Without seeing a sample of your fstab, not too clear how your system is setup. But I believe you can use the user option in the fstab entry something like this as explained here; empahsis is mine on the option relevant to your question:
- user/nouser - Permit any user to mount the filesystem. (This automatically implies noexec, nosuid,nodev unless overridden) / Only
permit root to mount the filesystem. This is also a default setting.
Now you need to know what the fstab entry format is like; here is a simple breakdown:
/thing/to/be/mounted /mount/point file_system_type options dump pass
Knowing that, the user option would be tagged onto the options list as another comma delimited item like this; and here is a theoretical fstab entry example for reference:
/dev/sdb1 /home/leetwanker/mount_point ext3 defaults,noatime,user 0 0
So in this example, the file system on /dev/sdb1 will be mounted on the mount point known as /home/leetwanker/mount_point which has an ext3 file format and has the options defaults,noatime,user as well as dump and pass values of 0.
With the user option in place in the fstab, reboot your system and you can then use mount and umount without any sudo restriction prompts or requirements.