Automating tasks
We discussed a facility called crontab for the
automatic scheduling of repetitive tasks. This allows you to
program an activity to be performed as often as every minute, or as
infrequently as every year. When managing your system,
crontab is an invaluable tool for performing tasks,
such as backups, which are important for the system to run
reliably, but which can be forgotten if left to you to perform
yourself.
Worked example
How can Sam arrange for their mailbox to be backed up to
.mailbackup in their home directory each morning at 6
am?
Solution: Sam should use crontab
-e to edit their personal crontab file so that it
includes:
# At 6.00am each day
# copy /var/mail/sam to ~sam/.mailbackup
0 6 * * * /bin/cp /var/mail/sam ~sam/.mailbackup
This will perform the file copy, and if any error message is
generated, it will be mailed to Sam. Note the use of
~sam to denote Sam's home directory.
Many Linux distributions, including Red Hat and SuSE, include
directories /etc/cron.hourly,
/etc/cron.daily and /etc/cron.weekly. The
executable scripts placed in these directories are run on an
hourly, daily or weekly basis.
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