How to install i386 package under amd64 ubuntu/debian

• All existing answers I found are for the pre-multiarch era (chroot)
• https://help.ubuntu.com/community/MultiArch says it is OK to install i386 package on amd64 under the multiarch environment, but doesn't say how.

So, how to install i386 package on amd64 under the ubuntu/debian multiarch environment?

This is the follow-up for Why I can't see Ubuntu restricted packages, where the sl-modem-daemon package doesn't have the amd64 but only i386 version in Ubuntu. Following https://askubuntu.com/questions/29665/how-do-i-apt-get-a-32-bit-package-on-a-64-bit-installation, I tried,

apt-get install sl-modem-daemon:i386

but still get the reply that package not found.

Solution 1:

Found the answer in the Debian wiki (the ubuntu community MultiArch wiki is incomplete) -- https://wiki.debian.org/Multiarch/HOWTO. I.e., the step I'm missing is

To add an extra architecture (in Debian from dpkg 1.16.2 onwards):

dpkg --add-architecture <arch>

Having done that (and apt-get update of course), I'm now able to do apt-get install sl-modem-daemon:i386.

Thank you user55325 for riding the journey with me.

UPDATE: Found one that explains this explicitly:

How to enable 32-bit support for 64-bit Ubuntu 13.10 or greater
http://www.unixmen.com/enable-32-bit-support-64-bit-ubuntu-13-10-greater/