HOWTOFIX system not booting with NSSWITCH(_nsdispatch): nis, passwd_compat, endp

[disa]

Hi,
just for future reference: if you find yourself with this error on the serial console of a pfsense installation while booting

 init: NSSWITCH(_nsdispatch): nis, passwd_compat, endpwent, not found, and no fallback provided
Enter full pathname of shell or RETURN for /bin/sh:

and you are on linux the problem is within modem-manager messing with your serial port!
When modem-manager (the part of NetworkManager that handles modems like yuor internet key) sees a new serial port (In my case I plugged an usb-to-serial adapter) it will start probing it with AT commands to see if it's really a modem!

What you have to do is blacklist that serial device from modem-manager, so create an udev rule to do it:

cat /etc/udev/rules.d/10-modem-manager-dont-mess-with-my-serial.rules 
ATTRS{idVendor}=="067b", ATTRS{idProduct}=="2303", ENV{ID_MM_DEVICE_IGNORE}="1"

to get your vendor and product you'll need to run

udevadm info –attribute-walk --name=/dev/ttyUSB0

reference:
http://qulogic.blogspot.it/2010/08/got-bus-pirate.html
http://us.generation-nt.com/answer/bug-683839-modemmanager-fiddles-ttyusb-devices-without-asking-first-help-208603212.html
http://forum.pfsense.org/index.php?topic=30937.0