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Clarify the difference between user and system crontabs.

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PR:	66963
Submitted by:	platanthera <platanthera@web.de> and
		Bill Moran <wmoran@potentialtech.com>
This commit is contained in:
Daniel Harris 2004-05-22 14:54:17 +00:00
parent 1fcf2be98e
commit b053b73066
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=20968
1 changed files with 46 additions and 6 deletions

52
en_US.ISO8859-1/books/handbook/config/chapter.sgml
View file

@ -441,8 +441,29 @@ exit 0
<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>User crontabs allow individual users to schedule tasks without the
need for root privileges. 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 one is different from
<filename>/etc/crontab</filename> (the system crontab). Because of the
system crontab, there's usually no need 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;
@ -531,16 +552,30 @@ HOME=/var/log
<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, and 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
<filename>crontab</filename> files: just pass the
<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,
@ -549,6 +584,11 @@ HOME=/var/log
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>
</sect1>