You can put a job in /etc/cron.daily to do this for you - this would start at 3.00am or 4.00am I can't remember how it's set up on Mandriva by default. Job would be something like:
CODE
#!/bin/bash
#
# Updates system
# sync repos so that they have new package list
urpmi.update -a
# update full system
urpmi --auto-select --auto
then you save this as /etc/cron.daily/sysupdates or whatever filename you like instead of sysupdates, and then do:
CODE
chmod +x /etc/cron.daily/sysupdates
to make it executable. It's important to add the #!/bin/bash at the beginning or your job will never run - I found this once, even though I could run it manually.