建立虛擬機 in Cent OS by KVM

甚麼是 CentOS

CentOS，全名為Community Enterprise Operating System，
是一種免費、開源的Linux發行版，

主要目標是提供一個穩定、可預測且易於管理的平台，專為企業級應用而設計。

它是基於Red Hat Enterprise Linux (RHEL)的源碼重新構建的，因此能夠與RHEL高度兼容，擁有相同的軟件包管理系統和軟件庫。

CentOS提供了一個穩健的環境，適合運行高要求的服務器和應用，並且保持免費使用，廣受全球許多企業和專業人士的信賴和使用。

同時它的社區支持也非常活躍，提供了大量的文檔、論壇和IRC頻道來幫助使用者解決問題。

甚麼是 KVM

KVM（Kernel-based Virtual Machine）是一種開源的虛擬化技術，
內建於Linux內核中，允許Linux作業系統上運行多個隔離的虛擬機器。

透過使用硬體加速功能（如Intel VT或AMD-V），
KVM為每個虛擬機器提供了私有的虛擬硬體，包括處理器、記憶體、磁盤、網絡接口等，從而實現近乎原生的性能。

它支持多種作業系統，包括Linux、Windows及其他Unix系統。
作為一個高效且可擴展的虛擬化解決方案，KVM廣泛應用於雲計算、虛擬私人服務器（VPS）和企業數據中心。

如何確定能建立虛擬主機

檢查虛擬化支持

# 結果必須大於 0
egrep -c '(vmx|svm)' /proc/cpuinfo

檢查基本資源

# 詳細獲得CPU資訊
lscpu

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

# 簡易獲得CPU核心數
nproc

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

# 簡易查詢當前 RAM 記憶體狀態
free -h

# 簡易查詢當前 Memory 記憶體狀態
free -m

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

基礎設定與下載 KVM

# 如果系統不具有相關軟件倉庫 要先下載
sudo yum install epel-release

# 更新安裝的包
sudo yum update

# 下載相關的軟件包
sudo yum install qemu-kvm qemu-img virt-manager libvirt libvirt-python libvirt-client virt-install virt-viewer bridge-utils

將 SELinux 關閉編輯 /etc/sysconfig/selinux 檔案設定

# SELinux=enforcing
SELinux=disabled

重新開機載入設定

sudo reboot

確認已經載入 KVM

lsmod | grep kvm

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

# 啟動 libvirtd 服務
sudo systemctl start libvirtd
# 設定開機自動啟動
sudo systemctl enable libvirtd

建立虛擬主機

建立指令

# 下方分別設置 vm 名稱、RAM、CPU、儲存位置、size(記憶體)
sudo virt-install --name=vm --ram=6144 --vcpus=6 --disk path=/var/lib/libvirt/images/vm.img,size=20 --os-variant=centos7 --graphics none --console pty,target_type=serial --location='http://mirror.centos.org/centos/7/os/x86_64/' --extra-args='console=ttyS0,115200n8 serial'

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

備註 :
    安裝過程可能有點久，如果長時間卡在一畫面，可能會是記憶體不足或是網路問題導致下載失敗，可以直接跳到最後方刪除該虛擬雞的所有資訊，調整後再重新建立虛擬機。

設定並安裝 OS

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

透過上方指令後，會出現這畫面開始作業系統基本設定。

透過 UI (VNC方式) 進行設定
特過文字介面進行設定

這裡透過文字介面即可( 輸入 2 後，按 Enter )

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

接下來依序進行設定

語言設定 ( 輸入 1 後，按 Enter )

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

直接選擇英文即可

時區設定 ( 輸入 2 後，按 Enter )

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

直接選擇時區，選擇台北即可

儲存位置 ( 輸入 5 後，按 Enter )

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

一路按 C 即可，直接安裝整個磁碟，可以根據個人需求做調整。

管理員密碼 ( 輸入 8 後，按 Enter )

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

連續輸入兩次管理員密碼

新增使用者 ( 輸入 9 後，按 Enter )

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

依序設定名稱、密碼、管理員群組等等
結束按 c 回去菜單頁面

開始安裝

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

按 b 開始安裝

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

安裝完成，按 enter 繼續

登入與退出 VM

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

輸入使用者名稱與密碼可以直接進入

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

與一般關機不同，必須透過 ctrl+] 方能退出

備註:
    使用注音輸入法，系統會誤以為要輸入】，請切換輸入法後再輸入 ctrl+] 方能退出

連線虛擬主機與查看虛擬主機資訊

# 列出所有 vm 資訊
virsh --connect qemu:///system list

Image Not Showing Possible Reasons

The image was uploaded to a note which you don't have access to
The note which the image was originally uploaded to has been deleted

沒錯，剛運行的虛擬機正在執行

# 查看指定vm詳細資訊 (vm 更換成虛連線虛擬機名稱)
virsh --connect qemu:///system domifaddr vm

很好，還有其虛擬機的IP位址(可用ssh連線)

# 連線 指定名稱虛擬機 (vm 更換成虛連線虛擬機名稱)
virsh --connect qemu:///system console vm

# 亦可透過 ssh 進行連線 
# (user 更換成vm中存在的user名稱)
# (vm-ip 更換成虛連線虛擬機IP)
ssh user@vm-ip

OK，兩種連線方式都沒問題

刪除虛擬主機

# 強制關機並刪除定義 (vm 更換成虛連線虛擬機名稱)
virsh --connect qemu:///system destroy vm
virsh --connect qemu:///system undefine vm

# 刪除vm本身的image資訊
# 此處與前方設定的vm儲存位置有關係
sudo rm /var/lib/libvirt/images/vm.img