The following error occurs when trying to save a debug file (System → Advanced → Save Debug):

Error Downloading File
Debug could not be downloaded.

It stays at 81.00% (Dump ZFS Configuration) for quite a while and then shows the abovementioned error (see screenshot). When that box is closed, a 2nd error appears after a short while:

Failed
[Errno 32] Broken pipe

Details:

Error: Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/middlewared/job.py", line 361, in run
await self.future
File "/usr/local/lib/python3.8/site-packages/middlewared/job.py", line 399, in __run_body
rv = await self.middleware.run_in_thread(self.method, *([self] + args))
File "/usr/local/lib/python3.8/site-packages/middlewared/utils/run_in_thread.py", line 10, in run_in_thread
return await self.loop.run_in_executor(self.run_in_thread_executor, functools.partial(method, *args, **kwargs))
File "/usr/local/lib/python3.8/site-packages/middlewared/utils/io_thread_pool_executor.py", line 25, in run
result = self.fn(*self.args, **self.kwargs)
File "/usr/local/lib/python3.8/site-packages/middlewared/schema.py", line 977, in nf
return f(*args, **kwargs)
File "/usr/local/lib/python3.8/site-packages/middlewared/plugins/system.py", line 787, in debug
shutil.copyfileobj(f, job.pipes.output.w)
File "/usr/local/lib/python3.8/shutil.py", line 205, in copyfileobj
fdst_write(buf)
BrokenPipeError: [Errno 32] Broken pipe

To reproduce:

1) set pool to readonly (unsure if it matters)
2) create a recursive snapshot on the pool
3) create a 2nd pool
4) zfs send -R firstpool@snap | zfs receive -Fd secondpool
5) System → Advanced → Save Debug

I went to the command line and ran freenas-debug -a > debug_a and attached the output.

Exporting the 2nd pool and rebooting fixes the first error message. In that case the “Save Debug” works, however the 2nd error still appears (“Broken pipe”).