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A simple C++ interface to NASA's SRTM Elevation data. I use this code in my Flood Maps project. This code will only run on a Unix operating system.

Download it here: nasagrid.tgz

I've just started using BackupPC to backup my file server. It's a disk-based solution - so if you want to archive to removable media such as DVD-R or tape, you need a separate archive step.

The advantage of BackupPC is supposed to be that it can do remote backups of every …

Some low-life spammer has started forging messages from my domain. My mail server is receiving many deliveries per second, all bounces for users that don't exist at my domain. Unfortunately I have (had) a catch-all alias that put mails for all unknown users into my mailbox. Ooops.

I'm in the …

How does linkfile(1) know what the original user ID was, when it's run from inside a SUID program? Well, it's a mystery to me anyway.

Here's an example program:

int main() {
  system("linkfile /tmp/foo.lock");
  return 0;
}

This program simply calls linkfile /tmp/foo. When I run it …

My laptop is usually connected behind a restrictive firewall. Since port 25 is blocked, I can't send mail the normal way. Instead I just build a tunnel to my mail server using ssh -Nf -L25025:localhost:25 mailhost and configure Mail's SMTP server to point to localhost port 25025. Usually …

This is already well documented in the Debian FAQ, but here goes...

To get the source to the current directory:

$ apt-get source PACKAGE
$ cd PACKAGE_DIR

To change the build rules. For example, if you simply want to change a configure option:

$ vi debian/rules

To change the version number, you …

I use Exim version 4 on Debian Sarge, and I want to start using a "Real-time Black-hole List" (RBL) service. How the hell do I do that?

On Woody, with Exim version 3 it was easy. There was an option in the /etc/exim/exim.conf configuration file called rbl_domains …

One of the great things about Linux is that it's an open platform, so you can get round stupid DRM nonsense. The BBC produces lots of great stuff in real media format, but some of it isn't made available to people outside the UK. I want to review some of …

Here's the magic formula to boot into a Windows (slave) hard drive from Grub. Windows thinks that it's installed on the master, but I've moved it over to the slave position. Sadly it refused to boot from there. The trick is to tell the BIOS to remap the drives, and …

The 'Native Posix Thread Library' (NPTL) is not supported by User Mode Linux (UML). NPTL is the much-vaunted 'new' threading implementation in the Linux 2.6.x kernels. There can be many symptoms of this problem, but the one I seem to always get is a crash whenever a program …