Most operating systems offer a mechanism by which the insides of the OS can be probed and operational parameters can be set when needed. In Linux, this mechanism is provided by the so-called application programming interface (API) file systems (or virtual or pseudo-file systems). Unlike the other file systems (ext4, BtrFS, XFS, and so on) that we discussed in Chapter 7, virtual file systems are not backed by actual physical storage (such as hard disks). The API file systems are typically not listed explicitly in the system’s /etc/fstab configuration file, though you will still find them listed in the output of the
mount command or
The proc file system is a popular virtual ...