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I'm new in Linux and I want to schedule a reboot at midnight. How should I do it?

Edits:

  • I'm sorry I didn't put the complete details. I want a reboot every 3rd Saturday of the month at 23:30.

  • I don't know what's wrong but I cannot find crontab. What I have is cron.d; cron.daily; cron.weekly; cron.monthly;

I'm sorry for the noob question. Pls help me. Thanks.

Chris W.
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klauriens
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    Do you want it to reboot every night? – Matt Simmons Jun 27 '10 at 14:33
  • I'm sorry I didn.y put the complete details. I want a reboot every 3rd Saturday of the month at 23:30 – klauriens Jun 28 '10 at 17:08
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    /etc/crontab entry like 30 23 15-21 * 6 /sbin/shutdown -r now will reboot at 23:30 on the 3rd Saturday of every month. – Chris S Jun 28 '10 at 17:53
  • i dont know what's wrong but i cannot find the crontab..? what i have is the cron.d;cron.daily; cron.weekly; cron.monthly; I'm sorry for the noob question.Pls help me. thanks – klauriens Jun 30 '10 at 11:00
  • You don't need to edit a file for crontab, just use the command "crontab -e" as root and it will open a text editor for you. By "as root", we mean either type "su -" first and then enter the root password that was set up when the server was set up, or just type "sudo crontab -e" and enter your password. Which to use depends on your version of Linux. – Paul Kroon Jun 30 '10 at 11:13
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    The real question is why you'd want to be doing this regularly, do you have a leaky application or something? If you're scheduling regular reboots to solve a problem then you've probably got a bigger problem... – JamesHannah Jun 27 '10 at 14:05
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    I'm not voting down, because it's sort of a policy decision (and I think nightly reboots are a bit excessive), but regularly scheduling reboots across an infrastructure are a decent way of ensuring that machines have up to date kernels and all services running are patched. I've heard a 3 month uptime limit as being a good middle ground. – Matt Simmons Jun 27 '10 at 14:37
  • If this was a comment on the question, rather than an answer, I would upvote it. Actually I would change my mind, because the question was ambiguous about whether this was a one-time or regular thing. :) – intuited Jun 27 '10 at 14:37
  • @Matt Simmons: so you don't keep track of the patches you apply and reboot when its required? – symcbean Jun 27 '10 at 15:14
  • @symcbean - Sure, but if you reboot everything at the same time, then...well, you lose service availability AND it's chaos. I can see advancing the schedule because of a critical vulnerability, but every small kernel upgrade doesn't mean "install-it-now-or-dire-circumstances-ensue". – Matt Simmons Jun 28 '10 at 01:29
  • @Matt Simmons: If you can't reboot a server without losing service, then you've got architecture problems you really should fix. – symcbean Jun 28 '10 at 11:34
  • symcbean: Yes, however if you do updates and reboots across the board, all at once, you lose service because the other members of the service group go down too. I think we're arguing about the same thing ;-) – Matt Simmons Jun 28 '10 at 11:40
  • First, check to see what time it is on the system you want to reboot, using the date command. Is its clock in sync with your local time? If not, you may want to take that into consideration. – LonnieBest Sep 28 '21 at 09:42

6 Answers6

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Type shutdown -r 0:00 and it will reboot at midnight.

If you want to reboot each night, add a cron entry using crontab -e as root to run shutdown -r each midnight

@midnight shutdown -r now
Eric Fossum
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radius
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Another option is the at command, available on many Linux distributions. See the man page for more info, but the general syntax for your purpose would be:

echo "reboot" | at 0000 jun 27

To quote the OS X man page:

at - executes commands at a specified time

Sound like what we're talking about. ;)

sorin
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Zayne S Halsall
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Using crontab.

http://en.wikipedia.org/wiki/Crontab

Adding this entry to /etc/crontab should do:

0 0 * * * /sbin/shutdown -r now
radius
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Massimo
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    shutdown needs a time argument such as now – Dennis Williamson Jun 27 '10 at 13:19
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    This will do the reboot every night. I am not sure if this is what he wants. – cstamas Jun 27 '10 at 14:39
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    The original question made it sound like he wanted it rebooted every night. He actually wants it rebooted every 3rd Saturday, which would still be easiest with a crontab – Chris S Jun 28 '10 at 17:51
  • i dont know what's wrong but i cannot find the crontab..? what i have is the cron.d;cron.daily; cron.weekly; cron.monthly; I'm sorry for the noob question.Pls help me. thanks – klauriens Jun 30 '10 at 11:00
  • It depends on the distribution you're using, but usually you should find a file called "crontab" in your system's /etc directory. You should also be able to examine the current crontab using the command "crontab -l", and to edit it using "crontab -e". – Massimo Jun 30 '10 at 13:12
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As far as I know, you cannot use cron to schedule tasks for "last Friday of each month" or "third Thursday in each month". What you can do, however ugly it seems, is to have a script run every Saturday at 23:30 and then have this script determine if this particular Saturday is the third Saturday of the week (can be done using date and maybe cal commands).

I hope this helps. I have not found an elagant solution to this problem. I found this thread, because I was searching for a solution for the same problem.

ervingsb
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    the comments above of "30 23 15-21 * 6 /sbin/shutdown -r now" will work. It'll basically only run on the third week of the month, but only when it's also saturday – Sirex Mar 06 '12 at 14:47
  • I do not think this cron line works as you think it does. – ervingsb Mar 08 '12 at 09:36
  • I created the following two lines: "30 23 1-7 * 4 date" and "30 23 1-7 * 3 date". I got two mails last night both saying: "Wed Mar 7 23:30:02 CET 2012" – ervingsb Mar 08 '12 at 09:37
  • the last field matches the day of the week, with zero being sunday. the 4 cronjob should not have matched on a wednesday. – Sirex Mar 09 '12 at 15:35
  • That is what I meant. The rule you wrote do not mean what you think it means. It will trigger the job every day for a week. No matter the weekday. – ervingsb Mar 09 '12 at 19:47
  • hmmm, appears you're right. that's pretty crappy isn't it ! – Sirex Mar 12 '12 at 10:00
  • Yeah. Very. So what to do about this? I can hardly imagine that Linux and Unix admins do not have this scheduling need. – ervingsb Mar 12 '12 at 13:56
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1) at the command line type which reboot
2) once you know where reboot is located (usually /sbin/reboot) cd into one of the the directories in /etc/cron.daily , /etc/cron.weekly , /etc/cron.hourly etc... ie cd /etc/cron.weekly

3) create a file (using nano or vim) call it zzreboot and add the following lines:

#!/bin/sh
/sbin/reboot

The reason you want to call the file zzwhatever is to make sure it's the last job called after all other jobs. To make sure just do an ls -l in the directory and verify it's the last file.

Shawn Bakhtiar
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I know this is an old question, still I would like to answer it. On your terminal logged in as root follow below steps:

  1. #crontab -e this would open the cron file to write your cron jobs
  2. add a new line like30 23 15-21 * sat /path/to/reboot. This cron job would reboot the system every 3rd sat of the month at 11.30 pm.
  3. save and exit
Sumeet Boga
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