Why can’t unprivileged users mount block devices?
or

Why do I get “fusermount: option blkdev is privileged” error?

Unprivileged block device mounts work only if all the below requirements are met:

    ntfs-3g is compiled with integrated FUSE support
    the ntfs-3g binary is at least version 1.2506
    the ntfs-3g binary is set to setuid-root
    the user has access right to the volume
    the user has access right to the mount point

The root user can make an ntfs-3g binary setuid-root as shown below
chown root $(which ntfs-3g)
chmod 4755 $(which ntfs-3g) In such case the driver will also be able

    to fix common FUSE kernel module loading problems
    to create the required but sometimes incorrectly removed or missing FUSE device file

Please note that using setuid-root can result unforeseen privilege escalation and its usage is discouraged. Only the absolutely trusted users must be granted such access. Below is an example how this can be done for users in the ntfsuser group to be able to mount any NTFS volume if they have also the needed volume access rights. chown root.ntfsuser $(which ntfs-3g)
chmod 4750 $(which ntfs-3g) The setuid-root ntfs-3g driver applies the principle of least privilege during its lifetime as a safety measure.

Why don’t the ‘user’ and ‘users’ options work in /etc/fstab?

The ‘mount’ command doesn’t invoke the ntfs-3g binary with the needed privilege after it has checked and approved the user is entitled to mount a given device on a specified mount point, hereby the user can’t open the device he got the approval in /etc/fstab. This is a problem in the ‘mount’ utility.

Solution: Use at least NTFS-3G 1.2506 with setuid-root set and make sure the user has access rights to the volume and mount point.