About this issue:

# ls
bash: /usr/bin/ls: No such file or directory

ASSI (alias Achim) send me the following (thanks for info :-) ):
> 
> Try the fix mentioned in the FAQ part of
> 
> https://en.opensuse.org/openSUSE:Usr_merge
> Why and how the UsrMerge wasn't completed much earlier on your system 
> remains to be determined if that is the reason for your troubles.
> 

OK, but there was nothing really helpful:
# /usr/lib64/ld-linux-x86-64.so.2 /usr/bin/ln -s
/usr/lib64/ld-linux-x86-64.so.2 /lib64/ld-linux-x86-64.so.2
/usr/bin/ln: failed to create symbolic link '/lib64/ld-linux-x86-64.so.2': File
exists
# /usr/lib64/ld-linux-x86-64.so.2 /usr/bin/ln -s /usr/lib64/libc.so.6
/lib64/libc.so.6
/usr/bin/ln: failed to create symbolic link '/lib64/libc.so.6': File exists

# cd /usr; ln -s . /usr/usr
OK, was working

What I did (I don't know if this was an good idea - I will see after the zypper
dup:
# ls -l /
bin -> usr/bin
lib -> usr/lib
lib64 -> usr/lib64

to
# ls -l /
bin -> /usr/bin
lib -> /usr/lib
lib64 -> /usr/lib64

After the changes (see previous mail) and a new zypper dup:

# zypper ref ; unmount ~/bin ; zypper dup --download-in-advance
--allow-vendor-change ; mount ~/bin 
Repository 'Mozilla' is up to date.                                             
Repository 'Haupt-Repository (NON-OSS)' is up to date.                          
Repository 'Haupt-Repository (OSS)' is up to date.                              
Repository 'Hauptaktualisierungs-Repository' is up to date.                     
Repository 'packman' is up to date.                                             
All repositories have been refreshed.
Error: Try the command: umount
Loading repository data...
Reading installed packages...
Warning: You are about to do a distribution upgrade with all enabled
repositories. Make sure these repositories are compatible before you continue.
See 'man zypper' for more information about this command.
Computing distribution upgrade...

The following package is going to be upgraded:
  filesystem

1 package to upgrade.
Overall download size: 67.7 KiB. Already cached: 0 B. No additional space will
be used or freed after the operation.
Continue? [y/n/v/...? shows all options] (y): 
Retrieving package filesystem-84.87-7.1.x86_64                                 
                                                      (1/1),  67.7 KiB (  1.3
KiB unpacked)
Retrieving: filesystem-84.87-7.1.x86_64.rpm
.........................................................................................................................[done]

Checking for file conflicts:
........................................................................................................................................[done]
error: unpacking of archive failed on file /root/bin: cpio: chown failed -
Device or resource busy
error: filesystem-84.87-7.1.x86_64: install failed
error: filesystem-84.87-6.1.x86_64: erase skipped
(1/1) Installing: filesystem-84.87-7.1.x86_64
......................................................................................................................[error]
Installation of filesystem-84.87-7.1.x86_64 failed:
Error: Subprocess failed. Error: RPM failed: Command exited with status 1.
Abort, retry, ignore? [a/r/i] (a): r
error: unpacking of archive failed on file /root/bin: cpio: chown failed -
Device or resource busy
error: filesystem-84.87-7.1.x86_64: install failed
error: filesystem-84.87-6.1.x86_64: erase skipped
(1/1) Installing: filesystem-84.87-7.1.x86_64
......................................................................................................................[error]
Installation of filesystem-84.87-7.1.x86_64 failed:
Error: Subprocess failed. Error: RPM failed: Command exited with status 1.
Abort, retry, ignore? [a/r/i] (a): 
Problem occurred during or after installation or removal of packages:
Installation has been aborted as directed.
Please see the above error message for a hint.

And journalctl -xe

Sep 03 18:33:06 x dbus-daemon[1113]: [system] Activating via systemd: service
name='org.opensuse.Snapper' unit='snapperd.service' requested by ':1.316'
(uid=0 pid=3>
Sep 03 18:33:06 x systemd[1]: Starting DBus interface for snapper...
������������������ Subject: A start job for unit snapperd.service has begun execution
������������������ Defined-By: systemd
������������������ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
������������������ 
������������������ A start job for unit snapperd.service has begun execution.
������������������ 
������������������ The job identifier is 13285.
Sep 03 18:33:06 x dbus-daemon[1113]: [system] Successfully activated service
'org.opensuse.Snapper'
Sep 03 18:33:06 x systemd[1]: Started DBus interface for snapper.
������������������ Subject: A start job for unit snapperd.service has finished successfully
������������������ Defined-By: systemd
������������������ Support: https://lists.freedesktop.org/mailman/listinfo/systemd-devel
������������������ 
������������������ A start job for unit snapperd.service has finished successfully.
������������������ 
������������������ The job identifier is 13285.
Sep 03 18:33:13 x [RPM][747]: Transaction ID 631381c9 started
Sep 03 18:33:13 x [RPM][747]: install filesystem-84.87-7.1.x86_64: success
Sep 03 18:33:13 x [RPM][747]: erase filesystem-84.87-6.1.x86_64: success
Sep 03 18:33:13 x [RPM][747]: install filesystem-84.87-7.1.x86_64: failure
Sep 03 18:33:13 x [RPM][747]: 1 elements failed, 0 scripts failed
Sep 03 18:33:13 x [RPM][747]: Transaction ID 631381c9 finished: -1
Sep 03 18:33:16 x [RPM][782]: Transaction ID 631381cc started
Sep 03 18:33:16 x [RPM][782]: install filesystem-84.87-7.1.x86_64: success
Sep 03 18:33:16 x [RPM][782]: erase filesystem-84.87-6.1.x86_64: success
Sep 03 18:33:16 x [RPM][782]: install filesystem-84.87-7.1.x86_64: failure
Sep 03 18:33:16 x [RPM][782]: 1 elements failed, 0 scripts failed
Sep 03 18:33:16 x [RPM][782]: Transaction ID 631381cc finished: -1
lines 1059-1133/1133 (END)