Linux利用Sysctl命令调整内核参数
<p><span><strong>前言</strong></span></p>
<p>
sysctl 命令被用于在内核运行时动态地修改内核的运行参数，可用的内核参数在目录 /proc/sys 中。它包含一些TCP/IP堆栈和虚拟内存系统的高级选项， 这可以让有经验的管理员提高引人注目的系统性能。用sysctl可以读取设置超过五百个系统变量。</p>
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<span><strong>1、常见用法</strong></span></p>
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列出所有的变量并查看</p>
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<code class="bash plain">sysctl -a | </code><code class="bash functions">less</code>
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修改某变量的值</p>
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<code class="bash plain">sysctl -w 变量名=变量值</code>
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<code class="bash comments">#sysctl -w vm.max_map_count=262144</code>
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读一个指定的变量，例如 kernel.msgmnb：</p>
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<code class="bash plain">$ sysctl kernel.msgmnb </code>
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<code class="bash plain">kern.maxproc: 65536</code>
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要设置一个指定的变量，直接用 <code>variable=value</code> 这样的语法：</p>
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<code class="bash plain">$ </code><code class="bash functions">sudo</code> <code class="bash plain">sysctl kernel.msgmnb=1024</code>
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<code class="bash plain">kernel.msgmnb: 1024</code>
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可以使用sysctl修改系统变量，也可以通过编辑sysctl.conf文件来修改系统变量。sysctl.conf 看起来很像 rc.conf。它用 <code>variable=value</code> 的形式来设定值。指定的值在系统进入多用户模式之后被设定。并不是所有的变量都可以在这个模式下设定。</p>
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sysctl 变量的设置通常是字符串、数字或者布尔型。 (布尔型用 1 来表示'yes'，用 0 来表示'no')。</p>
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<code class="bash plain">sysctl -w kernel.sysrq=0</code>
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<code class="bash plain">sysctl -w kernel.core_uses_pid=1</code>
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<code class="bash plain">sysctl -w net.ipv4.conf.default.accept_redirects=0</code>
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<code class="bash plain">sysctl -w net.ipv4.conf.default.accept_source_route=0</code>
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<code class="bash plain">sysctl -w net.ipv4.conf.default.rp_filter=1</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_syncookies=1</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_max_syn_backlog=2048</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_fin_timeout=30</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_synack_retries=2</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_keepalive_time=3600</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_window_scaling=1</code>
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<code class="bash plain">sysctl -w net.ipv4.tcp_sack=1</code>
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<span><strong>2、关于sysctl文件的配置</strong></span></p>
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sysctl设置定义在 sur/lib/sysctl.d/ , /run/sysctl.d 和 /etc/sysctrl.d 目录下。一些软件的设置则位于 /usr/lib/sysctl.d 目录下。想要覆盖整个文件系统参数的话，则在 /etc/sysctl.d 目录下新建一个同名的文件，然后写上你的配置。新建自己的配置也是一样。</p>
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在 /etc/sysctl.d 目录下，新建文件，写上自己的配置。</p>
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<strong>最后</strong></p>
<p>
有些软件配置内核参数用的到。</p>
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<span><strong>总结</strong></span></p>
<p>
以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。</p>
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原文链接：http://www.jianshu.com/p/ed7f9292d6a3</p>
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