/tmp isn't cleaned up upon boot. Here's the trivial patch:
--- rc.sysinit.orig Mon Nov 20 15:00:51 2000
+++ rc.sysinit Mon Nov 20 15:23:59 2000
@@ -218,6 +218,9 @@
mount -f /
mount -f /proc
+# Remove all files in /tmp
+action "Clearing /tmp" rm -rf /tmp/.[^.] /tmp/.??* /tmp/*
# Update quotas if fsck was run on /.
if [ X"$_RUN_QUOTACHECK" = X1 -a -x /sbin/quotacheck ]; then
action "Checking root filesystem quotas" /sbin/quotacheck -v /
/tmp is cleaned by the tmpwatch cron script.