44

It seems I can shutdown using sudo shutdown by specifying a time or minutes.

Is there a way to specify datetime for shutdown?

75

You can do this directly from the shutdown command, see man shutdown:

SYNOPSIS
   /sbin/shutdown [-akrhPHfFnc] [-t sec] time [warning message]

[...]

   time   When to shutdown.

So, for example:

shutdown -h 21:45

That will run shutdown -h at 21:45.


For commands that don't offer this functionality, you can try one of:

A. Using at

The at daemon is designed for precisely this. Depending on your OS, you may need to install it. On Debian based systems, this can be done with:

sudo apt-get install at

There are three ways of giving a command to at:

  1. Pipe it:

    $ echo "ls > a.txt" | at now + 1 min
    warning: commands will be executed using /bin/sh
    job 3 at Thu Apr  4 20:16:00 2013
    
  2. Save the command you want to run in a text file, and then pass that file to at:

    $ echo "ls > a.txt" > cmd.txt
    $ at now + 1 min < cmd.txt
    warning: commands will be executed using /bin/sh
    job 3 at Thu Apr  4 20:16:00 2013
    
  3. You can also pass at commands from STDIN:

    $ at now + 1 min
    warning: commands will be executed using /bin/sh
    at> ls
    

    Then, press CtrlD to exit the at shell. The ls command will be run in one minute.

You can give very precise times in the format of [[CC]YY]MMDDhhmm[.ss], as in

$ at -t 201403142134.12 < script.sh

This will run the script script.sh at 21:34 and 12 seconds on the 14th of March 2014.

B. Using cron (though this not a good idea for shutdown)

The other approach is using the cron scheduler which is designed to perform tasks at specific times. It is usually used for tasks that will be repeated but you can also give a specific time. Each user has their own "crontabs" which control what jobs are executed and when. The general format of a crontab is:

*     *     *     *     *  command to be executed
-     -     -     -     -
|     |     |     |     |
|     |     |     |     +----- day of week (0 - 6) (Sunday=0)
|     |     |     +------- month (1 - 12)
|     |     +--------- day of month (1 - 31)
|     +----------- hour (0 - 23)
+------------- min (0 - 59)

So, for example, this will run ls every day at 14:04:

04 14 * * * ls

To set up a cronjob for a specific date:

  1. Create a new crontab by running crontab -e. This will bring up a window of your favorite text editor.

  2. Add this line to the file that just opened. This particular example will run at 14:34 on the 15th of March 2014 if that day is a Friday (so, OK, it might run more than once):

    34 14 15 5  /path/to/command        
    
  3. Save the file and exit the editor.

This SO answer suggests a way to have it run only once but I have never used it so I can't vouch for it.

  • 2
    Scheduling a shutdown with cron is a really bad habit. Suddenly you will wonder why the server is down every Monday morning. – Ouki Mar 20 '14 at 2:12
  • 4
    @Ouki I-m sorry but I just don't see where I recommend using cron for shutdown. I mention in a parenthesis that it is possible (it is) but do not recommend it. We tend to like comprehensive answers here which is why I offered the other alternatives while never suggesting they should be used for shutdown. I feel for that bad experience though, that couldn't have been pleasant. – terdon Mar 20 '14 at 2:24
  • 2
    This is more about suggestion, as you are mixing shutdown scheduling and cron in the same answer... Whether it is a workstation or a 1000 users mail server (my sad experience) is more about the consequences of a bad habit. – Ouki Mar 20 '14 at 2:39
  • 3
    I'm with Ouki here. When discussing shutdown, one should not include cron. (esp. with someone who won't know why that's a horrible idea.) – Ricky Beam Mar 20 '14 at 2:57
  • 2
    I'm a little confused that this answer seems to lead with information already assumed by the question. It looks like the OP knows how to specify a time for shutdown, but wants to know how to specify both a date and a time. That is addressed in this answer, but it's provided as if it's extra information, when it's what was being asked for in the first place. – Weeble Mar 21 '14 at 12:19
23

No you can't specify a date at the shutdown command but two alternatives exist:

1) The easiest is to use the at command. The following example will execute shutdown +5 at a specific time and day:

echo "shutdown +5" | at 10:05am 2019-01-19

2) if you don't mind using you calculator and want to shutdown in say 24hours (24*60=1440 minutes) and you're absolutely sure the system will not reboot in between:

shutdown -r +1440
  • 2
    The reason for my answer above: terdon's answer is correct and very comprehensive but too chatty (IMHO at least) – ndemou Dec 23 '14 at 11:18
  • 2
    If by chatty you mean helpful and comprehensive... Your answer didn't even explain the at command . – Anthony Nov 14 '16 at 18:37
  • @Anthony I believe this way of using at deserves no explanation. I can see you believe otherwise. Different minds, different views. – ndemou Nov 15 '16 at 7:41
  • This answer is no longer true. The van Smoorenburg, Upstart, and systemd shutdown commands do not allow a date specification. But the nosh toolset's shutdown does, supporting the long-standing BSD syntax. – JdeBP Jan 7 at 14:35
  • @JdeBP: what alternative of the two do you believe is no longer true and have you tested and verified they are not? I've just tested both commands in 3 systems (Ubuntu 18.04,16.04 & CentOS 7) and they worked fine. Regarding the rest of your comment ("The van Smoorenburg...") I'm not sure if it's a clarification of your statement that this answer is no longer true or a general comment. Maybe you should post an answer with a bit more information. – ndemou Jan 8 at 9:22
6

It will shutdown your system at 12:00 :

$ sudo shutdown -h 12:00

Options:

-h, -P, --poweroff

Power-off the machine.

-r, --reboot

Reboot the machine.

-c

Cancel a pending shutdown.

  • 5
    Your method not showing how to shutdown on a specific date... – Askar Mar 26 '14 at 1:21

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