[system-administrators-guide] Improvements from upstream version
stephenw
stephenw at fedoraproject.org
Tue Dec 9 22:33:49 UTC 2014
commit 9a9ac7d1cfa66cfc4a128df6a84899b8ec1684b6
Author: Stephen Wadeley <swadeley at redhat.com>
Date: Tue Dec 9 23:32:41 2014 +0100
Improvements from upstream version
en-US/Automating_System_Tasks.xml | 769 ++++++++++++++++++++++++++-----------
1 files changed, 535 insertions(+), 234 deletions(-)
---
diff --git a/en-US/Automating_System_Tasks.xml b/en-US/Automating_System_Tasks.xml
index 8891224..d9e6afc 100644
--- a/en-US/Automating_System_Tasks.xml
+++ b/en-US/Automating_System_Tasks.xml
@@ -3,65 +3,130 @@
]>
<chapter id="ch-Automating_System_Tasks">
<title>Automating System Tasks</title>
- <indexterm significance="normal">
+ <indexterm>
<primary>Automated Tasks</primary>
</indexterm>
- <para>In Linux, tasks, which are also known as <firstterm>jobs</firstterm>, can be configured to run automatically within a specified period of time, on a specified date, or when the system load average is below a specified number. &MAJOROS; is pre-configured to run important system tasks to keep the system updated. For example, the slocate database used by the <command>locate</command> command is updated daily. A system administrator can use automated tasks to perform periodic backups, monitor the system, run custom scripts, and more.</para>
- <para>&MAJOROS; comes with several automated tasks utilities: <command>cron</command>, <command>at</command>, and <command>batch</command>.</para>
- <indexterm significance="normal">
- <primary>Cron</primary>
- </indexterm>
+ <para>
+ Tasks, also known as <firstterm>jobs</firstterm>, can be configured to run automatically within a specified period of time, on a specified date, or when the system load average decreases below 0.8.
+ </para>
+ <para>
+ &MAJOROS; is pre-configured to run important system tasks to keep the system updated. For example, the <database>slocate</database> database used by the <command>locate</command> command is updated daily. A system administrator can use automated tasks to perform periodic backups, monitor the system, run custom scripts, and so on.
+ </para>
+ <para>
+ &MAJOROS; comes with the following automated task utilities: <command>cron</command>, <command>anacron</command>, <command>at</command>, and <command>batch</command>.
+ </para>
+ <para>
+ Every utility is intended for scheduling a different job type: while Cron and Anacron schedule recurring jobs, At and Batch schedule one-time jobs (refer to <xref linkend="s1-autotasks-cron-anacron" /> and <xref linkend="s1-autotasks-at-batch" /> respectively).
+ </para>
+ <para>
+ &MAJOROS; supports the use of <systemitem>systemd.timer</systemitem> for executing a job at a specific time. See man <filename>systemd.timer(5)</filename> for more information.
+ </para>
<section id="s1-autotasks-cron-anacron">
<title>Cron and Anacron</title>
- <indexterm significance="normal">
- <primary>anacron</primary>
- </indexterm>
- <indexterm significance="normal">
- <primary>
- <filename>cron</filename>
- </primary>
- </indexterm>
- <para>Both, Cron and Anacron, are daemons that can be used to schedule the execution of recurring tasks according to a combination of the time, day of the month, month, day of the week, and week.</para>
- <para>Cron assumes that the system is on continuously. If the system is not on when a job is scheduled, it is not executed. Cron allows jobs to be run as often as every minute. Anacron does not assume the system is always on, remembers every scheduled job, and executes it the next time the system is up. However, Anacron can only run a job once a day.
- To schedule recurring jobs, refer to <xref linkend="s2-configuring-anacron-jobs"/> or <xref linkend="s2-configuring-cron-jobs"/>. To schedule one-time jobs, refer to <xref linkend="s1-autotasks-at-batch"/>.</para>
- <para>To use the cron service, the <filename>cronie</filename> RPM package must be installed and the <command>crond</command> service must be running. <filename>anacron</filename> is a sub-package of <filename>cronie</filename>. To determine if these packages are installed, use the <command>rpm -q cronie cronie-anacron</command> command. </para>
- <section id="s2-autotasks-cron-service">
- <title>Starting and Stopping the Service</title>
- <para>To determine if the service is running, use the following command:</para>
- <screen><command>systemctl is-active crond.service</command></screen>
- <para>To start the cron service, type the following at a shell prompt as <systemitem class="username">root</systemitem>:</para>
- <screen><command>systemctl start crond.service</command></screen>
- <para>To stop the service, run the following command as <systemitem class="username">root</systemitem>:</para>
- <screen><command>systemctl stop crond.service</command></screen>
- <para>It is recommended that you start the service at boot time. To do so, use the following command as <systemitem class="username">root</systemitem>:</para>
- <screen><command>systemctl enable crond.service</command></screen>
- <para>
- See <xref linkend="ch-Services_and_Daemons" /> for more information on how to configure services in &MAJOROS;.
+ <indexterm>
+ <primary>anacron</primary>
+ </indexterm>
+ <indexterm>
+ <primary>cron</primary>
+ </indexterm>
+ <para>
+ Both Cron and Anacron are daemons that can schedule execution of recurring tasks to a certain point in time defined by the exact time, day of the month, month, day of the week, and week.
+ </para>
+ <para>
+ Cron jobs can run as often as every minute. However, the utility assumes that the system is running continuously and if the system is not on at the time when a job is scheduled, the job is not executed.
+ </para>
+ <para>
+ On the other hand, Anacron remembers the scheduled jobs if the system is not running at the time when the job is scheduled. The job is then executed as soon as the system is up. However, Anacron can only run a job once a day.
+ </para>
+ <section id="sect-Cron-Installing">
+ <title>Installing Cron and Anacron</title>
+ <para>
+ To install Cron and Anacron, you need to install the <package>cronie</package> package with Cron and the <package>cronie-anacron</package> package with Anacron (<package>cronie-anacron</package> is a sub-package of <package>cronie</package>).
+ </para>
+ <para>
+ To determine if the packages are already installed on your system, issue the following command:
+ </para>
+ <synopsis><command>rpm -q cronie cronie-anacron</command></synopsis>
+ <para>
+ The command returns full names of the <package>cronie</package> and <package>cronie-anacron</package> packages if already installed, or notifies you that the packages are not available.
+ </para>
+ <para>
+ To install these packages, use the <command>yum</command> command in the following form as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>yum install <replaceable>package</replaceable></command></synopsis>
+ <para>
+ For example, to install both Cron and Anacron, type the following at a shell prompt:
+ </para>
+ <screen>~]# <command>yum install cronie cronie-anacron</command></screen>
+ <para>
+ For more information on how to install new packages in &MAJOROS;, see <xref linkend="sec-Installing" />.
+ </para>
+ </section>
+ <section id="sect-Cron-Running">
+ <title>Running the Crond Service</title>
+ <para>
+ The cron and anacron jobs are both picked by the <systemitem class="daemon">crond</systemitem> service. This section provides information on how to start, stop, and restart the <systemitem class="service">crond</systemitem> service, and shows how to configure it to start automatically at boot time. <!--For more information on how to manage system service in &MAJOROSVER; in general, see <xref linkend="chap-Managing_Services_with_systemd" />.-->
</para>
+ <section id="sect-Cron-service">
+ <title>Starting and Stopping the Cron Service</title>
+ <para>
+ To determine if the service is running, use the following command:
+ </para>
+ <synopsis><command>systemctl status crond.service</command></synopsis>
+ <para>
+ To run the <systemitem class="service">crond</systemitem> service in the current session, type the following at a shell prompt as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl start crond.service</command></synopsis>
+ <para>
+ To configure the service to start automatically at boot time, use the following command as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl enable crond.service</command></synopsis>
+ </section>
+ <section id="sect-Crond_Stopping">
+ <title>Stopping the Cron Service</title>
+ <para>
+ To stop the <systemitem class="service">crond</systemitem> service in the current session, type the following at a shell prompt as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl stop crond.service</command></synopsis>
+ <para>
+ To prevent the service from starting automatically at boot time, use the following command as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl disable crond.service</command></synopsis>
+ </section>
+ <section id="sect-Crond_Restarting">
+ <title>Restarting the Cron Service</title>
+ <para>
+ To restart the <systemitem class="service">crond</systemitem> service, type the following at a shell prompt as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl restart crond.service</command></synopsis>
+ <para>
+ This command stops the service and starts it again in quick succession.
+ </para>
+ </section>
</section>
<section id="s2-configuring-anacron-jobs">
<title>Configuring Anacron Jobs</title>
- <indexterm significance="normal">
+ <indexterm>
<primary>anacron</primary>
<secondary>anacron configuration file</secondary>
</indexterm>
- <indexterm significance="normal">
+ <indexterm>
<primary>
<filename>anacrontab</filename>
</primary>
</indexterm>
- <indexterm
- significance="normal">
+ <indexterm>
<primary>anacron</primary>
<secondary>user-defined tasks</secondary>
</indexterm>
- <indexterm
- significance="normal">
+ <indexterm>
<primary>
<filename>/var/spool/anacron</filename>
</primary>
</indexterm>
- <para>The main configuration file to schedule jobs is <filename>/etc/anacrontab</filename> (only <systemitem class="username">root</systemitem> is allowed to modify this file), which contains the following lines:</para>
+ <para>
+ The main configuration file to schedule jobs is the <filename>/etc/anacrontab</filename> file, which can be only accessed by the <systemitem class="username">root</systemitem> user. The file contains the following:
+ </para>
<programlisting>SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
@@ -75,39 +140,88 @@ START_HOURS_RANGE=3-22
7 25 cron.weekly nice run-parts /etc/cron.weekly
@monthly 45 cron.monthly nice run-parts /etc/cron.monthly</programlisting>
<para>
- The first three lines are variables used to configure the environment in which the anacron tasks are run. The <computeroutput>SHELL</computeroutput> variable tells the system which shell environment to use (in this example the bash shell). The <computeroutput>PATH</computeroutput> variable defines the path used to execute commands. The output of the anacron jobs are emailed to the username defined with the <computeroutput>MAILTO</computeroutput> variable. If the <computeroutput>MAILTO</computeroutput> variable is not defined, (i.e. is empty, <computeroutput>MAILTO=</computeroutput>), email is not sent.
-</para>
+ The first three lines define the variables that configure the environment in which the anacron tasks run:
+ </para>
+ <itemizedlist>
+ <listitem>
+ <para><varname>SHELL</varname> — shell environment used for running jobs (in the example, the Bash shell)
+ </para>
+ </listitem>
+ <listitem>
+ <para><varname>PATH</varname> — paths to executable programs
+ </para>
+ </listitem>
+ <listitem>
+ <para><varname>MAILTO</varname> — username of the user who receives the output of the anacron jobs by email
+ </para>
+ <para>
+ If the <varname>MAILTO</varname> variable is not defined (<code>MAILTO=</code>), the email is not sent.
+ </para>
+ </listitem>
+ </itemizedlist>
<para>
- The next two lines are variables that modify the time for each scheduled job. The <computeroutput>RANDOM_DELAY</computeroutput> variable denotes the maximum number of minutes that will be added to the <filename>delay in minutes</filename> variable which is specified for each job. The minimum delay value is set, by default, to 6 minutes. A <computeroutput>RANDOM_DELAY</computeroutput> set to 12 would therefore add, randomly, between 6 and 12 minutes to the <filename>delay in minutes</filename> for each job in that particular anacrontab. <computeroutput>RANDOM_DELAY</computeroutput> can also be set to a value below 6, or even 0. When set to 0, no random delay is added. This proves to be useful when, for example, more computers that share one network connection need to download the same data every day. The <computeroutput>START_HOURS_RANGE</computeroutput> variable defines an interval (in hours) when scheduled jobs can be run. In case this time interval is missed, for example
, due to a power down, then scheduled jobs are not executed that day.
-</para>
- <para>The rest of the lines in the <filename>/etc/anacrontab</filename> file represent scheduled jobs and have the following format:
-</para>
- <programlisting>period in days delay in minutes job-identifier command</programlisting>
+ The next two variables modify the scheduled time for the defined jobs:
+ </para>
<itemizedlist>
<listitem>
+ <para><varname>RANDOM_DELAY</varname> — maximum number of minutes that will be added to the <varname>delay in minutes</varname> variable which is specified for each job
+ </para>
<para>
- <computeroutput>period in days</computeroutput> — specifies the frequency of execution of a job in days. This variable can be represented by an integer or a macro (<computeroutput>@daily</computeroutput>, <computeroutput>@weekly</computeroutput>, <computeroutput>@monthly</computeroutput>), where <computeroutput>@daily</computeroutput> denotes the same value as the integer 1, <computeroutput>@weekly</computeroutput> the same as 7, and <computeroutput>@monthly</computeroutput> specifies that the job is run once a month, independent on the length of the month.
- </para>
+ The minimum delay value is set, by default, to 6 minutes.
+ </para>
+ <para>
+ If <varname>RANDOM_DELAY</varname> is, for example, set to <literal>12</literal>, then between 6 and 12 minutes are added to the <varname>delay in minutes</varname> for each job in that particular anacrontab. <varname>RANDOM_DELAY</varname> can also be set to a value below <literal>6</literal>, including <literal>0</literal>. When set to <literal>0</literal>, no random delay is added. This proves to be useful when, for example, more computers that share one network connection need to download the same data every day.
+ </para>
+ </listitem>
+ <listitem>
+ <para><varname>START_HOURS_RANGE</varname> — interval, when scheduled jobs can be run, in hours
+ </para>
+ <para>
+ In case the time interval is missed, for example due to a power failure, the scheduled jobs are not executed that day.
+ </para>
</listitem>
+ </itemizedlist>
+ <para>
+ The remaining lines in the <filename>/etc/anacrontab</filename> file represent scheduled jobs and follow this format:
+ </para>
+ <screen>
+period in days delay in minutes job-identifier command
+</screen>
+ <itemizedlist>
<listitem>
+ <para><varname>period in days</varname> — frequency of job execution in days
+ </para>
<para>
- <computeroutput>delay in minutes</computeroutput> — specifies the number of minutes anacron waits, if necessary, before executing a job. This variable is represented by an integer where 0 means no delay.
+ The property value can be defined as an integer or a macro (<literal>@daily</literal>, <literal>@weekly</literal>, <literal>@monthly</literal>), where <literal>@daily</literal> denotes the same value as integer 1, <literal>@weekly</literal> the same as 7, and <literal>@monthly</literal> specifies that the job is run once a month regardless of the length of the month.
</para>
</listitem>
<listitem>
+ <para><varname>delay in minutes</varname> — number of minutes anacron waits before executing the job
+ </para>
<para>
- <computeroutput>job-identifier</computeroutput> — specifies a unique name of a job which is used in the log files.
- </para>
+ The property value is defined as an integer. If the value is set to <literal>0</literal>, no delay applies.
+ </para>
+ <!--TODO uncomment when fixing https://bugzilla.redhat.com/show_bug.cgi?id=768078 <note>
+ <para>
+ The <varname>delay in minutes</varname> is ignored if anacron is started in the foreground with the <option>-n</option> (run jobs now) or <option>-s</option> (serialize execution of jobs) option.
+ </para>
+ </note> -->
+ </listitem>
+ <listitem>
+ <para><varname>job-identifier</varname> — unique name referring to a particular job used in the log files
+ </para>
</listitem>
<listitem>
+ <para><varname>command</varname> — command to be executed
+ </para>
<para>
- <computeroutput>command</computeroutput> — specifies the command to execute. The command can either be a command such as <computeroutput>ls /proc >> /tmp/proc</computeroutput> or a command to execute a custom script.
- </para>
+ The command can be either a command such as <command>ls /proc >> /tmp/proc</command> or a command which executes a custom script.
+ </para>
</listitem>
</itemizedlist>
<para>Any lines that begin with a hash sign (#) are comments and are not processed.</para>
<section id="s3-anacron-examples">
- <title>Examples of Anacron Jobs </title>
+ <title>Examples of Anacron Jobs</title>
<para>The following example shows a simple <filename>/etc/anacrontab</filename> file:</para>
<programlisting>SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
@@ -121,43 +235,44 @@ START_HOURS_RANGE=16-20
#period in days delay in minutes job-identifier command
1 20 dailyjob nice run-parts /etc/cron.daily
7 25 weeklyjob /etc/weeklyjob.bash
- at monthly 45 monthlyjob ls /proc >> /tmp/proc</programlisting>
+ at monthly 45 monthlyjob ls /proc >> /tmp/proc</programlisting>
+ <para>
+ All jobs defined in this <filename>anacrontab</filename> file are randomly delayed by 6-30 minutes and can be executed between 16:00 and 20:00.
+ </para>
<para>
- All jobs defined in this <filename>anacrontab</filename> file are randomly delayed by 6-30 minutes and can be executed between 16:00 and 20:00. Thus, the first defined job will run anywhere between 16:26 and 16:50 every day. The command specified for this job will execute all present programs in the <filename>/etc/cron.daily</filename> directory (using the <command>run-parts</command> script which takes a directory as a command-line argument and sequentially executes every program within that directory). The second specified job will be executed once a week and will execute the <filename>weeklyjob.bash</filename> script in the <filename>/etc</filename> directory. The third job is executed once a month and runs a command to write the contents of the <filename>/proc</filename> to the <filename>/tmp/proc</filename> file (e.g. <computeroutput>ls /proc >> /tmp/proc</computeroutput>).
-</para>
-<section id="s3-disabling-anacron">
-<title>Disabling Anacron</title>
-<para>
- In case your system is continuously on and you do not require anacron to run your scheduled jobs, you may uninstall the <filename>cronie-anacron</filename> package. Thus, you will be able to define jobs using crontabs only.
-</para>
-</section>
+ The first defined job is triggered daily between 16:26 and 16:50 (RANDOM_DELAY is between 6 and 30 minutes; the <property>delay in minutes</property> property adds 20 minutes). The command specified for this job executes all present programs in the <filename class="directory">/etc/cron.daily/</filename> directory using the <command>run-parts</command> script (the <command>run-parts</command> scripts accepts a directory as a command-line argument and sequentially executes every program in the directory). See the <filename>run-parts</filename> man page for more information on the <command>run-parts</command> script.
+ </para>
+ <para>
+ The second job executes the <filename>weeklyjob.bash</filename> script in the <filename class="directory">/etc/</filename> directory once a week.
+ </para>
+ <para>
+ The third job runs a command, which writes the contents of <filename>/proc</filename> to the <filename>/tmp/proc</filename> file (<command>ls /proc >> /tmp/proc</command>) once a month.
+ </para>
</section>
</section>
<section id="s2-configuring-cron-jobs">
<title>Configuring Cron Jobs</title>
- <indexterm
- significance="normal">
+ <indexterm>
<primary>cron</primary>
<secondary>user-defined tasks</secondary>
</indexterm>
- <indexterm
- significance="normal">
+ <indexterm>
<primary>
<filename>/var/spool/cron</filename>
</primary>
</indexterm>
- <indexterm significance="normal">
+ <indexterm>
<primary>cron</primary>
<secondary>cron configuration file</secondary>
</indexterm>
- <indexterm significance="normal">
+ <indexterm>
<primary>
<filename>crontab</filename>
</primary>
</indexterm>
<para>
- The configuration file to configure cron jobs, <filename>/etc/crontab</filename> (only <systemitem class="username">root</systemitem> is allowed to modify this file), contains the following lines:
- </para>
+ The configuration file for cron jobs is <filename>/etc/crontab</filename>, which can be only modified by the <systemitem class="username">root</systemitem> user. The file contains the following:
+ </para>
<programlisting>SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
@@ -170,180 +285,359 @@ HOME=/
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
-# * * * * * user command to be executed</programlisting>
+# * * * * * user-name command to be executed</programlisting>
<para>
- The first three lines contain the same variables as an <filename>anacrontab</filename> file, <computeroutput>SHELL</computeroutput>, <computeroutput>PATH</computeroutput> and <computeroutput>MAILTO</computeroutput>. For more information about these variables, refer to <xref linkend="s2-configuring-anacron-jobs"/>. The fourth line contains the <computeroutput>HOME</computeroutput> variable. The <computeroutput>HOME</computeroutput> variable can be used to set the home directory to use when executing commands or scripts.
- </para>
+ The first three lines contain the same variable definitions as an <filename>anacrontab</filename> file: <varname>SHELL</varname>, <varname>PATH</varname>, and <varname>MAILTO</varname>. For more information about these variables, see <xref linkend="s2-configuring-anacron-jobs" />.
+ </para>
<para>
- The rest of the lines in the <filename>/etc/crontab</filename> file represent scheduled jobs and have the following format:
- </para>
- <programlisting>minute hour day month day of week user command</programlisting>
+ In addition, the file can define the <computeroutput>HOME</computeroutput> variable. The <varname>HOME</varname> variable defines the directory, which will be used as the home directory when executing commands or scripts run by the job.
+ </para>
+ <para>
+ The remaining lines in the <filename>/etc/crontab</filename> file represent scheduled jobs and have the following format:
+ </para>
+ <screen>minute hour day month day of week username command</screen>
+ <para>
+ The following define the time when the job is to be run:
+ </para>
<itemizedlist>
<listitem>
- <para>
- <computeroutput>minute</computeroutput> — any integer from 0 to 59</para>
+ <para><varname>minute</varname> — any integer from 0 to 59
+ </para>
</listitem>
<listitem>
- <para>
- <computeroutput>hour</computeroutput> — any integer from 0 to 23</para>
+ <para><varname>hour</varname> — any integer from 0 to 23
+ </para>
</listitem>
<listitem>
- <para>
- <computeroutput>day</computeroutput> — any integer from 1 to 31 (must be a valid day if a month is specified)</para>
+ <para><varname>day</varname> — any integer from 1 to 31 (must be a valid day if a month is specified)
+ </para>
</listitem>
<listitem>
- <para>
- <computeroutput>month</computeroutput> — any integer from 1 to 12 (or the short name of the month such as jan or feb)</para>
+ <para><varname>month</varname> — any integer from 1 to 12 (or the short name of the month such as jan or feb)
+ </para>
</listitem>
<listitem>
- <para>
- <computeroutput>day of week</computeroutput> — any integer from 0 to 7, where 0 or 7 represents Sunday (or the short name of the week such as sun or mon)</para>
+ <para><varname>day of week</varname> — any integer from 0 to 7, where 0 or 7 represents Sunday (or the short name of the week such as sun or mon)
+ </para>
</listitem>
+ </itemizedlist>
+ <para>
+ The following define other job properties:
+ </para>
+ <itemizedlist>
<listitem>
- <para>
- <computeroutput>user</computeroutput> — specifies the user under which the jobs are run
+ <para><varname>username</varname> — specifies the user under which the jobs are run.
</para>
</listitem>
<listitem>
+ <para><varname>command</varname> — the command to be executed.
+ </para>
<para>
- <computeroutput>command</computeroutput> — the command to execute (the command can either be a command such as <command>ls /proc >> /tmp/proc</command> or the command to execute a custom script)</para>
+ The command can be either a command such as <command>ls /proc /tmp/proc</command> or a command which executes a custom script.
+ </para>
</listitem>
</itemizedlist>
- <para>For any of the above values, an asterisk (*) can be used to specify all valid values. For example, an asterisk for the month value means execute the command every month within the constraints of the other values.</para>
- <para>A hyphen (-) between integers specifies a range of integers. For example, <userinput>1-4</userinput> means the integers 1, 2, 3, and 4.</para>
- <para>A list of values separated by commas (,) specifies a list. For example, <userinput>3, 4, 6, 8</userinput> indicates those four specific integers.</para>
- <para>The forward slash (/) can be used to specify step values. The value of an integer can be skipped within a range by following the range with <userinput>/<replaceable>integer</replaceable></userinput>. For example, <userinput>0-59/2</userinput> can be used to define every other minute in the minute field. Step values can also be used with an asterisk. For instance, the value <userinput>*/3</userinput> can be used in the month field to run the task every third month.</para>
- <para>Any lines that begin with a hash sign (#) are comments and are not processed.</para>
- <para>Users other than <systemitem class="username">root</systemitem> can configure cron tasks by using the <command>crontab</command> utility. All user-defined crontabs are stored in the <filename>/var/spool/cron/</filename> directory and are executed using the usernames of the users that created them. To create a crontab as a user, login as that user and type the command <command>crontab -e</command> to edit the user's crontab using the editor specified by the <computeroutput>VISUAL</computeroutput> or <computeroutput>EDITOR</computeroutput> environment variable. The file uses the same format as <filename>/etc/crontab</filename>. When the changes to the crontab are saved, the crontab is stored according to username and written to the file <filename>/var/spool/cron/<replaceable>username</replaceable>
- </filename>. To list the contents of your own personal crontab file, use the <command>crontab -l</command> command. </para>
- <note>
- <title>Do not specify a user</title>
- <para>
- When using the <command>crontab</command> utility, there is no need to specify a user when defining a job.
- </para>
- </note>
- <para>The <filename>/etc/cron.d/</filename> directory contains files that have the same syntax as the <filename>/etc/crontab</filename> file. Only <systemitem class="username">root</systemitem> is allowed to create and modify files in this directory.</para>
+ <para>
+ For any of the above values, an asterisk (*) can be used to specify all valid values. If you, for example, define the month value as an asterisk, the job will be executed every month within the constraints of the other values.
+ </para>
+ <para>
+ A hyphen (-) between integers specifies a range of integers. For example, <userinput>1-4</userinput> means the integers 1, 2, 3, and 4.
+ </para>
+ <para>
+ A list of values separated by commas (,) specifies a list. For example, <userinput>3,4,6,8</userinput> indicates exactly these four integers.
+ </para>
+ <para>
+ The forward slash (/) can be used to specify step values. The value of an integer will be skipped within a range following the range with <userinput>/<replaceable>integer</replaceable></userinput>. For example, the minute value defined as <userinput>0-59/2</userinput> denotes every other minute in the minute field. Step values can also be used with an asterisk. For instance, if the month value is defined as <userinput>*/3</userinput>, the task will run every third month.
+ </para>
+ <para>
+ Any lines that begin with a hash sign (#) are comments and are not processed.
+ </para>
+ <para>
+ Users other than <systemitem class="username">root</systemitem> can configure cron tasks with the <command>crontab</command> utility. The user-defined crontabs are stored in the <filename class="directory">/var/spool/cron/</filename> directory and executed as if run by the users that created them.
+ </para>
+ <para>
+ To create a crontab as a specific user, login as that user and type the command <command>crontab -e</command> to edit the user's crontab with the editor specified in the <computeroutput>VISUAL</computeroutput> or <computeroutput>EDITOR</computeroutput> environment variable. The file uses the same format as <filename>/etc/crontab</filename>. When the changes to the crontab are saved, the crontab is stored according to the user name and written to the file <filename>/var/spool/cron/<replaceable>username</replaceable></filename>. To list the contents of the current user's crontab file, use the <command>crontab -l</command> command.
+ </para>
+ <para>
+ The <filename class="directory">/etc/cron.d/</filename> directory contains files that have the same syntax as the <filename>/etc/crontab</filename> file. Only <systemitem class="username">root</systemitem> is allowed to create and modify files in this directory.
+ </para>
<note>
<title>Do not restart the daemon to apply the changes</title>
- <para>The cron daemon checks the <filename>/etc/anacrontab</filename> file, the <filename>/etc/crontab</filename> file, the <filename>/etc/cron.d/</filename> directory, and the <filename>/var/spool/cron/</filename> directory every minute for any changes. If any changes are found, they are loaded into memory. Thus, the daemon does not need to be restarted if an anacrontab or a crontab file is changed.</para>
+ <para>The cron daemon checks the <filename>/etc/anacrontab</filename> file, the <filename>/etc/crontab</filename> file, the <filename class="directory">/etc/cron.d/</filename> directory, and the <filename>/var/spool/cron/</filename> directory every minute for changes and the detected changes are loaded into memory. It is therefore not necessary to restart the daemon after an anacrontab or a crontab file have been changed.</para>
</note>
</section>
<section id="s2-autotasks-cron-access">
<title>Controlling Access to Cron</title>
- <para>The <filename>/etc/cron.allow</filename> and <filename>/etc/cron.deny</filename> files are used to restrict access to cron. The format of both access control files is one username on each line. Whitespace is not permitted in either file. The cron daemon (<command>crond</command>) does not have to be restarted if the access control files are modified. The access control files are checked each time a user tries to add or delete a cron job.</para>
- <para>The <systemitem class="username">root</systemitem> user can always use cron, regardless of the usernames listed in the access control files.</para>
- <para>If the file <filename>cron.allow</filename> exists, only users listed in it are allowed to use cron, and the <filename>cron.deny</filename> file is ignored.</para>
- <para>If <filename>cron.allow</filename> does not exist, users listed in <filename>cron.deny</filename> are not allowed to use cron.</para>
- <para>Access can also be controlled through Pluggable Authentication Modules (PAM). These settings are stored in <filename>/etc/security/access.conf</filename>. For example, adding the following line in this file forbids creating crontabs for all users except the <systemitem class="username">root</systemitem> user:
+ <para>
+ To restrict the access to Cron, you can use the <filename>/etc/cron.allow</filename> and <filename>/etc/cron.deny</filename> files. These access control files use the same format with one user name on each line. Mind that no whitespace characters are permitted in either file.
+ </para>
+ <para>
+ If the <filename>cron.allow</filename> file exists, only users listed in the file are allowed to use cron, and the <filename>cron.deny</filename> file is ignored.
+ </para>
+ <para>
+ If the <filename>cron.allow</filename> file does not exist, users listed in the <filename>cron.deny</filename> file are not allowed to use Cron.
+ </para>
+ <para>
+ The Cron daemon (<systemitem class="daemon">crond</systemitem>) does not have to be restarted if the access control files are modified. The access control files are checked each time a user tries to add or delete a cron job.
+ </para>
+ <para>
+ The <systemitem class="username">root</systemitem> user can always use cron, regardless of the user names listed in the access control files.
+ </para>
+ <para>
+ You can control the access also through Pluggable Authentication Modules (PAM). The settings are stored in the <filename>/etc/security/access.conf</filename> file. For example, after adding the following line to the file, no other user but the <systemitem class="username">root</systemitem> user can create crontabs:
</para>
<programlisting>-:ALL EXCEPT root :cron</programlisting>
<para>
- The forbidden jobs are logged in an appropriate log file or, when using “crontab -e”, returned to the standard output. For more information, refer to <filename>access.conf.5</filename> (i.e. <command>man 5 access.conf</command>).
+ The forbidden jobs are logged in an appropriate log file or, when using <command>crontab -e</command>, returned to the standard output. For more information, see the <filename>access.conf.5</filename> manual page.
</para>
</section>
<section id="s2-black-white-listing-of-cron-jobs">
- <title>Black/White Listing of Cron Jobs</title>
+ <title>Black and White Listing of Cron Jobs</title>
<para>
- Black/White listing of jobs is used to omit parts of the defined jobs that do not need to be executed. When calling the <command>run-parts</command> script on a cron folder, such as <filename>/etc/cron.daily</filename>, we can define which of the programs in this folder will not be executed by <command>run-parts</command>.
- </para>
- <para>To define a black list, create a <filename>jobs.deny</filename> file in the folder that <command>run-parts</command> will be executing from. For example, if we need to omit a particular program from /etc/cron.daily, then, a file <filename>/etc/cron.daily/jobs.deny</filename> has to be created. In this file, specify the names of the omitted programs from the same directory. These will not be executed when a command, such as <computeroutput>run-parts /etc/cron.daily</computeroutput>, is executed by a specific job.</para>
- <para>To define a white list, create a <filename>jobs.allow</filename> file.</para>
- <para>
- The principles of <filename>jobs.deny</filename> and <filename>jobs.allow</filename> are the same as those of <filename>cron.deny</filename> and <filename>cron.allow</filename> described in section <xref linkend="s2-autotasks-cron-access"/>.
- </para>
+ Black and white listing of jobs is used to define parts of a job that do not need to be executed. This is useful when calling the <application>run-parts</application> script on a Cron directory, such as <filename class="directory">/etc/cron.daily/</filename>: if the user adds programs located in the directory to the job black list, the <application>run-parts</application> script will not execute these programs.
+ </para>
+ <para>
+ To define a black list, create a <filename>jobs.deny</filename> file in the directory that <command>run-parts</command> scripts will be executing from. For example, if you need to omit a particular program from <filename>/etc/cron.daily/</filename>, create the <filename>/etc/cron.daily/jobs.deny</filename> file. In this file, specify the names of the programs to be omitted from execution (only programs located in the same directory can be enlisted). If a job runs a command which runs the programs from the <filename>/etc/cron.daily/</filename> directory, such as <command>run-parts /etc/cron.daily</command>, the programs defined in the <filename>jobs.deny</filename> file will not be executed.
+ </para>
+ <para>
+ To define a white list, create a <filename>jobs.allow</filename> file.
+ </para>
+ <para>
+ The principles of <filename>jobs.deny</filename> and <filename>jobs.allow</filename> are the same as those of <filename>cron.deny</filename> and <filename>cron.allow</filename> described in section <xref linkend="s2-autotasks-cron-access" />.
+ </para>
</section>
</section>
<section id="s1-autotasks-at-batch">
<title>At and Batch</title>
- <indexterm significance="normal">
+ <indexterm>
<primary>
<command>at</command>
</primary>
</indexterm>
- <indexterm significance="normal">
+ <indexterm>
<primary>
<command>batch</command>
</primary>
</indexterm>
- <para>While cron is used to schedule recurring tasks, the <command>at</command> command is used to schedule a one-time task at a specific time and the <command>batch</command> command is used to schedule a one-time task to be executed when the systems load average drops below 0.8.</para>
- <para>To use <command>at</command> or <command>batch</command>, the <filename>at</filename> RPM package must be installed, and the <command>atd</command> service must be running. To determine if the package is installed, use the <command>rpm -q at</command> command. To determine if the service is running, use the following command:</para>
- <screen><command>systemctl is-active atd.service</command></screen>
+ <para>
+ While Cron is used to schedule recurring tasks, the <application>At</application> utility is used to schedule a one-time task at a specific time and the <application>Batch</application> utility is used to schedule a one-time task to be executed when the system load average drops below 0.8.</para>
+ <section id="sect-At_and_Batch_Installation">
+ <title>Installing At and Batch</title>
+ <para>
+ To determine if the <package>at</package> package is already installed on your system, issue the following command:
+ </para>
+ <synopsis><command>rpm -q at</command></synopsis>
+ <para>
+ The command returns the full name of the <package>at</package> package if already installed or notifies you that the package is not available.
+ </para>
+ <para>
+ To install the packages, use the <command>yum</command> command in the following form as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>yum install <replaceable>package</replaceable></command></synopsis>
+ <para>
+ For example, to install both At and Batch, type the following at a shell prompt:
+ </para>
+ <screen>~]# <command>yum install at</command></screen>
+ <para>
+ For more information on how to install new packages in &MAJOROS;, see <xref linkend="sec-Installing" />.
+ </para>
+ </section>
+ <section id="sect-Atd-Running">
+ <title>Running the At Service</title>
+ <para>
+ The At and Batch jobs are both picked by the <systemitem class="daemon">atd</systemitem> service. This section provides information on how to start, stop, and restart the <systemitem class="service">atd</systemitem> service, and shows how to configure it to start automatically at boot time. <!--For more information on how to manage system services in &MAJOROSVER; in general, see <xref linkend="chap-Managing_Services_with_systemd" />.-->
+ </para>
+ <section id="sect-Atd-service">
+ <title>Starting and Stopping the At Service</title>
+ <para>
+ To determine if the service is running, use the following command:
+ </para>
+ <synopsis><command>systemctl status atd.service</command></synopsis>
+ <para>
+ To run the <systemitem class="service">atd</systemitem> service in the current session, type the following at a shell prompt as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl start atd.service</command></synopsis>
+ <para>
+ To configure the service to start automatically at boot time, use the following command as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl enable atd.service</command></synopsis>
+ <note>
+ <para>
+ It is recommended that you configure your system to start the <systemitem class="service">atd</systemitem> service automatically at boot time.
+ </para>
+ </note>
+ </section>
+ <section id="sect-Atd_Stopping">
+ <title>Stopping the At Service</title>
+ <para>
+ To stop the <systemitem class="service">atd</systemitem> service, type the following at a shell prompt as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl stop atd.service</command></synopsis>
+ <para>
+ To prevent the service from starting automatically at boot time, use the following command as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl disable atd.service</command></synopsis>
+ </section>
+ <section id="sect-Atd_Restarting">
+ <title>Restarting the At Service</title>
+ <para>
+ To restart the <systemitem class="service">atd</systemitem> service, type the following at a shell prompt as <systemitem class="username">root</systemitem>:
+ </para>
+ <synopsis><command>systemctl restart atd.service</command></synopsis>
+ <para>
+ This command stops the service and starts it again in quick succession.
+ </para>
+ </section>
+ </section>
<section id="s2-autotasks-at-configuring">
- <title>Configuring At Jobs</title>
- <para>To schedule a one-time job at a specific time, type the command <command>at <replaceable>time</replaceable>
- </command>, where <command><replaceable>time</replaceable>
- </command> is the time to execute the command.</para>
- <para>The argument <replaceable>time</replaceable> can be one of the following:</para>
- <itemizedlist>
- <listitem>
- <para>HH:MM format — For example, 04:00 specifies 4:00 a.m. If the time is already past, it is executed at the specified time the next day.</para>
- </listitem>
- <listitem>
- <para>midnight — Specifies 12:00 a.m.</para>
- </listitem>
- <listitem>
- <para>noon — Specifies 12:00 p.m.</para>
- </listitem>
- <listitem>
- <para>teatime — Specifies 4:00 p.m.</para>
- </listitem>
- <listitem>
- <para>month-name day year format — For example, January 15 2002 specifies the 15th day of January in the year 2002. The year is optional.</para>
- </listitem>
- <listitem>
- <para>MMDDYY, MM/DD/YY, or MM.DD.YY formats — For example, 011502 for the 15th day of January in the year 2002.</para>
- </listitem>
- <listitem>
- <para>now + time — time is in minutes, hours, days, or weeks. For example, now + 5 days specifies that the command should be executed at the same time five days from now.</para>
- </listitem>
- </itemizedlist>
- <para>The time must be specified first, followed by the optional date. For more information about the time format, read the <filename>/usr/share/doc/at/timespec</filename> text file.</para>
- <para>After typing the <command>at</command> command with the time argument, the <prompt>at></prompt> prompt is displayed. Type the command to execute, press <keycap>Enter</keycap>, and press <keycombo><keycap>Ctrl</keycap>
- <keycap>D</keycap>
- </keycombo> . Multiple commands can be specified by typing each command followed by the <keycap>Enter</keycap> key. After typing all the commands, press <keycap>Enter</keycap> to go to a blank line and press <keycombo><keycap>Ctrl</keycap>
- <keycap>D</keycap>
- </keycombo> . Alternatively, a shell script can be entered at the prompt, pressing <keycap>Enter</keycap> after each line in the script, and pressing <keycombo><keycap>Ctrl</keycap>
- <keycap>D</keycap>
- </keycombo> on a blank line to exit. If a script is entered, the shell used is the shell set in the user's <envar>SHELL</envar> environment, the user's login shell, or <command>/bin/sh</command> (whichever is found first).</para>
- <para>If the set of commands or script tries to display information to standard output, the output is emailed to the user.</para>
- <para>Use the command <command>atq</command> to view pending jobs. See <xref linkend="s2-autotasks-at-batch-viewing"/> for more information.</para>
- <para>Usage of the <command>at</command> command can be restricted. For more information, refer to <xref linkend="s2-autotasks-at-batch-controlling-access"/> for details.</para>
+ <title>Configuring an At Job</title>
+ <para>To schedule a one-time job for a specific time with the <application>At</application> utility, do the following:</para>
+ <procedure>
+ <step>
+ <para>
+ On the command line, type the command <command>at <replaceable>TIME</replaceable></command>, where <command><replaceable>TIME</replaceable></command> is the time when the command is to be executed.
+ </para>
+ <para>The <replaceable>TIME</replaceable> argument can be defined in any of the following formats:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal><replaceable>HH</replaceable>:<replaceable>MM</replaceable></literal> specifies the exact hour and minute; For example, <literal>04:00</literal> specifies 4:00 a.m.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal>midnight</literal> specifies 12:00 a.m.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal>noon</literal> specifies 12:00 p.m.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal>teatime</literal> specifies 4:00 p.m.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal><replaceable>MONTH</replaceable><replaceable>DAY</replaceable><replaceable>YEAR</replaceable></literal> format; For example, <literal>January 15 2012</literal> specifies the 15th day of January in the year 2012. The year value is optional.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal><replaceable>MMDDYY</replaceable></literal>, <literal><replaceable>MM</replaceable>/<replaceable>DD</replaceable>/<replaceable>YY</replaceable></literal>, or <literal><replaceable>MM</replaceable>.<replaceable>DD</replaceable>.<replaceable>YY</replaceable></literal> formats; For example, <literal>011512</literal> for the 15th day of January in the year 2012.
+ </para>
+ </listitem>
+ <listitem>
+ <para><literal>now + <replaceable>TIME</replaceable></literal> where <replaceable>TIME</replaceable> is defined as an integer and the value type: minutes, hours, days, or weeks. For example, <userinput>now + 5 days</userinput> specifies that the command will be executed at the same time five days from now.</para>
+ <para>The time must be specified first, followed by the optional date. For more information about the time format, see the <filename>/usr/share/doc/at-<replaceable><version></replaceable>/timespec</filename> text file.</para>
+ </listitem>
+ </itemizedlist>
+ <para>
+ If the specified time has past, the job is executed at the time the next day.
+ </para>
+ </step>
+ <step>
+ <para>
+ In the displayed <prompt>at></prompt> prompt, define the job commands:
+ </para>
+ <stepalternatives>
+ <step>
+ <para>
+ Type the command the job should execute and press <keycap>Enter</keycap>. Optionally, repeat the step to provide multiple commands.
+ </para>
+ </step>
+ <step>
+ <para>
+ Enter a shell script at the prompt and press <keycap>Enter</keycap> after each line in the script.
+ </para>
+ <para>
+ The job will use the shell set in the user's <envar>SHELL</envar> environment, the user's login shell, or <command>/bin/sh</command> (whichever is found first).
+ </para>
+ </step>
+ </stepalternatives>
+ </step>
+ <step>
+ <para>
+ Once finished, press <keycombo><keycap>Ctrl</keycap><keycap>D</keycap></keycombo> on an empty line to exit the prompt.
+ </para>
+ </step>
+ </procedure>
+ <para>
+ If the set of commands or the script tries to display information to standard output, the output is emailed to the user.
+ </para>
+ <para>
+ To view the list of pending jobs, use the <command>atq</command> command. See <xref linkend="s2-autotasks-at-batch-viewing" /> for more information.
+ </para>
+ <para>
+ You can also restrict the usage of the <command>at</command> command. For more information, see <xref linkend="s2-autotasks-at-batch-controlling-access" /> for details.
+ </para>
</section>
<section id="s2-autotasks-batch-configuring">
- <title>Configuring Batch Jobs</title>
- <para>To execute a one-time task when the load average is below 0.8, use the <command>batch</command> command.</para>
- <para>After typing the <command>batch</command> command, the <prompt>at></prompt> prompt is displayed. Type the command to execute, press <keycap>Enter</keycap>, and press <keycombo><keycap>Ctrl</keycap>
- <keycap>D</keycap>
- </keycombo> . Multiple commands can be specified by typing each command followed by the <keycap>Enter</keycap> key. After typing all the commands, press <keycap>Enter</keycap> to go to a blank line and press <keycombo><keycap>Ctrl</keycap>
- <keycap>D</keycap>
- </keycombo> . Alternatively, a shell script can be entered at the prompt, pressing <keycap>Enter</keycap> after each line in the script, and pressing <keycombo><keycap>Ctrl</keycap>
- <keycap>D</keycap>
- </keycombo> on a blank line to exit. If a script is entered, the shell used is the shell set in the user's <envar>SHELL</envar> environment, the user's login shell, or <command>/bin/sh</command> (whichever is found first). As soon as the load average is below 0.8, the set of commands or script is executed.</para>
- <para>If the set of commands or script tries to display information to standard out, the output is emailed to the user.</para>
- <para>Use the command <command>atq</command> to view pending jobs. See <xref linkend="s2-autotasks-at-batch-viewing"/> for more information.</para>
- <para>Usage of the <command>batch</command> command can be restricted. For more information, refer to <xref linkend="s2-autotasks-at-batch-controlling-access"/> for details.</para>
+ <title>Configuring a Batch Job</title>
+ <para>
+ The <application>Batch</application> application executes the defined one-time tasks when the system load average decreases below 0.8.
+ </para>
+ <para>
+ To define a Batch job, do the following:
+ </para>
+ <procedure>
+ <step>
+ <para>
+ On the command line, type the command <command>batch</command>.
+ </para>
+ </step>
+ <step>
+ <para>
+ In the displayed <prompt>at></prompt> prompt, define the job commands:
+ </para>
+ <stepalternatives>
+ <step>
+ <para>
+ Type the command the job should execute and press <keycap>Enter</keycap>. Optionally, repeat the step to provide multiple commands.
+ </para>
+ </step>
+ <step>
+ <para>
+ Enter a shell script at the prompt and press <keycap>Enter</keycap> after each line in the script.
+ </para>
+ <para>
+ If a script is entered, the job uses the shell set in the user's <envar>SHELL</envar> environment, the user's login shell, or <command>/bin/sh</command> (whichever is found first).
+ </para>
+ </step>
+ </stepalternatives>
+ </step>
+ <step>
+ <para>
+ Once finished, press <keycombo><keycap>Ctrl</keycap><keycap>D</keycap></keycombo> on an empty line to exit the prompt.
+ </para>
+ </step>
+ </procedure>
+ <para>
+ If the set of commands or the script tries to display information to standard output, the output is emailed to the user.
+ </para>
+ <para>
+ To view the list of pending jobs, use the <command>atq</command> command. See <xref linkend="s2-autotasks-at-batch-viewing" /> for more information.
+ </para>
+ <para>
+ You can also restrict the usage of the <command>batch</command> command. For more information, see <xref linkend="s2-autotasks-at-batch-controlling-access" /> for details.
+ </para>
</section>
<section id="s2-autotasks-at-batch-viewing">
<title>Viewing Pending Jobs</title>
- <para>To view pending <command>at</command> and <command>batch</command> jobs, use the <command>atq</command> command. The <command>atq</command> command displays a list of pending jobs, with each job on a line. Each line follows the job number, date, hour, job class, and username format. Users can only view their own jobs. If the <systemitem class="username">root</systemitem> user executes the <command>atq</command> command, all jobs for all users are displayed.</para>
+ <para>To view the pending <command>At</command> and <command>Batch</command> jobs, run the <command>atq</command> command. The <command>atq</command> command displays a list of pending jobs, with each job on a separate line. Each line follows the job number, date, hour, job class, and user name format. Users can only view their own jobs. If the <systemitem class="username">root</systemitem> user executes the <command>atq</command> command, all jobs for all users are displayed.</para>
</section>
<section id="s2-autotasks-commandline-options">
<title>Additional Command Line Options</title>
- <para>Additional command line options for <command>at</command> and <command>batch</command> include:</para>
+ <para>Additional command line options for <command>at</command> and <command>batch</command> include the following:</para>
<table id="tb-at-command-line-options">
- <title>
- <command>at</command> and <command>batch</command> Command Line Options</title>
+ <title><command>at</command> and <command>batch</command> Command Line Options</title>
<tgroup cols="2">
<colspec colname="option" colnum="1" colwidth="20*"/>
<colspec colname="description" colnum="2" colwidth="50*"/>
<thead>
<row>
<entry>
- Option
- </entry>
+ Option
+ </entry>
<entry>
- Description
- </entry>
+ Description
+ </entry>
</row>
</thead>
<tbody>
@@ -352,24 +646,24 @@ HOME=/
<option>-f</option>
</entry>
<entry>
- Read the commands or shell script from a file instead of specifying them at the prompt.
- </entry>
+ Read the commands or shell script from a file instead of specifying them at the prompt.
+ </entry>
</row>
<row>
<entry>
<option>-m</option>
</entry>
<entry>
- Send email to the user when the job has been completed.
- </entry>
+ Send email to the user when the job has been completed.
+ </entry>
</row>
<row>
<entry>
<option>-v</option>
</entry>
<entry>
- Display the time that the job is executed.
- </entry>
+ Display the time that the job is executed.
+ </entry>
</row>
</tbody>
</tgroup>
@@ -377,69 +671,76 @@ HOME=/
</section>
<section id="s2-autotasks-at-batch-controlling-access">
<title>Controlling Access to At and Batch</title>
- <para>The <filename>/etc/at.allow</filename> and <filename>/etc/at.deny</filename> files can be used to restrict access to the <command>at</command> and <command>batch</command> commands. The format of both access control files is one username on each line. Whitespace is not permitted in either file. The <command>at</command> daemon (<command>atd</command>) does not have to be restarted if the access control files are modified. The access control files are read each time a user tries to execute the <command>at</command> or <command>batch</command> commands.</para>
- <para>The <systemitem class="username">root</systemitem> user can always execute <command>at</command> and <command>batch</command> commands, regardless of the access control files.</para>
- <para>If the file <filename>at.allow</filename> exists, only users listed in it are allowed to use <command>at</command> or <command>batch</command>, and the <filename>at.deny</filename> file is ignored.</para>
- <para>If <filename>at.allow</filename> does not exist, users listed in <filename>at.deny</filename> are not allowed to use <command>at</command> or <command>batch</command>.</para>
- </section>
- <section id="s2-autotasks-at-batch-service">
- <title>Starting and Stopping the Service</title>
- <para>To start the <command>at</command> service, use the following command as <systemitem class="username">root</systemitem>:</para>
- <screen><command>systemctl start atd.service</command></screen>
- <para>To stop the service, as <systemitem class="username">root</systemitem>, type the following at a shell prompt:</para>
- <screen><command>systemctl stop atd.service</command></screen>
- <para>It is recommended that you start the service at boot time. To do so, run the following command as <systemitem class="username">root</systemitem>:</para>
- <screen><command>systemctl enable atd.service</command></screen>
<para>
- See <xref linkend="ch-Services_and_Daemons" /> for more information on how to configure services in &MAJOROS;.
+ You can restrict the access to the <command>at</command> and <command>batch</command> commands using the <filename>/etc/at.allow</filename> and <filename>/etc/at.deny</filename> files. These access control files use the same format defining one user name on each line. Mind that no whitespace are permitted in either file.
+ </para>
+ <para>
+ If the file <filename>at.allow</filename> exists, only users listed in the file are allowed to use <command>at</command> or <command>batch</command>, and the <filename>at.deny</filename> file is ignored.
+ </para>
+ <para>
+ If <filename>at.allow</filename> does not exist, users listed in <filename>at.deny</filename> are not allowed to use <command>at</command> or <command>batch</command>.
+ </para>
+ <para>
+ The <command>at</command> daemon (<command>atd</command>) does not have to be restarted if the access control files are modified. The access control files are read each time a user tries to execute the <command>at</command> or <command>batch</command> commands.
+ </para>
+ <para>
+ The <systemitem class="username">root</systemitem> user can always execute <command>at</command> and <command>batch</command> commands, regardless of the content of the access control files.
</para>
</section>
</section>
<section id="s1-autotasks-additional-resources">
<title>Additional Resources</title>
- <indexterm significance="normal">
+ <indexterm>
<primary>cron</primary>
<secondary>additional resources</secondary>
</indexterm>
- <indexterm significance="normal">
+ <indexterm>
<primary>at</primary>
<secondary>additional resources</secondary>
</indexterm>
- <indexterm significance="normal">
+ <indexterm>
<primary>batch</primary>
<secondary>additional resources</secondary>
</indexterm>
- <para>To learn more about configuring automated tasks, refer to the following resources.</para>
- <section id="s2-autotasks-installed-docs">
- <title>Installed Documentation</title>
- <itemizedlist>
- <listitem>
- <para>
- <filename>cron</filename> man page — contains an overview of cron.</para>
- </listitem>
- <listitem>
- <para>
- <filename>crontab</filename> man pages in sections 1 and 5 — The man page in section 1 contains an overview of the <filename>crontab</filename> file. The man page in section 5 contains the format for the file and some example entries.</para>
- </listitem>
- <listitem>
- <para>
- <filename>anacron</filename> man page — contains an overview of anacron.
+ <para>To learn more about configuring automated tasks, see the following installed documentation:</para>
+ <itemizedlist>
+ <listitem>
+ <para><filename>cron(8)</filename> man page contains an overview of cron.</para>
+ </listitem>
+ <listitem>
+ <para><filename>crontab</filename> man pages in sections 1 and 5:</para>
+ <itemizedlist>
+ <listitem>
+ <para>
+ The manual page in section 1 contains an overview of the <filename>crontab</filename> file.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The man page in section 5 contains the format for the file and some example entries.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </listitem>
+ <listitem>
+ <para><filename>anacron(8)</filename> manual page contains an overview of anacron.
</para>
- </listitem>
- <listitem>
- <para>
- <filename>anacrontab</filename> man page — contains an overview of the <filename>anacrontab</filename> file.
+ </listitem>
+ <listitem>
+ <para><filename>anacrontab(5)</filename> manual page contains an overview of the <filename>anacrontab</filename> file.
</para>
- </listitem>
- <listitem>
- <para>
- <filename>/usr/share/doc/at/timespec</filename> contains more detailed information about the times that can be specified for cron jobs.</para>
- </listitem>
- <listitem>
- <para>
- <filename>at</filename> man page — description of <command>at</command> and <command>batch</command> and their command line options.</para>
- </listitem>
- </itemizedlist>
- </section>
+ </listitem>
+ <listitem>
+ <para><filename>run-parts(4)</filename> manual page contains an overview of the <command>run-parts</command> script.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para><filename>/usr/share/doc/at/timespec</filename> contains detailed information about the time values that can be used in cron job definitions.</para>
+ </listitem>
+ <listitem>
+ <para><filename>at</filename> manual page contains descriptions of <command>at</command> and <command>batch</command> and their command line options.</para>
+ </listitem>
+ </itemizedlist>
</section>
</chapter>
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