Walkthrough: making a proot-sandbox for sioworkers.

* Use debootstrap to create a new ubuntu/debian instance
* Chroot there and 
  -> `apt-get install g++`
  -> Install apt-rdepends
      (it's in universe or multiverse or sth (not in main) - change sources.list)


  -> Use apt-rdepends g++ > somewhere

* Walk through the generated file and indent packages you would like to skip
* You can skip libc (without -dev) and get simpler libc-udeb
* copy it do `deps`
* ln -s UBU/var/cache/apt/archives archives
* mkdir packages

* generate needed packages:
grep '^\w'  deps | sed 's/$/_*/' | xargs -L1 find archives/ -name | while read P; do cp $P packages; done;

* Put libc-udeb there if you selected it

* unpack them
for i in packages/*.deb; do dpkg-deb -X $i BOX/; done;

* extract proot.tgz into BOX

* Prune docs

* Test it!
  -> Make some a.cpp file 
  -> cd BOX
  -> run
LD_LIBRARY_PATH="$PWD/usr/lib:$PWD/lib"  bin/proot -r . -b ../:/tmp/ usr/bin/g++ --version
LD_LIBRARY_PATH="$PWD/usr/lib:$PWD/lib"  bin/proot -r . -b ../:/tmp/ usr/bin/g++ -O2 -static -lm -s /tmp/a.cpp -o /tmp/a.out

  -> or to check if proot and g++ links with correct libraries
    (notice that after proot started, paths are relative to it's chroot)
LD_DEBUG=libs LD_LIBRARY_PATH="$PWD/usr/lib:$PWD/lib"  bin/proot -r . -b ../:/tmp/ usr/bin/g++ -O2 -static -lm -s /tmp/a.cpp -o /tmp/a.out