详解使用rpm命令从CentOS系统盘安装计划任务程序crontab
<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>
<p>
估计是最小化安装的时候默认不会安装此程序，公司的环境有的已经安装了，有的却没有。</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>准备文件</strong></span></p>
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将光盘CentOS-6.5-x86_64-bin-DVD1放入光驱，进入Packages目录，或者将以下文件复制到要安装的系统中：</p>
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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</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</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 </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</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</code>
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<span><strong>开始安装</strong></span></p>
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<code class="bash comments"># rpm -ivh procmail-3.22-25.1.el6.x86_64.rpm </code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:procmail </code><code class="bash comments">########################################### </code>
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<code class="bash comments"># rpm -ivh sendmail-8.14.4-8.el6.x86_64.rpm </code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:sendmail </code><code class="bash comments">########################################### </code>
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<code class="bash comments"># rpm -ivh cronie-1.4.4-12.el6.x86_64.rpm </code>
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<code class="bash plain">error: Failed dependencies:</code>
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<code class="bash spaces"> </code><code class="bash plain">dailyjobs is needed by cronie-1.4.4-12.el6.x86_64</code>
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安装cronie-1.4.4-12.el6.x86_64.rpm时提示缺少依赖项，经过测试可以直接使用“–nodeps”选项忽略它。</p>
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<code class="bash comments"># rpm -ivh cronie-1.4.4-12.el6.x86_64.rpm --nodeps</code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:cronie </code><code class="bash comments">########################################### </code>
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<code class="bash comments"># rpm -ivh crontabs-1.10-33.el6.noarch.rpm </code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:crontabs </code><code class="bash comments">########################################### </code>
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<code class="bash comments"># rpm -ivh cronie-anacron-1.4.4-12.el6.x86_64.rpm </code>
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<code class="bash plain">Preparing... </code><code class="bash comments">########################################### </code>
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<code class="bash spaces"> </code><code class="bash plain">1:cronie-anacron </code><code class="bash comments">########################################### </code>
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<code class="bash plain"></code><code class="bash comments"># crontab -l</code>
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<code class="bash plain">no </code><code class="bash functions">crontab</code> <code class="bash keyword">for</code> <code class="bash plain">root</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>
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<p>
也可以使用 info crontab 命令查看详细的帮助信息。</p>
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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>
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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>
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crontab -l //列出某个用户cron服务的详细内容</p>
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crontab -r //删除没个用户的cron服务</p>
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crontab -e //编辑某个用户的cron服务</p>
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比如说root查看自己的cron设置:crontab -u root -l</p>
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再例如，root想删除fred的cron设置:crontab -u fred -r</p>
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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>
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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>
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<span><strong>服务状态控制</strong></span></p>
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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>
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<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>
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<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>
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<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>
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<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>
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或者使用</p>
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<code class="bash comments"># service crond start </code>
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<code class="bash comments"># service crond stop </code>
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<code class="bash comments"># service crond restart </code>
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<code class="bash comments"># service crond reload </code>
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<code class="bash comments"># service crond status</code>
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<span><strong>开机启动</strong></span></p>
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你也可以将这个服务在系统启动的时候自动启动:</p>
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在/etc/rc.d/rc.local这个脚本的末尾加上:</p>
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<code class="bash plain">/sbin/service</code> <code class="bash plain">crond start</code>
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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>
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<span><strong>总结</strong></span></p>
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以上所述是小编给大家介绍的使用rpm命令从CentOS系统盘安装计划任务程序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>
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原文链接：http://blog.csdn.net/testcs_dn/article/details/48781553</p>
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