I have boinc running and can control it fine with the GUI provided by boindmgr, but I can automate things a bit more if I can figure out how to do (a couple of) things with a cli.

The two main things I want to automate (right now), is suspending/resuming BOINC from doing work.
Whenever I want to do that I press "Suspend"/"Resume" button on the "Projects" tab in boincmgr. (I only contribute to one project - )
Reading the documentation for boinccmd led me to think I needed to use `boinccmd --project <URL> suspend` and `boinccmd --project <URL> resume` - But that is where my confusion starts. What is that <URL>? What I want to do is 100% local, so it shouldn't be necessary to use any url, and using `
boinccmd --get_project_status` the "master URL" is shown as "http://www.primegrid.com/", but when I use that as an argument to `boinccmd` I get "Operation failed: authentication error". (Using that url is also what is done in the example script on
https://boinc.berkeley.edu/wiki/Boinccmd_tool
)

I installed BOINC from the Debian (so this is on Linux) packages so what I'm using is probably not the newest version. but it's version 7.14.2

Depends how you (or Debian) have set up your connection between BOINC Manager and the boinc client. It may have a password set.

If there is a password, it will be stored in a file called gui_rpc_auth.cfg in the BOINC data directory. The same password will need to be used on the command line with boinccmd - the 'authentication error' happens when a password is expected, but not given.

Depends how you (or Debian) have set up your connection between BOINC Manager and the boinc client. It may have a password set.

If there is a password, it will be stored in a file called gui_rpc_auth.cfg in the BOINC data directory. The same password will need to be used on the command line with boinccmd - the 'authentication error' happens when a password is expected, but not given.

There is a password set in `gui_rpc_auth.cfg`, but `boinccmd` works fine in several other cases, so I assumed it wasn't necessary to supply hostname and password, but I've just tried and it actually works then.

So now I'm just wondering when I need to supply hostname and password:
`boinccmd --get_project_status` works without.

It's explained in the link you gave in your first post:

https://boinc.berkeley.edu/wiki/Boinccmd_tool

or should be. The basic principle is that 'for information' commands (the state queries group) don't need a password, but 'change something' commands (the control operations group) do.