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OracleLinux9.1 : Initial settings after OS installation

1.Install bash completion extension package

2.Disabling SELinux

First, disable selinux. selinux is a feature that improves auditing and security in Linux, but when enabled, it can limit the behavior of services and the contents of the configuration considerably.
Therefore, it is basically a case of invalidation in many cases.

SELinux operating modes

Enforcing : SELinux functionality is enabled and access control is enabled
Permissive : SElinux will warn, but no access restrictions will be placed
disabled : Both SElinux function and access control are disabled
①Current SELinux status

②Switching to [permissive] mode

③Switch to [enforcing] mode

④To completely disable SELinux, a reboot is required by adding selinux=0 to the kernel command line as follows

※ To return SELinux to active, do the following (reboot after changes)

3.System Modernization

Update packages as soon as possible after OS installation.
However, when a dnf update is performed, a kernel update is also performed at the same time.
A kernel update may require rebooting the system or stopping services, or worse, a kernel panic may occur and the system may not boot. It is wiser to exclude the kernel from the update.
Run dnf -y update with "--exclude=kernel*" after it.
Kernel can be excluded from updates

4.Services to be stopped due to security measures

Stop the following services that you deem unnecessary.

5.Adding Repositories

5.1 Add EPEL repository

5.2 Add Remi's RPM repository

6.Network configuration (command line configuration method)

6.1 Host Name Change

Change the host name to Lepard

6.2 Static IP address setting

If the default setting is to obtain an IP address via DHCP during OS installation, change the network settings to a fixed IP address if necessary.
First, find out the name of your network interface with the following command
This time it is "ens160"

In Oraclelinux8, this could be changed by rewriting the ifcfg-xxx file found in network-scripts, but in Oraclelinux9, the ifcfg format is deprecated and by default, NetworkManager will create new profiles in this format The "nmcli" command is no longer used to change it. Use the "nmcli" command to change it.
Change the static IPv4 address to "".

7.Network configuration (how to configure via GUI)

7.1 Static IP address setting

Change the address of the IPv4 configuration

7.2 Host Name Change

Change the host name to Lepard

8.Vim Settings

①Installing Vim Extensions
②Apply and reflect Vim
③Configure Vim as a user-specific environment

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