diff --git a/README.md b/README.md
index fefad50..8a03f30 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,8 @@ installation can still be done through the terminal.
 For [impermanence](https://nixos.wiki/wiki/Impermanence), partitioning should be done as outlined in the [tmpfs
 as root](https://elis.nu/blog/2020/05/nixos-tmpfs-as-root/) blogpost, but with `/nix` as a [LUKS-encrypted file
 system](https://nixos.org/manual/nixos/stable/index.html#sec-luks-file-systems). The boot partition will not be
-encrypted, since that is poorly supported by systemd-boot. Persistent files will be saved under `/nix/persist`.
+encrypted, since that is poorly supported by systemd-boot. Persistent files will be saved under `/nix/persist`. To
+find out which of our darlings will be erased on reboot do `tree -x /` or `ncdu -x /`.
 
 The following is based on the [tmpfs as root](https://elis.nu/blog/2020/05/nixos-tmpfs-as-root/) blogpost, the NixOS
 manual's [partitioning](https://nixos.org/manual/nixos/stable/index.html#sec-installation-manual-partitioning),
@@ -83,40 +84,45 @@ mkpasswd > /mnt/nix/persist/passwordfile
 chmod 400 /mnt/nix/persist/passwordfile
 ```
 
-
-## Hardware Configuration
+### Hardware Configuration
 `hosts/*/hardware.nix`, while initially generated by `nixos-generate-config --show-hardware-config`, _is_ manually
 modified.
 
-
-## Impermanence
-To find out which of our darlings will be erased on reboot do `tree -x /`.
-
-
-## Upgrading
-```bash
-sudo nixos-rebuild switch --flake .
-```
-
-
-## State Version
-Nixpkgs uses `stateVersion` so sparingly that
-auditing the entire nixpkgs repo is [easy
+### State Version
+Nixpkgs uses `stateVersion` so sparingly that auditing the entire nixpkgs repo is [easy
 enough](https://sourcegraph.com/search?q=context%3Aglobal+repo%3A%5Egithub%5C.com%3FNixOS%2Fnixpkgs%24++lang%3ANix+stateVersion+AND+23.11).
 
 
-## Debugging
+## Useful Commands
 ```bash
+# upgrade system
+sudo nixos-rebuild switch --flake .
+
+# start build environment with user's default shell instead of bash
+nix develop --command $SHELL
+
+# nix shell with python packages
+# https://discourse.nixos.org/t/nix-shell-for-python-packages/16575
+# https://github.com/NixOS/nix/issues/5567
+nix shell --impure --expr 'with builtins.getFlake "nixpkgs"; with legacyPackages.x86_64-linux; python3.withPackages (ps: with ps; [ numpy ])'
+```
+
+### Debugging
+```bash
+# load flake into repl
 nix repl
 :lf .
+
 # print the value of a configuration settings
 :p nixosConfigurations.omega.config.services.openssh.ports
+
 # print _why_ the value is as it is (source of defaults, overwrites)
 :p nixosConfigurations.omega.options.services.openssh.ports
+
 # print value of home-manager setting
 :p nixosConfigurations.omega.config.home-manager.users.caspervk.programs.ssh.matchBlocks
+
 # print version of package in nixpkgs
 :p inputs.nixpkgs.outputs.legacyPackages.x86_64-linux.openssh.version
 ```
 
-