cron

Schedule One-Time Commands with the UNIX at Tool

Kyle Rankin — Mon, 19 Nov 2018 12:30:00 +0000

Cron is nice and all, but don't forget about its cousin at.

When I first started using Linux, it was like being tossed into the deep end of the UNIX pool. You were expected to use the command line heavily along with all the standard utilities and services that came with your distribution. At lot has changed since then, and nowadays, you can use a standard Linux desktop without ever having to open a terminal or use old UNIX services. Even as a sysadmin, these days, you often are a few layers of abstraction above some of these core services.

I say all of this to point out that for us old-timers, it's easy to take for granted that everyone around us innately knows about all the command-line tools we use. Yet, even though I've been using Linux for 20 years, I still learn about new (to me) command-line tools all the time. In this "Back to Basics" article series, I plan to cover some of the command-line tools that those new to Linux may never have used before. For those of you who are more advanced, I'll spread out this series, so you can expect future articles to be more technical. In this article, I describe how to use the at utility to schedule jobs to run at a later date.

at vs. Cron

at is one of those commands that isn't discussed very much. When people talk about scheduling commands, typically cron gets the most coverage. Cron allows you to schedule commands to be run on a periodic basis. With cron, you can run a command as frequently as every minute or as seldom as once a day, week, month or even year. You also can define more sophisticated rules, so commands run, for example, every five minutes, every weekday, every other hour and many other combinations. System administrators sometimes will use cron to schedule a local script to collect metrics every minute or to schedule backups.

On the other hand, although the at command also allows you to schedule commands, it serves a completely different purpose from cron. While cron lets you schedule commands to run periodically, at lets you schedule commands that run only once at a particular time in the future. This means that at fills a different and usually more immediate need from cron.

Using at

At one point, the at command came standard on most Linux distributions, but these days, even on servers, you may find yourself having to install the at package explicitly. Once installed, the easiest way to use at is to type it on the command line followed by the time you want the command to run:

Go to Full Article

Video On Demand: 8 Signs You're Beyond Cron

LJ Staff — Wed, 29 Apr 2015 17:30:24 +0000

by LJ Staff

Our latest free webinar is now available on demand!

View Now!
Scheduling Crontabs With an Enterprise Scheduler

Cron job scheduling is probably your ticket to automating processes on your UNIX boxes. But how are you automating the rest of your environment?

Though cron is easy to use, it provides limited options for event-driven and enterprise-wide job scheduling. Because today's enterprises are larger and more interconnected than ever before, crontab scheduling just won’t be able to deliver the level of automation you desire.

Join Mike Diehl, and Pat Cameron, Director of Automation Technology at HelpSystems, as they discuss the eight primary advantages of moving beyond cron job scheduling. In this webinar, you’ll learn about integrating cron with an enterprise scheduler, which gives you the ability to:

Integrate your cron job schedules across your enterprise
Import existing UNIX crontab data into Skybot Scheduler
Schedule new jobs with the familiar cron syntax

Go to Full Article

New GeekGuide: Beyond Cron

Carlie Fairchild — Thu, 02 Apr 2015 16:45:10 +0000

by Carlie Fairchild

How to Know When You've Outgrown Cron Scheduling--and What to Do Next

If you've spent any time around UNIX, you've no doubt learned to use and appreciate cron, the ubiquitous job scheduler that comes with almost every version of UNIX that exists. Cron is simple and easy to use, and most important, it just works. It sure beats having to remember to run your backups by hand, for example.

But cron does have its limits. Today's enterprises are larger, more interdependent, and more interconnected than ever before, and cron just hasn't kept up. These days, virtual servers can spring into existence on demand. There are accounting jobs that have to run after billing jobs have completed, but before the backups run. And, there are enterprises that connect Web servers, databases, and file servers. These enterprises may be in one server room, or they may span several data centers.

Go to Full Article