fstab
The fstab (/etc/fstab) (or file systems table) file is a system configuration file commonly found on Unix systems. It is part of the util-linux package. The fstab file typically lists all available disks and disk partitions, and indicates how they are to be initialized or otherwise integrated into the overall system’s file system. fstab is still used for basic system configuration, notably of a system’s main hard drive and startup file system, but for other uses has been superseded in recent years by automatic mounting.
The fstab file is most commonly used by the mount command, which reads the fstab file to determine which options should be used when mounting the specified device. It is the duty of the system administrator to properly create and maintain this file.
The file has other names on some versions of Unix; for instance, it is /etc/vfstab on Solaris.
mtab
The mtab (contraction of mounted file systems table) file is a system information file, commonly found on Unix-like systems. This file lists all currently mounted filesystems along with their initialization options. mtab has a lot in common with fstab, the main distinction being that the latter lists all available filesystems whereas the former lists only currently mounted ones. Therefore mtab is usually in a format similar to that of fstab. Most of the time it is possible to directly use lines from mtab in fstab.
The file commonly resides in /etc/mtab.