External storage

The writable part of the Realtek flash — the overlay that holds everything opkg installs — is 6 MiB. That is enough for the packages this port ships and not much else.

The Qualcomm half of the router owns a separate 55 MiB partition and exports it over SMB to this side only. The base firmware mounts it at /mnt/extern and can install packages onto it. The stock Realtek firmware mounted the same share, so this is not a new arrangement — it is the one the device was built with.

Nothing has to be installed. The mount is part of the base image.

Using it

hh71vm-extern-mount status          # is it mounted, and how much space is left
hh71vm-extern-reset status          # is first-boot cleanup still pending
hh71vm-extern-pkg   status
hh71vm-extern-pkg   space
hh71vm-extern-pkg   list            # what is installed over there
hh71vm-extern-pkg   install <package|file.ipk>
hh71vm-extern-pkg   remove  <package>

hh71vm-extern-pkg install is the wrapper you want rather than opkg install -d extern directly. It mounts the share first, and it checks that the package actually fits before starting — opkg's own check is against Installed-Size, which on OpenWrt 19.07 is the size of the compressed payload and can undercount by a factor of three. The difference is between a clean refusal and a share that fills up half way through.

It also puts the share's bin directories on PATH: /etc/profile.d/hh71vm-extern.sh does that for login shells, and /etc/init.d/hh71vm-extern-services does it for services.

Firmware upgrades

External packages are installation state, just like packages installed in the normal OpenWrt overlay. A successful sysupgrade starts with an empty package area even though the underlying Qualcomm storage survives the upgrade.

On the first boot of every new image, cleanup is marked as pending. Once the expected Qualcomm CIFS share is mounted, the firmware removes these fixed OpenWrt-owned directories:

• opkg - external package files and their package database;
• bin - the legacy location used before external opkg support;
• control and xray-loopback-test - old Xray development artifacts;
• xray - optional Xray data files.

It then creates an empty opkg directory and publishes the external destination again. Files and directories elsewhere under /mnt/extern, including Qualcomm data, are not scanned or removed. Cleanup refuses unexpected mounts, nested mounts, symbolic links or unexpected file types, and remains pending for the next mount attempt. An interrupted cleanup is safe to repeat.

If the share is late or unavailable, package installation remains disabled until cleanup finishes. Check it with hh71vm-extern-reset status and retry the mount with hh71vm-extern-mount mount. Afterward, reinstall any wanted external package normally:

opkg update
hh71vm-extern-pkg install xray-core

A normal reboot does not clean external packages. Reinstalling the same firmware with sysupgrade does, because the overlay and its package state are new again. A factory reset (the RESET button or firstboot) cleans them for the same reason. Configuration preserved by sysupgrade remains under the normal /etc paths. Files placed inside the external opkg destination, including destination-local configuration files, are package payload and are removed. sysupgrade -n also discards the normal saved configuration.

This cleanup is why the external area is suitable for large installable programs, rather than files that must survive a firmware replacement.

Configuration

/etc/config/hh71vm-extern:

config mount 'extern'
	option enabled '1'
	option share   '//192.168.225.1/shared_rom'
	option target  '/mnt/extern'
	option options 'guest,sec=none,vers=1.0,nodev,nosuid,noatime'
	option tries   '10'
	option delay   '3'
	option opkg_dest '1'

Two of those defaults are deliberate and should not be changed casually:

• vers=1.0 is mandatory, not a preference. The other side is Samba configured with security = SHARE, which speaks SMB1 only, while Linux 4.14 defaults to SMB2.1 and above. Without it the mount fails with Host is down.
• there is no noexec. The entire point of the space is to run from it what does not fit in the overlay. The stock firmware did use noexec; this port does not.

tries and delay exist because the share only appears once the Qualcomm half's smbd is up, which can be later than our boot. The mount retries in the background rather than failing.

Set enabled to 0 to turn the whole thing off.

Limits

• The share is on the other half of the device. If that half is restarted or its smbd stops, the mount goes away with it and anything running from there stops.
• It is SMB1 over an internal link, not local storage. It is fine for program files and data; it is not the place for something latency-sensitive.
• Services installed there need an init script that waits for the share, because hh71vm-extern-services starts them after the mount helper has had its turn but the mount itself can still be late.