Re: primary device changing from boot to boot

[Tim Harvey <tharvey gateworks com>]

On Tue, Sep 5, 2017 at 9:56 AM, Pičugins Arsenijs <crimier yandex ru> wrote:
> I don't know if it's going to help you with this issue, but if you can hardcode a path to the serial port 
> somewhere, take a look in the "/dev/serial/by-id" directory - it has symlinks to /dev/tty* entries that 
> correspond to hardware serial ports currently connected. Names of the symlinks are generated from some kind 
> of hardware IDs, so should be the same, no matter the order of enumeration (unless your hardware doesn't 
> expose an unique ID that udev, or whatever makes those symlinks, could use)

It is true that the symlinks in /dev/serial/by-id are constant but I
don't know how to get nm to use them as nmcli is particularlly finiky
about what is allowed for the 'ifname' param.

root@ventana:~# ls /dev/serial/by-id/
usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if00
usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if02
usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if04

root@ventana: ~# nmcli connection add type gsm ifname
"usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if00" con-name
mymodem apn vzwinternet
Error: 'ifname':
'usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if00' is not a valid
interface nor '*'.

root@ventana: ~# nmcli connection add type gsm ifname
"/dev/serial/by-id/usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if00"
con-name mymodem apn vzwinternet
Error: 'ifname':
'usb-Sierra_Wireless_Inc._HL7xxx_014284000070452-if00' is not a valid
interface nor '*'.

I'm not sure what the rules are for ifname for type gsm... seems to
accept 'foo', but apparently not just anything.

Tim