The POSBox runs a heavily modified Raspbian Linux installation, a Debian derivative for the Raspberry Pi. It also runs a barebones installation of Odoo which provides the webserver and the drivers. The hardware drivers are implemented as Odoo modules. Those modules are all prefixed with hw_* and they are the only modules that are running on the POSBox. Odoo is only used for the framework it provides. No business data is processed or stored on the POSBox. The Odoo instance is a shallow git clone of the 8.0 branch.

The root partition on the POSBox is mounted read-only, ensuring that we don’t wear out the SD card by writing to it too much. It also ensures that the filesystem cannot be corrupted by cutting the power to the POSBox. Linux applications expect to be able to write to certain directories though. So we provide a ramdisk for /etc and /var (Raspbian automatically provides one for /tmp). These ramdisks are setup by, which we run before all other init scripts by running it in /etc/init.d/rcS. The ramdisks are named /etc_ram and /var_ram respectively. Most data from /etc and /var is copied to these tmpfs ramdisks. In order to restrict the size of the ramdisks, we do not copy over certain things to them (eg. apt related data). We then bind mount them over the original directories. So when an application writes to /etc/foo/bar it’s actually writing to /etc_ram/foo/bar. We also bind mount / to /root_bypass_ramdisks to be able to get to the real /etc and /var during development.

How to edit config

If you have the POSBox’s IP address and an SSH client you can access the POSBox’s system remotely.

Login: pi Password: raspberry

Beware that root (/) is mounted read only and so you cannot use write.

If you want to use it you need to reboot in normal mode.

sudo su
mount -o rw,remount /
mount -o rw,remount /root_bypass_ramdisks

sync and reboot posbox


How to update odoo command-line options

edit /root_bypass_ramdisks/etc/init.d/odoo

nano /root_bypass_ramdisks/etc/init.d/odoo

add hw_printer_network to --load parameter

$LOGFILE --load=web,hw_proxy,hw_posbox_homepage,hw_posbox_upgrade,hw_scale,hw_scanner,hw_escpos,hw_blackbox_be,hw_screen,hw_printer_network

How to edit odoo source

Comment out line 354 in hw_escpos/controllers/

nano /home/pi/odoo/addons/hw_escpos/controllets/

i.e. replace driver.push_task('printstatus') with

# driver.push_task('printstatus')

sync and reboot posbox