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Micro-Tutorial: Schedule a One-Time Job
raindog308
Administrator, Veteran
BuyVM is relocating from San Jose to and I need to shut down my KVM node cleanly before 9pm on Saturday. I could login and do it then but...laziness is a virtue.
I could put it in cron, but I only want it to execute once.
I've noticed everyone knows about cron, but fewer people know about at(1). 'at' is the way to schedule a one-time job.
Example of scheduling a shutdown at 11pm Friday:
# at 11pm friday /sbin/shutdown -h now commands will be executed using /bin/ksh job 1358578800.c at Fri Jan 18 23:00:00 2013 # atq Rank Execution Date Owner Job Queue 1st Jan 18, 2013 23:00 root 1358578800.c c #
Might look a little funky because it's OpenBSD, but the same would work on Linux. Linux will execute the commands using /bin/bash
'atq' is the command to display queued jobs
atrm allows you to remove a job (or at -r in some Unices)
There's also 'batch' which you can find on the at(1) man page - it executes jobs only when the system load level is below a certain threshold.
Comments
ive used cron before, the day of week, day of month and month combination doesnt happen too often, But yes at works well, There is also a version for windows
atis definitely an under-utilized command. I never see anyone mention it. Then again, it's usually more common that someone needs to do something repeatedly on a regular schedule, I guess.I use at on my scripts where the next run schedule is dynamic. Depending on the results the script launches itself with
at now + count time-units.atd must be running though, for the "at" scheduling to work. It is usually pruned / stopped, so check it before relying on "at".