Linux on Virtual Machine (QEMU)

contributed by < Dung-Ru Tsai >

Ubuntu Image on QEMU

1. Build and Install QEMU

git clone https://gitlab.com/qemu-project/qemu.git
cd qemu
git submodule init
git submodule update --recursive
git checkout v6.1.0
mkdir build
cd build
../configure --prefix=/usr/local/bin \
             --enable-debug \
             --enable-virtfs
make -j8
sudo make install

Dependency:

sudo apt-get install git libglib2.0-dev libfdt-dev libpixman-1-dev zlib1g-dev

2. Bridge host network with TAP interface

Setting up Qemu with a tap interface

• Create a bridge interface on Host (by netplan)

vim /etc/netplan/01-network-manager-all.yaml
===== copy start =====
network:
  version: 2
  renderer: networkd

  ethernets:
    eno1:
      dhcp4: false
      dhcp6: false

  bridges:
    br0:
      interfaces: [eno1]
      addresses: [192.168.100.4/24]
      gateway4: 192.168.100.254
      mtu: 1500
      nameservers:
        addresses: [8.8.8.8]
      parameters:
          stp: false
          forward-delay: 4
      dhcp4: false
      dhcp6: true
===== copy end =====
sudo netplan apply

• Create tap0 interface
  bridge network with tap

sudo ip tuntap add dev tap0 mode tap
sudo ip link set dev tap0 master br0
sudo ip link set dev tap0 up

3. Create Disk image

qemu-img create -f qcow2 kvm-generic.qcow2 30G

4. Install Ubuntu ISO

qemu ubuntu20.04
qemu quick reference

#!/bin/bash
PREFIX=/home/jake/mount_1TB/gns3server
ISO=${PREFIX}/ubuntu-20.04.3-live-server-amd64.iso # Installation media
NET=br0 # bridge name
OS=linux # os type
VM_DISK=${PREFIX}/kvm-generic.qcow2 # VM image on disk
sudo qemu-system-x86_64 \
  -machine type=q35,accel=hvf \
  -smp 2 \
  -hda ${VM_DISK}\
  -cdrom ${ISO} \
  -m 4096 \
  -vga virtio \
  -usb \
  -device usb-tablet \
  -enable-kvm \
  -cpu host \
  -display default \
  -boot d \
  -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no \
  -device e1000,netdev=mynet0,mac=52:55:00:d1:55:01

QEMU Parameter help

qemu-system-x86_64 -accel ?
qemu-system-x86_64 -netdev ?

• Connect to VNC: 127.0.0.1:5900
  

5. Running the system

#!/bin/bash
PREFIX=/home/jake/mount_1TB/gns3server
NET=br0 # bridge name
OS=linux # os type
VM_DISK=${PREFIX}/kvm-generic.qcow2 # VM image on disk

sudo ip tuntap add dev tap0 mode tap
sudo ip link set dev tap0 master br0
sudo ip link set dev tap0 up

sudo qemu-system-x86_64 \
  -machine type=q35,accel=hvf \
  -smp 4 \
  -hda ${VM_DISK}\
  -m 4096 \
  -vga virtio \
  -usb \
  -device usb-tablet \
  -enable-kvm \
  -cpu host \
  -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no \
  -device e1000,netdev=mynet0,mac=52:55:00:d1:55:01 \
  -serial telnet:127.0.0.1:4322,server,nowait \
  -display default
  -nographic

Another example
6. Redirect GRUB output to serial console (optional)

SerialConsoleHowto

• Connect to VNC
  
• Edit the /etc/default/grub, redirect serial message to ttyS0

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.
 
GRUB_DEFAULT=0
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"
 
# Uncomment to disable graphical terminal (grub-pc only)
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
...

• Update the GRUB

sudo update-grub
reboot
# Open another terminal
telnet 127.0.0.1 4322

7. Connect with ssh

ssh dutsai@your-vm-ip

• Install/running scripts

Enlarge the disk on VM

https://www.linuxtechi.com/extend-lvm-partitions/
https://www.tecmint.com/extend-and-reduce-lvms-in-linux/

• Add new the partition

qemu-img resize kvm-generic.qcow2 +60G
sudo fdisk -l
sudo fdisk -cu /dev/sda

To Create new partition Press n.

Change the type using t.
Type 8e to change the partition type to Linux LVM.
Press w to write the changes.
sudo sudo fdisk -l #check 

• Add new physical volume and add to volume group

# Add physical volume
sudo pvcreate /dev/sda4
$ sudo pvs
  PV         VG        Fmt  Attr PSize   PFree
  /dev/sda3  ubuntu-vg lvm2 a--  <29.00g    0
  /dev/sda4  ubuntu-vg lvm2 a--   29.26g    0
# Extend Volume Group
sudo vgextend ubuntu-vg /dev/sda4
$ sudo vgs # check volume
  VG        #PV #LV #SN Attr   VSize   VFree
  ubuntu-vg   1   1   0 wz--n- <29.00g <9.00g

• Resize Logical Volume

# Get LV Path
sudo lvdisplay 
# Do it
$ sudo lvextend  /dev/ubuntu-vg/ubuntu-lv -l+100%FREE
$ sudo resize2fs -p /dev/ubuntu-vg/ubuntu-lv

$ df -h /
Filesystem                         Size  Used Avail Use% Mounted on
/dev/mapper/ubuntu--vg-ubuntu--lv   28G   19G  8.1G  70% /

---

< obsoleted >

ARM64 QEMU Environment Setting

Method01: buildroot

1. Set up the QEMU for aarch64

wget https://download.qemu.org/qemu-2.12.1.tar.xz
tar xvJf qemu-2.12.1.tar.xz
cd qemu-2.12.1
./configure --target-list=aarch64-softmmu
# Work with VirtIO + 9P
sudo apt-get install libcap-dev libattr1-dev
./configure --enable-virtfs --target-list=aarch64-softmmu
make

--enable-virtfs : 使得 VirtIO + 9P 可以運作，
--target-list : 只產生可以運行 aarch64 架構的 qemu

耐心等待一段時間之後，在 aarch64-softmmu 目錄下可以找到
qemu-system-aarch64

• Install the binary qemu-system-aarch64 to /usr/bin/

#$ sudo cp qemu-2.12.1/aarch64-softmmu/qemu-system-aarch64 /usr/bin
sudo make install

Buildroot Guide

• 第3章 行程(process)環境:https://hackmd.io/s/rJf1ONuye
• from link: Taiwan linux study group

2. Build AArch64 image with buildroot

$ sudo apt-get install libncurses-dev
$ git clone https://github.com/buildroot/buildroot
$ make list-defconfigs
# Generate the .config
$ make qemu_aarch64_virt_defconfig

$ make menuconfig
# 使用Kernel 5.0 header
$ make linux-menuconfig
# 開啟 9P File System
$ make

• 設定Kernel 5.0 教學
• 9P File System9P File System 設定教學

3. Run the emulation Qemu

$ qemu-system-aarch64 -M virt \
-cpu cortex-a53 \
-nographic -smp 1 \
-kernel output/images/Image \
-append "root=/dev/vda console=ttyAMA0" \
-netdev user,id=eth0 -device virtio-net-device,netdev=eth0 \
-drive file=output/images/rootfs.ext4,if=none,format=raw,id=hd0 \
-device virtio-blk-device,drive=hd0 \
-fsdev local,security_model=passthrough,id=fsdev0,path=/tmp \
-device virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=host_mount

注意最後兩行 -fsdev and -device, 是為了掛載 host 的目錄才有的

4. 掛載 host 的目錄

mkdir share
mount -t 9p -o trans=virtio host_mount share -oversion=9p2000.L

Reference:
0xff07
9psetup

Method-02: Kernel source

1. Set up the QEMU for aarch64

wget https://download.qemu.org/qemu-2.12.1.tar.xz
tar xvJf qemu-2.12.1.tar.xz
cd qemu-2.12.1
./configure --target-list=aarch64-softmmu
# Work with VirtIO + 9P
sudo apt-get install libcap-dev libattr1-dev
./configure --enable-virtfs --target-list=aarch64-softmmu
make

--enable-virtfs : 使得 VirtIO + 9P 可以運作，
--target-list : 只產生可以運行 aarch64 架構的 qemu

耐心等待一段時間之後，在 aarch64-softmmu 目錄下可以找到
qemu-system-aarch64

• Install the binary qemu-system-aarch64 to /usr/bin/

$ sudo cp qemu-2.12.1/aarch64-softmmu/qemu-system-aarch64 /usr/bin
sudo make install

2. Create initramfs cpio (Create the file system)

$ git clone https://github.com/buildroot/buildroot
$ make list-defconfigs
$ make qemu_aarch64_virt_defconfig
$ make menuconfig

• Target options —> Target Architecture: 選擇 AArch64 little-endian
• Toolcahin —> Toolchain type: 選擇 External toolchain
  Toolchain: 選擇 Linaro AArch64 2018.05
• System configuration —> Run a getty (login prompt) after boot
  TTY port 改為 ttyAMA0
• Filesystem images —> cpio the root filesystem (for use as an initial RAM filesystem)

儲存之後，進行 make。若無異常，可以在 output/images 目錄底下找到 rootfs.cpio

3. Build aarch64 Kernel from source

Kernel Source code

• Linux Kernel
• Preempty Kernel patch
• Building the preeempty kernel on ubuntu

git clone https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-stable
cd linux-stable
sudo apt-get install gcc-aarch64-linux-gnu

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig

Edit the .config for 9P

CONFIG_CMDLINE="console-ttyAMA0"
# points at your buildrootimage
CONFIG_INITRAMFS_SOURCE="/home/jake/QEMU/rootfs.cpio"  
# needed for virtfs mount
CONFIG_NET_9P=y               
CONFIG_NET_9P_VIRTIO=y

一切就緒就開始編譯核心

## Build the Kernel
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-

The image path will show at arch/arm64/boot/Image or linux/vmlinux

4. Run the emulation QEMU

#!/bin/bash
qemu-system-aarch64 \
-machine virt \
-machine type=virt \
-cpu cortex-a57 \
-nographic -smp 1 \
-m 8192 \
-kernel /home/jake/QEMU/linux-stable/arch/arm64/boot/Image \
--append "console=ttyAMA0" \
-fsdev local,security_model=passthrough,id=test_dev,path=/home/jake/Workspace/ -device virtio-9p-pci,id=fsdev0,fsdev=test_dev,mount_tag=host_mount 

• -kernel : 指定第二步驟編譯好的 image path
• -fsdev, path : 指定共享目錄的路徑
  • path 是在 host 這邊要目錄分享的路徑，這邊是用 /home/jake/Workspace/
  • 而最後面那個 mount_tag=host_mount 是到時候在 guest 裡面 mount 時會用到.

5. 掛載 host 的目錄

透過 VirtIO + 9P 使得 guest 與 host 共享目錄:
mount -t 9p -o trans=virtio host_mount /mnt

• Exit the QEMU:
  Ctrl+a X

Reference

• Video: Starting Linux kernel exploration with Eukabuka
• QEMU Source :https://www.qemu.org/download/#source
• Running Linux in QEMU’s aarch64 system emulation mode
• atlantis0914

X86_64 QEMU Environment Setting

[PASS]

Method-01 buildroot source

1. Build the QEMU

wget https://download.qemu.org/qemu-4.2.0.tar.xz
tar xvJf qemu-4.2.0.tar.xz
cd qemu-4.2.0
# Work with VirtIO + 9P
sudo apt-get install libcap-dev libattr1-dev
sudo apt install build-essential kernel-package fakeroot libncurses5-dev libssl-dev ccache flex bison libelf-dev
sudo apt-get install libglib2.0-dev libfdt-dev libpixman-1-dev zlib1g-dev install libnfs-dev libiscsi-dev

./configure --enable-virtfs --target-list=x86_64-softmmu --enable-debug
make -j8
... wait for a while
sudo make install

--enable-virtfs: Enable the virtual file IO system

2. Build the Linux from buildroot

Check the basic build guide incat README

make list-defconfigs
make qemu_x86_64_defconfig
make
# find the kernel, bootloader, root filesystem, etc. in output/images

3. Run the qemu with Linux

Check the qemu startup guide
cat board/qemu/x86_64/readme.txt

qemu-system-x86_64 -M pc \
    -kernel output/images/bzImage \
    -drive file=output/images/rootfs.ext2,if=virtio,format=raw \
    -append "rootwait root=/dev/vda console=tty1 console=ttyS0" \
    -serial stdio \
    -net nic,model=virtio \
    -net user
# Optionally add -smp N to emulate a SMP system with N CPUs.

udhcpc: sending select for 10.0.2.15
udhcpc: lease of 10.0.2.15 obtained, lease time 86400
deleting routers
random: mktemp: uninitialized urandom read (6 bytes read)
adding dns 10.0.2.3
OK

Welcome to Buildroot
buildroot login: root

Method-02 Kernel Source

1. Build the QEMU

sudo apt update -y
sudo apt install libcap-ng-dev libattr1-dev build-essential kernel-package fakeroot libncurses5-dev libssl-dev ccache flex bison libelf-dev libglib2.0-dev libfdt-dev libpixman-1-dev zlib1g-dev libnfs-dev libiscsi-dev ninja-build

wget https://download.qemu.org/qemu-6.2.0.tar.xz
tar xvJf qemu-6.2.0.tar.xz
cd qemu-6.2.0

./configure --enable-virtfs --target-list=x86_64-softmmu --enable-debug
make -j8
... wait for a while
sudo make install

--enable-virtfs: Enable the virtual file IO system

2.1 Create the root file system

$ git clone https://github.com/buildroot/buildroot
$ make list-defconfigs
$ make qemu_x86_64_defconfig
$ make menuconfig

• Target options —> Target Architecture: 選擇 x86_64
• Filesystem images —> ext2/3/4 root file system

cpio the root filesystem (for use as an initial RAM filesystem)

儲存之後，進行 make。若無異常，可以在 output/images 目錄底下找到 rootfs.cpio

2.2 Build Kernel from linux source

• Prepare the environment for developing Linux kernel with qemu
• https://mirrors.edge.kernel.org/pub/linux/kernel/

make ARCH=x86_64 x86_64_defconfig 
make ARCH=x86_64 menuconfig
make -j8

• Kernel hacking -> Compile the kernel with debug info -> Provide GDB scripts for kernel debugging
• Reduce debugging information option off
• Force unload the kernel module: MODULE_FORCE_UNLOAD
• KGDB

CONFIG_DEBUG_INFO=y
CONFIG_FRAME_POINTER=y
CONFIG_HAVE_ARCH_KGDB=y
CONFIG_KGDB=y
CONFIG_KGDB_SERIAL_CONSOLE=y

• Ensure the following 9P options are enabled in the kernel configuration.

    CONFIG_NET_9P=y
    CONFIG_NET_9P_VIRTIO=y
    CONFIG_NET_9P_DEBUG=y (Optional)
    CONFIG_9P_FS=y
    CONFIG_9P_FS_POSIX_ACL=y
    CONFIG_PCI=y
    CONFIG_VIRTIO_PCI=y
    CONFIG_PCI_HOST_GENERIC=y (only needed for the QEMU Arm 'virt' board)

The final image will show in arch/x86/boot/bzImage.

• ramfile system only

# Only for ramfile system when you choose in builtroot Filesystem images is cpio:
CONFIG_INITRAMFS_SOURCE="/home/jake/QEMU/rootfs.cpio"

3.1 Run qemu with own Linux Kernel (No File system)

qemu-system-x86_64 -s -S\
-kernel arch/x86/boot/bzImage \
-hda /dev/zero \
-append "root=/dev/zero console=ttyS0" \
-serial stdio -display none

Try the KGDB

cd linux
gdb ./vmlinux
(gdb) target remote localhost:1234
(gdb) break start_kernel
(gdb) c
Continuing.

Breakpoint 1, start_kernel () at init/main.c:786
786	{

3.2 Run qemu with own Linux Kernel with Files system

qemu-system-x86_64 -kernel arch/x86/boot/bzImage \
-boot c -m 2049M \
-append "root=/dev/sda rw console=ttyS0,115200 acpi=off nokaslr" \
-hda output/images/rootfs.ext4 \
-fsdev local,security_model=passthrough,id=fsdev0,path=/home/dutsai/Workspace_vm \
-device virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=host_mount \
-nographic \
-monitor telnet::45454,server,nowait \
-serial mon:stdio

• -kernel : 指定第二步驟編譯好的 image path
• -fsdev, path : 指定共享目錄的路徑
  • path 是在 host 這邊要目錄分享的路徑，這邊用 /home/dutsai/Workspace_vm
  • mount_tag=host_mount 在 guest 裡面 mount 時會用.
• -serial mon:stdio Send Ctrl+C to guest
  • Ctrl+a X to exit qemu.

4. Mount host folder

https://wiki.qemu.org/Documentation/9psetup

# In qemu
mount -t 9p -o trans=virtio host_mount /root -oversion=9p2000.L

5. KGDB

qemu-system-x86_64 \
-kernel linux-5.16.14/arch/x86/boot/bzImage \
-boot c -m 4096M \
-append "root=/dev/sda rw console=ttyS0,115200 acpi=off nokaslr" \
-hda buildroot/output/images/rootfs.ext4 \
-fsdev local,security_model=passthrough,id=fsdev0,path=/home/dutsai/Workspace_vm \
-device virtio-9p-pci,id=fs0,fsdev=fsdev0,mount_tag=host_mount \
-nographic \
-monitor telnet::45454,server,nowait \
-serial mon:stdio \
-S -gdb tcp::33004

Try to open another terminal to run gdb.

cd linux
gdb ./vmlinux
(gdb) target remote localhost:33004
(gdb) break start_kernel
(gdb) c
Continuing.

Breakpoint 1, start_kernel () at init/main.c:786
786	{

Method-03 Ycoto

RISC-V Embedded Linux - Get started with Buildroot/Yocto

Update Linux Kernel

Kernel Source code

• Linux Kernel
• Preempty Kernel patch
• Building the preeempty kernel on ubuntu

• Get from Newest release
• Ubuntu 22.04 is Jammy Jellyfish
• 將 memchr() 放入核心並重新 compile
  Source code: https://www.kernel.org/

$ sudo apt-get install liblz4-tool libc6-dev libncurses5-dev openssl wget ca-certificates bc libzstd-dev zstd
$ sudo apt-get install git fakeroot build-essential ncurses-dev xz-utils libssl-dev bc flex libelf-dev bison dwarves

$ wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.17.9.tar.xz
$ cp /boot/config-`uname -r` .config
$ make menuconfig
選擇 load 再選擇 save
# make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig
$ scripts/config --disable SYSTEM_TRUSTED_KEYS
$ scripts/config --disable SYSTEM_REVOCATION_KEYS
CONFIG_DEBUG_INFO_BTF=n
# Build
$ make -j12
$ make modules -j12
# Install
$ sudo make INSTALL_MOD_STRIP=1 modules_install -j 4
$ sudo make install
$ sudo mkinitramfs /lib/modules/5.17.9/ -o /boot/initrd.img-5.17.9
$ sudo update-grub2
# Install Method2
$ su -c "make modules_install install"

Update the GRUB

vim /etc/default/grub

GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 5.10.130-0510130-generic"
# GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=8
$ sudo update-grub

Patch RT (Linux)

• Install the ubuntu 16.04
• Building and Install the preeempt kernel on Ubuntu
• Kernel Version https://www.kernel.org/pub/linux/kernel/
  • linux-4.4.60
• Preempt RT Version https://www.kernel.org/pub/linux/kernel/projects/rt/
  • patch-4.4.60-rt73 (Linux preempt RT 4.4.60-rt73+)
  • https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/4.4/older/patch-4.4.60-rt73.patch.gz
• Linux RT Kernel config replace the .config file
  • Must turn off Check for stack overflows
  • sudo apt-get install libssl-dev

build kernel command

$ sudo apt-get update
$ sudo apt-get install build-essential linux-tools-common linux-tools-generic cmake automake libtool libusb-1.0-0-dev openssh-server samba vim linux-headers-`uname -r` can-utils libpopt-dev

$ mkdir -p kernel

$cd kernel
# Download the kernel linux-4.4.60.tar.gz and patch-4.4.60-rt73.patch.gz 
$ wget https://mirrors.edge.kernel.org/pub/linux/kernel/v4.x/linux-4.4.60.tar.gz
$ wget https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/4.4/older/patch-4.4.60-rt73.patch.gz
$ tar -xzvf linux-4.4.60.tar.gz
$ cd linux-4.4.60
$ gzip -cd ../patch-4.4.60-rt73.patch.gz | patch -p1 --verbose
$ sudo apt-get install libncurses-dev libssl-dev
# Change .config file
$ make menuconfig

##Graphical Menu##

# Processor type and features ---> [Enter]
# Preemption Model (Voluntary Kernel Preemption (Desktop)) [Enter]
# Fully Preemptible Kernel (RT) [Enter] #Select
# [Esc][Esc]
# <Save> [Enter]
/*
# Kernel hacking --> [Enter]
# Memory Debugging [Enter]
# Check for stack overflows #Already deselected - do not select
# [Esc][Esc]
# [Right Arrow][Right Arrow]
# .config
# <Okay> [Enter]
# <Exit> [Enter]
# [Esc][Esc]
# [Right Arrow]
# <Exit> [Enter]
*/
make
sudo make modules_install -j3
sudo make install -j3 

• Linux RT Kernel .config simple replace the .config file in Linux-4.4.60
• EGSE .config full

After install the kernel

• Verify and update. Verify that
  initrd.img-4.4.60-rt73,
  vmlinuz-4.4.60-rt73, and
  config-4.4.60-rt73 exist. They should have been created in the previous step.

$cd /boot
$ ls

Set the default kernel

1. Go to see the menuentry in

vim /boot/grub/grub.cfg

search your menuentry version and copy it.

menuentry 'Ubuntu, with Linux 4.4.60-rt73'

2. sudo vim /etc/default/grub

$ sudo vim /etc/default/grub
    GRUB_DEFAULT='Advanced options for Ubuntu>Ubuntu, with Linux 4.4.60-rt73'
    GRUB_CMDLINE_LINUX_DEFAULT="isolcpus=1"

CPU Isolation

sudo vim /etc/default/grub ===> add GRUB_CMDLINE_LINUX_DEFAULT="isolcpus=1"
sudo update-grub
sudo reboot
# Loogin Permission
sudo vim /etc/ssh/sshd_config ===> modify "PermitRootLogin yes"

3. sudo update-grub
   • it will show the error message, please change the GRUB_DEFAULT by use the correct one on error message.
4. In BIOS, Turn off Hyper threading

Lima macOS

1st Start

limactl start --name=default template://ubuntu-lts
limactl shell default

https://github.com/lima-vm/lima

sudo apt-get install sshfs build-essential linux-tools-common linux-tools-generic  automake* linux-headers-`uname -r` net-tools wireless-tools

linux-image-5.4.0-109-generic_5.4.0-109.123_arm64.deb

sudo apt install linux-modules-extra-`uname -r`

• YAML file on mac:

vim /Users/dutsai/.lima/default

# Ubuntu 20.04 LTS (Focal Fossa)

# This example requires Lima v0.7.0 or later.
images:
# Try to use release-yyyyMMdd image if available. Note that release-yyyyMMdd will be removed after several months.
- location: "https://cloud-images.ubuntu.com/releases/20.04/release-20220302/ubuntu-20.04-server-cloudimg-amd64.img"
  arch: "x86_64"
  digest: "sha256:243157ea0390890d6e60ce5e08e0249b16e23b6b313b63aed50f39f92b020afe"
- location: "https://cloud-images.ubuntu.com/releases/20.04/release-20220302/ubuntu-20.04-server-cloudimg-arm64.img"
  arch: "aarch64"
  digest: "sha256:fb2b4efdbf0011bd2a9fd49e9d31efdd252966c889f07b5d246351ec5734a329"
# Fallback to the latest release image.
# Hint: run `limactl prune` to invalidate the cache
- location: "https://cloud-images.ubuntu.com/releases/20.04/release/ubuntu-20.04-server-cloudimg-amd64.img"
  arch: "x86_64"
- location: "https://cloud-images.ubuntu.com/releases/20.04/release/ubuntu-20.04-server-cloudimg-arm64.img"
  arch: "aarch64"

mounts:
- location: "~"
- location: "~/Workspace_mac/vwifi"
  writable: true
- location: "/tmp/lima"
  writable: true

User mode Linux

https://hackmd.io/@sysprog/user-mode-linux-env

$ sudo apt install build-essential libncurses-dev flex bison
$ sudo apt install xz-utils wget ca-certificates bc fakeroot
$ wget https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.12.tar.xz
$ tar xvf linux-5.12.tar.xz
$ make mrproper
$ make defconfig ARCH=um SUBARCH=x86_64
$ make linux ARCH=um SUBARCH=x86_64 -j `nproc`

• Root file system

$ export REPO=http://dl-cdn.alpinelinux.org/alpine/v3.13/main
$ mkdir -p rootfs
$ curl $REPO/x86_64/APKINDEX.tar.gz | tar -xz -C /tmp/
$ export APK_TOOL=`grep -A1 apk-tools-static /tmp/APKINDEX | cut -c3- | xargs printf "%s-%s.apk"`
$ curl $REPO/x86_64/$APK_TOOL | fakeroot tar -xz -C rootfs
$ fakeroot rootfs/sbin/apk.static \
    --repository $REPO --update-cache \
    --allow-untrusted \
    --root $PWD/rootfs --initdb add alpine-base
$ echo $REPO > rootfs/etc/apk/repositories
$ echo "LABEL=ALPINE_ROOT / auto defaults 1 1" >> rootfs/etc/fstab

• UML.sh

howto-usermode-linux

Original Assignment info: F08: smallsys