CLOCKCTL(4)             NetBSD Kernel Interfaces Manual            CLOCKCTL(4)

     clockctl -- Clock subsystem user control

     pseudo-device clockctl

     The clockctl interface brings clock control to non-root users.  Any user
     with write access to /dev/clockctl will be able to perform operations
     such as settimeofday(2), clock_settime(2), adjtime(2), or ntp_adjtime(2),
     which are normally restricted to the super-user.  Using the clockctl
     pseudo-device, it is possible to run daemons such as ntpd(8) as non-priv-
     ileged users, thus reducing the security exposure if a compromise is
     found in such a daemon.

     The clockctl pseudo-device driver provides an ioctl(2) call for each
     privileged clock-related system call.  The system call stubs in C library
     will use the ioctl(2) on /dev/clockctl if the special file is present and
     accessible, or will revert to the plain super-user-restricted system call
     if the special file is not accessible.

     The following ioctl(2) calls are defined in <sys/clockctl.h>:

               This will run the settimeofday(2) system call.  Argument should
               be a pointer to a struct clockctl_settimeofday:

               struct clockctl_settimeofday {
                       const struct timeval *tv;
                       const void *tzp;

               This will run the clock_settime(2) system call.  Argument
               should be a pointer to a struct clockctl_clock_settime:

               struct clockctl_clock_settime {
                       clockid_t clock_id;
                       struct timespec *tp;

               This will run the adjtime(2) system call.  Argument should be a
               pointer to a struct clockctl_adjtime:

               struct clockctl_adjtime {
                       const struct timeval *delta;
                       struct timeval *olddelta;

               This will run the ntp_adjtime(2) system call.  Argument should
               be a pointer to a struct clockctl_ntp_adjtime:

               struct clockctl_ntp_adjtime {
                       struct timex *tp;

     adjtime(2), clock_settime(2), ioctl(2), settimeofday(2)

     clockctl appeared in NetBSD 1.6.

NetBSD 8.0                     February 19, 2009                    NetBSD 8.0

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