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$ nproc :  CPU 16 core $ cat /proc/meminfo :  RAM: 32GB $ df -H :  HDD: 500GB $ hostnamectl :    CentOS Linux 7 (Core) $ ip a s : show IP address.

I. Using root accout $  passwd 'user name' II. Change from current user $  passwd (Enter new password and confirm new password )

When you SSH to Linux Server and meet this error: user@hostname ~]$ ssh root@pong @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that a host key has just been changed. The fingerprint for the RSA key sent by the remote host is 6e:45:f9:a8:af:38:3d:a1:a5:c7:76:1d:02:f8:77:00. Please contact your system administrator. Add correct host key in /home/hostname /.ssh/known_hosts to get rid of this message. Offending RSA key in /var/lib/sss/pubconf/known_hosts:4 RSA host key for pong has changed and you have requested strict checking. Host key verification failed. => Way how to fix this problem, using this statement: ssh-keygen -R Example: ssh-keygen -R 422.62.159.23

The Install I'm not going to walk you through the VirtualBox install because it's simple and straight forward. I will however, go through the steps of installing CentOS in VirtualBox. Once you have VirtualBox installed, open it up and click on the New icon on the top left of the toolbar. Name your VM anything you want, but make sure you choose  Linux  as the type and  Red Hat (64-bit)  as the version. Next, choose the amount of memory you'd like to reserve for this VM. I usually just go with the suggested amount, which in this case is 768MB. The next prompt will ask you to add a virtual hard disk. Go ahead and select  Create a virtual hard disk now  which should be the default. Next, you can select whichever type of VM hard disk type you'd like. I usually just select VDI. The next prompt will ask you if you'd like dynamic storage or fixed storage. Select  dynamic . Dynamic storage means that VirtualBox will only use the amount ...

Bước 1 : Mơ file  ~/.bashrc để edit. Từ terminal gõ lệnh $vi  ~/.bashrc Bước 2 : Bấm phím 'Esc' sau đó nhấn 'i' để insert nội dung, ví dụ set biến môi trường JAVA_HOME: $  export JAVA_HOME=/usr/lib/jvm/java $ export PATH=$PATH:$JAVA_HOME/bin Bước 3 : Bấm 'Esc' sau đó nhấn 'x' để lưu.  Bước 4 : Load lại thông tin $ source  ~/.bashrc