CLOCKCTL(4) Kernel Interfaces Manual CLOCKCTL(4)
NAME
clockctlClock subsystem user control
SYNOPSIS
pseudo-device clockctl
DESCRIPTION
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-privileged 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>:
CLOCKCTL_SETTIMEOFDAY
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; };
CLOCKCTL_CLOCK_SETTIME
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; };
CLOCKCTL_ADJTIME
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; };
CLOCKCTL_NTP_ADJTIME
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; };
SEE ALSO
HISTORY
clockctl appeared in NetBSD 1.6.