crscott@sdrc.UUCP (Scott_Klosterman) (12/29/89)
After installing 3.2.1 you will find the following
entry in /usr/spool/cron/crontabs/root
2 1 * * 0 umask 033;
cd /etc;if test -f wtmp; then mv -f wtmp OLDwtmp;
touch wtmp; fi
This may have been present in 3.2 but I don't re-
call it. Maybe some-one at SGI could comment as to
when exactly the line is adding as a comment and
when it is not. But if you have a home-brewed system
for accounting which depends on /etc/wtmp you may
experience technical difficulties :-)
Scott Klosterman
SGI Sys. Admin.
vjs@rhyolite.wpd.sgi.com (Vernon Schryver) (12/29/89)
/etc/wtmp is rotated to prevent unhappy consequences of infinite growth. The general scheme is ancient, having been copied from 2000/3000 days. The next release has a slightly handier scheme, where wtmp is rotated only if it is "big". This is handy for the common case, where the "last" command is the only thing that looks at wtmp and the machine is used by few people so wtmp grows slowly. The last command will also have facilities to suppress some of the extraneous lines, and to specify an alternate file, such as /etc/OLDwtmp. An accounting scheme which relies on wtmp and last seems novel. However, one should not argue with success. Such a system would no doubt want to do its own wtmp rotating, by modifying /usr/spool/cron/crontabs/root. With each new release, you might want to consider merging your changes with ours. Anyone with such a system should beware that not only do we not promise to not change either output of the last command or the structure of utmp and wtmp, but we intend to change both in the release after next. This is part of a grand plan to get 4.3 BSD style host names into wtmp. Do not be surprised to see a "shadow wtmp" in the next release, used by the last and w commands to produce new-style output. Vernon Schryver Silicon Graphics vjs@sgi.com