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When our CentOS system provides any services on a network, those services are accessible through a port number. All network services are configured to be accessed on a particular port number. By examining which ports are active on our system we can know what services (and points of attack) are available on our system. The ability to examine this information is important for troubleshooting network services and securing our systems. One great tool for this is the '''netstat''' command.
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<td style="border-bottom: thin solid black;font-weight:bold;background-color:#ffffff;">Command(s)</td>
<td style="border-bottom: thin solid black;font-weight:bold;background-color:#ffffff;">Purpose</td>
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<td width="20%" style="border-bottom: thin solid black;"><b><code><span style="color:#3366CC;font-size:1.2em;">uname -rv</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">hostname</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">ps -ef</span></code></b></td>
<td width="20%" style="border-bottom: thin solid black;">Basic Linux OS information such as '''kernel''' version, '''host-name''' of Linux server, and all '''processes''' that are running on the system after installation.</td>
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<td width="20%" style="border-bottom: thin solid black;"><b><code><span style="color:#3366CC;font-size:1.2em;">rpm -q -a | wc -l'''</span></code></b><br><b><code><span style="color:#3366CC;font-size:1.2em;">rpm -q -a -l | wc -l'''</span></code></b><br><b><code><span style=" pointer-events:none;cursor:default;color:#3366CC;font-size:1.2em;">rpm -q -l gedit | wc -l</span></code></b></td>
<td width="20%" style="border-bottom: thin solid black;">Obtain number of installed packages in the rpm database. Option '''-q''' is to "query" informationo, option '''-a''' means for all installed packages, option '''-l''' means all files installed as opposed to just the application.</td>
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<td width="20%" style="border-bottom: thin solid black;"><b><code><span style="pointer-events: none;cursor: default;color:#3366CC;font-size:1.2em;">ifconfig</span></code></b><br><b><code><span style="pointer-events: none;cursor: default;color:#3366CC;font-size:1.2em;">route -n</span></code></b><br><b><code><span style="pointer-events: none;cursor: default;color:#3366CC;font-size:1.2em;">nslookup</span></code></b></td>
<td width="20%" style="border-bottom: thin solid black;">Obtain network connectivity confirmation including: '''IP ADDRESS''', '''Netmask''', '''routing''' (default gateway), and the default '''Domain Name Server'''.</td>
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# Perform this section on your '''c7host''' machine.
