LinuxTips(RedHat)_en Package management with YUM
Package management with YUMCentOS and Fedora have YUM (Yello...
LinuxTips(RedHat)_en
LinuxTips(RedHat)_en LinuxTips(RedHat)_en Import the public key
Import the public keyWhen installing a package with the rpm ...
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)_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)_en Check the Linux network environment.
Check the Linux network environment.●Use "ip -a" to check th...
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)_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)_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)_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.
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.
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)_en Include daemon processes in the display
In the case of Linux, there are processes that run specifically for system maintenance without the need to give any instructions.These processes are called daemons, and they wait until there is a request from the user, and when there is a request, they create a new process and execute the process.The process created here is called a child process, and if it is set to run at a certain date and time in advance, it will execute the reserved process at the reserved date and time.Basically, these daemons are executed according to the user's settings, but some of them are default (standard) settings. Since these daemons are not operated by the user in a control terminal such as a console or terminal emulator, they will not be displayed in the control terminal when the ps command is executed, but you can display these processes by adding the option "-x".
LinuxTips(RedHat)_en Terminate the process
To terminate a running process, use the kill command.You nee...
LinuxTips(RedHat)_en Configuring the default gateway (router)
●Confirmation of the current default gatewayExecute the "route -n" command. "-n" is an option to display the hostname as IP.●Remove the default gatewaySet "del" as the argument of the route command, and set the IP address of the default gateway device (192.168.11.1) that you want to delete after "default gw".●Setting up a new default gatewaySet "add" as the argument of the route command, and set the IP address (192.168.11.2) of the default gateway device you want to set after "default gw".
LinuxTips(RedHat)_en Display various information about the CPU
●Display the CPU information installed on the PC.To display the CPU information installed in the PC, refer to the "/proc/cpuinfo" file.This information is used to know the CPU load for top command, etc.