How to create a Debian image

This chapter is translated from https://github.com/OpenXiangShan/NEMU/tree/master/resource/debian.

qemu-riscv64-static is used to create a debian image. We recommend using debian 10 or ubuntu 19.04. (Maybe docker can help you)

• Create an empty image and create partitions

dd if=/dev/zero of=debian.img bs=1G count=16  # Here image size is 16G
sudo cfdisk debian.img # Create two partitions, first 12GB is used as rootfs, left 4GB is used as swap
sudo losetup --partscan --show --find debian.img # Start the loop device
ls /dev/loop0* # You should see /dev/loop0p1 and /dev/loop0p2

• Create ext4 and swap file systems

sudo mkfs.ext4 /dev/loop0p1
sudo mkswap /dev/loop0p2

• Mount the ext4 partition

sudo mount /dev/loop0p1 /mnt

• Install debian base system. Operations of the following two commands are from guidance of debian community

sudo apt-get install debootstrap qemu-user-static binfmt-support debian-ports-archive-keyring
sudo debootstrap --arch=riscv64 --keyring /usr/share/keyrings/debian-ports-archive-keyring.gpg --include=debian-ports-archive-keyring unstable /mnt http://deb.debian.org/debian-ports

To install an x86 operating system, type

sudo debootstrap --arch=i386 --keyring /usr/share/keyrings/debian-archive-keyring.gpg --include=debian-archive-keyring stable /mnt http://deb.debian.org/debian

You can install the newest package manually from the listed mirrors of debian official image website if gpg key error is given when running the above debootstrap command. After updating the debian-ports-archive-keyring package, you can execute the above debootstrap command again. The following commands are available on July 3, 2022:

wget http://ftp.cn.debian.org/debian/pool/main/d/debian-ports-archive-keyring/debian-ports-archive-keyring_2022.02.15\~deb11u1_all.deb .
sudo dpkg -i debian-ports-archive-keyring_2022.02.15\~deb11u1_all.deb

• Access the image

sudo chroot /mnt /bin/bash

Riscv64 executable files in the image is executed by qemu-riscv64-static actually.

• Install the packages needed for the system (You can choose on your actual situation)

apt-get update
apt-get install gcc build-essential
apt-get install tmux libreadline-dev
apt-get install net-tools openssh-server
# fix long delay of openssh server
apt-get install haveged
agt-get install sbt

• Add swap partition in /etc/fstab

/dev/mmcblk0p2 none swap sw 0 0

• Add write and execute permissions to /root/ directory so that normal users on host can access it

chmod +w,+x /root

• Write required test files in /root/ directory in advance, such as hello.c, etc

• Add following contents to /root/.bashrc in order to run commands automatically after login (You can modify on your actual situation):

TMP_DIR=/run/mytest

cmd=(
# enbale swap
  "swapon -a"

# show system information
  "uname -a"
  "cat /etc/issue"
  "cat /proc/cpuinfo"
  "df -ah"
  "free -h"

# show time
  "date"
  "uptime"

# create and switch to tmp directory
  "mkdir $TMP_DIR"
  "cd $TMP_DIR"

# compile and run hello
  "ls /root"
  "ls /root/hello"
  "cat /root/hello/hello.c"
  "gcc -time /root/hello/hello.c -o $TMP_DIR/hello"
  "ls -lh $TMP_DIR"
  "$TMP_DIR/hello"

# compile and run x86-nemu
  "ls /root/nemu"
  "cp -r /root/nemu $TMP_DIR"
  "export NEMU_HOME=$TMP_DIR/nemu"
  "make -C $TMP_DIR/nemu ISA=x86"
  "ls -lh /root/nemu-prog"
  "file /root/nemu-prog/amtest-x86-nemu.elf"
  "$TMP_DIR/nemu/build/x86-nemu --batch --mainargs=h /root/nemu-prog/amtest-x86-nemu.bin"
  "file /root/nemu-prog/microbench-x86-nemu.elf"
  "$TMP_DIR/nemu/build/x86-nemu --batch --mainargs=test /root/nemu-prog/microbench-x86-nemu.bin"

# compile and run riscv64-nemu
  "make -C $TMP_DIR/nemu clean"
  "make -C $TMP_DIR/nemu ISA=riscv64"
  "$TMP_DIR/nemu/build/riscv64-nemu --batch /root/nemu-prog/linux-hello-riscv64-nemu.bin"
)

prompt="`whoami`@`hostname`:`pwd`#"

echo -e "\n============ Now running preset commands =============\n"

for ((i = 0; i < ${#cmd[@]}; i++)); do
  c=${cmd[$i]}
  echo "$prompt $c"
  $c
  echo ""
done

echo -e "\n============ End of preset commands =============\n"

/root/nemutrap/good-trap

• You can choose one of the following methods to avoid input when login if you test in an inconvenient input environment. (Such as NEMU, verilator simulation, etc)

  • Login through emergency mode

  cd /lib/systemd/system
  # Login through emergency mode. It can save nearly half of the login time as unnecessary services are not started
  ln -sf emergency.target default.target
  # Run bash directly and skip login prompt
  vim emergency.service
    -ExecStart=-/lib/systemd/systemd-sulogin-shell emergency
    +ExecStart=-/bin/bash
  

  • Login without password，see here

  cd /lib/systemd/system
  vim serial-getty@.service
    -ExecStart=-/sbin/agetty -o '-p -- \\u' --keep-baud 115200,57600,38400,9600 %I $TERM
    +ExecStart=-/sbin/agetty -a root --keep-baud 115200,57600,38400,9600 %I $TERM
  

• Exit and unmount the image

exit  # Entered with `chroot` command before
sudo umount /mnt  # Do not forget to umount! Image will be damaged if you reopen `debian.img` through writeable access without umount. (Such as  implemented as file system of qemu)
sudo losetup -d /dev/loop0  # Delete loop device

• You can use the image after modifying the img in init_sdcard() of nemu/src/device/sdcard.c. We tested on i9-9900k and the debian login prompt appeared after about 90s.

• Opening image through writeable access means that, crash consistency may be damaged when NEMU encounters an error or being exited directly with Ctrl+C. You can repair the partition with fsck command at that time.