What is fcron ?
Fcron is a scheduler. It aims at replacing Vixie Cron, so it implements
most of its functionalities.
But contrary to Vixie Cron, fcron does not need your system to be up 7 days a week, 24 hours a day : it also works well with systems which are running only occasionnally (contrary to anacrontab).
In other words, fcron does both the job of Vixie Cron and anacron, but does even more and better :)) ...
To do so, fcron allows you to use the standard mode in which you tell it to execute one command at a given date and hour (for instance every day at 6am), or to run a command depending to the system up time. For example :
Run the task 'save /home/ directory' every 3h15 of system up time.
Of course, in order to make it really useful, the time remaining
until next execution is saved each time the system is stopped.
You can also say :
run that command once between 2am and 5am
which will be done if the system is running at any time in this interval.
Fcron also includes a useful system of options, which can be applied either to every lines following the declaration or to a single line. Some of the supported options allow you to:
- run jobs one after the other (not in parallel),
- set the max system load average value under which the job should be run,
- set a nice value for a job,
- run jobs at fcron's startup if they should have been run during system down time,
- mail user to tell him a job has not run and why,
- a better management of the mailing of outputs,
- and much more !
Last, but not least, fcron is very well suited for being run by scripts : you can run several instances of fcron simultaneously, have fcron exit after it has run the pending jobs, ...
For more details about what fcron can do, you may want to have a look on its manual page.
- a Linux/Unix system.
Fcron should work on every POSIX system, but it has been developed on Linux.
Fcron has been reported to work correctly on:
- LFS (take a look at the Beyond LFS book to find the installation informations)
- FreeBSD 4.2
- OpenBSD 2.8
- NetBSD 2.0
- Solaris 8
- HP-UX 11.11
- AIX (fcron 3.0.3)
- a running syslog (or you won't have any log).
- a running mail system (sendmail or postfix for example)
(or users will not be able to read their jobs output).
- (optional) a PAM library.
- (optional) a SE Linux compliant system.