rootfs

Quick Start on X86_64

Download linux-5.0 source code
Change to linux-5.0 directory

cp run_ubuntu_x86_64.sh ../
cp rootfs_ubuntu_x86_64.tar.xz
cp x86_64_ubuntu_defconfig ../arch/x86/configs/ubuntu_defconfig
cd ..
./run_ubuntu_x86_64.sh build_kernel
sudo ./run_ubuntu_x86_64.sh build_rootfs
sudo ./run_ubuntu_x86_64.sh run

username: root

password: 111111

build rootfs

Get the ubuntu-base-18.04-base-amd64.tar.gz

http://cdimage.ubuntu.com/ubuntu-base/releases/18.04.3/release/ubuntu-base-18.04-base-amd64.tar.gz

Unpack and Mount

sudo tar xvf ubuntu-base-18.04-base-amd64.tar.gz -C rootfs_ubuntu_x86_64
sudo ./mount.sh -m rootfs_ubuntu_x86_64/

Copy宿主机的/etc/resolve.conf文件

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 114.114.114.114
nameserver 8.8.8.8

Operation in rootfs

# apt update
# apt install systemd (init process)
# apt install vim
# apt install ifupdown/netplan
# apt install iputils-ping
# apt install pciutils
# atp install module-init-tools

set hostname, user, password
compress rootfs-ubuntu-x86-64

sudo tar cfv rootfs_ubuntu_x86_64.tar rootfs_ubuntu_x86_64

Access QEMU Monitor

telnet 127.0.0.1 4445

Use the libvirt NAT default Network

Create virtual tap device and add it to virbr0

sudo ip tuntap add dev mytap1 mode tap
sudo brctl addif virbr0 mytap1
sudo ip link set mytap1 up

Add the following QEMU command line arguments

-netdev tap,ifname=mytap1,id=myhostnet0,script=no \
-device virtio-net-pci,netdev=myhostnet0 \

Convert raw image to qcow2

qemu-img convert -f raw -O qcow2 rootfs_ubuntu_x86_64.ext4 rootfs_ubuntu_x86_64.qcow2

Tracing I/O Interactions

All primary exits from kvm to QEMU are via the return path of KVM_RUN ioctl. Fortunately for us QEMU already has built in instrumentation for tracing. We will leverage that to selectively trace the return path of KVM_RUN and record the exit reasons

There is a second class of KVM-QEMU interaction that go through the ioeventfs,irqfd mechanism which we will instrument later.

Compile QEMU with log trace backend

(qemu) trace-event virtio_notify on 
(qemu) trace-event virtio_queue_notify on

Problems

Fixed the following problems:

During boot, Kernel is stuck with the information looks like so: Time out waiting for the device dev-ttyAMA0.device.
- Solution: Change BindsTo=dev-%i.device to BindsTo=dev-%i in $rootfs_path/lib/systemd/system/serial-getty@.service
Problem: Kernel enter the bash command directly without login.
- Solution: apt install systemd. Without systemd kernel runs /bin/sh and enter the bash command directly.

Share files between host and VM, enable the following build configuration options:

CONFIG_NET_9P=y (defconfig)
CONFIG_9P_FS=y  (defconfig)
CONFIG_VIRTIO_PCI=y (defconfig)
CONFIG_NET_9P_VIRTIO=y (defconfig)
CONFIG_9P_FS_POSIX_ACL=y (add manually)
CONFIG_NET_9P_DEBUG=y (Optional)

Connect to internet
- Solution: apt install ifupdown/netplan

Second222None / rootfs