I need to configure my network connection using some low level commands, but I believe the autoconfiguration in Raspbian is complicating this.
How can I disable it? And if I do, can I easily restore it again?
And if I do, can I easily restore it again?
Yes. I'll describe the disabling part first, and a simple method for manually connecting to a network using either ethernet or encrypted wifi.
This should work on all versions of Raspbian; although jessie (v. 8) uses systemd, the pesky daemons are still enabled through SysV scripts.
sudo update-rc.d ifplugd disable sudo update-rc.d dhcpcd disable
Note that more recent versions of Raspbian may not use
ifplugd, in which case, don't worry about it.
The other part is the ifup/down stuff. Edit
/etc/network/interfaces and delete everything after these two lines:
auto lo iface lo inet loopback
That's all. You should keep a backup copy of your current version, without which restoring things afterward will be difficult.
This will leave you with no active hardware interface when you reboot. I'll describe how to make sure you get connected if you are running headless. If you aren't (i.e. you have a screen and keyboard) you can use the commands inside parentheses below directly from the commandline, in order, prefaced w/
Presuming ethernet and DHCP, add the following to
/etc/rc.local to reconnect. Pay attention to the structure of the last line, particularly the final
&, unless you are doing this directly from the command line, in which case you can ignore that (you want only what is inside the parentheses and not the parentheses themselves -- you'll also have to use
sudo in this case):
( ip link set eth0 up dhclient -v eth0 ) &> /var/log/local_inet.log &
This will leave you with output in
/var/log/local_inet.log; it will get ovewritten at each boot. If you are using a wifi adapter, DHCP, and WPA, instead try:
( ip link set wlan0 up wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf dhclient -v wlan0 ) &> /var/log/local_inet.log &
Again, if you are doing this from the command line you are interested only in what is inside the parentheses. The above presumes you have
/etc/wpa_supplicant/wpa_supplicant.conf set up correctly (and that the kernel module for your wifi adapter loads automatically, which it should).
To reverse the above and put everything back to the way it was:
update-rc.d -f ifplugd remove update-rc.d ifplugd defaults update-rc.d -f dhcpcd remove update-rc.d dhcpcd defaults
-f is probable unnecessary, but it won't hurt (note
man update-rc.d is demonstrably wrong about some things, but that is another story page). You have to do the "remove" before you can re-enable.
Next, since you kept a backup of
/etc/network/interfaces, put it back and reboot.
sudo update-rc.d dhcpcd disable
it worked for me