docs(zbm): Explain network device naming (#21)

README.md

@@ -99,7 +99,9 @@ The script will create a single ZFS zpool `zpool` on the zpool partition with da
 
 ## Options
 
-The following options can be given either by exporting them as shell variables prior to script execution or in a file named `archzbm_settings.env` that lives in your current working directory where you're about to execute the script. File format is identical to shell variable assignments of the form `VAR=value` or `VAR='value'`.
+The following options can be given either by exporting them as shell variables prior to script execution or in a file named `archzbm_settings.env` that lives in your current working directory where you're about to execute the script. You can walk yourself through an interactive questionnaire that helps create a valid `archzbm_settings.env` file. Check out [Command line setup help](#command-line-setup-help) for details on the questionnaire.
+
+If you instead want to define settings yourself with an `archzbm_settings.env` file its file format is identical to shell variable assignments of the form `VAR=value` or `VAR='value'`.
 
 If `./archzbm_settings.env` exists the script will `source` its content and `export` all variables for use in future steps.
 
@@ -205,6 +207,18 @@ ARCHZBM_NET_DEVICE='eth0'
 ARCHZBM_NET_AUTOCONF='dhcp'
 ```
 
+> In ZFSBootMenu the device names that go into `ARCHZBM_NET_DEVICE` are raw unchanged kernel device names such as `eth0`. If you're unsure which device name to use in your Arch Linux live CD ISO image check `dmesg` output. During boot typically a kernel module will first assign the raw kernel device name then later `systemd` will enforce [Predictable Network Interface Names](https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/).
+>
+> In `dmesg | grep` on a physical PC with an MSI B550-A Pro mainboard from 2020 that comes with one onboard Realtek RTL8111H network adapter governed by the Realtek RTL-8169 Gigabit Ethernet driver from the `r8169` kernel module you will for example see:
+> ```
+> # dmesg -T | grep eth
+> [time] r8169 0000:2a:00.0 eth0: RTL8168h/8111h, 04:7c:16:00:01:02, XID 541, IRQ 95
+> [time] r8169 0000:2a:00.0 eth0: jumbo features [frames: 9194 bytes, tx checksumming: ko]
+> [time] r8169 0000:2a:00.0 enp42s0: renamed from eth0
+> ```
+>
+> Notice how a Predictable Network Interface Name comes in on line 3. What *__you__* need here is the `eth0` part.
+
 #### SSH
 
 If you want networking indicated by the fact that at least one of the `ARCHZBM_NET_*` variables is set or one of the `ARCHZBM_SSH_*` vars we assume that you want an SSH daemon as well. This comes in the form of a `dropbear` daemon with minimal configurability. Use the following variables to define Dropbear's behavior.
@@ -225,6 +239,24 @@ ssh-rsa Eahajei8,,ssh-ed25519 kaeD0mas ...
 
 This syntax crutch allows you to use the full range of Dropbear-supported `authorized_keys` stanzas, see [man 8 dropbear](https://man.archlinux.org/man/extra/dropbear/dropbear.8.en) for what's available. Whether or not this is useful to you is another topic :) At least the functionality for stanzas is there by separating values in `ARCHZBM_SSH_AUTH_KEYS` with double-commas.
 
+## Command line setup help
+
+An interactive questionnaure can guide you through settings and goes like this:
+
+![Command line setup questionnaire](https://i.imgur.com/QntUYRH.mp4)
+
+To do the questionnaire yourself start this script with the `setup` argument:
+
+```
+export SCRIPT_URL='https://quico.space/quico-os-setup/arch-zbm/raw/branch/main/setup.sh' && curl -s "${SCRIPT_URL}" | bash -s -- setup
+```
+
+When done rerun it without that argument:
+
+```
+export SCRIPT_URL='https://quico.space/quico-os-setup/arch-zbm/raw/branch/main/setup.sh' && curl -s "${SCRIPT_URL}" | bash
+```
+
 # Steps
 
 The script takes the following installation steps.