yum thorugh proxy.

# vi ~/.bash_profile

Add this at the bottom.

export http_proxy=http://ip:port

Now reboot.That would do.

If I forget these...

Writting this 'cause these are very common problems. But when you try to repair these, you end up with one-o-one suggessions. Each of these happened to me and I fixed them at various points of time. So I am keeping track of them here. Oh Yes..I use fedora. Always. But these should be general for any distro.

1. Repairing grub.

#grub-install --recheck /dev/hda
if /dev/hda holds the boot partition.
This recreates the device map.

2. Cannot log on after cleaning /tmp directory

Problem with permission. Probably you have removed /tmp itself
#touch /tmp
#chmod -R 777 /tmp

3. Enabled xdmcp and cannot log-on locally :). Its fun, isn't it?

This is very funny. However do these and keep hoping that you need not reformat your machine.
Did I say refomatting ? Laughing ? Ok ...Before viewing this, go enable XDMCP by running gdmsetup and try to login locally.
Anyways...

#init 3
# cp /usr/share/gdm/defaults.conf /etc/gdm/custom.conf
#startx
or
#init 6