Why doesn't a 32bit .deb package install on 64bit Ubuntu?

Question

My .deb package, built on 32-bit Ubuntu and containing executables compiled with gcc, won't install on the 64-bit version of the OS (the error message says 'Wrong architecture i386'). This is confusing to me because I thought that in general 32-bit software worked on 64-bit hardware, but not vice-versa.

Will it be possible for me to produce a .deb file that I can install on a 64-bit OS, using my 32-bit machine? Is it just a matter of using the appropriate compiler flags to produce the executables (and if so what are they), or is the .deb file itself somehow specific to one processor architecture?

Answer 1

The deb installer is probably refusing to install your package because it was (correctly) labeled with a conflicting Architecture: field. i386 code can be executed on an amd64 machine, but it requires that all the appropriate dependencies (32-bit libraries, etc.) be present. It's better to build separate packages for each architecture.

Yes, you can build for 64-bit on your 32-bit machine. It's called cross-compiling, and it requires that you create a build environment for that purpose. To get started, you might want to look up the dpkg-cross and apt-cross tools.

Alternatively, you can just install a virtual machine running a 64-bit OS, and build for your secondary architecture there.