CentOS 7 on VM @ Hyper-V

• Virtual Machine (VM) Specs

  • External Virtual Switch, CentOS-GbE, created.

  • ISO CentOS-7 List | mirror.vcu.edu | torrent

    D:\SCRATCH\[NO_SYNCH]\VMs\CentOS\CentOS-7-x86_64-DVD-1804.iso

  • Generation 2 (VM)

  • 2 vCPUs

  • Dynamic Memory: 512MB/256MB/1GB (START/MIN/MAX)

  • VHDX: 40GB (42949672960 byte); 1MB block size
    Modified on 1^st launch @ VM creation. (See PowerShell script).

    Stop-VM -VM $VMname -Force
    New-VHD -Path $VHDStoragePath -SizeBytes $VHDXSizeBytes -Dynamic -BlockSizeBytes 1MB
    

• Create VM @ PowerShell
  

  Hyper-V specific settings ...

  • Installation Destination

    • Local Standard Disks
      40 GiB
Msft Virtual Disk
sda / 2014.5 KiB free

      • per VM config @

        • @ CentOS (VM)

          # Config client (user acct)
          mkdir ~/.ssh 
          chmod 700 ~/.ssh
          touch ~/.ssh/authorized_keys
          chmod 600 ~/.ssh/authorized_keys
          
          # Config server (sshd)
          sudo vim /etc/ssh/sshd_config
          PubkeyAuthentication yes
          # required by ssh-copy-id (to receive pub key):
          PasswordAuthentication yes
          

          • ssh ... Pubkey login WILL FAIL if owner|perms|SELinux-context is wrong.
            Debug login issues:

            ls -ZA ~/.ssh
            systemctl status sshd -l     
            grep AVC /var/log/{secure,audit.log}
            

        • @ host

          • Create key-pair; send public key to VM.

            # Generate key pair 
            ssh-keygen -t ed25519 -a 100  
            # ... prompts for save-path & passphrase 
            # Send newly generated pub key to VM user acct @ ~/.ssh/authorized_keys
            ssh-copy-id -i $_ID_FILE $_USER@$_VM
            # ... prompts for password
            

            • Sending the key requires PasswordAuth... enabled @ sshd_config .
              Disable that afterward (at VM) to better secure.

          • Add identity @ ~/.ssh/config

            Host $_VM 
              HostName 192.168.1.10 # IP or HOST.DOMAIN
              User $_USER
              CheckHostIP yes
              IdentityFile ~/.ssh/centosvm_ed25519
            

            • Note that "Host" here is the VM, not the host accessing it.
              And "Host" name ($_VM) has no meaning beyond this SSH tool;
              can be any name; is merely the SSH configuration reference.
              

        SSH access (thereafter)

        • ssh $_VM, or override User with $_USER@$_VM.
          Either one references this configuration.

          • Sessions (concurrent)
            tty1 @ first connect (terminal 1).
            tty2-tty6 (Up @ Alt+RightArrow; Down @ Alt +LeftArrow)
            tty to see current terminal number.
            
            • Alt+Arrows work only @ Hyper-V > Connect, not @ any external console (cmd.exe, PowerShell, WSL, ConEmu, or mintty).

        Backup /home

        • @ VM

          cd /home
          sudo tar -caf /home/$USER.tgz -C /home $USER
          

        • @ host

          rsync -auz root@$_VM:/home/$_USER.tgz ~/etc/platforms/$_VM/$_USER.tgz
          

        Update home

        • @ host

          # .tgz selected files and folders @ ~
          find ~ -maxdepth 1 \( \
              -name 'etc' \
              -o -name '.passgo' \
              -o -name '.bash*' \
              \) | tar -caf updates.tgz --files-from -
          # push the .tgz
          rsync -auz updates.tgz $_USER@$_VM:/home/$_USER/updates.tgz
          

        Enable Dynamic Memory In-Guest

        @ /etc/udev/rules.d/100-balloon.rules (create)
        SUBSYSTEM=="memory", ACTION=="add", ATTR{state}="online"

        • No; removed it; perhaps unnecessary @ Gen 2 Hyper-V

        • Install Extra Hyper-V Tools
          yum install -y hyperv-daemons

        • Disable CentOS Disk I/O Scheduler (Hyper-V handles optimization)

          su root 
          cat /sys/block/sda/queue/scheduler
          noop [deadline] cfq
          echo noop > /sys/block/sda/queue/scheduler
          cat /sys/block/sda/queue/scheduler
          [noop] deadline cfq
          exit
          

        Other install/search

        su
        yum check-update
        yum update
        # EPEL [Extra Packages for Enterprise Linux]  https://fedoraproject.org/wiki/EPEL
        yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
        # And to better handle dependencies (though does not work @ Hyper-V, nor containers):
        #subscription-manager repos --enable "rhel-*-optional-rpms" --enable "rhel-*-extras-rpms"
        yum list installed | grep hyperv 
        yum list install httpd 
        shutdown now     # poweroff
        shutdown -r now  # reboot 
        reboot           # works too
        

        # Install VS Code
        rpm --import https://packages.microsoft.com/keys/microsoft.asc
        sh -c 'echo -e "[code]\nname=Visual Studio Code\nbaseurl=https://packages.microsoft.com/yumrepos/vscode\nenabled=1\ngpgcheck=1\ngpgkey=https://packages.microsoft.com/keys/microsoft.asc" > /etc/yum.repos.d/vscode.repo'
        
        yum check-update
        sudo yum install code