cron, atd, anacron, other wtf

[Matthew Garrett]

On Tue, Jan 10, 2006 at 11:52:43PM -0500, John Richard Moser wrote:

>  S89cron
>  S89anacron
>  S89atd:    Periodic Command schedulers -- THREE?  Please pick one to
>             use and stick with it.  If we need to use others, we'll turn
>             them on, we obviously know what we're doing if we know we
>             need any of these

There's a clear difference between these three applications, and merging 
them would be a fairly significant amount of development effort.

cron - executes recurring commands that should occur at a specific time
anacron - executes recurring commands that should take place with a 
 given frequency. 

(The difference between them is that if a task is scheduled in cron and 
the machine is switched off, it won't be executed until the next time 
it's due to run. anacron will attempt to catch up when the machine comes 
back up)

atd - executes a non-recurring command at a specific time

The fact that all three exist is something of a holdover from legacy 
Unix, but it's not possible to just remove one of them.

> The question of sysklogd and klogd comes to mind as well-- are these
> different, do we need 2?

They are different, yes. sysklogd starts the system logger (responsible 
for tracking events that come from userspace), and klogd starts the 
kernel logger (responsible for tracking events that come from the 
kernel).

-- 
Matthew Garrett | mjg59 at srcf.ucam.org