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Check your Linux distribution and version.

Check your Linux distribution and version. ●For CentOS7 system [root@Lion ~]# cat /etc/redhat-release CentOS Linux release 7.6.1810 (Core) ●For Fedora systems [root@Lion ~]# cat /etc/fedora-release ●For Ubuntu systems [root@Lion ~]# cat /etc/lsb-release
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Show loaded kernel modules

Display the loaded kernel modules In order to prevent the kernel from becoming bloated, Linux does not include programs other than those that are minimally necessary for operation in the kernel, but allows them to be added or detached depending on the environment. The things that can be added or detached in this way are called "modules," and typical ones include SCSI adapters, PC cards, and device drivers. The command to display what modules are currently installed is the "lsmod" command. You will need root privileges to execute this command.
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View detailed information about kernel modules.

View detailed information about kernel modules. To display detailed information about each loaded module, use the modinfo command. Specify the module for which you want to know the detailed information as an argument and execute it.
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Check the installed RPM packages.

Check the installed RPM packages. Red Hat Enterprise Linux and CentOS, which was developed based on Red Hat Enterprise Linux, use a package management tool called RPM (Redhat Package Manager).。 RPM is a handy management tool that allows you to easily install and uninstall software and manage RPM packages with dependencies in mind, preventing you from accidentally removing RPM packages that you need. If you want to use this RPM, use the "rpm" command. Use the "-q" option to examine the RPM packages already installed, and the "-a" option to list the installed packages. rpm -qa" alone will show you all the packages installed on your Linux system, and is not suitable for checking specific packages. It is not suitable for checking a specific package. To check if a specific package is installed, specify the PRM package you want to check in "rpm -qa".
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Display RPM package information

Display RPM package information To find out what features a particular package provides, use the -q option to make a query, and the -i sub-option in combination to display that information. Specify the package name of the package for which you want to display information as an argument.
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The directory where the RPM package is installed

Display the directory where the RPM package is installed. To find out where the relevant files are when you install a particular package, run the rpm command with the To check where the related files are located after installing a particular package, run the rpm command with the "-ql" option. Specify the package name as an argument.
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Check which RPM package a particular program is included in.

Check which RPM package a particular program is included in. To check which RPM package a particular program is included in, add the "-qf" option to the rpm command and specify the program (executable file) as an argument. [root@Lion ~]# rpm -qf /usr/sbin/dovecot dovecot-2.2.36-3.el7.x86_64
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Test the installation of RPM packages.

Test the installation of RPM packages. Sometimes, due to dependencies, conflicts, or other problems, an error message will be displayed when executing the install command and the installation will fail. It is possible to test for such problems before installation. To do so, run the rpm command with the "--test" option and execute the installation. [root@Lion ~]# rpm -ivh --test zlib-devel-1.2.3-4vl5.i386.rpm ↑Test the installation of the rpm package
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Show RPM dependent packages

Show RPM dependent packages Dependencies are often a problem when manipulating packages, such as installing, upgrading, or removing RPM packages. So to avoid these problems, it is important to check the dependencies in advance. To check what package a particular package depends on, run the rpm command with the "-q" option in combination with the "-R" option to display the name of the dependent package.
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Install the RPM package

Install the RPM package To install the rpm package, run the ...
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Package management with YUM

Package management with YUM CentOS and Fedora have YUM (Yell...
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Import the public key

Import the public key When installing a package with the rpm...
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RPM Database

RPM Database ●Rebuild the RPM database. Information about RPM packages is stored in the RPM database. When searching for information about a package, this RPM database plays an important role, but sometimes it gets corrupted. In such a case, the RPM database can be rebuilt by running the rpm command with the "--rebuilddb" option. [root@Lion ~]# rpm --rebuilddb [root@Lion ~]# ●Create a new RPM package database. To create a new RPM package database, run the rpm command with the "--initdb" option.
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Check the IP address.

To check the IP address, use the "ifconfig" command. In addition to checking the IP address, the ifconfig command can also be used to change it. On CentOS7, you can also run the "ip" command with the "a" option instead of ifconfig. Currently, ifconfig is being replaced by the ip command, and ifconfig may no longer be available in the future.
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Check the Linux network environment.

Check the Linux network environment. ●Use "ip -a" to check t...