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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
a /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.
p 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
a /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.
p
The following
.Xr ioctl 2
calls are defined in
n sys/clockctl.h : l -tag -width CLOCKCTL t Dv CLOCKCTL_SETTIMEOFDAY This will run the
.Xr settimeofday 2
system call.
Argument should be a pointer to a
.Va struct clockctl_settimeofday :
d -literal struct clockctl_settimeofday {
const struct timeval *tv;
const void *tzp;
};
.Ed
t 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 :
d -literal struct clockctl_clock_settime {
clockid_t clock_id;
struct timespec *tp;
};
.Ed
t Dv CLOCKCTL_ADJTIME This will run the
.Xr adjtime 2
system call.
Argument should be a pointer to a
.Va struct clockctl_adjtime :
d -literal struct clockctl_adjtime {
const struct timeval *delta;
struct timeval *olddelta;
};
.Ed
t 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 :
d -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 .