CLOCKCTL(4)

CLOCKCTL(4) | Kernel Interfaces Manual | CLOCKCTL(4)

# NAME

clockctl — Clock 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

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

# HISTORY

clockctl appeared in NetBSD 1.6.

February 19, 2009 | NetBSD 7.0