My question is a bit of a tricky one.
My RPi has 2 wireless interfaces and I have 2 wireless routers with different SSIDs. I am just looking for a configuration where the first wifi device always connects to the first AP and the second device to the other AP.
For example, like this:
wlan0 ------> ssid_one
wlan1 ------> ssid_two
Is it possible to solve this within the /etc/network/interfaces [+wpa_conf[s]] files?
I have never tried this, but it should be simple.
Your /etc/network/interfaces probably contains a line like /etc/wpa_supplicant/wpa_supplicant.conf
Copy the wlan0 block.
I would make a new /etc/wpa_supplicant/wpa_supplicant2.conf with the appropriate SSID etc.
You probably want to use wpa-conf instead of wpa-roam
sudo ifdown wlan1 and sudo ifup wlan1, this two command works pretty well, without any problem, but for sudo ifdown wlan0 I give some error, like ifdown: interface wlan0 not configured, but sudo ifdown --f wlan0 works well with a little message: RTNETLINK answers: No such process. Anyway, thanks for the answer, and here is my interfaces file: link