Build proot-rs

Build for android platform. Currently (2021-08-11), only 32-bit arm proot-rs is supported
```
CARGO_BUILD_TARGET=arm-unknown-linux-musleabi cargo make build
```
Push the binary to your android device. Although proot-rs is built for arm, we can still test on arch64 android phone.
```
adb push target/arm-unknown-linux-musleabi/debug/proot-rs /data/local/tmp/proot-rs
```

Prepare alpine rootfs

Download rootfs and push it to your device

wget <https://dl-cdn.alpinelinux.org/alpine/v3.14/releases/armv7/alpine-minirootfs-3.14.0-armv7.tar.gz>
adb push alpine-minirootfs-3.14.0-armv7.tar.gz /data/local/tmp/

Enter adb shell with adb shell, and perform the following:

cd /data/local/tmp
mkdir rootfs
# unpack alpine rootfs to "./rootfs/"
tar -C ./rootfs/ -xvf alpine-minirootfs-3.14.0-armv7.tar.gz

Before starting proot-rs, we need to set up the dns server address so that we can access the network in the rootfs:
```
echo "nameserver 8.8.8.8" > rootfs/etc/resolv.conf
```

Run proot-rs

Now run proot-rs with

./proot-rs --rootfs=./rootfs --bind /dev:/dev --bind /proc:/proc

You should now have a shell in our new rootfs:

# set necessary environment variable
export PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
ls -la /etc/os-release

Run neofetch

Install neofetch with apk
```
apk update
apk add neofetch
```

Run nginx

Install nginx with apk
```
apk update
apk add nginx
```

Some necessary preparations

Edit /etc/nginx/http.d/default.conf

apk add vim
vim /etc/nginx/http.d/default.conf

Change the content to:

server {
        listen 8080 default_server;
        listen [::]:8080 default_server;

        location / {
                root /;
                autoindex on;
        }
}

Create dir /run/nginx
```
mdkir /run/nginx
```
Test nginx configs
```
nginx -t
```

Launch a static file server
```
nginx 
```
nginx will be run in the background

Visit with curl

apk add curl
curl <http://192.168.123.245:8080>

echo "It works!" > /tmp/file
curl <http://192.168.123.245:8080/tmp/file>

Visit from another PC

add alpine to mkrootfs.sh