详解Linux查看实时网卡流量的几种方式
<p>在工作中，我们经常需要查看服务器的实时网卡流量。通常，我们会通过这几种方式查看Linux服务器的实时网卡流量。</p>
<p>
<strong>1. sar -n DEV 1 2</strong></p>
<p>
sar命令包含在sysstat工具包中，提供系统的众多统计数据。其在不同的系统上命令有些差异，某些系统提供的sar支持基于网络接口的数据统计，也可以查看设备上每秒收发包的个数和流量。</p>
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<code class="bash plain">sar –n DEV 1 2</code>
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命令后面1 2 意思是：每一秒钟取1次值，取2次。</p>
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DEV显示网络接口信息</p>
<p>
另外，-n参数很有用，他有6个不同的开关：DEV | EDEV | NFS | NFSD | SOCK | ALL ，其代表的含义如下：</p>
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DEV显示网络接口信息。</li>
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EDEV显示关于网络错误的统计数据。</li>
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NFS统计活动的NFS客户端的信息。</li>
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NFSD统计NFS服务器的信息</li>
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SOCK显示套接字信息</li>
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ALL显示所有5个开关</li>
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<code class="bash plain">$ sar -n DEV 1 2</code>
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<code class="bash plain">Linux 2.6.32-431.el6.x86_64 (CDVM-213017031) 05</code><code class="bash plain">/04/2017</code> <code class="bash plain">_x86_64_ (4 CPU)</code>
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<code class="bash plain">08:05:30 PM IFACE rxpck</code><code class="bash plain">/s</code> <code class="bash plain">txpck</code><code class="bash plain">/s</code> <code class="bash plain">rxkB</code><code class="bash plain">/s</code> <code class="bash plain">txkB</code><code class="bash plain">/s</code> <code class="bash plain">rxcmp</code><code class="bash plain">/s</code> <code class="bash plain">txcmp</code><code class="bash plain">/s</code> <code class="bash plain">rxmcst</code><code class="bash plain">/s</code>
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<code class="bash plain">08:05:31 PM lo 0.00 0.00 0.00 0.00 0.00 0.00 0.00</code>
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<code class="bash plain">08:05:31 PM eth0 1788.00 1923.00 930.47 335.60 0.00 0.00 0.00</code>
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<code class="bash plain">08:05:31 PM IFACE rxpck</code><code class="bash plain">/s</code> <code class="bash plain">txpck</code><code class="bash plain">/s</code> <code class="bash plain">rxkB</code><code class="bash plain">/s</code> <code class="bash plain">txkB</code><code class="bash plain">/s</code> <code class="bash plain">rxcmp</code><code class="bash plain">/s</code> <code class="bash plain">txcmp</code><code class="bash plain">/s</code> <code class="bash plain">rxmcst</code><code class="bash plain">/s</code>
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<code class="bash plain">08:05:32 PM lo 0.00 0.00 0.00 0.00 0.00 0.00 0.00</code>
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<code class="bash plain">08:05:32 PM eth0 1387.00 1469.00 652.12 256.98 0.00 0.00 0.00</code>
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<code class="bash plain">Average: IFACE rxpck</code><code class="bash plain">/s</code> <code class="bash plain">txpck</code><code class="bash plain">/s</code> <code class="bash plain">rxkB</code><code class="bash plain">/s</code> <code class="bash plain">txkB</code><code class="bash plain">/s</code> <code class="bash plain">rxcmp</code><code class="bash plain">/s</code> <code class="bash plain">txcmp</code><code class="bash plain">/s</code> <code class="bash plain">rxmcst</code><code class="bash plain">/s</code>
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<code class="bash plain">Average: lo 0.00 0.00 0.00 0.00 0.00 0.00 0.00</code>
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<code class="bash plain">Average: eth0 1587.50 1696.00 791.29 296.29 0.00 0.00 0.00</code>
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参数说明：</p>
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IFACE：LAN接口</li>
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rxpck/s：每秒钟接收的数据包</li>
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txpck/s：每秒钟发送的数据包</li>
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rxbyt/s：每秒钟接收的字节数</li>
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txbyt/s：每秒钟发送的字节数</li>
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rxcmp/s：每秒钟接收的压缩数据包</li>
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txcmp/s：每秒钟发送的压缩数据包</li>
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rxmcst/s：每秒钟接收的多播数据包</li>
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rxerr/s：每秒钟接收的坏数据包</li>
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txerr/s：每秒钟发送的坏数据包</li>
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coll/s：每秒冲突数</li>
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rxdrop/s：因为缓冲充满，每秒钟丢弃的已接收数据包数</li>
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txdrop/s：因为缓冲充满，每秒钟丢弃的已发送数据包数</li>
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txcarr/s：发送数据包时，每秒载波错误数</li>
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rxfram/s：每秒接收数据包的帧对齐错误数</li>
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rxfifo/s：接收的数据包每秒FIFO过速的错误数</li>
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txfifo/s：发送的数据包每秒FIFO过速的错误数</li>
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<p>
这种方式简单，直观，推荐使用。</p>
<p>
<strong>2.实时监控脚本</strong></p>
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<code class="bash preprocessor bold">#!/bin/bash</code>
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<code class="bash plain">ethn=$1</code>
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<code class="bash keyword">while</code> <code class="bash functions">true</code>
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<code class="bash keyword">do</code>
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<code class="bash spaces"> </code><code class="bash plain">RX_pre=$(</code><code class="bash functions">cat</code> <code class="bash plain">/proc/net/dev</code> <code class="bash plain">| </code><code class="bash functions">grep</code> <code class="bash plain">$ethn | </code><code class="bash functions">sed</code> <code class="bash string">'s/:/ /g'</code> <code class="bash plain">| </code><code class="bash functions">awk</code> <code class="bash string">'{print $2}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash plain">TX_pre=$(</code><code class="bash functions">cat</code> <code class="bash plain">/proc/net/dev</code> <code class="bash plain">| </code><code class="bash functions">grep</code> <code class="bash plain">$ethn | </code><code class="bash functions">sed</code> <code class="bash string">'s/:/ /g'</code> <code class="bash plain">| </code><code class="bash functions">awk</code> <code class="bash string">'{print $10}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash functions">sleep</code> <code class="bash plain">1</code>
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<code class="bash spaces"> </code><code class="bash plain">RX_next=$(</code><code class="bash functions">cat</code> <code class="bash plain">/proc/net/dev</code> <code class="bash plain">| </code><code class="bash functions">grep</code> <code class="bash plain">$ethn | </code><code class="bash functions">sed</code> <code class="bash string">'s/:/ /g'</code> <code class="bash plain">| </code><code class="bash functions">awk</code> <code class="bash string">'{print $2}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash plain">TX_next=$(</code><code class="bash functions">cat</code> <code class="bash plain">/proc/net/dev</code> <code class="bash plain">| </code><code class="bash functions">grep</code> <code class="bash plain">$ethn | </code><code class="bash functions">sed</code> <code class="bash string">'s/:/ /g'</code> <code class="bash plain">| </code><code class="bash functions">awk</code> <code class="bash string">'{print $10}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash functions">clear</code>
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<code class="bash spaces"> </code><code class="bash functions">echo</code> <code class="bash plain">-e </code><code class="bash string">"\t RX `date +%k:%M:%S` TX"</code>
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<code class="bash spaces"> </code><code class="bash plain">RX=$((${RX_next}-${RX_pre}))</code>
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<code class="bash spaces"> </code><code class="bash plain">TX=$((${TX_next}-${TX_pre}))</code>
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<code class="bash spaces"> </code><code class="bash keyword">if</code> <code class="bash plain">[[ $RX -lt 1024 ]];</code><code class="bash keyword">then</code>
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<code class="bash spaces"> </code><code class="bash plain">RX=</code><code class="bash string">"${RX}B/s"</code>
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<code class="bash spaces"> </code><code class="bash keyword">elif</code> <code class="bash plain">[[ $RX -gt 1048576 ]];</code><code class="bash keyword">then</code>
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<code class="bash spaces"> </code><code class="bash plain">RX=$(</code><code class="bash functions">echo</code> <code class="bash plain">$RX | </code><code class="bash functions">awk</code> <code class="bash string">'{print $1/1048576 "MB/s"}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash keyword">else</code>
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<code class="bash spaces"> </code><code class="bash plain">RX=$(</code><code class="bash functions">echo</code> <code class="bash plain">$RX | </code><code class="bash functions">awk</code> <code class="bash string">'{print $1/1024 "KB/s"}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash keyword">fi</code>
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<code class="bash spaces"> </code><code class="bash keyword">if</code> <code class="bash plain">[[ $TX -lt 1024 ]];</code><code class="bash keyword">then</code>
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<code class="bash spaces"> </code><code class="bash plain">TX=</code><code class="bash string">"${TX}B/s"</code>
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<code class="bash spaces"> </code><code class="bash keyword">elif</code> <code class="bash plain">[[ $TX -gt 1048576 ]];</code><code class="bash keyword">then</code>
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<code class="bash spaces"> </code><code class="bash plain">TX=$(</code><code class="bash functions">echo</code> <code class="bash plain">$TX | </code><code class="bash functions">awk</code> <code class="bash string">'{print $1/1048576 "MB/s"}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash keyword">else</code>
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<code class="bash spaces"> </code><code class="bash plain">TX=$(</code><code class="bash functions">echo</code> <code class="bash plain">$TX | </code><code class="bash functions">awk</code> <code class="bash string">'{print $1/1024 "KB/s"}'</code><code class="bash plain">)</code>
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<code class="bash spaces"> </code><code class="bash keyword">fi</code>
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<code class="bash spaces"> </code><code class="bash functions">echo</code> <code class="bash plain">-e </code><code class="bash string">"$ethn \t $RX $TX "</code>
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<code class="bash keyword">done</code>
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<p>
此脚本不需要额外再安装软件，并且可自定义欲查看接口，精确到小数，可根据流量大小灵活显示单位，默认采集间隔为1秒。</p>
<p>
用法为：</p>
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1、将脚本保存为可执行脚本文件，比如叫net.sh。</p>
<p>
2、chmod +x ./net.sh 将文件改成可执行脚本。</p>
<p>
3、sh net.sh eth0即可开始监看接口eth0流量，按ctrl+c退出。</p>
<p>
脚本是通过读取运行时文件系统/proc/net/dev中的网络实时数据，并通过简单计算得到的。关于目录/proc/net/dev，请参考下文。</p>
<p>
<strong>3. cat /proc/net/dev</strong></p>
<p>
Linux 内核提供了一种通过 /proc 文件系统，在运行时访问内核内部数据结构、改变内核设置的机制。proc文件系统是一个伪文件系统，它只存在内存当中，而不占用外存空间。它以文件系统的方式为访问系统内核数据的操作提供接口。用户和应用程序可以通过proc得到系统的信息，并可以改变内核的某些参数。由于系统的信息，如进程，是动态改变的，所以用户或应用程序读取proc文件时，proc文件系统是动态从系统内核读出所需信息并提交的。/proc文件系统中包含了很多目录，其中/proc/net/dev 保存了网络适配器及统计信息。</p>
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<code class="bash plain">$ </code><code class="bash functions">cat</code> <code class="bash plain">/proc/net/dev</code>
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<code class="bash plain">Inter-| Receive | Transmit</code>
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<code class="bash spaces"> </code><code class="bash plain">face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed</code>
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<code class="bash spaces"> </code><code class="bash plain">lo:137052296 108029 0 0 0 0 0 0 137052296 108029 0 0 0 0 0 0</code>
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<code class="bash spaces"> </code><code class="bash plain">eth0:13661574714188 31346790620 0 0 0 0 0 0 5097461049535 27671144304 0 0 0 0 0 0</code>
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<p>
最左边的表示接口的名字，Receive表示收包，Transmit表示发送包；</p>
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bytes表示收发的字节数；</li>
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packets表示收发正确的包量；</li>
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errs表示收发错误的包量；</li>
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drop表示收发丢弃的包量；</li>
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<p>
其实，我们平时经常用的很多查看网卡实时流量的命令，都是通过读取该目录下的实时流量，并通过简单计算得到的。</p>
<p>
<strong>4. 使用watch命令，配合ifconfig、more /proc/net/dev、cat /proc/net/dev来实时监控。比如执行 watch -n 1 "ifconfig eth0"</strong></p>
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<code class="plain plain">Every 1.0s: ifconfig eth0Thu May 4 20:26:45 2017</code>
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<code class="plain plain">eth0 Link encap:Ethernet HWaddr FA:16:3E:7E:55:D1</code>
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<div class="line number4 index3 alt1">
<code class="plain spaces"> </code><code class="plain plain">inet addr:10.213.17.31 Bcast:10.213.23.255 Mask:255.255.248.0</code>
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<div class="line number5 index4 alt2">
<code class="plain spaces"> </code><code class="plain plain">inet6 addr: fe80::f816:3eff:fe7e:55d1/64 Scope:Link</code>
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<div class="line number6 index5 alt1">
<code class="plain spaces"> </code><code class="plain plain">UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1</code>
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<div class="line number7 index6 alt2">
<code class="plain spaces"> </code><code class="plain plain">RX packets:31350149703 errors:0 dropped:0 overruns:0 frame:0</code>
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<div class="line number8 index7 alt1">
<code class="plain spaces"> </code><code class="plain plain">TX packets:27674701465 errors:0 dropped:0 overruns:0 carrier:0</code>
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<div class="line number9 index8 alt2">
<code class="plain spaces"> </code><code class="plain plain">collisions:0 txqueuelen:1000</code>
</div>
<div class="line number10 index9 alt1">
<code class="plain spaces"> </code><code class="plain plain">RX bytes:13663400883450 (12.4 TiB) TX bytes:5098104759633 (4.6 TiB)</code>
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</td>
</tr></tbody></table>
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<div class="codetool" id="codetool">
<div class="code_n">
<textarea></textarea>
</div>
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</div>
<p>
watch可以帮你监测一个命令的运行结果，省得你一遍遍的手动运行。在Linux下，watch是周期性的执行下个程序，并全屏显示执行结果。</p>
<p>
最后，除了上面提供的几种，还有很多种方式可以来看当前系统的网卡流量，我就不再一一复述了，上述方式如果不能满足你的需求，请自行google一下吧。</p>
<p>
根据其易用性以及可读性，强烈推荐方法1和方法2。希望对大家的学习有所帮助，也希望大家多多支持。</p>
<p>
原文链接：http://www.jianshu.com/p/b9e942f3682c?utm_source=tuicool&utm_medium=referral</p>
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