Find unofficial packages installed on a Raspberry Pi running Raspbian

nonraspbian

#!/bin/sh
# nonraspbian -
#
# Find packages installed on my Pi which aren't from the official
# Raspberry Pi repositories. 


aptitude search '?narrow(?installed,!?or(?origin("Raspberry Pi Foundation"),?origin("Raspbian")))'


# NOTES

# This one-liner was handy on a Raspberry Pi Zero W (which has an ARM 6
# processor) when I used the SD card from my Pi 3B (which is ARM 7)
# and many programs were segfaulting or printing "Illegal instruction".

# It turned out the problem was that I had installed some newer
# packages directly from Debian and Debian Backports, but Debian
# presumes an ARM 7 at minimum.

# I needed to downgrade all the ARM 7 packages with their ARM 6
# equivalents. But how could I find out which ones those were?

# Turns out, the oft overlooked aptitude program can do that fairly
# easily. Just find all the packages that aren't from the official
# repositories. 

####
# SOME IDEAS THAT WOULDN'T HAVE WORKED:

# * Searching by architecture
#
#   Since both Debian and the Raspberry Pi foundation label their
#   architecture the same, one can't simply search on ?architecture(armhf).
#   (I think the RPi foundation should have used "arm6hf".)

# * Using file(1) to check the ABI version using magic numbers.
#
#   Both ARM7 (gphoto2) and ARM6 (gpg) return the same thing:
#
#       $ file /usr/bin/gphoto2
#       /usr/bin/gphoto2:
#       ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV),
#       dynamically linked, interpreter /lib/ld-linux-armhf.so.3,
#       for GNU/Linux 2.6.32,
#       BuildID[sha1]=870c02a0c42d47af0a3917ee1f79f4187dcddc66,
#       stripped
#
#       $ file /usr/bin/gpg
#       /usr/bin/gpg: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), 
#       dynamically linked, interpreter /lib/ld-linux-armhf.so.3,
#       for GNU/Linux 2.6.32,
#       BuildID[sha1]=09978c06faef2b023ac5cc94acb04cb03cdb2f3f,
#       stripped

# * Likewise, using file(1) on shared libraries (found using ldd(1)) fails.