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docs:guide-user:base-system:cron [2020/10/04 03:26] – [Introduction] correct vgaeteradocs:guide-user:base-system:cron [2023/08/08 11:30] – Added my cronjob to keep last N snapshots of config torxgewinde
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-====== Scheduled tasks ======+====== Scheduling tasks with cron ======
 {{section>meta:infobox:howto_links#basic_skills&noheader&nofooter&noeditbutton}} {{section>meta:infobox:howto_links#basic_skills&noheader&nofooter&noeditbutton}}
  
 ===== Introduction ===== ===== Introduction =====
-  * OpenWrt allows to run jobs (programs, scripts) at specified times using [[wp>Cron|cron]] service+  * OpenWrt can run scheduled tasks using [[wp>Cron|cron]] service. 
-  * The cron implementation is provided by BusyBox and its functionality may be limited+  * This how-to describes the method for setting up cron jobs
-  * This how-to describes the methods for setting up cron jobs.+  * See also [[docs:guide-user:advanced:watchcat|Watchcat]] to reboot based on schedule or connectivity.
  
-===== Web interface ===== +===== Goals ===== 
-Manage cron jobs using web interface. +  * Run programs or scripts at a specific time. 
-  - Navigate to **[[http://openwrt.lan/|LuCI]] -> System -> Scheduled Tasks**.+  * Automate scheduled task management. 
 + 
 +===== Web interface instructions ===== 
 +Set up cron jobs using web interface. 
 +  - Navigate to **LuCI -> System -> Scheduled Tasks**.
   - Edit the configuration and click the **Save** button.   - Edit the configuration and click the **Save** button.
  
-===== Command-line interface ===== +===== Command-line instructions ===== 
-Manage cron jobs using command-line interface.+Set up cron jobs using command-line interface.
  
 <code bash>  <code bash> 
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 This will edit the configuraion ''/etc/crontabs/root'' file in [[docs:guide-user:base-system:user.beginner.cli#editing_files|vi editor]]. This will edit the configuraion ''/etc/crontabs/root'' file in [[docs:guide-user:base-system:user.beginner.cli#editing_files|vi editor]].
  
-:!: There should be a end-of-line character on the last line of the crontab file.+:!: There should be a EOL character on the last line of the crontab file.
 Just leave an empty line at the end to be sure. Just leave an empty line at the end to be sure.
  
 ===== Task specification ===== ===== Task specification =====
 Each line is a separate task written in the specification: Each line is a separate task written in the specification:
 +
 <code> <code>
 * * * * * command to execute * * * * * command to execute
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 Examples of time specification: Examples of time specification:
-  + 
-^  min\\ 0-59  ^  hour\\ 0-23  ^  day/month\\ 1-31  ^  month\\ 1-12  ^  day/week\\ 0-6 ^ Description ^ +^  min\\ 0-59  ^  hour\\ 0-23  ^  day/month\\ 1-31  ^  month\\ 1-12  ^  day/week\\ 0-6  ^ Description ^ 
-  */5                         | Every 5 minutes | + */5          | Every 5 minutes | 
-  12      */3  |                  | Every 3 hours at 12 minutes | + 12   */3  |       | Every 3 hours at 12 minutes | 
-  57      11       15    | 1,6,12 |     | At 11:57 Hrs  on 15th of Jan, June & Dec | + 57   11   15  | 1,6,12 |   | At 11:57 Hrs on 15th of Jan, June & Dec | 
-  25                      |  1-5  | At 6:25 AM every weekday (Mon-Fri) | + 25        |  1-5  | At 6:25 AM every weekday (Mon-Fri) | 
-           |  4,12,26          | At midnight on 4th, 12th and 26th of every month | +    |  4,12,26     | At midnight on 4th, 12th and 26th of every month | 
-|  5,10   |  9,14  |    10          |  0,4  | At 9:05AM, 9:10AM, 2:05PM and 2:10PM every Sunday and Thursday |+|  5,10  |  9,14  |  10    |  0,4  | At 9:05AM, 9:10AM, 2:05PM and 2:10PM every Sunday and Thursday |
  
 :!: 0 (zero) is treated as Sunday. :!: 0 (zero) is treated as Sunday.
-If you set the day of the week to 7, busybox will go bonkers and run your command every day.+If you set the day of the week to 7, BusyBox will go bonkers and run your command every day
 + 
 +**Table of shortcuts:** 
 + 
 +^ Shortcut ^ Equivalent ^ Description ^ 
 +| ''@yearly'' | ''0 0 1 1 *'' | Every year | 
 +| ''@annually'' | ''0 0 1 1 *'' | Every year | 
 +| ''@monthly'' | ''0 0 1 * *'' | Every month | 
 +| ''@weekly'' | ''0 0 * * 0'' | Every week | 
 +| ''@daily'' | ''0 0 * * *'' | Every day | 
 +| ''@midnight'' | ''0 0 * * *'' | Every day | 
 +| ''@hourly'' | ''0 * * * *'' | Every hour | 
 + 
 +:!:  Time shortcuts are not enabled by default. Shortcuts require compiling busybox with FEATURE_CROND_SPECIAL_TIMES enabled in the busybox compile options.
  
 ===== Troubleshooting ===== ===== Troubleshooting =====
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 </code> </code>
  
-Not all messages are logged, to increase logging change ''cronloglevel'' property in [[docs:guide-user:base-system:system_configuration|/etc/config/system]].+Not all messages are logged, to increase logging change ''[[docs:guide-user:base-system:system_configuration|cronloglevel]]'' option.
  
 ===== Extras ===== ===== Extras =====
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   * [[man>crontab(1)]], [[man>crontab(5)]]   * [[man>crontab(1)]], [[man>crontab(5)]]
   * [[https://busybox.net/downloads/BusyBox.html#crontab|BusyBox crontab]]   * [[https://busybox.net/downloads/BusyBox.html#crontab|BusyBox crontab]]
-  * [[http://adminschoice.com/crontab-quick-reference|Crontab – Quick Reference]]+  * [[http://adminschoice.com/crontab-quick-reference|Crontab quick reference]]
  
 ==== Periodic reboot ==== ==== Periodic reboot ====
-A simple solution for some hard-to-solve problems (memory leak, performance degradation, ...) is to reboot the router periodically, for instance every night.+A simple workaround for some hard-to-solve problems (memory leak, performance degradation, ...) is to reboot the router periodically, for instance every night.
  
 However, this is not as simple as it seems, because the router usually does not have a real-time clock. However, this is not as simple as it seems, because the router usually does not have a real-time clock.
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 So, in the boot process the clock gets set backwards a few seconds to that file's timestamp. So, in the boot process the clock gets set backwards a few seconds to that file's timestamp.
 Then cron starts and notices a few seconds later that the required boot moment has again arrived and reboots again... Then cron starts and notices a few seconds later that the required boot moment has again arrived and reboots again...
-(At the end of the boot process ntpd starts, and it may also take a while before ntpd gets and sets the correct time, so cron may start the reboot in between.)+At the end of the boot process ntpd starts, and it may also take a while before ntpd gets and sets the correct time, so cron may start the reboot in between.
  
 One solution for cron is to use a delay and touch a file in ''/etc'' before reboot. One solution for cron is to use a delay and touch a file in ''/etc'' before reboot.
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 There is usually no programmable circuitry to actually power off the unit. There is usually no programmable circuitry to actually power off the unit.
 ''reboot'' does work, in case you should want to reboot the router periodically. ''reboot'' does work, in case you should want to reboot the router periodically.
- 
-However, a more flexible approach is to use use the [[packages:pkgdata:watchcat|watchcat]] package. 
- 
-<code bash> 
-opkg update 
-opkg install watchcat luci-app-watchcat 
-</code> 
  
 ==== Periodic network restart ==== ==== Periodic network restart ====
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 ==== Alarm clock ==== ==== Alarm clock ====
-If you have [[wp>Daylight saving time]] you could write yourself a nice alarm clock ;-)+If you have [[wp>Daylight saving time|DST]] you could write yourself a nice alarm clock.
 When DST starts in central Europe, clocks advance from 02:00 CET to 03:00 CEST on last Sunday in March. When DST starts in central Europe, clocks advance from 02:00 CET to 03:00 CEST on last Sunday in March.
-Six day before that, you could make your WOL wake you 10 minutes earlier. +Six day before that, you could make your WoL wake you 10 minutes earlier. 
-Later won't work, you'll be late ;-)+Later won't work, you'll be late.
 When DST ends in central Europe, clocks retreat from 03:00 CEST to 02:00 CET on last Sunday in October. When DST ends in central Europe, clocks retreat from 03:00 CEST to 02:00 CET on last Sunday in October.
  
 <code bash> <code bash>
-#min hour day month dayofweek command +# min hour day month dayofweek command 
-59 05 * * 1 /usr/bin/wol -h 192.168.1.255 xx:xx:xx:xx:xx:xx # Mo +59 05 * * 1 /usr/bin/wol -h 192.168.1.255 xx:xx:xx:xx:xx:xx 
-#crontab must (as fstab) end with the last line as space or a comment+# crontab must end with the last line as space or a comment 
 +</code> 
 + 
 +==== Keep number of configs / snapshots of config ==== 
 +To keep a number N of configurations/settings at the directory "/root", you can also use cron. This way you can access and restore configurations of the past 100 days. The cronjob can easily be extended to copy the config to another device, to be able to replicate a broken OpenWRT device from scratch. 
 + 
 +<code bash> 
 +#Make a new backup/configurations snapshot at nighttime 00:01 am, keep last N=100 snapshots 
 +#01 00 * * * sysupgrade -b "/root/backup-${HOSTNAME}.tar.gz" # <-- keep just one config 
 +01 00 * * * find "/root" -type f -name "backup-*.tar.gz" | sort -r | awk 'NR > 100' | xargs rm -f; sysupgrade -b "/root/backup-${HOSTNAME}-$(date +\%Y-\%m-\%d-\%H-\%M-\%S).tar.gz"
 </code> </code>
  
  • Last modified: 2023/10/14 06:55
  • by vgaetera