system restarts (unknown cause)

[Filipe Bonjour]

Hi,

> I have been using Linux for several years and Ubuntu for a short time, 
> however, I would like to know why my desktop restarts at about 07:40 
> CDT every day. The system is completely unattended. Is the there some 
> scheduled task doing it? I have tried to list the crontab for root but 
> am advised there is not one... (sudo cron -u root -l reports no 
> crontab for root).

I appreciate that you found out that there were no restarts (though that 
was just lucky: you changed the post's subject, so it doesn't appear in 
the same thread :) ). This is just a comment about cron. If I type your 
command "cron -u root -l" I get the following:

cron: invalid option -- u

In any case typing "cron -l" as root would most likely only mean that 
the root user does not have a personal crontab file. The system crontabs 
are separate:

/etc/crontab
/etc/crond
/etc/cron.daily
/etc/cron.hourly
/etc/cron.monthly
/etc/cron.weekly

For a problem that happens every day, you should look inside 
/etc/cron.daily.

Filipe