CentOS下使用yum命令安装计划任务程序crontab的方法
<p><span><strong> 概述</strong></span></p>
<p>
利用“任务计划”，可以将任何脚本、程序或文档安排在某个最方便的时间运行。通俗的讲就是定时执行某个脚本、程序。</p>
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<span><strong>常见用途</strong></span></p>
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定时关机</p>
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定时检查更新</p>
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定时对系统配置、数据库、日志进行备份</p>
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定时清理垃圾文件</p>
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<span><strong>检测是否已安装</strong></span></p>
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<code class="bash comments"># crontab</code>
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<code class="bash plain">-</code><code class="bash functions">bash</code><code class="bash plain">: </code><code class="bash functions">crontab</code><code class="bash plain">: </code><code class="bash functions">command</code> <code class="bash plain">not found</code>
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执行 crontab 命令如果报 command not found，就表明没有安装.</p>
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<span><strong>开始安装</strong></span></p>
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<code class="bash comments"># yum -y install vixie-cron</code>
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<code class="bash plain">Loaded plugins: fastestmirror, refresh-packagekit, security</code>
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<code class="bash plain">Existing lock </code><code class="bash plain">/var/run/yum</code><code class="bash plain">.pid: another copy is running as pid 25960.</code>
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<code class="bash plain">Another app is currently holding the yum lock; waiting </code><code class="bash keyword">for</code> <code class="bash plain">it to </code><code class="bash functions">exit</code><code class="bash plain">...</code>
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可能是系统自动升级正在运行，yum在锁定状态中。</p>
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可以通过强制关掉yum进程：</p>
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<code class="bash comments">#rm -f /var/run/yum.pid</code>
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然后就可以使用yum了。</p>
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<code class="bash comments"># yum -y install vixie-cron</code>
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<code class="bash plain">Loaded plugins: fastestmirror, refresh-packagekit, security</code>
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<code class="bash plain">Determining fastest mirrors</code>
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<code class="bash spaces"> </code><code class="bash plain">* base: mirrors.btte.net</code>
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<code class="bash spaces"> </code><code class="bash plain">* extras: mirrors.sina.cn</code>
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<code class="bash spaces"> </code><code class="bash plain">* updates: mirrors.sina.cn</code>
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<code class="bash plain">base | 3.7 kB 00:00 </code>
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<code class="bash plain">extras | 3.4 kB 00:00 </code>
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<code class="bash plain">extras</code><code class="bash plain">/primary_db</code> <code class="bash plain">| 32 kB 00:00 </code>
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<code class="bash plain">updates | 3.4 kB 00:00 </code>
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<code class="bash plain">updates</code><code class="bash plain">/primary_db</code> <code class="bash plain">| 1.9 MB 00:07 </code>
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<code class="bash plain">Setting up Install Process</code>
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<code class="bash plain">Resolving Dependencies</code>
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<code class="bash plain">--> Running transaction check</code>
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<code class="bash plain">---> Package cronie.x86_64 0:1.4.4-15.el6 will be installed</code>
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<code class="bash plain">--> Processing Dependency: dailyjobs </code><code class="bash keyword">for</code> <code class="bash plain">package: cronie-1.4.4-15.el6.x86_64</code>
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<code class="bash plain">--> Processing Dependency: </code><code class="bash plain">/usr/sbin/sendmail</code> <code class="bash keyword">for</code> <code class="bash plain">package: cronie-1.4.4-15.el6.x86_64</code>
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<code class="bash plain">--> Running transaction check</code>
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<code class="bash plain">---> Package cronie-anacron.x86_64 0:1.4.4-15.el6 will be installed</code>
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<code class="bash plain">--> Processing Dependency: crontabs </code><code class="bash keyword">for</code> <code class="bash plain">package: cronie-anacron-1.4.4-15.el6.x86_64</code>
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<code class="bash plain">---> Package sendmail.x86_64 0:8.14.4-9.el6 will be installed</code>
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<code class="bash plain">--> Processing Dependency: procmail </code><code class="bash keyword">for</code> <code class="bash plain">package: sendmail-8.14.4-9.el6.x86_64</code>
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<code class="bash plain">--> Running transaction check</code>
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<code class="bash plain">---> Package crontabs.noarch 0:1.10-33.el6 will be installed</code>
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<code class="bash plain">---> Package procmail.x86_64 0:3.22-25.1.el6_5.1 will be installed</code>
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<code class="bash plain">--> Finished Dependency Resolution</code>
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<code class="bash plain">Dependencies Resolved</code>
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<code class="bash plain">===============================================================================================================================================================================================</code>
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<code class="bash spaces"> </code><code class="bash plain">Package Arch Version Repository Size</code>
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<code class="bash plain">===============================================================================================================================================================================================</code>
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<code class="bash plain">Installing:</code>
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<code class="bash spaces"> </code><code class="bash plain">cronie x86_64 1.4.4-15.el6 base 74 k</code>
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<code class="bash plain">Installing </code><code class="bash keyword">for</code> <code class="bash plain">dependencies:</code>
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<code class="bash spaces"> </code><code class="bash plain">cronie-anacron x86_64 1.4.4-15.el6 base 31 k</code>
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<code class="bash spaces"> </code><code class="bash plain">crontabs noarch 1.10-33.el6 base 10 k</code>
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<code class="bash spaces"> </code><code class="bash plain">procmail x86_64 3.22-25.1.el6_5.1 base 162 k</code>
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<code class="bash spaces"> </code><code class="bash plain">sendmail x86_64 8.14.4-9.el6 base 716 k</code>
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<code class="bash plain">Transaction Summary</code>
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<code class="bash plain">===============================================================================================================================================================================================</code>
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<code class="bash plain">Install 5 Package(s)</code>
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<code class="bash plain">Total download size: 994 k</code>
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<code class="bash plain">Installed size: 2.1 M</code>
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<code class="bash plain">Downloading Packages:</code>
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<code class="bash plain">(1</code><code class="bash plain">/5</code><code class="bash plain">): cronie-1.4.4-15.el6.x86_64.rpm | 74 kB 00:00 </code>
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<code class="bash plain">(2</code><code class="bash plain">/5</code><code class="bash plain">): cronie-anacron-1.4.4-15.el6.x86_64.rpm | 31 kB 00:00 </code>
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<code class="bash plain">(3</code><code class="bash plain">/5</code><code class="bash plain">): crontabs-1.10-33.el6.noarch.rpm | 10 kB 00:00 </code>
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<code class="bash plain">(4</code><code class="bash plain">/5</code><code class="bash plain">): procmail-3.22-25.1.el6_5.1.x86_64.rpm | 162 kB 00:00 </code>
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<code class="bash plain">(5</code><code class="bash plain">/5</code><code class="bash plain">): sendmail-8.14.4-9.el6.x86_64.rpm | 716 kB 00:00 </code>
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<code class="bash plain">-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------</code>
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<code class="bash plain">Total 1.3 MB</code><code class="bash plain">/s</code> <code class="bash plain">| 994 kB 00:00 </code>
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<code class="bash plain">Running rpm_check_debug</code>
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<code class="bash plain">Running Transaction Test</code>
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<code class="bash plain">Transaction Test Succeeded</code>
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<code class="bash plain">Running Transaction</code>
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<code class="bash spaces"> </code><code class="bash plain">Installing : procmail-3.22-25.1.el6_5.1.x86_64 1</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Installing : sendmail-8.14.4-9.el6.x86_64 2</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Installing : cronie-1.4.4-15.el6.x86_64 3</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Installing : crontabs-1.10-33.el6.noarch 4</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Installing : cronie-anacron-1.4.4-15.el6.x86_64 5</code><code class="bash plain">/5</code>
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<code class="bash plain">ERROR:dbus.proxies:Introspect error on :1.2513:</code><code class="bash plain">/org/freedesktop/PackageKit</code><code class="bash plain">: dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.</code>
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<code class="bash plain">Unable to send message to PackageKit</code>
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<code class="bash spaces"> </code><code class="bash plain">Verifying : crontabs-1.10-33.el6.noarch 1</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Verifying : cronie-anacron-1.4.4-15.el6.x86_64 2</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Verifying : sendmail-8.14.4-9.el6.x86_64 3</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Verifying : cronie-1.4.4-15.el6.x86_64 4</code><code class="bash plain">/5</code>
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<code class="bash spaces"> </code><code class="bash plain">Verifying : procmail-3.22-25.1.el6_5.1.x86_64 5</code><code class="bash plain">/5</code>
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<code class="bash plain">Installed:</code>
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<code class="bash spaces"> </code><code class="bash plain">cronie.x86_64 0:1.4.4</code>
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<code class="bash plain">15.el6 </code>
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<code class="bash plain">Dependency Installed:</code>
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<code class="bash spaces"> </code><code class="bash plain">cronie-anacron.x86_64 0:1.4.4-15.el6 crontabs.noarch 0:1.10-33.el6 procmail.x86_64 0:3.22-25.1.el6_5.1 sendmail.x86_64 0:8.14.4-9.el6 </code>
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<code class="bash plain">Complete!</code>
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<span><strong>查看命令帮助</strong></span></p>
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crontab 并不支持-h或–help之类的选项，不过还是可以通过它查看命令帮助</p>
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<code class="bash comments"># crontab -h</code>
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<code class="bash functions">crontab</code><code class="bash plain">：无效选项 -- h</code>
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<code class="bash functions">crontab</code><code class="bash plain">: usage error: unrecognized option</code>
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<code class="bash plain">usage: </code><code class="bash functions">crontab</code> <code class="bash plain">[-u user] </code><code class="bash functions">file</code>
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<code class="bash spaces"> </code><code class="bash functions">crontab</code> <code class="bash plain">[-u user] [ -e | -l | -r ]</code>
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<code class="bash spaces"> </code><code class="bash plain">(default operation is replace, per 1003.2)</code>
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<code class="bash spaces"> </code><code class="bash plain">-e (edit user's </code><code class="bash functions">crontab</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash plain">-l (list user's </code><code class="bash functions">crontab</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash plain">-r (delete user's </code><code class="bash functions">crontab</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash plain">-i (prompt before deleting user's </code><code class="bash functions">crontab</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash plain">-s (selinux context)</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
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</div>
</div>
<p>
也可以使用 info crontab 命令查看详细的帮助信息。</p>
<p>
cron服务提供crontab命令来设定cron服务的，以下是这个命令的一些参数与说明:</p>
<p>
crontab -u //设定某个用户的cron服务，一般root用户在执行这个命令的时候需要此参数</p>
<p>
crontab -l //列出某个用户cron服务的详细内容</p>
<p>
crontab -r //删除没个用户的cron服务</p>
<p>
crontab -e //编辑某个用户的cron服务</p>
<p>
比如说root查看自己的cron设置:crontab -u root -l</p>
<p>
再例如，root想删除fred的cron设置:crontab -u fred -r</p>
<p>
在编辑cron服务时，编辑的内容有一些格式和约定，输入:crontab -u root -e</p>
<p>
进入vi编辑模式，编辑的内容一定要符合下面的格式:/1 * * * ls >> /tmp/ls.txt</p>
<p>
<span><strong>服务状态控制</strong></span></p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_521856">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
<td class="gutter">
<div class="line number1 index0 alt2">
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<code class="bash plain">/sbin/service</code> <code class="bash plain">crond start </code><code class="bash plain">//</code><code class="bash plain">启动服务 </code>
</div>
<div class="line number2 index1 alt1">
<code class="bash plain">/sbin/service</code> <code class="bash plain">crond stop </code><code class="bash plain">//</code><code class="bash plain">关闭服务 </code>
</div>
<div class="line number3 index2 alt2">
<code class="bash plain">/sbin/service</code> <code class="bash plain">crond restart </code><code class="bash plain">//</code><code class="bash plain">重启服务 </code>
</div>
<div class="line number4 index3 alt1">
<code class="bash plain">/sbin/service</code> <code class="bash plain">crond reload </code><code class="bash plain">//</code><code class="bash plain">重新载入配置 </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash plain">/sbin/service</code> <code class="bash plain">crond status </code><code class="bash plain">//</code><code class="bash plain">查看状态</code>
</div>
</div>
</td>
</tr></tbody></table>
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<div class="codetool" id="codetool">
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<p>
或者使用</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_763264">
<div class="toolbar">
<span>?</span>
</div>
<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
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</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash comments"># service crond start </code>
</div>
<div class="line number2 index1 alt1">
<code class="bash comments"># service crond stop </code>
</div>
<div class="line number3 index2 alt2">
<code class="bash comments"># service crond restart </code>
</div>
<div class="line number4 index3 alt1">
<code class="bash comments"># service crond reload </code>
</div>
<div class="line number5 index4 alt2">
<code class="bash comments"># service crond status</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
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</div>
<p>
<span><strong>开机启动</strong></span></p>
<p>
你也可以将这个服务在系统启动的时候自动启动:</p>
<p>
在/etc/rc.d/rc.local这个脚本的末尾加上:</p>
<div class="jb51code">
<div>
<div class="syntaxhighlighterbash" id="highlighter_180513">
<div class="toolbar">
<span>?</span>
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<table border="0" cellpadding="0" cellspacing="0"><tbody><tr>
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</td>
<td class="code">
<div class="container">
<div class="line number1 index0 alt2">
<code class="bash plain">/sbin/service</code> <code class="bash plain">crond start</code>
</div>
</div>
</td>
</tr></tbody></table>
</div>
</div>
<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
</div>
</div>
<p>
现在Cron这个服务已经在进程里面了，我们就可以用这个服务了。</p>
<p>
<span><strong>总结</strong></span></p>
<p>
以上所述是小编给大家介绍的CentOS下使用yum命令安装计划任务程序crontab，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！</p>
<p>
原文链接：http://blog.csdn.net/testcs_dn/article/details/48780971</p>
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