Debian buster shipped with a "merged `/usr`", which means that `/bin`, `/lib` and `/sbin` are now symlinks to their counterparts in `/usr`. There are concerns that this behavior is buggy and triggers problems in all sorts of places. In particular, the `dpkg` maintainers are quite unhappy about the change and do not support it as a configuration: https://wiki.debian.org/Teams/Dpkg/MergedUsr ... which is disturbing, considering the `dpkg` is such a core component of a Debian system. That wiki page provides a hackish script to "migrate away" from usrmerge but no one, as far as I know, has done that in production. It definitely looks nasty. We should consider : * [ ] whether this is a real problem (probably?) * [x] which machines have usrmerge (20 machines or 27%, detailed below) * [x] whether new machines should have it (probably not? not having usrmerge is *not* a problem, and having it has risks, so let's not risk it?) * [ ] whether we need to fix old machines There are two ways of fixing the installers: * pass `--no-merged-usr` to deboostrap * use `mmdebstrap` The latter has the advantage of being faster, at the cost of being possibly less reliable and compatible. Next steps: 1. [x] fix cloud installer - fixed in the wiki and tsa-misc 2. [x] fix robot installer - fixed in the wiki and tsa-misc 3. [x] fix ganeti installer - reported as [bug 959745](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=959745), mentioned in the wiki, reported [in the puppet module](https://gitlab.com/shared-puppet-modules-group/puppet-ganeti/-/issues/7)