docs/82296: ttys(5) man page misleads about use for non-getty processes

[Chris Lightfoot]

>Number:         82296
>Category:       docs
>Synopsis:       ttys(5) man page misleads about use for non-getty processes
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jun 15 21:50:15 GMT 2005
>Closed-Date:
>Last-Modified:
>Originator:     Chris Lightfoot
>Release:        5.2.1-RELEASE-p13
>Organization:
>Environment:
FreeBSD very.unfortu.net 5.2.1-RELEASE-p13 FreeBSD 5.2.1-RELEASE-p13 #5: Wed Dec 29 16:45:15 GMT 2004     james at very.unfortu.net:/usr/obj/usr/src/sys/VERY  i386

>Description:
The ttys(5) man page states in respect of each line of /etc/ttys,

     The first field is normally the name of the terminal special file as it
     is found in /dev.  However, it can be any arbitrary string when the asso-
     ciated command is not related to a tty.

However, this is not true -- the new_session command in init.c will drop any /etc/ttys line whose first field does not give the name of a file in /dev which can be opened: (line 937 et seq)

        /*
         * Attempt to open the device, if we get "device not configured"
         * then don't add the device to the session list.
         */
        if ((fd = open(sp->se_device, O_RDONLY | O_NONBLOCK, 0)) < 0) {
                if (errno == ENXIO || errno == ENOENT) {
                        free_session(sp);
                        return (0);
                }
        } else
                close(fd);

The same error is present in ttys(5) in the 5.4-RC2 release in respect of the init source code on that release.
>How-To-Repeat:
Obey advice of man page to run a non-getty process from init; observe that it doesn't work.
>Fix:
Change the man page or the code in init.c. The latter looks harder since I don't think init.c knows whether a given line refers to a getty process or not.
>Release-Note:
>Audit-Trail:
>Unformatted: