Thread: using sys/mount.h and mounting a USB thumb drive

I am working on a small program written in C to mount and unmount a USB thumb drive on a Linux Ubuntu (Please see code below for mounting and unmounting). The problem I am facing is that each time I mount, I cannot unmount and I keep getting "Device or resource busy" error....

Both operations work fine if I mount/unmount my USB from the command prompt using the following command:

Code:

mount -t vfat /dev/sda1 /media/usb0
umount -f /media/usb0

To mount my USB thumb drive using C code I write the following:

Code:

int mountUSB()
{
	int mountAttempts;
	int status;	

	mountAttempts = 0;
	status = 0;
	
	do
	{	
		status = mount("/dev/sda1", "/media/usb0", "vfat", MS_MGC_VAL | MS_NOSUID, "");
		if(status != SUCCESS)
			sleep(1);
		mountAttempts++;
	}while(status != SUCCESS && mountAttempts < 3);
	
	printf("USB mount - status = %s\n", strerror(errno));
}

to unmount:

Code:

void umountUSB()
{
	int status;
	status = umount("/media/usb0");
	
	printf("USB unmount - status = %s\n", strerror(errno));	
}

Can anyone tell me if I have the flags set correctly and whether or not I am using "vfat" correctly? I searched online but I couldn't find exact filesystem string descriptions.

I also read the man page for mounting but not sure which flags I need to set to be able to read, write, delete, copy, and create files/directories.

Any input is greatly appreciated.

Thanks bernt,
I played with it some more and to my surprise, adding MS_RDONLY flag during the mount makes it work - not sure why since I can still write to the USB as well as delete, change content and other operations....

This is the new call that I perform and it seems to work:

Code:

status = mount("/dev/sda1", "/media/usb0", "vfat", MS_MGC_VAL | MS_RDONLY | MS_NOSUID, "");

Thanks again for your comments.