The command findmnt is used to find mounted filesystems in Linux. This command will look for a particular filesystem in /etc/fstab, /etc/mtab or /proc/self/mountinfo.
This article explains many of the options of the findmnt command.
Full article here:
Linux findmnt Command To Find Mounted Filesystems (LinOxide)
8 examples of findmnt command to check mounted file systems on Linux (BinaryTides)