procfs under the directory (not to be confused with the directory). This difference means checking the value of some parameter requires opening a file in a virtual file system, reading its contents, parsing them and closing the file. The sysctl system call does exist on Linux, but it has been deprecated and does not have a wrapper function in glibc; it is usually unavailable due to many distributions configuring the kernel without CONFIG_SYSCTL_SYSCALL; so it is not recommended for use. Examples When IP forwarding is enabled, the operating system kernel will act as a router. In FreeBSD, NetBSD, OpenBSD, DragonFly BSD, and Darwin/Mac OS X, the parameter can be set to to enable this behavior. In Linux, the parameter is called . In most systems, the command will enable a certain behavior. This will persist until the next reboot. If the behavior should be enabled whenever the system boots, the line can be added/rewritten to the file . Additionally, some sysctl variables cannot be modified after the system is booted. These variables (depending on the variable, the version and flavor of BSD) need to either be set statically in the kernel at compile time or set in . See also hw.sensors ioctl References External links sysctl-explorer.net – An initiative to facilitate the access of Linux' sysctl reference documentation Application programming interfaces Berkeley Software Distribution DragonFly BSD FreeBSD Linux NetBSD OpenBSD Operating system technology System calls Unix Unix process- and task-management-related software