DNS resolving fails

[dantes]

Hallo,

have installed ubuntu not long ago, parallel to a Win OS.

main problem i face and reoccurs, is that the resolv.conf file somehow keeps reseting itself, and forget the DNS servers i edited and saved. that, of course, leads to me not being able to access websites by name domains. internet connection is activated, pinging, and the rest is fine, just no DNS resolving.

i have to mention- after i : sudo gedit /etc/resolv.conf and edit in the primary and secondary DNS servers, im able to access the Web, but in the course of time, or at any fresh restart- it FORGETS...

does anyone have any idea suggetions ( have to add that im new to linux and still not fluent with all the syntax).

thanks

[pmcoleman]

My resolv.conf file is managed by NetworkManager.

Thoughts here:
One, your gui based settings override the sudo gedited version.
Two, assuming you are using a SOHO router and a default gateway for your machine, that the DNS setting are not correct in the router.

Here is what mine looks like:

### BEGIN INFO
#
# Modified_by:  NetworkManager
# Process:      /usr/bin/NetworkManager
# Process_id:   5619
#
### END INFO



nameserver 172.16.32.161

Where the nameserver IP address is the default gateway of my main router which points to the DNS servers maintained by the ISP. The second router I run in the subnet points the outside DNS queries from the Intranet that it cannot resolve to the main router. In other words one router can handle the internal DNS issues and the second router is used for Internet DNS.

The second router here handles the DHCP assignments and IP addresses are assigned on MAC addresses. The NICs are set for dhcp. Thus when ever I make a change to the subnet assignments in the router(s), the resolve.conf file is automatically updated to reflect the new Internet DNS route (the IP the world sees) as soon as I reboot any of the machines.

I am thinking that there are other daemons, network managers and such that are modifying the resolve.conf file each time you reboot the system. Try looking in these other places to determine that the DNS and default gateway settings are correct for your system.

[rcgreen]

If you have a normal installation of Ubuntu, it will look on your
network for a DHCP server. The DHCP server will send an IP address
to your computer, and tell it the address of a DNS server. Ubuntu
will automatically add the DNS server address to /etc/resolv.conf.

If you are connected directly to your Internet Service Provider, it is
their server that does this for you. If you have a home router, it will perform this function. The program on your computer that talks to
the DHCP server is the DHCP client daemon (DHCPCD).

If you open a terminal and type the command man dhcpcd
it should give you the manual for configuration of it.

A quick and sloppy fix would be to write protect the /etc/resolv.conf
file, but once you know how the system works, you can discover
why it is getting a bad DNS server address, and fix the underlying
problem.

[dantes]

hello again,

thanks for your comments. i have a full installation of Ubuntu on a second pc, and experience the same problem there.
i'm using a Speedtouch Alcatel adsl modem (quite old as i got it from my ISP several years back),
this modem is then connected to a Edimax router, that connects my home Lan.
there is no problem with the Lan on my Win OS pcs, just the Linux ones are experiencing this problem.

my resolv.conf file is reset to : " nameserver 10.0.0.138" , where it suppose to get its IP address and DNS server info from the DHCP server. although it get the IP address and connection to the Web,
no DNS resolving is enabled. that's why i do it manually, in the resolv.conf.

in my network manager, the settings are for Automatic DHCP ( it does ask me in the bottom line for a DHCP client which i can leave either empty or with my address- it doesn't change my stat).

after a while the resolv.conf self resets to : "nameserver 10.0.0.138" .

is there a need to upgrade my Speedtouch Firmware? ( its NOT a USB modem).

thanks.

[rcgreen]

I'd go into the control panel on the Windows OS
and check the configuration, the IP address, gateway
and dns. Chances are that the router is the DHCP
server. Often it is also the dns server for the LAN.