#STEP1: Install requirements.
## Assumes a clean Ubuntu 20.04 host OS
sudo apt-get install debian-ports-archive-keyring
sudo apt-get update
sudo apt-get install gcc-riscv64-linux-gnu qemu-system-misc opensbi qemu-user-static binfmt-support debootstrap libguestfs-tools

wget http://za.archive.ubuntu.com/ubuntu/pool/universe/u/u-boot/u-boot-qemu_2020.04+dfsg-2ubuntu1_all.deb
sudo dpkg -i u-boot-qemu_2020.04+dfsg-2ubuntu1_all.deb

#STEP2: Create a RISC-V filesystem using chroot
## Basically a space on your local HD that looks like an install of linux with all the libraraies and executables you expect to see from / availble from a designated folder.  Provides the ability to have an alternative filesystem accessible from within a host filesystem

sudo debootstrap --arch=riscv64 --keyring /usr/share/keyrings/debian-ports-archive-keyring.gpg --include=debian-ports-archive-keyring unstable /tmp/riscv64-chroot http://deb.debian.org/debian-ports

#STEP3: Configure this new file system by 'logging in' and running some commands
sudo chroot /tmp/riscv64-chroot

## Update chroot FS     
apt-get update

## Configure a 'network'
cat >>/etc/network/interfaces <<EOF         

## Copy and paste the following lines into the prompt you now have.  You're writing the following lines to the interfaces file using cat.
## 'EOF' is "End Of File" and is a signals to cat that you're done
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp
EOF

## Set a root password
passwd

## Disable the getty on hvc0 as hvc0 and ttyS0 share the same console device in qemu.
ln -sf /dev/null /etc/systemd/system/serial-getty@hvc0.service  

## Install kernel and bootloader infrastructure
apt-get install linux-image-riscv64 u-boot-menu

## Install and configure ntp tools
apt-get install openntpd ntpdate openssh-server
sed -i 's/^DAEMON_OPTS="/DAEMON_OPTS="-s /' /etc/default/openntpd

## Configure syslinux-style boot menu
cat >>/etc/default/u-boot <<EOF
U_BOOT_PARAMETERS="rw noquiet root=/dev/vda1"
U_BOOT_FDT_DIR="noexist"
EOF
u-boot-update
exit

#STEP4: Turn the Chroot FS you just made into a disk image (like an iso or CD you'd install an OS from)
sudo virt-make-fs --partition=gpt --type=ext4 --size=10G /tmp/riscv64-chroot/ rootfs.img
sudo chown ${USER} rootfs.img

#STEP5: Boot it and login with username:root and the password you set above

qemu-system-riscv64 -nographic -machine virt -m 1.9G \
 -bios /usr/lib/riscv64-linux-gnu/opensbi/qemu/virt/fw_jump.elf \
 -kernel /usr/lib/u-boot/qemu-riscv64_smode/uboot.elf \
 -object rng-random,filename=/dev/urandom,id=rng0 -device virtio-rng-device,rng=rng0 \
 -append "console=ttyS0 rw root=/dev/vda1" \
 -device virtio-blk-device,drive=hd0 -drive file=rootfs.img,format=raw,id=hd0 \
 -device virtio-net-device,netdev=usernet -netdev user,id=usernet,hostfwd=tcp::22222-:22


#STEP5: Setup ssh 
## While logged into the emulated machine run the following to install ssh, sudo and make youself a non-root user

apt install openssh-server sudo
service ssh restart

adduser yourname

usermod -aG sudo yourname

#STEP6: Test your new user and ssh work:
## Logout of the emulation or open a new terminal and from the host run:

ssh yourname@localhost -p 22222

#STEP7: On your host OS, cross-compile a helloworld (or whatever code you want) and copy the object file over to the emulator to run it.
## EG:
*****main.c******
#include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}
******************
riscv64-linux-gnu-gcc -o mainRV main.c

scp -P 22222 mainRV yourname@localhost:

## Login to the emulator and run the code:
./mainRV

------------------
#LASTLY Some general notes:
- To Exit QEMU and shutdown the emulation:
    Ctrl-A x
- The way this has been done means you have access to a limited repo from debian of packages that have already been compiled and ported to RISC-V
- You can search this repo using apt eg:
$ apt-cache search keyword
(Or easier - install aptitude and search with it if you're familiar with it)

See here for docs on Debian port: https://wiki.debian.org/RISC-V