ghost user processes

[Francois Normant]

In article <1991Jun21.200251.9745 at uokmax.ecn.uoknor.edu> stsiegem at uokmax.ecn.uoknor.edu (Stephan Siegemund-Broka) writes:
>Does anyone out there know a fix for the corrupted utmp database?
>It seems that rlogin sessions when they exit don't properly zero out
>the data base in utmp and so finger or w report ghost sessions that
>aren't really there (they don't show up in ps for example).
>Thanks.

Here is a daemon posted on this newsgroup a few month ago by
John F. Haugh II        | Distribution to  | UUCP: ...!cs.utexas.edu!rpp386!jfh
Ma Bell: (512) 832-8832 | GEnie PROHIBITED :-) |  Domain: jfh at rpp386.cactus.org

In article <1991Mar25.164317.9775 at rs6000.cmp.ilstu.edu> dbeedle at rs6000.cmp.ilstu.edu (Dave Beedle) writes:
>     Hi all.  I've got a strange problem going on with AIX 3003.  When I do
>a who or an Finger I see one user (not the same all the time) who appears
>to have been logged on for 26 (or more) days.  The user is not currently
>logged on and has no processes running.  What is going on?  We recently
>installed xwindows, pcsim, AIX access, and a compiler or two.

I've mentioned this several times, so here is the source code.  This code
is being provided without warrantee (or even a copyright notice).  Use it
at your own risk.

Compile this program with "cc -o /etc/utmpd utmpd.c" and run in the background
with "nohup /etc/utmpd < /dev/null > /dev/null 2>&1 &" from your /etc/rc file.
I use it on this system to clean up utmp file entries left over from various
programs that create sessions on pty devices.

DISCLAIMER: I speak for myself only.  My employers are not responsible for
what I post here and will not provide support for this code or anything it
may do to your system.  Use at your own risk.
--
---- begin utmpd.c ----
#include <sys/types.h>
#include <utmp.h>
#include <fcntl.h>

main ()
{
        int     fd;
        struct  utmp    utmp;

        while (1) {
                if ((fd = open ("/etc/utmp", O_RDWR)) < 0)
                        exit (1);

                while (read (fd, &utmp, sizeof utmp) == sizeof utmp) {
                        if (utmp.ut_type == USER_PROCESS &&
                                        kill (utmp.ut_pid, 0) != 0) {
                                lseek (fd, - (long) sizeof utmp, 1);
                                utmp.ut_type = DEAD_PROCESS;
                                write (fd, &utmp, sizeof utmp);
                        }
                }
                close (fd);
                }
                close (fd);
                sleep (60);
        }
}
---- end utmpd.c ----


and adapted by

David Crow        (512) 823-4834    IBM VNET: dlcrow at austin
 AIX Systems Graphics Development    Internet: crow at waterloo.austin.ibm.com

    This is the code that John Haugh posted to clean out the utmp file.
  I have changed it a little bit since he posted it, so it is not exactly
  the same.  I think that the only thing that I did was take out a while
  loop that encompassed the entire program and made it more like a daemon.
  As John says in the comment, this is public domain.  This is NOT an
  official program from IBM.


/*
 * this code is in the public domain.  do with it as you
 * please.  - jfh. 12/19/90
 */

#include <sys/types.h>
#include <utmp.h>
#include <fcntl.h>

main ()
{
    int    fd;
    struct    utmp    utmp;

    if ((fd = open ("/etc/utmp", O_RDWR)) < 0) {
        printf("Could not open /etc/utmp\n");
        exit (1);
    }

    while (read (fd, &utmp, sizeof utmp) == sizeof utmp) {
        if (utmp.ut_type != DEAD_PROCESS && kill (utmp.ut_pid, 0) != 0) {
            lseek (fd, - (long) sizeof utmp, 1);
            utmp.ut_type = DEAD_PROCESS;
            if ( write (fd, &utmp, sizeof utmp) != sizeof utmp ) {
                close(fd);
                printf("Could not write to /etc/utmp\n");
                exit(1);
            }
        }    
    }    
    close (fd);
}

-- 
Francois Normant - fn at math.yale.edu
Yale University - Mathematics Department
Box 2155 - Yale Station
New Haven CT 06520