February 19, 2009 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 NetBSD1.6.