Questions tagged [scheduling]

A technique for scheduling tasks to be run at a specific time or on a specific event.

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4
votes
3answers
9k views

Conditional crontab command in bash script

How do I invoke a crontab command so that I can schedule to run a script with a 20 minute delay based on some condition? Edit: What if I wanted a command that schedules a script to be executed only ...
9
votes
4answers
2k views

How to prevent atd from running past jobs?

The at daemon is a great tool! However, if a job is scheduled for 8:00 am and the machine is off at that time, at will run the job whenever the machine is booted. What I would like to do is stop it ...
10
votes
3answers
2k views

Does Linux kernel 3.x use the CFS process scheduler?

Does the latest version of the Linux kernel (3.x) still use the Completely Fair Scheduler (CFS) for process scheduling which was introduced in 2.6.x ? If it doesn't, which one does it use, and how ...
5
votes
1answer
917 views

Unix/Linux process scheduler logs

Where can I actually see what decisions did a process scheduler make over a time period? Are there scheduling specific logs maintained by Unix/Linux systems I could take a look or should I be looking ...
11
votes
1answer
2k views

Why can a system become unresponsive?

I just executed dot (a program for drawing directed graphs) with an input file that was so big that it couldn't be rendered in a reasonable amount of time. My whole system froze. I could barely make ...
15
votes
2answers
2k views

What is a simple way to schedule a single event to happen at some time in the future?

There are often times that I want my computer to do a single task, but not right now. For example, I could have it notify me in 30 minutes that it is time to leave work. Or maybe I want it to run a ...
25
votes
1answer
4k views

High CPU usage with CFS?

I asked a previous question to try and isolate the source of an increase in CPU usage when moving an application from RHEL 5 to RHEL 6. The analysis that I did for that seems to indicate that it is ...
9
votes
1answer
6k views

Isolating cause of higher CPU usage on RHEL 6 vs RHEL 5

I'm currently looking to move our system from RHEL 5 to RHEL 6, but I've run into a snag with unexpectedly high CPU usage on the RHEL 6 machines. It appears that this may be due at least in some part ...
8
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2answers
9k views

How can you determine which process scheduler is being used? [duplicate]

I.e. is it the O(1) scheduler, the CFS scheduler, or an older one?
3
votes
2answers
507 views

How does a script/program executes in unix?

I have a doubt about the execution pattern of a unix script. For example a script containing lines: command B function C() { Myscript // Myscript is a script command D } command E and suppose ...
3
votes
3answers
3k views

How to schedule something run once using anacron?

Frequently within my scripts I schedule auxiliary tasks for later in the form: at now + 8 hours <<< "rm -f workfile.$$ >> $worklog 2>&1 " or at 11pm + $(date +%M) minutes <&...
11
votes
2answers
1k views

What are the effects, if any, of scheduler priorities and policies for threads in an uncontended cpuset?

I have a Linux system where we have used cgroups to create two cpu_exclusive cpusets, A and B, and where we have migrated all user threads and all unbound kernel threads to a cgroup attached to cpuset ...
7
votes
1answer
314 views

Prioritise X applications with focus

Is there a way to prioritise X applications with focus, preferably both in terms of CPU and I/O? Something like all X applications are niced and ioniced down in priority, but when they gain focus ...
3
votes
4answers
1k views

Is there any handy command line tool to manage Cron jobs?

Would someone suggest any handy command line (NOT web) tool or script which adds, enables and disables Cron jobs? I am looking, for example, for the following (or similar) behavior: sh manageCron.sh -...
2
votes
1answer
511 views

Get pid of long running command executed via at

I would like to spawn a persistent netcat server. My command of choice is the following: echo "bash -c \"while [ 1 ]; do nc -l -p 1111 >> check; done\"" | at now I am wondering how I can get ...
0
votes
1answer
2k views

Disk Scheduler in Linux

I am studying about Disk Scheduling in my OS class. Thought about the disk scheduler in Linux. When I run cat /sys/block/sda/queue/scheduler noop anticipatory deadline [cfq] Someone explain about ...
3
votes
2answers
2k views

How can I queue processes?

I have a surveillance camera and a program records videos when motion is detected. Basically, this program saves the video in a very heavy format. My solution was to call a script that converts the ...
11
votes
3answers
14k views

Which Scheduling algorithm is used in Linux?

Recently in an interview I was asked about the Scheduling algorithm used by Linux Operating system. What is the algorithm used any why? Also, what algorithm is used in in real-time operating systems ...
3
votes
1answer
2k views

Scheduled task on reboot

How can I schedule a task to run on next reboot? I understand that we have tools like cron and at to help with scheduling. But they seem to allow scheduling at a specific time and not on specific ...
9
votes
4answers
7k views

Simple queuing system?

Given a commodity PC, we would like to use it to execute some tasks in the background round the clock. Basically, we would like to have commands like: add-task *insert command here* list-tasks ...
4
votes
3answers
837 views

GNU: Delayed jobs Queue

Is there a simple way for me to add a shell command to a list of jobs to have run on the system when I'm not logged in? For example: I SSH into my system, decide that I want to read an ebook later, ...
5
votes
1answer
684 views

Linux process scheduling - Cap/Weight based?

I am just trying to understand the basics of Linux scheduler. Is Linux scheduler a Cap based or weight based scheduler? I was previously using Xen. Now I am moving from Xen to KVM. I read VMs are ...
2
votes
1answer
5k views

What happens the most, context switches or mode switches?

Which happens the most, context switches or mode switches? I have two answers myself, but I do not know which one is correct: Context switches happen in user mode, but this does not mean that a ...
1
vote
4answers
406 views

Faster delayed execution than 1 minute?

I am working on a program that can "upgrade itself" by install a new package. In order to accomplish this, I am using the at command to specify that a shell script should be run one minute in the ...
4
votes
3answers
2k views

How to monitor or kill a process which has been started by cron?

I have some bots, which are run by the System scheduler at given time interval. But sometimes due to some logical error I have to stop these bots manually. How can I find these processes run by the ...
3
votes
3answers
830 views

Changing the disk scheduler on the fly

Can the Linux disk scheduler be changed on the fly by writing to /sys/block/sda/queue/scheduler? Should applications (e.g. Mysql) be stopped / started when changing?
5
votes
2answers
1k views

How do I execute a script later?

I need to compile gcc45 on my computer and that's a lengthy and resource-intensive process for my computer, so I'd prefer to have it do it while I sleep (at night). What's the closest thing to: $ @...
12
votes
2answers
14k views

Bash Script on Startup? (Linux)

Is there any way to make/run a bash script on reboot (like in Debian/Ubuntu for instance, since thats what my 2 boxes at home have) Also, any recommended guides for doing cron jobs? I'm completely ...
189
votes
3answers
475k views

How can get a list of all scheduled cron jobs on my machine?

My sysadmin has set up a bunch of cron jobs on my machine. I'd like to know exactly what is scheduled for what time. How can I get that list?
3
votes
2answers
4k views

Add a one-off scheduled task through a shell script?

I'd like to execute a task at a given time, once. I know I can just use crontab -e to add it there, but I'd like to do that through a shellscript. crontab -e gives me some temporary file to edit ...
10
votes
1answer
4k views

How can you schedule a computer to boot at a specific time?

Usually BIOSes have an option to schedule a time to which to boot at. Is there a Unix/Linux interface to specify the scheduled boot?
4
votes
3answers
1k views

Are there any Workload Management subsystems for Linux?

Asked this on superuser, got no response: Can anyone tell me of the status/state of WLM (Workload Management) kernel scheduler systems in Linux? Alternatively, any user-space process goal-based load ...
19
votes
1answer
7k views

How do I view the IO priority of a process?

How can I view the IO priority of a process? like to see for example if something has been ionice-ed.
9
votes
3answers
1k views

how to queue a command to run after another command finishes?

Sometimes I start a program that takes a very long time to finish (emerge), then realize that I should go to bed instead of waiting for it. If I know this in the first place I would run program; halt ...
7
votes
4answers
480 views

Scheduling commands by system inactivity

So cron or at can schedule our commands to run at the exact time we need them to, but can we schedule commands to run when systems are inactive? Something like: echo "some_commands" | when 'cpu <...
3
votes
1answer
588 views

How does fcron know whether the job was run?

I recently migrated from vixie-cron to fcron, on my laptop. How does fcron knows if a particular job was run in given period of time? As a file can change during running, what constitute a different ...
166
votes
9answers
362k views

Where are cron errors logged?

If I setup cron jobs incorrectly they appear to silently fail. Where should I look for an error log to understand what went wrong?