Cron - Revision history

Hazardchem: /* Configuration */ Add notes about busybox-suid

2026-04-09T03:13:53Z

Configuration: Add notes about busybox-suid

← Older revision		Revision as of 03:13, 9 April 2026
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	{{Note\|Whenever an alternative cron implementation is used, ensure that the {{ic\|crond}} service is stopped and removed from [[OpenRC]] as follows:{{Cmd\|<nowiki># rc-service crond stop		{{Note\|Whenever an alternative cron implementation is used, ensure that the {{ic\|crond}} service is stopped and removed from [[OpenRC]] as follows:{{Cmd\|<nowiki># rc-service crond stop
	# rc-update del crond </nowiki>}} }}		# rc-update del crond </nowiki>}} }}

			{{Note\|If editing crotab and getting suid issues, ensure that {{ic\|busybox-suid}} is installed and might need updating with:{{Cmd\|<nowiki># apk add --update busybox-suid </nowiki>}} }}

	== Asynchronous job processing ==		== Asynchronous job processing ==

Prabuanand: clarified on dcron feature compared to cronie

2025-10-10T06:45:56Z

clarified on dcron feature compared to cronie

← Older revision		Revision as of 06:45, 10 October 2025
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	== Asynchronous job processing ==		== Asynchronous job processing ==

	For systems that do not run continuously, like laptops or regular desktop computers, cron jobs with large time intervals between invocations may not be executed at all if the system is suspended or powered off during the cron job's scheduled time. To work around this, ~~many <code>crond</code> implementations provide~~ special directives like <code>@daily</code> and <code>@monthly</code> ~~which~~ keep track of the last execution time and still execute if the system was down while the job was supposed to run.		For systems that do not run continuously, like laptops or regular desktop computers, cron jobs with large time intervals between invocations may not be executed at all if the system is suspended or powered off during the cron job's scheduled time. To work around this, [[#Cronie\|Cronie]] provides {{ic\|anacron}}. However, in [[#dcron\|dcron]] special directives like <code>@daily</code> and <code>@monthly</code> keep track of the last execution time and still execute if the system was down while the job was supposed to run.

	== Cronie ==		== Cronie ==
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	== See also ==		== See also ==

	* [https://github.com/cronie-crond/cronie Official cronie website]		* [https://github.com/cronie-crond/cronie Official cronie website]
	* [https://www.jimpryor.net/linux/dcron.html Official dcron website]		* [https://www.jimpryor.net/linux/dcron.html Official dcron website]

Prabuanand: updated based on email thread https://lists.alpinelinux.org/~alpine/users/%3C9e46853a-fcdd-5673-d243-65c244026117%40web.de%3E

2025-08-31T03:14:37Z

updated based on email thread https://lists.alpinelinux.org/~alpine/users/%3C9e46853a-fcdd-5673-d243-65c244026117%40web.de%3E

← Older revision		Revision as of 03:14, 31 August 2025
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	== Busybox crond ==		== Busybox crond ==

	{{ic\|crond}} is the builtin cron implementation from [[BusyBox]].		{{ic\|crond}} is the builtin cron implementation from [[BusyBox]]. Since Busybox follows only [https://pubs.opengroup.org/onlinepubs/9799919799/utilities/crontab.html POSIX] standard, only "0" is supported for Sunday. It does not understand "7" as a valid day of the week.

	=== Configuration ===		=== Configuration ===

Prabuanand: removed :Category:Desktop as per Help_talk:Style

2025-05-25T15:45:31Z

removed Category:Desktop as per Help_talk:Style

← Older revision		Revision as of 15:45, 25 May 2025
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	* [https://crontab.guru/ crontab Generator]		* [https://crontab.guru/ crontab Generator]
	* [https://wiki.archlinux.org/title/Cron Archwiki Cron page]		* [https://wiki.archlinux.org/title/Cron Archwiki Cron page]

	[[Category:System Administration‏‎ ]]		[[Category:System Administration‏‎ ]]
	~~[[Category:Desktop]]~~

Prabuanand: added verification steps from Setting up ZFS with native encryption page

2025-04-02T09:45:04Z

added verification steps from Setting up ZFS with native encryption page

← Older revision		Revision as of 09:45, 2 April 2025
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	This page documents the working of [https://en.wikipedia.org/wiki/Cron Cron], a job scheduler on Unix-like operating systems. Cron is most suitable for scheduling repetitive tasks. Scheduling one-time tasks can be accomplished using the associated at utility.		This page documents the working of [https://en.wikipedia.org/wiki/Cron Cron], a job scheduler on Unix-like operating systems. Cron is most suitable for scheduling repetitive tasks. Scheduling one-time tasks can be accomplished using the associated at utility.
	There are many cron implementations, but Alpine Linux comes inbuilt with the [[BusyBox]] version of cron. Some of the other packages available in Alpine Linux are {{Pkg\|cronie}}, {{Pkg\|fcron}} and {{Pkg\|dcron}}.		There are many cron implementations, but Alpine Linux comes inbuilt with the [[BusyBox]] version of cron. Some of the other packages available in Alpine Linux are {{Pkg\|cronie}}, {{Pkg\|fcron}} and {{Pkg\|dcron}}.

	{{Note\|Whenever an alternative cron implementation is used, ensure that the default <code>crond</code> from [[BusyBox]] is stopped and removed from [[OpenRC]] as follows:{{Cmd\|<nowiki># rc-service crond stop
	~~# rc-update del crond </nowiki>}}}}~~

	== Basic example ==		== Basic example ==
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	This script queries the uk time server pool - modify this to suit your location, or just use pool.ntp.org. Refer for [https://www.pool.ntp.org/zone/@ more info].		This script queries the uk time server pool - modify this to suit your location, or just use pool.ntp.org. Refer for [https://www.pool.ntp.org/zone/@ more info].

			To check whether any {{ic\|cron}} service is running, verify the output for the command : {{cmd\|<nowiki># rc-update \|grep cron
			crond \| default </nowiki>}}

			== Busybox crond ==

			{{ic\|crond}} is the builtin cron implementation from [[BusyBox]].

			=== Configuration ===

			The {{ic\|crond}} service from [[BusyBox]] is managed by [[OpenRC]].

			To immediately start, stop and restart the {{ic\|crond}} service: {{cmd\|# rc-service crond start}}

			To add {{ic\|crond}} service to the boot sequence: {{cmd\|# rc-update add crond}}

			{{Note\|Whenever an alternative cron implementation is used, ensure that the {{ic\|crond}} service is stopped and removed from [[OpenRC]] as follows:{{Cmd\|<nowiki># rc-service crond stop
			# rc-update del crond </nowiki>}} }}

	== Asynchronous job processing ==		== Asynchronous job processing ==

	For systems that do not run continuously, like laptops or regular desktop computers, cron jobs with large time intervals between invocations may not be executed at all if the system is suspended or powered off during the cron job's scheduled time. To work around this, many <code>crond</code> implementations provide special directives like <code>@daily</code> and <code>@monthly</code> which keep track of the last execution time and still execute if the system was down while the job was supposed to run~~. Examples of how to achieve this in different <code>crond</code> implementations can be found in this page~~.		For systems that do not run continuously, like laptops or regular desktop computers, cron jobs with large time intervals between invocations may not be executed at all if the system is suspended or powered off during the cron job's scheduled time. To work around this, many <code>crond</code> implementations provide special directives like <code>@daily</code> and <code>@monthly</code> which keep track of the last execution time and still execute if the system was down while the job was supposed to run.

	== Cronie ==		== Cronie ==

Prabuanand: added instruction about making the file executable

2025-03-22T09:37:46Z

added instruction about making the file executable

← Older revision		Revision as of 09:37, 22 March 2025
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	The below example uses a cron job to keep the time in sync. This example works with all versions of cron including the [[BusyBox]] version of cron. Add the following file or a symlink to {{Path\|/etc/periodic/daily}} folder or use another folder under the {{Path\|/etc/periodic/}} hierarchy if you want to run the script more/less frequently.		The below example uses a cron job to keep the time in sync. This example works with all versions of cron including the [[BusyBox]] version of cron. Add the following file or a symlink to {{Path\|/etc/periodic/daily}} folder or use another folder under the {{Path\|/etc/periodic/}} hierarchy if you want to run the script more/less frequently.

	Create ~~an example~~ script file ~~called~~ {{Path\|/etc/periodic/daily/do-ntp}} as follows:{{Cat\|/etc/periodic/daily/do-ntp\|<nowiki>#!/bin/sh		Create a script file {{Path\|/etc/periodic/daily/do-ntp}} as follows:{{Cat\|/etc/periodic/daily/do-ntp\|<nowiki>#!/bin/sh
	ntpd -d -q -n -p uk.pool.ntp.org</nowiki>}}		ntpd -d -q -n -p uk.pool.ntp.org</nowiki>}}
			Make the script file executable:{{Cmd\|# chmod +x /etc/periodic/daily/do-ntp}}

	This script queries the uk time server pool - modify this to suit your location, or just use pool.ntp.org. Refer for [https://www.pool.ntp.org/zone/@ more info].		This script queries the uk time server pool - modify this to suit your location, or just use pool.ntp.org. Refer for [https://www.pool.ntp.org/zone/@ more info].

Prabuanand: rephrased sentence and changed headings to make the page consistent

2025-03-22T09:15:59Z

rephrased sentence and changed headings to make the page consistent

← Older revision		Revision as of 09:15, 22 March 2025
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	== Cronie ==		== Cronie ==

	The {{Pkg\|cronie}} package comes with <code>anacron</Code> tool~~, which does this kind of~~ [[#Asynchronous job processing\|asynchronous job processing]]. To use it, first install the {{Pkg\|cronie}} package: {{Cmd\|# apk add {{Pkg\|cronie}}}}		The {{Pkg\|cronie}} package comes with <code>anacron</Code> tool for [[#Asynchronous job processing\|asynchronous job processing]]. To use it, first install the {{Pkg\|cronie}} package: {{Cmd\|# apk add {{Pkg\|cronie}}}}

	Finally, start {{Pkg\|cronie}} and tell [[OpenRC]] to start it at boot:{{Cmd\|<nowiki>		Finally, start {{Pkg\|cronie}} and tell [[OpenRC]] to start it at boot:{{Cmd\|<nowiki>
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	</nowiki>}}		</nowiki>}}

	=== ~~Anacron configuration~~ ===		=== Configuration ===

	Here are the steps to use <code>anacron</Code> in Alpine Linux:		Here are the steps to use <code>anacron</Code> tool from cronie in Alpine Linux.

	# Add the line {{Codeline\|<code>@reboot /usr/sbin/anacron -s</code>}} to the crontab of the '''root''' user:		# Add the line {{Codeline\|<code>@reboot /usr/sbin/anacron -s</code>}} to the crontab of the '''root''' user:
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	# Edit the configuration file {{Path\|/etc/anacrontab}} where jobs are listed as per the above crontab syntax, and test the configuration validity by <Code>anacron -T</Code>.		# Edit the configuration file {{Path\|/etc/anacrontab}} where jobs are listed as per the above crontab syntax, and test the configuration validity by <Code>anacron -T</Code>.
	# Reboot the computer to test the working of anacron. The syslog file {{Path\|/var/log/messages}} captures messages from anacron and can be searched by <Code>cat /var/log/messages \|grep anacron</Code>.		# Reboot the computer to test the working of anacron. The syslog file {{Path\|/var/log/messages}} captures messages from anacron and can be searched by <Code>cat /var/log/messages \|grep anacron</Code>.
			For more information about {{Pkg\|cronie}}'s options and its <code>anacrontab</code> format, check out the <code>anacrontab(5)</code>, <code>anacron(8)</code> and <code>crond(8)</code> manpages, which you can install with the {{Pkg\|cronie-doc}} package.

	== dcron ==		== dcron ==
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	As you can see, the name or "ID" of a job is set in the style of a shell variable assignment. For more information about {{Pkg\|dcron}}'s options and its <code>crontab</code> format, check out the <code>crontab(1)</code> and <code>crond(8)</code> manpages, which you can install with the {{Pkg\|dcron-doc}} package.		As you can see, the name or "ID" of a job is set in the style of a shell variable assignment. For more information about {{Pkg\|dcron}}'s options and its <code>crontab</code> format, check out the <code>crontab(1)</code> and <code>crond(8)</code> manpages, which you can install with the {{Pkg\|dcron-doc}} package.

	== See ~~Also~~ ==		== See also ==
	* [https://wiki.archlinux.org/title/Cron Archwiki Cron page]
	* [https://github.com/cronie-crond/cronie Official cronie website]		* [https://github.com/cronie-crond/cronie Official cronie website]
	* [https://www.jimpryor.net/linux/dcron.html Official dcron website]		* [https://www.jimpryor.net/linux/dcron.html Official dcron website]
	* [https://crontab.guru/ crontab Generator]		* [https://crontab.guru/ crontab Generator]
			* [https://wiki.archlinux.org/title/Cron Archwiki Cron page]
	[[Category:System Administration‏‎ ]]		[[Category:System Administration‏‎ ]]
	[[Category:Desktop]]		[[Category:Desktop]]

Prabuanand: moved content from Alpine_Linux:FAQ#Using_a_cron_job_to_keep_the_time_in_sync

2025-03-22T08:56:49Z

moved content from Alpine_Linux:FAQ#Using_a_cron_job_to_keep_the_time_in_sync

← Older revision		Revision as of 08:56, 22 March 2025
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	There are many cron implementations, but Alpine Linux comes inbuilt with the [[BusyBox]] version of cron. Some of the other packages available in Alpine Linux are {{Pkg\|cronie}}, {{Pkg\|fcron}} and {{Pkg\|dcron}}.		There are many cron implementations, but Alpine Linux comes inbuilt with the [[BusyBox]] version of cron. Some of the other packages available in Alpine Linux are {{Pkg\|cronie}}, {{Pkg\|fcron}} and {{Pkg\|dcron}}.

	~~For systems that do not run continuously, like laptops or regular desktop computers,~~ cron ~~jobs with large time intervals between invocations may not be executed at all if the system~~ is ~~suspended or powered off during~~ the ~~cron job's scheduled time. To work around this, many~~ <code>crond</code> ~~implementations provide special directives like <code>@daily</code>~~ and <~~code~~>~~@monthly~~</~~code~~> ~~which keep track of the last execution time and still execute if the system was down while the job was supposed to run.~~		{{Note\|Whenever an alternative cron implementation is used, ensure that the default <code>crond</code> from [[BusyBox]] is stopped and removed from [[OpenRC]] as follows:{{Cmd\|<nowiki># rc-service crond stop
			# rc-update del crond </nowiki>}}}}

	~~Examples of how to achieve this in different <code>crond</code> implementations can be found below.~~		== Basic example ==

	~~{{Note\|Whenever an alternative~~ cron ~~implementation is used, ensure that~~ the ~~default <code>crond</code> from~~ [[BusyBox]] ~~is stopped and removed from [[OpenRC]]~~ as follows:{{~~Cmd~~\|<nowiki># rc-~~service crond stop~~		The below example uses a cron job to keep the time in sync. This example works with all versions of cron including the [[BusyBox]] version of cron. Add the following file or a symlink to {{Path\|/etc/periodic/daily}} folder or use another folder under the {{Path\|/etc/periodic/}} hierarchy if you want to run the script more/less frequently.
	~~# rc~~-~~update del crond~~ </nowiki>}}}}
			Create an example script file called {{Path\|/etc/periodic/daily/do-ntp}} as follows:{{Cat\|/etc/periodic/daily/do-ntp\|<nowiki>#!/bin/sh
			ntpd -d -q -n -p uk.pool.ntp.org</nowiki>}}

			This script queries the uk time server pool - modify this to suit your location, or just use pool.ntp.org. Refer for [https://www.pool.ntp.org/zone/@ more info].

			== Asynchronous job processing ==

			For systems that do not run continuously, like laptops or regular desktop computers, cron jobs with large time intervals between invocations may not be executed at all if the system is suspended or powered off during the cron job's scheduled time. To work around this, many <code>crond</code> implementations provide special directives like <code>@daily</code> and <code>@monthly</code> which keep track of the last execution time and still execute if the system was down while the job was supposed to run. Examples of how to achieve this in different <code>crond</code> implementations can be found in this page.

	== Cronie ==		== Cronie ==

	The {{Pkg\|cronie}} package comes with <code>anacron</Code> tool, which does this kind of asynchronous job processing. To use it, first install the {{Pkg\|cronie}} package and ~~configure it start at boot using~~ [[OpenRC]].		The {{Pkg\|cronie}} package comes with <code>anacron</Code> tool, which does this kind of [[#Asynchronous job processing\|asynchronous job processing]]. To use it, first install the {{Pkg\|cronie}} package: {{Cmd\|# apk add {{Pkg\|cronie}}}}

			Finally, start {{Pkg\|cronie}} and tell [[OpenRC]] to start it at boot:{{Cmd\|<nowiki>
			# rc-service cronie start
			# rc-update add cronie
			</nowiki>}}

	=== Anacron ===		=== Anacron configuration ===

	Here are the steps to use <code>anacron</Code> in Alpine Linux:		Here are the steps to use <code>anacron</Code> in Alpine Linux:
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	# Anacron needs the folder {{Path\|/var/spool/anacron}} to avoid the error {{Codeline\|cron.err anacron[2893]: Can't chdir to /var/spool/anacron: No such file or directory}}. So create the folder using the command:		# Anacron needs the folder {{Path\|/var/spool/anacron}} to avoid the error {{Codeline\|cron.err anacron[2893]: Can't chdir to /var/spool/anacron: No such file or directory}}. So create the folder using the command:
	#: {{Cmd\|# mkdir /var/spool/anacron}}		#: {{Cmd\|# mkdir /var/spool/anacron}}
	# Edit the configuration file {{Path\|/etc/anacrontab}} and test the configuration validity by <Code>anacron -T</Code>.		# Edit the configuration file {{Path\|/etc/anacrontab}} where jobs are listed as per the above crontab syntax, and test the configuration validity by <Code>anacron -T</Code>.
	# Reboot the computer to test the working of anacron. The syslog file {{Path\|/var/log/messages}} captures messages from anacron and can be searched by <Code>cat /var/log/messages \|grep anacron</Code>.		# Reboot the computer to test the working of anacron. The syslog file {{Path\|/var/log/messages}} captures messages from anacron and can be searched by <Code>cat /var/log/messages \|grep anacron</Code>.

Prabuanand: added wikitags and moved note about stopping busybox cron to introduction section

2025-02-15T01:36:59Z

added wikitags and moved note about stopping busybox cron to introduction section

← Older revision		Revision as of 01:36, 15 February 2025
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	Examples of how to achieve this in different <code>crond</code> implementations can be found below.		Examples of how to achieve this in different <code>crond</code> implementations can be found below.

			{{Note\|Whenever an alternative cron implementation is used, ensure that the default <code>crond</code> from [[BusyBox]] is stopped and removed from [[OpenRC]] as follows:{{Cmd\|<nowiki># rc-service crond stop
			# rc-update del crond </nowiki>}}}}

	== Cronie ==		== Cronie ==

	The {{Pkg\|cronie}} package comes with <code>anacron</Code> tool, which does this kind of asynchronous job processing.		The {{Pkg\|cronie}} package comes with <code>anacron</Code> tool, which does this kind of asynchronous job processing. To use it, first install the {{Pkg\|cronie}} package and configure it start at boot using [[OpenRC]].

	=== Anacron ===		=== Anacron ===
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	== dcron ==		== dcron ==

	Another available crond that fully integrates the features of <code>anacron</code> is {{Pkg\|dcron}}, "dillon's lightweight cron daemon". To use it, first install the {{Pkg\|dcron}} package:		Another available crond that fully integrates the features of <code>anacron</code> is {{Pkg\|dcron}}, "dillon's lightweight cron daemon". To use it, first install the {{Pkg\|dcron}} package:{{Cmd\|# apk add dcron}}

	# apk add ~~dcron~~

	~~Next, make sure that the default <code>crond</code> from [[BusyBox]] is stopped and removed from OpenRC:~~

	~~# rc-service crond stop~~
	~~# rc-update del crond~~

	~~Finally, start {{Pkg\|~~dcron}} ~~and tell OpenRC to start it at boot:~~

			Finally, start {{Pkg\|dcron}} and tell [[OpenRC]] to start it at boot:{{Cmd\|<nowiki>
	# rc-service dcron start		# rc-service dcron start
	# rc-update add dcron		# rc-update add dcron
			</nowiki>}}

	=== Configuration ===		=== Configuration ===

Unicorn at 20:09, 14 February 2025

2025-02-14T20:09:02Z

← Older revision		Revision as of 20:09, 14 February 2025
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	You can add directives to the crontab with the <code>crontab -e</code> command, also including the <code>@hourly</code>, <code>@daily</code>, <code>@weekly</code>, <code>@monthly</code> and <code>@yearly</code> directives.		You can add directives to the crontab with the <code>crontab -e</code> command, also including the <code>@hourly</code>, <code>@daily</code>, <code>@weekly</code>, <code>@monthly</code> and <code>@yearly</code> directives.

	The syntax of these special directives ~~differs~~ slightly differs from <code>anacron</code>. Here is how Alpine's default could be adjusted to use the {{Pkg\|dcron}} syntax with the special directives to ensure that they are executed even with systems that are not always running:		The syntax of these special directives slightly differs from <code>anacron</code>. Here is how Alpine's default could be adjusted to use the {{Pkg\|dcron}} syntax with the special directives to ensure that they are executed even with systems that are not always running:

	{{Cat\|/var/spool/cron/crontabs/root\|<nowiki># do daily/weekly/monthly maintenance		{{Cat\|/var/spool/cron/crontabs/root\|<nowiki># do daily/weekly/monthly maintenance