Virtualization on Linux

# Virtualization on Linux Most end-user machines (PC, laptop) run Windows or MacOS out of the box, but it always comes the day when one has to run a full-fledged Linux system be it to study operating systems, to run specific programs that are treated as second-class citizens on Windows and MacOS, or to simply chuang-bi. One is naturally presented with three choices: bare-metal, virtual machine, container. 1. **Bare-Metal:** To boot directly into Linux, making it the OS running directly on one's machine. 2. **Virtual Machine:** Provision a virtual environment in the OS that is currently running to run a full Linux system *as if* a program. 3. **Container:** This option is very restricted in terms of hardware control but requires much less machine resources compared to the previous two. [Debian Buster virt-manager 2.0.0](https://manpages.debian.org/buster/virtinst/virt-install.1.en.html) `--memory` deprecates `-r/--ram`. Create `test.yaml` with content: ``` variant: fcos version: 1.0.0 passwd: users: - name: user ssh_authorized_keys: - ssh-rsa AAA... ``` Compile it to the `ignition` file `test.ign` via: ``` fcct -p -s -o test.ign test.yaml ``` Set up the correct `SELinux` label: ``` chcon -t svirt_home_t test.ign ``` ``` virt-install \ --name test \ --memory 1024 \ --os-variant=fedora31 \ --import \ --graphics none \ --network bridge=virbr4 \ --disk size=8,backing_store="$HOME/.local/share/libvirt/images/fedora-coreos-32.20200715.3.0-qemu.x86_64.qcow2" \ --qemu-commandline="-fw_cfg name=opt/com.coreos/config,file=$HOME/test.ign" ``` ## Fedora packages ``` dnf install \ qemu-kvm-core \ libvirt \ libvirt-bash-completion \ virt-install ``` ## Install debian from serial console [Ref.](https://weblog.retiisi.eu/2018/04/debian-install-virtual-serial-port/) ``` virt-install \ --name sim \ --memorys 1024 \ --hvm \ --os-variant debian10 \ --network bridge=virbr1 \ --cdrom /var/lib/libvirt/images/debian-10.4.0-amd64-netinst.iso \ --boot hd,cdrom,useserial=on \ --disk size=4 \ --graphics none \ --console target_type=serial ``` Upon menu splash, don't install just yet. Pess `TAB`, and replace `--- quiet` with `console=ttyS0 vga=none`. Before you finish the installation, go back to menu, and choose `Execute a shell`. To make future boots use the serial consoel, mount the virtual file systems under `/target` and chroot into it: ``` mount -o bind /proc /target/proc mount -o bind /sys /target/sys mount -o bind /dev /target/dev chroot /target /bin/bash vi /etc/default/grub ``` Replace `GRUB_CMDLINE_LINUX=""` with `GRUB_CMDLINE_LINUX="console=ttyS0"`, and uncomment `GRUB_CONSOLE=serial`. Save and exit `vi`. Execute the following, and finish the installation. ``` update-grub umount /target/sys /target/dev /target/proc ``` ## Debian Functional libvirt server side (debian) install. ``` apt install --no-install-recommends qemu-kvm libvirt-clients libvirt-daemon-system qemu-utils ``` If dnsmasq is missing on the server side: ``` apt install dnsmasq ``` The default network might not be up: ``` virsh -c qemu:///system net-start default ``` If the default network complains about some interface taking the default subnet, reassign the default network ip range: ``` virsh -c qemu:///system net-edit0 default ``` If the virt-manager client complains about: ``` The remote host requires a version of netcat/nc which supports the -U option. ``` Uninstall all possible netcat packages and use `netcat-openbsd`: ``` apt remove netcat netcat-traditional netcat-openbsd apt install netcat-openbsd ``` ``` apt install --no-install-recommends virt-manager ``` ``` chmod u+s /usr/lib/qemu/qemu-bridge-helper echo "allow virbr0" >> /etc/qemu/bridge.conf ``` ## Check if cdrom is empty or not ## Reusing images ``` virt-install \ --os-variant debian10 \ --graphics none \ --network bridge=virbr0 \ --hvm \ --import \ --disk vol=default/deb1.qcow2 ``` ``` qemu-img -f qcow2 -b <from> <to> ``` ## PfSense ``` virt-install \ --name pfsense \ --memory 1024 \ --hvm \ --graphics none \ --boot hd,useserial=yes \ --disk path=/var/lib/libvirt/images/pfSense-CE-memstick-serial-2.4.5-RELEASE-p1-amd64.img \ --disk size=2 echo 'console="comconsole"' >> /boot/loader.conf ``` ## CentOS 7 Run everything in `screen`. The `vt102` emulation of screen is so much better. ``` virt-install \ --name Undercloud \ --memory 16384 \ --vcpus 8 \ --os-variant centos7.0 \ --disk /dev/sdb10,cache=none,io=native,bus=virtio \ --disk vol=default/CentOS-7-x86_64-NetInstall-2003.iso,device=cdrom \ --graphics none \ --boot hd,cdrom,useserial=on \ --network bridge=virbr1,model=virtio \ --network bridge=virbr2,model=virtio ``` 1. Press `TAB` on boot menu, and enter `console=ttyS0`. 2. Configure network. 3. NTP: `tw.pool.ntp.org`. 4. Mirror: `http://centos.cs.nctu.edu.tw/7/os/x86_64/`. 5. Use `LVM`. 6. Don't set `root` password. ``` umount /dev/mapper/centos_undercloud-home lvremove /dev/mapper/centos_undercloud-home lvresize /dev/mapper/centos_undercloud-root /dev/vda2 xfs_growfs /dev/mapper/centos_undercloud-root sed -i '/\/home/d' /etc/fstab ``` ### Install `virtualbmc` ``` pip3 install --upgrade --user pip pip install --user virtualbmc ```