Thank you for all your answers, this pointed me to tools I was not aware
of and to options I was not aware of in tools I knew.
`lsof` seems able to give me a lot of info, but has so many options that
I haven't yet found a way to give me something more or less useful.
But at least I now know that it can do a lot more than tell me who's
preventing me from unmounting a filesystem. 🙂
`pidstat`, `htop`, and `iotop` are closer to what I was imagining, but
they're also coarser. And AFAICT none of them give me info about the
network activity, focusing on CPU/MEM/DISK only.
One of my main uses is when a tool is sitting there without giving me
any feedback and I'm wondering what it is that it's doing.
E.g. recently this occurred with `bup`, where I wanted to see if it was
mostly talking to the remote `bup`, or mostly reading local files or
writing local files (so as to guess in which phase
it is, and whether it's making progress), or none of the above
(e.g. because the network connection got stuck).
Stefan
