Add docs for resource limits (#42)

SETUP.md

@@ -20,6 +20,22 @@ The server runs [Proxmox VE](https://www.proxmox.com/en/proxmox-virtual-environm
 
 The Nest VM is the VM that users will access and host their stuff on. It runs Debian 12 Bookworm. It's configured with all 8 CPU cores and 52 GiB of RAM.
 
+#### Resource Limits
+
+Every user on Nest has resource limits setup to prevent abuse of Nest and to make sure there's enough resources for everyone. The default limits are:
+- 50% (total) CPU time
+- 2GB memory
+- 15GB disk
+
+CPU time and memory are configured through systemd & cgroups. These default limits are defined in `/etc/systemd/system/user-.slice.d/50-memory.conf`, and can be overridden for users in `/etc/systemd/system/user-<id>.slice.d/50-memory.conf`.
+
+Note that to apply changes to either the CPU time or memory limits, you must run `systemctl daemon-reload`.
+
+Disk space limits are configured through `quota`. The following command is run by Nest Bot to set the default disk space limit:
+```sh
+setquota -u <user> 15G 15G 0 0 /
+```
+
 ### Secure VM
 
 The Secure VM is the VM that hosts all critical Nest services: