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manage utmp/wtmp entries for non-init clients


sessreg [-w wtmp-file] [-u utmp-file] [-L lastlog-file] [-l line-name] [-h host-name] [-s slot-number] [-x Xservers-file] [-t ttys-file] [-a] [-d] user-name

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Sessreg is a simple program for managing utmp/wtmp and lastlog entries for xdm sessions.

System V has a better interface to utmp than BSD; it dynamically allocates entries in the file, instead of writing them at fixed positions indexed by position in /etc/ttys.

To manage BSD-style utmp files, sessreg has two strategies. In conjunction with xdm, the -x option counts the number of lines in /etc/ttys and then adds to that the number of the line in the Xservers file which specifies the display. The display name must be specified as the "line-name" using the -l option. This sum is used as the "slot-number" in the utmp file that this entry will be written at. In the more general case, the -s option specifies the slot-number directly. If for some strange reason your system uses a file other than /etc/ttys to manage init, the -t option can direct sessreg to look elsewhere for a count of terminal sessions.

Conversely, System V managers will not ever need to use these options (-x, -s and -t). To make the program easier to document and explain, sessreg accepts the BSD-specific flags in the System V environment and ignores them.

BSD and Linux also have a host-name field in the utmp file which doesn’t exist in System V. This option is also ignored by the System V version of sessreg.


-w wtmp-file

This specifies an alternate wtmp file, instead of /var/log/wtmp. The special name "none" disables writing records to the wtmp file.

-u utmp-file

This specifies an alternate utmp file, instead of /var/run/utmp. The special name "none" disables writing records to the utmp file.

-L lastlog-file

This specifies an alternate lastlog file, instead of /var/log/lastlog, if the platform supports lastlog files. The special name "none" disables writing records to the lastlog file.

-l line-name

This describes the "line" name of the entry. For terminal sessions, this is the final pathname segment of the terminal device filename (e.g. ttyd0). For X sessions, it should probably be the local display name given to the users session (e.g. :0). If none is specified, the terminal name will be determined with ttyname(3) and stripped of leading components.

-h host-name

This is set for BSD hosts to indicate that the session was initiated from a remote host. In typical xdm usage, this options is not used.

-s slot-number

Each potential session has a unique slot number in BSD systems, most are identified by the position of the line-name in the /etc/ttysfile. This option overrides the default position determined with ttyslot(3). This option is inappropriate for use with xdm, the -x option is more useful.

-x Xservers-file

As X sessions are one-per-display, and each display is entered in this file, this options sets the slot-number to be the number of lines in the ttys-file plus the index into this file that the line-name is found.

-t ttys-file

This specifies an alternate file which the -x option will use to count the number of terminal sessions on a host.


This session should be added to utmp/wtmp.


This session should be deleted from utmp/wtmp. One of -a/-d must be specified.


In Xstartup, place a call like:

sessreg -a -l $DISPLAY -x /etc/X11/xdm/Xservers $USER

and in Xreset:

sessreg -d -l $DISPLAY -x /etc/X11/xdm/Xservers $USER

see also

xdm, utmpx


Keith Packard, MIT X Consortium

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