Many mainstream Linux distributions, such as Fedora and openSUSE have merged some of their top-level directories into the /usr directory of the file system. This process, called merge-usr (or usrmerge) removes redundant directories such as /bin and /sbin, turning them into symbolic links. Recently, Ubuntu and Debian have been working toward usrmerge systems, but Debian packagers have hit a snag. "The decision on whether /usr merge would be done by default has changed multiple times during the debootstrap development timeline. The initial support was coded in September 2016, and released in debootstrap version 1.0.83, in a disabled-by-default state. In October 2016 there was an attempt to enable it by default, but this was reverted in November, because the dpkg-shlibdeps program (which is used during package builds to automatically generate dependencies on packages that provide the needed shared libraries) broke. Therefore, Debian 9.0 (with the code name "Stretch") was released in June 2017 without this feature." Problems continue with the move, largely because Debian plans to support both traditional and usrmerge systems. Other distributions have typically avoided problems by having a firm cut-off date when packages were expected to work with the new file system layout. LWN has further details on Debian migration.