I just installed fedora Core 7 and out of the box firefox was able to connect to both localhost and to outside web sites. I attempted to change the hostname from localhost.localdomain to linuxserver.localdomain and rebooted the system. Now firefox can no longer resolve localhost but can go to external sites. I have attempted to restore everything to the way it was at installation but have not been able to connect to the localhost address again. Does anyone know how to restore to the install configuration, I can of course repeat the install but would prefer not to because I installed PHP mySql and Apache and have data in the database.

The output of the following commands would be useful to read.
cat /etc/hosts
cat /etc/hostname
And welcome to LQ!

A cat of /etc/hosts gives the following relevant data

127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6


There is no hostname file in /etc

Then things are not as they should be I am surprised your computer is running at all.
Unless FC is completely different from "normal" linux distros (which I doubt, but I am not familiar with FC), the following might sort it out:
All this has to be done as root:
First create the hostname file:
Than give it the right permissions:
And ownership:
Now either edit /etc/hostname with your preferred editor to read like this (it's just one line):
linuxserver
Or, even easier because it is just one line:
Now edit /etc/hosts and make it look like this:
That means that 127.0.0.1 (the "loopback address") is pointed to by linuxserver.localdomain and localhost and linuxserver
If you are not using IPv6 (and nobody seems to be, yet, I am awaiting the "Great Migration" (and possible "Great Chaos")) you do not need the next line that starts with ::1 and you can safely delete it, or leave it, until chaos hits us

Now reboot. Linux doesn't often need rebooting like windows does, but it does need a reboot if you have changed the hostname, because this is essential to many processes.

Then you should be good to go
If further problems, please come back here.

Did what you suggested but the situation persists, I can contact outside web sites but I am unable to connect to the local machine "localhost". Any other suggestions?

Fedora Core doesn't use /etc/hostname or /etc/HOSTNAME. Look at /etc/sysconfig/network. There should be a line defining the hostname.

Can you double check that the apache service is running?

Also try pinging localhost.

I appreciate all the help but I am still having grief.
A cat of /etc/hosts gives the following:
# Do not remove the following line, or various programs
# that require network functionality will fail.
#
127.0.0.1 linuxserver.localdomain localhost linuxserver
# ::1 localhost6.localdomain6

A cat of /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=linuxserver.localdomain

if I ping localhost I get the following:
ping localhost
PING linuxserver.localdomain (127.0.0.1) 56(84) bytes of data.
64 bytes from linuxserver.localdomain (127.0.0.1): icmp_seq=1 ttl=64 time=0.130 ms
64 bytes from linuxserver.localdomain (127.0.0.1): icmp_seq=2 ttl=64 time=0.128 ms

--- linuxserver.localdomain ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.127/0.128/0.130/0.009 ms


A cat of error_log (I believe this is the apache error log file shows the following error:
[Tue Nov 13 09:25:04 2007] [alert] (EAI 2)Name or service not known: mod_unique_id: unable to find IPv4 address of "localhost.localdomain"


Any Ideas on what I could have (*($(&$ up to produce this problem.

Apologies from me - my advice was not applicable to your distro (FC), as jschiwal pointed out.

Different linux distros do things differently. It's a pain, but you get used to it.

Here's a link that I think should help you, it spells out the differences between FC and Debian ((K)ubuntu): http://www.yolinux.com/TUTORIALS/Lin...etworking.html

Please read it, follow it, and get back here if you have further problems reconfiguring your hostname