Date: Fri, 21 May 2004 10:00:47 -0700 (PDT) From: Bill Moran <wmoran@potentialtech.com> To: freebsd-doc@FreeBSD.org Subject: Re: docs/66963: [patch] handbook - a note on /etc/crontab Message-ID: <200405211700.i4LH0lPg074906@freefall.freebsd.org>
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The following reply was made to PR docs/66963; it has been noted by GNATS. From: Bill Moran <wmoran@potentialtech.com> To: freebsd-gnats-submit@FreeBSD.org, platanthera@web.de Cc: Subject: Re: docs/66963: [patch] handbook - a note on /etc/crontab Date: Fri, 21 May 2004 12:55:25 -0400 Here is an updated patch that adds some additional explanation/notes: Rendered version availabe here: http://www.potentialtech.com/wmoran/configtuning-cron.html -- Bill Moran Potential Technologies http://www.potentialtech.com --- chapter-old.sgml Tue May 4 16:51:58 2004 +++ chapter.sgml Fri May 21 11:33:11 2004 @@ -441,8 +441,30 @@ <filename>crontab</filename> files store information about specific functions which <command>cron</command> is supposed to perform at certain times.</para> + + <para>The <command>cron</command> utility uses two different + types of configuration files, the system crontab and user crontabs. The + only difference between these two formats is the sixth field. In the + system crontab, the sixth field is the name of a user for the command + to run as. This gives the system crontab the ability to run commands + as any user. In a user crontab, the sixth field is the command to run, + and all commands run as the user who created the crontab; this is an + important security feature.</para> + + <note> + <para>The reason user crontabs exist is to allow individual users to + schedule tasks without the need for root priviledges. Commands in + a user's crontab run with the permissions of the user who owns the + crontab.</para> + <para>The root user can have a user crontab just like + any other user. This is a different crontab from + <filename>/etc/crontab</filename> (the system crontab). Because of the + system crontab, there's generally no reason to create a user crontab + for root.</para> + </note> - <para>Let us take a look at the <filename>/etc/crontab</filename> file:</para> + <para>Let us take a look at the <filename>/etc/crontab</filename> file + (the system crontab):</para> <programlisting># /etc/crontab - root's crontab for &os; @@ -526,21 +548,35 @@ <filename>/etc/crontab</filename> file. This field should be omitted for individual user <filename>crontab</filename> files.</para> - + <sect2 id="configtuning-installcrontab"> <title>Installing a Crontab</title> - - <para>To install your freshly written - <filename>crontab</filename>, just use the + + <important> + <para>You must not use the procedure described here to + edit/install the system crontab. Simply use your favorite + editor, the <command>cron</command> utility will notice that the file + has changed and immediately begin using the updated version. + See + <ulink url="http://www.freebsd.org/doc/en_US.ISO8859-1/books/faq/admin.html#ROOT-NOT-FOUND-CRON-ERRORS">; + this FAQ entry </ulink> for more information.</para> + </important> + + <para>To install a freshly written user + <filename>crontab</filename>, first use your favorite editor to create + a file in the proper format, then use the <command>crontab</command> utility. The most common usage is:</para> - <screen>&prompt.root; <userinput>crontab crontab</userinput></screen> + <screen>&prompt.user; <userinput>crontab crontab-file</userinput></screen> + + <para>In this example, <filename>crontab-file</filename> is the filename + of a <filename>crontab</filename> that was previously created.</para> <para>There is also an option to list installed <filename>crontab</filename> files, just pass the - <option>-l</option> to <command>crontab</command> and look + <option>-l</option> option to <command>crontab</command> and look over the output.</para> <para>For users who wish to begin their own crontab file from scratch, @@ -548,6 +584,11 @@ option is available. This will invoke the selected editor with an empty file. When the file is saved, it will be automatically installed by the <command>crontab</command> command. + </para> + + <para>If you later want to remove your user <filename>crontab</filename> + completely, use <command>crontab</command> with the <option>-r</option> + option. </para> </sect2>
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