Linux - Initial setting after Linux install

■ Register a user on the following file.
njoonk  ALL=(ALL)  ALL

$ cat /etc/sudoers
njoonk ALL=(ALL) ALL

@ Disallowing Root Access
■ Edit the following file, set the PeritRootLogin parameter to no
PermitRootLogin no

$ vim /etc/ssh/sshd_config
PermitRootLogin no

sshd should be restared on CentOs8.2

$ systemctl restart sshd
$ systemctl status sshd

■ Change a host name
@ Before

[root@localhost home]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=localhost.localdomain

@ After

[root@localhost home]# cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=centos04
GATEWAY=192.168.11.1

Check hostname information

[root@localhost home]# hostnamectl

■ Edit hosts file
@ Before

[root@localhost home]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

@ After

[root@localhost home]# cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
127.0.0.1 centos04
192.168.11.23 centos04 localhost

■ Just restart the network
$ /etc/init.d/network restart

@ Set DNS
@ Before

[root@centos04 sysconfig]# cat /etc/resolv.conf
search centos04

@ After

[root@centos04 sysconfig]# cat /etc/resolv.conf
search centos04
nameserver 192.168.11.1

Linux - Changing a DHCP for STATIC IP on CentOs8.2

■ Changing a DHCP for STATIC IP.

1, Add the static IP information as below

2, Edit or add nameserver 192.168.0.1 into /etc/resolv.conf

3, Restart network (Don't execute the following command on remote)

    $ sudo nmcli networking off

    $ sudo nmcli networking on

OR

    $ sudo systemctl restart NetworkManager.service

4, Check the logs

    $ sudo journalctl -fu NetworkManager

To resolve the conflicting or being different Mac address

 ■ You might meet the following error when importing an images on VirtualBox.

 ■ How to solve the troubleshooting on CentOs

1, Check the net

2, Edit /etc/udev/rules.d/70-persistent-net.rules

    $ vim /etc/udev/rules.d/70-persistent-net.rules

3, Check to work as a restarting the network.

■ How to install net-tools (ifconfig, etc) on CentOs 8.2

$ sudo yum -y install net-tools

MYSQL - How to install MYSQL8 on Ubuntu

■ How to install MYSQL8 on Ubuntu

1, Download repository package of MYSQL.

2, Install the Repository package of MYSQL.
    $ sudo dpkg -i mysql-apt-config_0.8.16-1_all.deb

3, Select Mysql Server & Cluster (Currently selected: mysql-8.0)

4, Select Mysql-8.0

5, Update the information of the package and install mysql8
    $ sudo apt install mysql-server

■ There is the following error when loading a image exported in Windows 10.

■ You should do the following process to solve the problem.

1, Open command prompt as Administrator.

2, Run bcdedit to check hypervisor status:

3, hypervisorlaunchtype should be disabled.

    $ bcdedit /set hypervisorlaunchtype off