pppd makes a resolv.conf backup, then pppd-dns immediately restores it

[Elie Morisse]

Steps to reproduce :
(1/Buy a serial or USB modem)
2/Configure through the "networking" method ( not "ppp" ), e.g adding those lines into /etc/network/interfaces and using the "usepeerdns" option :
auto ppp0
iface ppp0 inet ppp
  provider speedtch
3/Reboot. Score : ppp0 is up, but ISP DNS are not registered in /etc/resolv.conf, so I can't even ask for help on Ubuntu forums

What happens ? The problem is located inside the rcS.d folder : S40networking uppes ppp0, pppd negociates the ISP DNS, backups resolv.conf and after all writes down the ISP DNS into the file, but ere S55pppd-dns immediately restores the backup so the changes made by pppd are cancelled.

pppd-dns seems to be designed for the obsolete ( since years ) init.d/ppp script, not for init.d/networking, am i right ? If so, shouldn't it be removed along the whole obsolete stuff, then replaced by a if-up.d script ?

Anyway this is a very serious bug and is making every non-Ethernet modems owners very unhappy ( well actually only those requiring a connection at boot ), especially users of my speedtouch-ng package :( ( a configuration helper for Speedtouch USB/330 modems : http://moigeeknevro.com/speedtouch-ng/files/1.2.4/ )

I've fixed it through modifying the boot sequence order so the pppd-dns runs before networking, i.e :

sudo update-rc.d -f pppd-dns remove
sudo update-rc.d pppd-dns start 39 S .

Is this susceptible to break something ?

[Elie Morisse (lachienne)]

Please ! Why don't you fix it ? I just see that Debian make it a S38, just like you before..

[Stefan Daniel Schwarz (Wolfram Ravenwolf) (stefandanielschwarz)]

I've been bitten by this bug, too, until I figured out what's wrong. I wanted to report it, but found this bug report instead, so I'm adding a comment.

As Elie Morisse explained already, the boot order has changed from Breezy to Dapper, now /etc/init.d/pppd-dns is linked to /etc/rcS.d/S55pppd-dns instead of /etc/rcS.d/S38pppd-dns as it used to be. Since it runs after networking is brought up (which, thanks to pppoeconf, already has activated the ppp connection), it discards the (until then valid) /etc/resolv.conf. We end up with an established ppp connection but without DNS servers to resolve domain names.

The work-around would be to disconnect (sudo poff) and reconnect (pon), but a real fix is changing the boot order back to how it was set up under Breezy. I'm pretty sure a lot of people don't even notice that the ppp connection is up and that the DNS is being mangled, instead they will assume that there's no Internet connection after boot-up, despite having configured it that way. In addition to that, bringing up a working Internet connection on boot up is vital for headless servers, so I consider this bug of high importance.

Thanks,
-- Stefan D. Schwarz

[Stefan Daniel Schwarz (Wolfram Ravenwolf) (stefandanielschwarz)]

Here's how I fixed it:

sudo mv /etc/rcS.d/S55pppd-dns /etc/rcS.d/S38pppd-dns

By the way, /etc/rcS.d/S39dns-clean (Breezy) changed into /etc/rcS.d/S55dns-clean (Dapper) as well, although its comments clearly indicate "It should never be run while ppp is up." - which happens at S40networking! Somehow the boot order got mixed up quite a bit, causing hard to troubleshoot problems...

Thanks in advance for investigating and fixing this bug,
-- Stefan D. Schwarz

[Konstantinos Togias (ktogias)]

This bug is still present at Ubuntu 9.10 . I reproduced on a Ubuntu 9.10 server install and fixed it with the workaround described at the bug description.

[Torsten Spindler (tspindler)]

The bug also seems to hit network-manager based system connections that are established upon starting network-manager. This happens in Ubuntu 10.04 LTS.