DOKK / manpages / debian 10 / userv / uservd.8.en
USERVD(8) System Manager's Manual USERVD(8)

uservd — supply user services

userv [-daemon]

uservd is the daemon called by userv to have a task performed under different userid while maintaining limited trust between caller and callee.

There is one optional argument:

Requests that the program daemonise. If this flag is supplied, uservd will fork and completely detach from the controlling terminal. If this option is not supplied, uservd will remain in its starting process group and continue to use the supplied stderr stream for any runtime system messages; this is useful for running uservd as a child of init. Errors detected by uservd itself will be reported via syslog in either case.

uservd issues diagnostics of various kinds to syslog, with facility LOG_DAEMON. The syslog levels used are:

debug
Verbose messages about the activity of the userv daemon.
info
Two log messages about the nature and outcome of each request.
notice
Messages about the status of the daemon, including the startup message and the hourly socket check messages.
warning
If the uservd exits because it believes that it no longer controls the rendezvous socket (ie, its socket has become orphaned), this level will receive messages indicating why the daemon believes this and notifying of its shutdown.
err
A believed-recoverable error condition was detected by the userv server in itself, the client or the operating system (this includes resource shortages). The uservd will try to continue.
crit
The uservd detected a non-recoverable error condition after startup and will exit.
alert
not used.
emerg
not used.

The service configuration language has the facility to direct error and warning messages to syslog. The default facility and level is user.err, but the author of the configuration file(s) can override this.

The daemon's exit code will reflect how well things went:

0
The daemon was asked to detach itself from the controlling terminal and this appears to have been done successfully.
1*
The daemon got a SIGTERM or SIGINT and shut itself down.
2*
The daemon believed that it was no longer the uservd and so exited to clean up.
3
uservd was started with incorrect arguments.
4
A system call failure or other environmental problem occurred during startup.
5*
There was a non-recoverable error after startup; the uservd had to exit.
6
The daemon was asked to detach itself, but its detaching child died for some unexpected reason.
SIGABRT/SIGIOT*
An unexpected internal error, usually caused by a bug in uservd. This can also occur if an attempt to block signals using sigprocmask fails.

Outcomes marked * are not possible if the daemon is asked to detach itself - these exit statuses will be reaped by init instead and so will not usually be logged anywhere.

The daemon's per-request children will report the success or otherwise of its request in their exit status. These are not usually be logged unless they indicate a serious problem.

All of the environment variables passed to uservd will be inherited by services as part of the default environment. (If the set-environment configuration directive is used, then other system configuration files can modify the environment. Consult the specification.)

userv(1) init(8)

Ian Jackson, User service daemon and client specification.

GNU userv is Copyright 1996-2017 Ian Jackson; Copyright 2000 Ben Harris; and Copyright 2016-2017 Peter Benie.

GNU userv is licensed under the terms of the GNU General Public Licence, version 3 or (at your option) any later version, and it comes with NO WARRANTY, not even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for details.

You should have received a copy of the GNU General Public License along with userv, if not, see http://www.gnu.org/licenses/

uservd was initially written in 1996 by Ian Jackson. It became GNU uservd in 1999, and version 1.0 was released in 2000.

November 3, 1999 userv