.\"	$NetBSD: clockctl.4,v 1.8 2010/03/22 18:58:31 joerg Exp $
.\"
.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Emmanuel Dreyfus.
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.Dd February 19, 2009
.Dt CLOCKCTL 4
.Os
.Sh NAME
.Nm clockctl
.Nd Clock subsystem user control
.Sh SYNOPSIS
.Cd pseudo-device clockctl
.Sh DESCRIPTION
The
.Nm
interface brings clock control to non-root users.
Any user with write access to
.Pa /dev/clockctl
will be able to perform operations such as
.Xr settimeofday 2 ,
.Xr clock_settime 2 ,
.Xr adjtime 2 ,
or
.Xr ntp_adjtime 2 ,
which are normally restricted to the super-user.
Using the
.Nm
pseudo-device, it is possible to run daemons such as
.Xr ntpd 8
as non-privileged users, thus reducing the security exposure if a
compromise is found in such a daemon.
.Pp
The
.Nm
pseudo-device driver provides an
.Xr ioctl 2
call for each privileged clock-related system call.
The system call stubs in C library will use the
.Xr ioctl 2
on
.Pa /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.
.Pp
The following
.Xr ioctl 2
calls are defined in
.In sys/clockctl.h :
.Bl -tag -width CLOCKCTL
.It Dv CLOCKCTL_SETTIMEOFDAY
This will run the
.Xr settimeofday 2
system call.
Argument should be a pointer to a
.Va struct clockctl_settimeofday :
.Bd -literal
struct clockctl_settimeofday {
	const struct timeval *tv;
	const void *tzp;
};
.Ed
.It Dv CLOCKCTL_CLOCK_SETTIME
This will run the
.Xr clock_settime 2
system call.
Argument should be a pointer to a
.Va struct clockctl_clock_settime :
.Bd -literal
struct clockctl_clock_settime {
	clockid_t clock_id;
	struct timespec *tp;
};
.Ed
.It Dv CLOCKCTL_ADJTIME
This will run the
.Xr adjtime 2
system call.
Argument should be a pointer to a
.Va struct clockctl_adjtime :
.Bd -literal
struct clockctl_adjtime {
	const struct timeval *delta;
	struct timeval *olddelta;
};
.Ed
.It Dv CLOCKCTL_NTP_ADJTIME
This will run the
.Xr ntp_adjtime 2
system call.
Argument should be a pointer to a
.Va struct clockctl_ntp_adjtime :
.Bd -literal
struct clockctl_ntp_adjtime {
	struct timex *tp;
.\" Following member is commented out intentionally.
.\"	register_t retval;
};
.Ed
.El
.Sh SEE ALSO
.Xr adjtime 2 ,
.Xr clock_settime 2 ,
.Xr ioctl 2 ,
.Xr settimeofday 2
.Sh HISTORY
.Nm
appeared in
.Nx 1.6 .