My personal preference for Dynamic DNS is dyndns.org - but there are a lot of them out there. This step will take into account that you have gone with my recommendation. Go to their website and make an account (click on Members NIC) then 'New Account'. Once you confirm your account, you need to make a host first. Choose something easy that you will remember (the IP address, or any other field besides the host part isn't needed. Click on add). Once that is done, I personally recommend ddup (website) - go to the 'Download' section and grab the latest copy.
Go into the directory where the ddup tar file is.
cp ddup* /tmp/
tar -zxvf ddup*
cd ddup-3.0.1 (or whatever it installed it to)
sh install
Okay, run through the setup, and when it asks if you would like to make a configuration file, select yes. There was some confusion about this from some people, so I will clarify: your user name is what you signed up with dyndns.org, enter in your password, just let root use it, and then you're done! Let's make it global and test it out (make sure you're connected to the internet!), type:
cp /tmp/ddup-3.0.1/ddup /usr/bin
ddup --host (what_hostname_you_selected).dyndns.org
Okay, now to be 24/7 online:
You *WILL* need to edit this file to change it to your needs.
Next, type:
cp pppmonitor /usr/bin
A quick note: If you have entered anything below, and you notice that your boot script hangs and doesn't bring you to a login prompt, the steps you will need to follow to get to a login prompt and FIX whatever is making it hang are: 1. reboot your computer (ctrl+alt+del usually does a "graceful" shutdown, if not, the good o'le power switch will do it) 2. when the LILO: prompt comes up, type linux single 3. it will go into "single user mode" - this is one reason why you should never let your linux server (pysically) be allowed by anyone who you don't trust - it bypasses all passwords and gives you a root shell. 4. once the shell prompt comes up, type pico /etc/rc.d/rc.local 5. make the change necessary 6. type reboot and then just type linux at the LILO: prompt (or whatever you have setup to boot linux up *normally*.
Making all these programs run at boot-time.
pico /etc/rc.d/rc.local
add the following lines:
Save this file, make sure you *can* get online right now, reboot the computer, and watch in amazement :)
Enjoy,
Fandelem