DOKK / manpages / debian 10 / sac / writetmp.8.en
WRITETMP(8) System Manager's Manual WRITETMP(8)

writetmp - write special wtmp entries to a wtmp file.

writetmp [-w wtmp|-] [-X[3|4]] [-u user] [-l line] [-h host] [-i id] [-p pid] [-t type] [-c comment] [--help] [--version] [entry-type]

Writetmp is a utility to write special entries to a wtmp file. Useful as either a replacement for the functionality of the "halt -w" or "reboot -w" commands which are normally run at shutdown time or to write special wtmp entries to an alternate wtmp file to which such entries would normally not be written.

Under normal conditions radius radtwmp or tacacs accounting logs do not contain shutdown and boottime entries because the access control software is not setup to take into account these events. In the case of a quick shutdown or server crash, the wtmp file(s) will lose coherency. To avoid or minimize the amount of accounting error, it is necessary to write shutdown and boottime entries to such logs.

Also changes in time which are made manually with date or via the network with a program such as rdate are not reflected in the accounting logs, which, if the time difference is severe can improperly account time for logins active during the time change.

If an entry-type is specified on the command line, the -u, -l, -h, -i, -p, -t and -c options are ignored as writetmp will fill in the username, line, id, and host entries as required for that particular wtmp entry-type.

Writetmp understands the following entry types:

used just prior to a normal system shutdown. Also accepts halt or reboot as aliases for shutdown.
used at system initialization time, to indicate the system is booting.
Indicates the time is about to change.
Indicates the time has changed. The difference in time is determined from the timestamp on the last oldtime entry.
Indicates a change in runlevel (useless in an accounting sense).

Writetmp understands the following command line switches:

Outputs a verbose usage listing.
Displays the version of writetmp.
Select a different output file instead of the default (/var/log/wtmp).
Write to a wtmp file maintained by versions 3.3 or 3.4 Tacacs terminal server access control software.
Write to a wtmp file maintained by version 4.0 of Tacacs terminal server access control software.
Specify the username for the username field.
Specify the tty name for the line field.
Specify the hostname.
Specify the init id name. Not applicable to tacacs wtmp files.
Specify the pid number. Not appliccable to tacacs wtmp files.
Specify the type of wtmp entry for the ut_type field, not to be confused with entry-type. May be coded as a number or one of: unknown, runlevel, boottime, newtime, oldtime, init, login, user or dead.
Specify the comment for the tacacs 4 wtmp comment field (16 characters max).

Write a shutdown message to an alternate wtmp log:

writetmp -w /var/adm/xtmp shutdown

A shell script to update the time in an alternate wtmp file when netdate is run:

#!/bin/sh
writetmp -w /var/adm/xtmp oldtime
netdate clock.llnl.gov
writetmp -w /var/adm/xtmp newtime

Find out how often and for how long people run a specific program, such as pine:

#!/bin/sh
# /var/adm/cmdtmp must be globally writable.
cmdtmp=/var/adm/cmdtmp

writetmp -w $cmdtmp -u pine -l cmd$$ -h $USER -t user
/path/to/real-pine $*
writetmp -w $cmdtmp -l cmd$$ -t dead

/var/log/wtmp login database.

Steve Baker (ice@mama.indstate.edu)

Does not lock the wtmp file and does not guarantee a successful write. Could in theory corrupt a log file.

Rdate and netdate can take seconds to complete, so writing oldtime/newtime records around them may not be entirely accurate.

date(1), last(1), sac(8), netdate(8L), reboot(8)

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