats, as I'll describe shortly. fdisk is a user-space program, and although it relies on the kernel for disk I/O (among other things), it does not rely on the kernel for interpreting the partition table; fdisk does that itself.

Second, your dmesg output indicates that the kernel has not detected the partition on the disk. This could be related to one or more of the error ("failed") messages in that output. It could be that the disk is physically defective, although if that's the case the defect is probably quite subtle. If you're connecting the disk through a USB hub, try connecting it directly; I've seen some USB hubs that are flaky enough to cause this sort of problem.

Third, please be aware of the distinction between partitions and filesystems. Partitions are defined in simple data structures (partition tables) that identify particular sections of the disk (partitions). Filesystems are more complex data structures that are usually contained within partitions. Before a filesystem can be accessed, the partition containing it must be identified. It appears that this process has failed in your case. Because partition identification occurs before filesystem identification, the fact that the partition holds a FAT32 filesystem is almost certainly irrelevant.

Fourth, the presence of NTFS-3g on your computer should have no effect on the ability to detect and use FAT32 filesystems, and even less effect on the kernel's ability to identify partitions. In other words, NTFS-3g is irrelevant to your problem.

Overall, my suspicion is that your disk is defective or you're using it via a flaky hub. If so, there is no real solution other than to use another computer to copy the disk to another one that's more reliable.

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#3 2013-11-10 20:00:20

jthompson333
Member
Registered: 2013-11-10
Posts: 15

Re: Mounting FAT32 USB stick or drive with ntfs-3g installed

All valid points.  Thank you.  I was probably too tired to use common sense last night while messing wih it.

I think its either a partition issue or bad drive like you said.
Other older fat32 usb sticks I have mount just fine (that I just found in a box).

The strange part is that I can reboot with the usb stick in question plugged in, and it comes up mounted.

So I'm just going to copy the data off, and reformat it and see how it behaves.

I can't remember whether it was originally formatted as "Fat" on Mac or Windows to be honest.
(Not sure if that would make a difference).

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