Enormous utmp since mpsafetty
rwatson at FreeBSD.org
Wed Aug 27 11:50:18 UTC 2008
On Wed, 27 Aug 2008, Ollivier Robert wrote:
> According to Gary Jennejohn:
>> There are many more pseudo-ttys in /etc/ttys now. AFAIK utmp allocates an
>> entry for every one of them at startup.
> utmp concepts are ancient. It is indexed by the tty/pty number so can grow
> rather large but it should be a sparse one too. I remember talks about
> replacing it with something a bit more modern. Backward compatibility is
> assured through login(3) although it would break programs digging in the
> utmp file itself. SVR4 had utmp/utmpx and setutline/getutline BTW...
Right -- utmp growing to 256K would be an excellent example of utmp format
inefficiency. On the other hand, utmp growing to 998M is probably an example
of a bug rather than an inefficient design. freefall.FreeBSD.org, a
relatively busy shell box, has a utmp of around 5k, so common use doesn't
generally exercise that inefficiency...
Robert N M Watson
University of Cambridge
> cf. sessreg(1)
> System V has a better interface to utmp than BSD; it dynamically allo-
> cates entries in the file, instead of writing them at fixed positions
> indexed by position in /etc/ttys.
> Ollivier ROBERT -=- FreeBSD: The Power to Serve! -=- roberto at keltia.freenix.fr
> Darwin sidhe.keltia.net Version 9.2.0: Tue Feb 5 16:13:22 PST 2008; i386
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