Duplicati.Server users 50% CPU with nothing scheduled is some troubleshooting. Some translates to Linux, some doesn’t. One advantage of Linux over Windows is at least some allow “ls -lu” to detect file reads, so you can try ls -lurt ~/.config/Duplicati to see what’s been read. Also try -lrt and -lcrt.
Basically, troubleshooting could start with triage. You know CPU is busy. What’s up with disk and net?
Large-scale disk stats might be possible with things like sar or iotop. Network might try netstat or ntop.
If you’re still at Backup_PreBackupVerify, your status bar probably says “Verifying backend data …”, however not every step is shown, and so it might be somewhere a bit later. Still, it narrows the scope.
How deep into troubleshooting do you want to go? Are you talking about code and Linux system calls?
strace with -p on the child mono process, and using -f, seems to give a nice view of what’s going on in some selected area, and triage to the area is made easier with canned packages of system calls, e.g.:
-e trace=network
Trace all the network related system calls.
-e trace=desc
Trace all file descriptor related system calls.
I haven’t done C# debugging on mono yet. Tools do exist, but some need a process restart, and it might work out best if troubleshooting is done on the live problem – unless you think problem is reproducible…