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This is really a strange problem for me, as I have no idea where to begin looking for the problem.
I have a bit of linux experience, in that I have been able to build a server that has been running now for close to a year or so. It's Fedora Core 3 and runs apachie MYSQL etc. It's been working just fine with absolutely no problems until tonight.
I decided to upgrade the memory in the machine from 256MB to 512MB since I retired another box and had extra memory sticks.
I shut down the system and all appeared to be normal. It was last recycled about three weeks ago, but it normally runs for months at a time without any recycles. It is current with all updates as of the time Core 3 went out of maintenance mode.
After installing the additional memory, I booted up the machine and the only thing I noticed at first was that httpd "failed" on the bootup messages. Everything else appeared normal.
I then tried to log in as root and got the message that the host name could not be resolved and GNOME may not work correctly. I have never got that message before.
Once in root, I tried using a web browser, and it fails saying it can't find the web site.
PING works just fine if I use an IP address, but if I use a name like google (I can't use a real url because I have not made five posts), it says "unknown host".
Looking in the messages log I see where the host name failed to be resolved, so my suspecian is that the DNS workings are no longer working.
SAMBA is working just fine, and all my other PC's can access this machine and look at all the files. I can access my other machines from this server just fine as well.
What isn't working is Apachie which appears to be failing because it can not properly resolve it's domain name for itself.
Ping does not work if I use a name instead of an IP address.
In checking the network settings, everything looks like it should. I have three DNS's defined, which are the same as those in my router.
The system is setup with a static local IP address, and the router forwards the required ports to the machine for http access.
Like I said to start, this machine has been working just fine for many months, and I really did not change anything other than the memory. I put the original memory back in and it get's exactly the same error.
My MB can accept both SDRAM and DDR RAM so I installed 512MB of DDR and removed the SDRAM.
To go back to the old setup, I put the original SDRAM back in and removed the DDR ram.
The memory is good, as it works perfectly in my windows XP machine and does not give any errors in the linux machine when it boots up.
The linux machine is certainly faster at starting applications with the increased memory.
Since I really don't think this is a memory problem, I currently have the machine back running with the 512MB so I can access the files on it as it is also a primary file server for all my windows machines.
I sure would like to get the apachie server running again so that my web sites were active.
I have to confess, I do not have the slightest idea where to look for this problem since everything I look at looks normal.
So much of the network is working with the samba stuff that I do not suspect anything wrong with the network. All my other machines are working exactly like they always have, but just to be sure, I turned them all off, reset the router, and turned everything back on again. Everything works as before, with the linux machine failing to be able to resolve a domain name.
Here are a few snips of the messages log that I think show the problem.
Mar 15 21:42:33 tringate network: Setting network parameters: succeeded
Mar 15 21:42:33 tringate network: Bringing up loopback interface: succeeded
Mar 15 21:42:36 tringate network: Bringing up interface eth0: succeeded
Mar 15 21:42:45 tringate nss_wins: gethostbyname error for xxxxxxx.xxxxxx.com <---------------- first thing that looks wrong I x'ed out my real domain name.
Mar 15 21:42:45 tringate nfslock: rpc.statd startup succeeded
Mar 15 21:42:46 tringate kernel: SELinux: initialized (dev rpc_pipefs, type rpc_pipefs), uses genfs_contexts
Mar 15 21:42:46 tringate rpcidmapd: rpc.idmapd startup succeeded
Mar 15 21:42:46 tringate netfs: Mounting other filesystems: succeeded
Here is where httpd fails. the first warning message has been happening ever since I built the system, so it has nothing to do with the failure.
Mar 15 21:43:28 tringate gpm: gpm startup succeeded
Mar 15 21:43:32 tringate httpd: [Wed Mar 15 21:43:32 2006] [warn] The Alias directive in /etc/httpd/conf/httpd.conf at line 472 will probably never match because it overlaps an earlier AliasMatch.
Mar 15 21:43:35 tringate httpd: httpd startup failed
Mar 15 21:43:35 tringate iiim: htt startup succeeded
Here is the httpd error log from when I shut down the working system, and then the failed boot after ading the additional memory.
[Wed Mar 15 20:06:05 2006] [notice] caught SIGTERM, shutting down
[Wed Mar 15 20:31:56 2006] [notice] core dump file size limit raised to 4294967295 bytes
[Wed Mar 15 20:31:57 2006] [alert] (EAI 2)Name or service not known: mod_unique_id: unable to find IPv4 address of "xxxxxxx.xxxx.com"
[Wed Mar 15 21:03:20 2006] [notice] core dump file size limit raised to 4294967295 bytes
[Wed Mar 15 21:03:22 2006] [alert] (EAI 2)Name or service not known: mod_unique_id: unable to find IPv4 address of "xxxxxx.xxxxxxx.com"
Please be gentle with your suggestions on how to look for this problem. I am sure I will ask many really stupid qquestions as my trouble shooting skills are as close to zero as you can get.
Sorry for such a long post, but just wanted to tell everyone who might want to help as much as I could.
On the surface it looks pretty simply that somehow (probably not related to the memory upgrade but happened at an earlier time and shows up after reboot) name resolution on this system was changed. If the host's name can't be resolved, apache will complain and so will Gnome and a few other services. There should be an /etc/resolv.conf with your DNS servers listed by IP address:
Thank you so much for your "right on the money" answer. My problem turns out to be that my ISP changed their DNS servers so the IP addresses I had configured were no longer correct. All is working just fine again with a very simple configuration correction.
This brings up another question concerning the use of DHCP rather than a dedicated IP address.
My router is a linksys wireless and as far as I can see, there is no way to forward a specific port using a computer name, so that is why I assigned a static IP from those available in the private LAN range. This requires me to put the DNS addresses into the linux machine unlike if I had used DHCP which sends those addresses over to the linux machine each time the lease expires.
My problem is with the port forwarding and keeping the same address to forward that port to.
Is there some magical way I can get the best of both worlds? Have linux get the DNS addresses from the router, but not it's IP address?
I guess the current state I run in would require me to check the DNS addresses my ISP is using every so often, or at least when this kind of problem happens again. At least today I know that, but I easily have "senior moments" and something that is clear today, tends to get forgotten six months from now.
Most of the home routers have the ability to do pseudo-static IP addresses by assigning an IP address based on MAC address. In the GUI or whatever you use to set up your linksys there should be a section in the DHCP where you can input a client system's MAC address and pick the IP that you want it to always get from the DHCP server. The MAC is of course seen in the output from ifconfig (you probably already knew that, but if not then now you do.) With the DHCP server always giving out the same IP address you don't have to worry about port forwarding ever changing and can set the system back up to use DHCP.
Of course, most of the SOHO routers also do DNS forwarding, so you could instead set your nameserver to it's IP 192.168.0.1 or whatever it is.