8

tl;dr: In Ubuntu 20.04, folders such as /bin and /sbin are now symlinks to the same folders in /usr. Why was this change made and shouldn't the release notes mention it?

This took a few days, but I tracked down some issues I was having in system setup. As part of a preseed post-install set of commands, I unpack a .tar.gz onto new systems, which puts some files in various folders, including /bin. I've been doing this since Ubuntu 14.04. With Ubuntu 20.04, my systems weren't bootable after install (various failure to mount errors).

I finally narrowed the issue down to this unpacking step, and realized that I'm replacing the /bin folder and making many things inaccessible. What a lovely surprise. The fix is easy enough; dump files in /usr/bin, instead.

Specifically, the following symlinks are new in 20.04, apparently (below via multiple fresh installs):

$ lsb_release -ds
Ubuntu 20.04 LTS
$ ls -l / | grep -E "usr|bin|lib"
lrwxrwxrwx   1 root root     7 Apr 23 15:02 bin -> usr/bin/
lrwxrwxrwx   1 root root     7 Apr 23 15:02 lib -> usr/lib/
lrwxrwxrwx   1 root root     8 Apr 23 15:02 sbin -> usr/sbin/
drwxr-xr-x  11 root root  4096 Apr 23 15:05 usr/

Compare with 19.10 (edit: this system was upgraded from 18.04 I think; whoops):

$ lsb_release -ds
Ubuntu 19.10
$ ls -l / | grep -E "usr|bin|lib"
drwxr-xr-x   2 root root  4096 Dec 11 07:41 bin
drwxr-xr-x  20 root root  4096 Nov  4  2019 lib
drwxr-xr-x   2 root root  4096 Nov  3  2019 lib64
drwxr-xr-x   2 root root 12288 Apr  6 13:29 sbin
drwxr-xr-x  11 root root  4096 Aug  5  2019 usr

Arch does this, apparently starting years ago, and the overall topic is the Filesystem Hierachy Standard . It's not in the release notes: https://wiki.ubuntu.com/FocalFossa/ReleaseNotes

7
  • 1
    Possible duplicate of 2014's unix.stackexchange.com/questions/121235/…. Interestingly, my 20.04 systems (upgraded from 19.10 and earlier) are NOT linked, so the change for new installs might be several releases old.
    – user535733
    May 21, 2020 at 15:34
  • Thanks for the additional link! I would not consider this a duplicate, as there's two unanswered questions here: Why did Ubuntu just now make this change, and why did they not include it in release notes.
    – Gertlex
    May 21, 2020 at 15:39
  • Probably this is the case in fresh installs of LTS version. I have the links in 18.04, in 20.04 but not in an install off 19.04. Just an observation... I only do fresh installs, never release-upgraded.
    – mook765
    May 21, 2020 at 15:49
  • 1
    Right. The hope is that someone who has tracked down e.g. relevant mailing list discussion will use that as an answer.
    – Gertlex
    May 21, 2020 at 16:15
  • 1
    All this is great until someone run dpkg -x file.deb /. Then the system will be ruined almost completely.
    – N0rbert
    Jun 9, 2020 at 7:08

1 Answer 1

12
+50

I hadn't noticed this change, so I dug into it a little bit. I'm guessing it was not in the release notes because it was really an upstream change in Debian:

This Ubuntu announcement is the only official notification of the change I've seen

Merged-usr is now the default in Disco for new installations only

Some other general info

3
  • 1
    Good sleuthing! It sounds like this possibly took effect with 19.04, and based on other comments, mayyybe got included in a later point release of 18.04, so could affect fresh installs of that, too.
    – Gertlex
    Jun 9, 2020 at 21:29
  • Thanks for finding this!! I’ll test older Ubuntu from before. With docker you can try this easily. On Ubuntu 18.04 it certainly didn’t have this feature.
    – morhook
    Jun 10, 2020 at 5:48
  • Since 19.04 this feature is enabled on Ubuntu, I've re-checked answer with this command docker run -it ubuntu:19.04 ls -la
    – morhook
    Jun 15, 2020 at 7:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.