Click here for "Error Codes for Commercial Air Conditioners".(Japanese Version)

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LinuxTips(RedHat)_en

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/dovecotdovecot-2.2.36-3.el7.x86_64

LinuxTips(RedHat)_en

LinuxTips(RedHat)_en

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

LinuxTips(RedHat)_enRPM Package Management

LinuxTips(RedHat)_en

Show RPM dependent packages

Show RPM dependent packagesDependencies 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.

LinuxTips(RedHat)_enRPM Package Management

LinuxTips(RedHat)_en

Install the RPM package

Install the RPM packageTo install the rpm package, run the r...

LinuxTips(RedHat)_enRPM Package Management

LinuxTips(RedHat)_en

Package management with YUM

Package management with YUMCentOS and Fedora have YUM (Yello...

LinuxTips(RedHat)_enRPM Package Management

LinuxTips(RedHat)_en

Import the public key

Import the public keyWhen installing a package with the rpm ...

LinuxTips(RedHat)_enRPM Package Management

LinuxTips(RedHat)_en

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.

LinuxTips(RedHat)_enRPM Package Management

LinuxTips(RedHat)_en

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.

LinuxTips(RedHat)_enNetwork Management

LinuxTips(RedHat)_en

Check the Linux network environment.

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

LinuxTips(RedHat)_enNetwork Management

LinuxTips(RedHat)_en

Check the port status of Linux

The "IP address" is used to identify which computer on the network you are connecting to, and the "port number" is needed to identify which program running on that computer you are accessing.The port number is a 16-bit integer and ranges from 0 to 65535.To check which ports are waiting for a connection in Linux, use the ss command or netstat command.●well-known portsPort numbers (0-1023) are reserved in advance for well-known services and protocols used in TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).

LinuxTips(RedHat)_enNetwork Management

LinuxTips(RedHat)_en

Find IP address from hostname

Looking up an IP address from a host name is called "forward DNS lookup".This process can be done by making a query to the name server (DNS) to receive IP address information.●Use the dig command to find out the IP address.Try to find the IP address of the Yahoo hostname "https://www.yahoo.co.jp/".Check the ANSWER SECTION of the execution result, and you will see the IP address of "https://www.yahoo.co.jp/".

LinuxTips(RedHat)_enNetwork Management

LinuxTips(RedHat)_en

Look up a mail server by domain name

To find out which host is running as a mail server within a domain, you can check the MX (Mail Exchanger) record set for that domain.In this section we will examine the mailservers for the metro.tokyo.jp domain.From the result of the dig command, you can see that there is a mail server named ml1.tisc.tokyo.jp running in the metro.tokyo.jp domain.

LinuxTips(RedHat)_enNetwork Management

LinuxTips(RedHat)_en

Display the IRQ of the connected device

Display the IRQ of the connected deviceThe /proc/interrupts file can display IRQ (InterruptReQuest: Interrupt Request) information.There are 16 types of IRQ, ranging from 0 to 15, and the /proc/interrupts file contains information on which ones are used.

LinuxTips(RedHat)_en

Disk and device management

Display PCI device information

Display PCI device informationTo check the information of a PCI device in Linux, use the lspci command.This lspci command can be executed with the option "-v" to display more detailed information.You will need super user (root) privileges to run this command.

Disk and device managementLinuxTips(RedHat)_en

LinuxTips(RedHat)_en

Stop unnecessary services

Linux starts many unnecessary services (programs) that are not used immediately after installation.Services that are not used consume server resources unnecessarily just by being started and running, which is not desirable for security measures.There are two commands to stop services: service and chkconfig, but the service command will cancel the settings and start the stopped service when the server is restarted.Stop the service with the chkconfig command, which will keep the service stopped even after restarting the server.

LinuxTips(RedHat)_ensystems-management

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