PublishIP

PublishIP enables you to upload your computer's IP address to a remote computer. This enables you to:

have a web page at a static address that always points to your computer, even if your computer's address changes, and
track your computer's address and ISP in the unfortunate event your computer is stolen.

This is version 1.0 -- if you have any suggestions, please email me. Hope you find it useful.

How It Works / Requirements

This is a simple shell script that determines your computer's IP address and copies it to a remote computer. It requires that you have a remote machine accessible by ssh, with your keys created and installed. Although it has been written for Mac OS X, it could be adapted for Linux and other Unix variants with minimal effort.

Download / Install

PublishIP StartupItems package (gzipped, 5k)

The package is recommended if you want to install it as a StartupItem, since it includes the self-named directory, StartupParameters.plist, and the localization Resources to ensure it runs properly upon startup.

To install, unzip the package in /Library/StartupItems/ to have it run on every system reboot. Customize the variables for username, filename, and remote host appropriately. (This "package" is not a self-installing executable, just a tarred and gzipped directory.)

PublishIP standalone program (text, 3k)

The standalone program (included in the package) is fine if you want to set it up as a StartupItem yourself, or just run the program manually or as a cron job, or on a non-Mac platform.

To install, save it wherever you want (be sure to change its permissions to be executable). Customize the variables for username, filename, and remote host appropriately.

Some comments:

If your computer is assigned an address dynamically (as with DHCP), this will allow its new address to be published to a remote server.
You may want to publish to a web server, so you can either view the file it creates directly or from a web page (via a server-side include command).
This program requires ssh and scp. A key must be set up for a local user and the public key on the remote server.
By default the file is written to be readable/writable only by the remote user. If you wish the file to be world readable (such as by a web server), change the $mode variable.
The target directory (and file, if it already exists) must remain writable. (An alternate method would be to alter the script to write to a different file each time -- use the temp file name or create one based on the time of day).
For theft tracking, this script should be run at startup (in Mac OS X, the /Library/Startup Items/PublishIP/ directory).
Even better, run it regularly as a cron job in case the system isn't rebooted. This would also be necessary if the network is not up when the computer is turned on, for instance if a dialup account is used, or when the network changes without a reboot.
You should test the script regularly, since versions of ssh can change, login scripts can interfere with ssh, etc.
Verbose output is the default; for more silent action (no entry in the /var/log/system.log, nothing written to console), comment out or change the value of $verbose.
The file created contains just the IP address as returned by ifconfig -a (as called by CheckNetworkStatus), expecting it to be the second field after "inet". If your system does not support this command with a line starting with inet xx.xx.xx.xx, it may not work. I haven't tested for IPV6 network numbers. (I used to have this return the DNS name, but since that may not be assigned properly I no longer recommend doing that.)

Some caveats:

It will not be useful if you have been assigned a NAT address (such as 192.x.x.x or 10.x.x.x), since those are only local to your immediate network.
It will not work if the program is not run -- for example, if someone disables or erases it, does not reboot, cancels the cron job, or reformats the disk.
It may not be useful for theft tracking if you have a static IP address, since the computer won't automatically and silently reconfigure itself on the new network, as it would if both the old and new networks use dynamically assigned DHCP addresses. It may work once the network is correctly configured, though.
I have only tested this on Mac OS X 10.2.8 (Jaguar) and Mac OS X 10.3.3+ (Panther), which includes Darwin Kernel Versions 6.8, 7.3.0, and 7.50.

Revisions

Version 1.0, 29 Sep 2003. Initial release.