I have now changed the daily crontab line like so:
test -x /usr/sbin/anacron || ( cd / && run-parts --report -A trace-run-parts -B
trace-run-parts /etc/cron.daily )
Where trace-run-parts reads as follows:
#! /bin/bash
#
# Run as options -A, -B of run-parts cron.daily
msg=""
if [ "$2" ]; then
action="finished"
if [ "$2" != "0" ]; then
msg=", exit code $2"
fi
else
action="starting"
fi
logger -t 'run-parts daily' -p daemon.info "$action $1$msg"
This allowed me to understand the reasons of an error. Nevertheless, I'll keep
this customization because I like the way the daemon.log gets framed, cutting
out what parts belong to the end-of-day process.
I hope this patch will be added to future releases, so as to avoid losing processes due
to "Try `run-parts --help' for more information.\n" after upgrades.