Get dev library packages for arm on x64 Ubuntu host?

Question

I am building a project that requires a number of libraries, for windows I got prebuilt libs from MSYS2, for linux from the ubuntu repos, and now I am porting to android, so I need the same libraries for armhf and arm64. The good news is the ubuntu repos have everything I need, the bad news - I can't figure out how to get them using apt, that is get the libs with the entire dependency trees. It is possible to download individual packages from the web, but it gets kind of arduous to get the entire dependency tree, building the libraries from source - tremendously more so.

I can do sudo apt-get install package:uarch for i386 even though I am on a 64bit host, however when I try arm I get a unable to locate package. So how do I get them?

---

Note 1: I only need the libraries, I don't need toolchains, the NDK already has those.

Note 2: I did try asking on the ubuntu site, but I didn't get any feedback in like a day, and since the question is strictly about development I decided to try here.

Note 3: The question is not about recommending libraries.

EDIT: After dpkg --add-architecture armhf for update I get:

Hit:1 http://bg.archive.ubuntu.com/ubuntu xenial InRelease
Hit:3 http://bg.archive.ubuntu.com/ubuntu xenial-backports InRelease           
Get:2 http://bg.archive.ubuntu.com/ubuntu xenial-updates InRelease [95,7 kB]   
Ign:4 http://bg.archive.ubuntu.com/ubuntu xenial/main armhf Packages           
Ign:5 http://bg.archive.ubuntu.com/ubuntu xenial/restricted armhf Packages
Ign:6 http://bg.archive.ubuntu.com/ubuntu xenial/universe armhf Packages
Ign:7 http://bg.archive.ubuntu.com/ubuntu xenial/multiverse armhf Packages
Ign:4 http://bg.archive.ubuntu.com/ubuntu xenial/main armhf Packages
Ign:5 http://bg.archive.ubuntu.com/ubuntu xenial/restricted armhf Packages
Ign:6 http://bg.archive.ubuntu.com/ubuntu xenial/universe armhf Packages
Ign:7 http://bg.archive.ubuntu.com/ubuntu xenial/multiverse armhf Packages
Ign:4 http://bg.archive.ubuntu.com/ubuntu xenial/main armhf Packages     
Ign:5 http://bg.archive.ubuntu.com/ubuntu xenial/restricted armhf Packages
Ign:6 http://bg.archive.ubuntu.com/ubuntu xenial/universe armhf Packages 
Hit:8 http://security.ubuntu.com/ubuntu xenial-security InRelease        
Ign:7 http://bg.archive.ubuntu.com/ubuntu xenial/multiverse armhf Packages
Ign:9 http://bg.archive.ubuntu.com/ubuntu xenial-backports/main armhf Packages
Ign:10 http://bg.archive.ubuntu.com/ubuntu xenial-backports/universe armhf Packages
Err:4 http://bg.archive.ubuntu.com/ubuntu xenial/main armhf Packages
  404  Not Found [IP: 195.85.215.252 80]
Ign:5 http://bg.archive.ubuntu.com/ubuntu xenial/restricted armhf Packages
Ign:6 http://bg.archive.ubuntu.com/ubuntu xenial/universe armhf Packages
Ign:7 http://bg.archive.ubuntu.com/ubuntu xenial/multiverse armhf Packages
Ign:9 http://bg.archive.ubuntu.com/ubuntu xenial-backports/main armhf Packages
Ign:10 http://bg.archive.ubuntu.com/ubuntu xenial-backports/universe armhf Packages
Ign:9 http://bg.archive.ubuntu.com/ubuntu xenial-backports/main armhf Packages
Ign:10 http://bg.archive.ubuntu.com/ubuntu xenial-backports/universe armhf Packages
Get:11 http://bg.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages [383 kB]
Get:12 http://bg.archive.ubuntu.com/ubuntu xenial-updates/main i386 Packages [378 kB]
Ign:13 http://bg.archive.ubuntu.com/ubuntu xenial-updates/main armhf Packages  
Get:14 http://bg.archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages [323 kB]
Get:15 http://bg.archive.ubuntu.com/ubuntu xenial-updates/universe i386 Packages [320 kB]
Ign:16 http://bg.archive.ubuntu.com/ubuntu xenial-updates/universe armhf Packages
Ign:17 http://bg.archive.ubuntu.com/ubuntu xenial-updates/multiverse armhf Packages
Err:9 http://bg.archive.ubuntu.com/ubuntu xenial-backports/main armhf Packages
  404  Not Found [IP: 195.85.215.252 80]
Ign:10 http://bg.archive.ubuntu.com/ubuntu xenial-backports/universe armhf Packages
Ign:13 http://bg.archive.ubuntu.com/ubuntu xenial-updates/main armhf Packages
Ign:16 http://bg.archive.ubuntu.com/ubuntu xenial-updates/universe armhf Packages
Ign:17 http://bg.archive.ubuntu.com/ubuntu xenial-updates/multiverse armhf Packages
Ign:13 http://bg.archive.ubuntu.com/ubuntu xenial-updates/main armhf Packages
Ign:16 http://bg.archive.ubuntu.com/ubuntu xenial-updates/universe armhf Packages
Ign:17 http://bg.archive.ubuntu.com/ubuntu xenial-updates/multiverse armhf Packages
Err:13 http://bg.archive.ubuntu.com/ubuntu xenial-updates/main armhf Packages
  404  Not Found [IP: 195.85.215.252 80]
Ign:16 http://bg.archive.ubuntu.com/ubuntu xenial-updates/universe armhf Packages
Ign:17 http://bg.archive.ubuntu.com/ubuntu xenial-updates/multiverse armhf Packages
Ign:18 http://security.ubuntu.com/ubuntu xenial-security/main armhf Packages
Ign:19 http://security.ubuntu.com/ubuntu xenial-security/universe armhf Packages
Ign:18 http://security.ubuntu.com/ubuntu xenial-security/main armhf Packages
Ign:19 http://security.ubuntu.com/ubuntu xenial-security/universe armhf Packages
Ign:18 http://security.ubuntu.com/ubuntu xenial-security/main armhf Packages
Ign:19 http://security.ubuntu.com/ubuntu xenial-security/universe armhf Packages
Err:18 http://security.ubuntu.com/ubuntu xenial-security/main armhf Packages
  404  Not Found [IP: 91.189.91.26 80]
Ign:19 http://security.ubuntu.com/ubuntu xenial-security/universe armhf Packages
Fetched 95,7 kB in 1s (59,8 kB/s)
Reading package lists... Done
E: Failed to fetch http://bg.archive.ubuntu.com/ubuntu/dists/xenial/main/binary-armhf/Packages  404  Not Found [IP: 195.85.215.252 80]
E: Failed to fetch http://bg.archive.ubuntu.com/ubuntu/dists/xenial-backports/main/binary-armhf/Packages  404  Not Found [IP: 195.85.215.252 80]
E: Failed to fetch http://bg.archive.ubuntu.com/ubuntu/dists/xenial-updates/main/binary-armhf/Packages  404  Not Found [IP: 195.85.215.252 80]
E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/xenial-security/main/binary-armhf/Packages  404  Not Found [IP: 91.189.91.26 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.

Answer 1

Unlike Debian, the Ubuntu archives don't have everything in the right place already, in fact non-x86 packages are kept somewhere else altogether. The first thing to do is edit /etc/apt/sources.lst to add ports.ubuntu.com alongside archive.ubuntu.com/ubuntu for the repositories you want, e.g. for:

deb http://bg.archive.ubuntu.com/ubuntu/ xenial main restricted

the equivalent ports repo is:

deb http://bg.ports.ubuntu.com/ xenial main restricted

With those in place,

dpkg --add-architecture armhf

(repeat as appropriate for additional architectures), then updating as usual, does the trick. I've confirmed this on a fresh install of 16.04.1, but I'm pretty sure the same applies as far back as 12.04 too.

Per the multiarch documentation, you can shut the "ignored" and "not found" errors up by restricting entries to the relevant architectures, i.e.:

deb [arch=i386,amd64] http://archive.ubuntu.com...
deb [arch=armhf] http://ports.ubuntu.com...

For reference, Debian's census report has a convenient summary.