Is bash installed somewhere else? You can try “which bash” or “whereis bash” to search some places.
Are your /bin and /usr/bin different filesystems (e.g. as shown by df)? I thought that practice was fading.
Move all to /usr was Fedora’s move in 2012, and they cited rationale and what other distros were doing.
Preparing for a merged /usr in Debian was Debian talk. I’m not sure when or if the move has happened.
Update to 3.4.0 fails on CentOS 6 #990 is a claim that CentOS 6 was split, while CentOS 7 was unified.
(P.S. I see recent note explaining that was CentOS 6 which would be consistent with different partitions)
But if the first line in the duplicati script is #!/usr/bin/bash and it’s not there, that’s the error you’d find.
I’m not seeing previous reports of this in the forum is GitHub issues, though I do notice 2.0.4.4 uses /bin.
A workaround for just a couple of scripts is to edit the first line to match the actual location of interpreter, however (assuming you do have a separate /bin and /usr/bin somehow, and intend to keep that design) would be to create a symbolic link so that whatever is referenced goes to where your bash got installed:
So if /usr/bin/bash does not exist, you could make a symbolic link at /usr/bin/bash that will run /bin/bash:
ln -s /bin/bash /usr/bin/bash
and possibly there could be a similar issue for some other needed program. One thing at a time though.
Technically invoking things as “sh” might give different behavior, so “bash” or the above link may be better.
Bug 60625 Summary: local-propagation.c:562, condition `ins->opcode > MONO_CEE_LAST’ not met appears to show a 2017 fix. If your mono the latest available when you update your system the usual way?
https://www.mono-project.com/download/stable/#download-lin-centos also has directions, and unless you wish to be careful about breaking anything else using mono (I wonder if you have any), maybe just get that.