To set up the cronjob for yr present non-root user, do in terminal:
$ crontab -e
The above will open yr (non-root) user's crontab with his/her default editor.
Alternatively, to do so for the root crontab, but with yr present (presumably non-root) user environment parameters (default editor, etc.):
$ sudo -i crontab -e
In yr opened crontab, enter a new line:
0 01 01 * * /bin/tar -cvpz --exclude=/bckupftp --exclude=/ser --exclude=/proc --exclude=/lost+found --exclude=/mnt --exclude=/sys / | /usr/bin/split -d -b 750m - /bckupftp/backup$(/bin/date +\%Y\%m\%d-\%H\%M\%S).tar.gz
(I did not check the validity of yr tar cmd.)
Note that:
crontab uses a 24-hour clock, military style: 15 means 3pm, 03 means 3am, etc.
the above cron entry runs at 01:00 o'clock the first day of every month. In terminal , do: man crontab for more info on crontab formats.
in crontab, it's a good habit to prefix cmds with their full path. To find the full path of any non-built-in cmd, do in terminal $ which <cmd>. Thus the tar cmd becomes /bin/tar, split becomes /usr/bin/split, etc..
as soon as you save the newly edited crontab, the cron job becomes effective. No need to reboot, log out and back in, or restart whatever service.
when saving yr bckup file(s), the time stamp has the following format YYYYMMDD-HHMMSS. If you need it to be more precise, try replacing %S with %s in yr crontab entry.
I am certain (meaning "with 100% probability") you can find all the above explained in great details in AU, SE at large as well as in other fora. Remember that StartPage is yr friend.
