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• MiWifi_mini

Under construction

Translation(s): none

Models covered
Xiaomi ?MiWifi mini

Specs:

MediaTek MT7620A (includes wifi b/n chip) MIPS SoC 580 MHz, RAM 128MB, Wi-Fi 802.11ac (?MediaTek MT7612), Flash 16MB, 100MiB Ethernet.

Overall Status

Legend :
= OK ; Unsupported(No Driver) ; = Error (Couldn't get it working); [?] Unknown, Not Test ; [-] Not-applicable
= Configuration Required; = Only works with a non-free driver and or firmware

Important Note

This Debian installation is based on the Open WRT kernel and it's modified init system. Please, read this article, it's pretty the same, but it uses old version of ?OpenWrt(without procd). The reason we cannot use approach with preinit scripts is simple: From the Barrier Breaker ?OpenWrt release, preinit system runs in compatibility mode, so it is not executed with PID 1. And we need init to be executed from the PID 1 process.That's why we have to modify init program's C code to spawn debian init instead of procd.

Install OpenWRT on your router and make sure it works before attempting to install Debian. A working and configured OpenWRT system on the internal flash also works as a backup. If the USB drive containing the rootfs breaks, you will lose your Debian server, but at least the network routing still works with OpenWRT. Remember backups.

Installation

Build a custom OpenWRT image

Get ?OpenWrt code

mkdir ~/wrt
cd ~/wrt
git clone git://github.com/openwrt/openwrt.git
git checkout tags/v17.01.4

Configure ?OpenWrt build system

make menuconfig

Set image options:

• /Target System->?MediaTek Ralink MIPS

• /Subtarget->MT7620 based boards

• /Target Profile->Xiaomi ?MiWiFi Mini

• /Base system-> block-mount

• /Global build settings -> Enable rfkill support

• Kernel Modules/Other modules -> kmod-rfkill

This is for systemd

• /Global build settings -> Compile kernel with device tmpfs enabled

• /Global build settings -> Enable kernel cgroups

Set kernel options:

make kernel_menuconfig

• /Kernel type->MIPS FPU Emulator

• /File Systems->The Extended 4 (ext4) filesystem

Build ?OpenWrt system

make

Tweaking init

Now we need to patch init system, so that if debian root detected, we launch debian init.

cd openwrt/build_dir/target-mipsel_24kc_musl-1.1.16/procd-2017-08-08-66be6a23/initd

Create init patch. This patch will replace spawn_procd function with spawn_real_init. If debian root mounted, spawn_real_init function will execute debian init, else procd.

What the function spawn_real_init do? It checks, if debian root mounted, if yes - stops the watchdog timer, and exec debian init command. Otherwise it will exec procd.

cat <<EOF >> init_patch
> 53c53
> < spawn_procd(struct uloop_process *proc, int ret)
> ---
> > spawn_real_init(struct uloop_process *proc, int ret)
> 54a55,56
> >     char *deb_init_args[] = { "/sbin/init", "3", NULL};
> >     char *procd_args[] = { "/sbin/procd", NULL};
> 56d57
> < preinitchar *argv[] = { "/sbin/procd", NULL};
> 57a59
> >     int is_extroot_mounted = !stat("/etc/debian_version", &s);
> 70d71
> < preinitDEBUG(2, "Exec to real procd now\n");
> 79c80,88
> < preinitexecvp(argv[0], argv);
> ---
> > preinitif (is_extroot_mounted) {
> >         DEBUG(2, "Exec to debian init now\n");
> >         watchdog_set_magicclose(true);
> >         watchdog_set_stopped(true);
> >         execvp(deb_init_args[0], deb_init_args);
> >     } else {
> >         DEBUG(2, "Exec to openwrt procd now\n");
> >         execvp(procd_args[0], procd_args);
> >     }
> 119c128
> < preinitpreinit_proc.cb = spawn_procd;
> ---
> > preinitpreinit_proc.cb = spawn_real_init;
> EOF

Patching!

patch preinit.c init_patch

Build

Build ?OpenWrt again, with modified init.

make

Flash image

Use open wrt guide.

Create debian rootfs

mkdir ~/debian_root_fs
cd ~/debian_root_fs
debootstrap --arch mipsel stretch .

Configure debian rootfs

Follow the instructions from the above-mentioned article. Install sysvinit system instead of Systemd (I was not able to get Systemd working ). Also install ssh server and configure static network interface ip.

Prepare usb media

Use gparted, create ms-dos partition table on thumb drive, and create two partitions: ext4 partition for debian rootfs, and swap. Then copy created debian rootfs on flash drive.

mount /dev/sd*1 /mnt
cp -r ~/debian_root_fs/* /mnt

Ok, now we have a router with Openwrt system, configured to launch debian init, if debian root is mounted (i.e. file /debian_version is present). And we have a debian root filesystem on the flash along with swap partition on it. What we need to do now is configure ?OpenWrt system to mount root filesystem from flash drive(if flash drive is plugged in the router) during the preinit stage. So we need to do some router configuration.

OpenWRT extroot configuration

config mount
    option target '/'
    option fstype 'ext4'
    option options 'rw,sync'
    option enabled '1'
    option enabled_fsck '0'
    option device '/dev/sda1'

Launch!

We are ready now. Switch off the router, plug in your flash drive, connect ethernet cable to any port of the router and to you computer, configure your network interface on the computer according to debian rootfs network interface configuration (i.e. both interfaces should be in the same subnet, and turn the router on. You should be able to connnect to the router through ssh.

WiFi

System Summary

lspci

lspci -nn

lsusb

lsusb -v | grep -E '\<(Bus|iProduct|bDeviceClass|bDeviceProtocol)' 2>/dev/null

Resources

Attachments

Some configuration files and sample outputs.

Useful Links

Credits

CategoryDebianOn CategoryDebianOn