nodev

Nodev is a mount option used in Unix-like operating systems, most commonly associated with Linux. When a filesystem is mounted with the nodev option, the kernel is instructed not to interpret character or block special device files that reside on that filesystem. In practice, this means that device files on the mounted tree cannot be used to perform device I/O; attempts to use such files are blocked or treated as ordinary files, depending on the exact operation and kernel behavior. Regular files and standard data I/O are unaffected.

Nodev is one of several security-related mount options often used alongside nosuid and noexec. While nosuid prevents the execution of set-user-id or set-group-id programs, and noexec disallows running executables from the filesystem, nodev focuses specifically on device files. These options can help reduce the risk posed by untrusted or removable media, shared partitions, or network-mounted shares by preventing indirect access to hardware devices through the filesystem.

Usage typically involves specifying the option in a mount command or in the filesystem table (fstab). For example, a filesystem entry might include nodev in its options to ensure device files on that mount point are not interpreted. The effect is applied at mount time and can be overridden by remounting with different options.

Notes and caveats: the exact behavior can vary slightly between kernel versions and filesystems, but the general principle remains that device files on a nodev-mounted filesystem are not treated as devices. This option does not alter access to regular files and does not apply globally to the entire system, only to the specific mounted filesystem.