Merge pull request '26-install-zfs-only-when-needed' (#27 ) from 26-install-zfs-only-when-needed into main

Reviewed-on: #27
Merge remote-tracking branch 'origin/26-install-zfs-only-when-needed' into 26-install-zfs-only-when-needed
2025-01-17 20:11:11 +00:00 · 2025-01-17 21:09:40 +01:00 · 2025-01-17 21:09:19 +01:00 · 2025-01-17 21:08:44 +01:00 · 2025-01-17 21:05:53 +01:00 · 2025-01-02 01:00:06 +01:00
3 changed files with 2007 additions and 270 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -0,0 +1,2 @@
+archzbm_settings.env
+.idea
--- a/README.md
+++ b/README.md
@@ -2,39 +2,342 @@

 Helper script to install Arch Linux with ZFSBootMenu from within a running Arch Linux live CD ISO image

-# Prep
+## Prep

 We expect minimal prep on your end. Please make sure that before execution the following conditions are met.

+### UEFI
+
+On a UEFI system ensure these conditions are met. See [How to prep](#how-to-prep) for details on how to meet these conditions.
+
+- One GPT-partitioned disk
 - Arch Linux live CD ISO image sees exactly one partition with partition type code `BF00` ("Solaris root")
- Arch Linux live CD ISO image sees exactly one partition with partition type code `EF00` ("EFI system partition")
+- Arch Linux live CD ISO image sees exactly one partition with partition type code `EF00` ("EFI System Partition")
+- The `EF00` EFI partition is mountable, in practical terms this usually only means it has a file system.
 - No ZFS zpool exists

-The script will create a single ZFS zpool `zpool` on the `BF00` partition with dataset child `zpool/root` which itself has one child `zpool/root/archlinux`, that's where Arch Linux gets installed. Parallel to `zpool/root` it'll create `zpool/data` with a `zpool/data/home` child dataset that gets mounted at `/home`.
+### Legacy BIOS

-The script will use the `EF00` partition to install a ZFSBootMenu EFI executable if `efibootmgr` says that no such `ZFSBootMenu` entry exists. If ZFSBootMenu gets added to the EFI partition it'll become primary boot option.
+If you are instead running a legacy BIOS machine ensure these conditions are met. See [How to prep](#how-to-prep) for details on how to meet these conditions.
+
+- One MBR-partitioned disk
+- Arch Linux live CD ISO image sees exactly one partition with partition type code `bf` ("Solaris root")
+- Arch Linux live CD ISO image sees exactly one partition with partition type code `83` ("Linux")
+- The `83` Linux partition is mountable, in practical terms this usually only means it has a file system.
+- No ZFS zpool exists
+
+Neither with a UEFI nor legacy BIOS system are any of these conditions a requirement from ZFSBootMenu. We're just setting requirements to easily identify if you intend to do a UEFI or a legacy BIOS install. Subsequently the script has no logic to detect UEFI or legacy BIOS mode, that's legwork left to the reader :) The Internet seems to agree that a good quick check is to see if your Arch Linux live CD ISO image has directory `/sys/firmware/efi`.
+```
+[ -d /sys/firmware/efi ] && echo 'Likely a UEFI system' || echo 'Probably a legacy BIOS system'
+```
+If you're unsure nothing's stopping you from just giving it a go with a best guess and if that fails you know you guessed wrong.
+
+## How to prep
+
+### UEFI
+
+On a blank example disk `/dev/sda` you can fulfill the UEFI requirements (one `EF00` partition with a file system plus one `BF00` partition) for example like so:
+```
+sgdisk --new '1::+512M' --new '2' --typecode '1:EF00' --typecode '2:BF00' /dev/sda
+mkfs.vfat /dev/sda1
+```
+> `--new '1::+512M'`: Create partition number `1`. The field separator `:` separates the partition number from start sector. In this case start sector is unspecified so start sector sits at whatever the system's default is for this operation. On a blank disk on an Arch Linux live CD ISO image this will default to sector `2048`. Partition ends at whatever the beginning is `+512M` meaning plus 512 Mebibytes.
+>
+> `--new '2'`: Create partition number `2`. Both field number 2, the start sector, and field number 3, the end sector, are unspecified, there's no field separator `:`. Field number 2 will be the first free sector - in this case right after partition 1 - and field number 3 will be end of disk. Thus partition `2` will fill the remaining free disk space.
+>
+> `--typecode '1:EF00'`: Partition 1 gets partition type code `EF00`, an EFI System Partition.
+>
+> `--typecode '2:BF00'`: Partition 2 gets partition type code `BF00`, a Solaris root partition.
+
+The result will be something like this at which point you can start the `setup.sh` script, see [How to run this?](#how-to-run-this) below for more details.
+```
+# lsblk --paths --output 'NAME,SIZE,FSTYPE,PARTTYPE,PARTTYPENAME,PTTYPE' /dev/sda
+NAME         SIZE FSTYPE PARTTYPE                             PARTTYPENAME PTTYPE
+/dev/sda      10G                                                          gpt
+├─/dev/sda1  512M vfat   c12a7328-f81f-11d2-ba4b-00a0c93ec93b EFI System   gpt
+└─/dev/sda2  9.5G        6a85cf4d-1dd2-11b2-99a6-080020736631 Solaris root gpt
+```
+
+### Legacy BIOS
+
+For a legacy BIOS machine you'll be using a Master Boot Record (MBR) on your disk.
+```
+printf -- '%s\n' 'label: dos' 'start=1MiB, size=512MiB, type=83, bootable' 'start=513MiB, size=+, type=bf' | sfdisk /dev/sda
+mkfs.vfat /dev/sda1
+```
+> `label: dos`: Create the following partition layout in a Master Boot Record.
+>
+> `start=1MiB, size=512MiB, type=83, bootable`: Partition 1 begins 1 Mebibyte after disk start and is 512 Mebibyte in size. We're setting its bootable flag and setting partition type code `83` ("Linux").
+>
+> `start=513MiB, size=+, type=bf`: Partition 2 begins right at the start of Mebibyte 513, this is the very next sector after the end of partition 1. It takes up the remaining disk space, we're assigning type code `bf` ("Solaris").
+
+The result will be something like this at which point you can start the `setup.sh` script, see [How to run this?](#how-to-run-this) below for more details.
+```
+# lsblk --paths --output 'NAME,SIZE,FSTYPE,PARTTYPE,PARTTYPENAME,PTTYPE' /dev/sda
+NAME         SIZE FSTYPE PARTTYPE PARTTYPENAME PTTYPE
+/dev/sda      10G                              dos
+├─/dev/sda1  512M vfat   0x83     Linux        dos
+└─/dev/sda2  9.5G        0xbf     Solaris      dos
+```
+
+# Partition naming
+
+Since this script works with UEFI and legacy BIOS mode we'll be addressing both disk layout schemes with umbrella terms for the rest of this document for better readability: "The zpool partition" will be GPT `BF00` partition and MBR `bf` partition. You'll parse the text accordingly. "The boot partition" will be GPT `EF00` partition as well as the MBR `83` partition.
+
+# ZFS dataset layout
+
+The script will create a single ZFS zpool `zpool` on the zpool partition with dataset child `zpool/root` which itself has one child `zpool/root/archlinux`, that's where Arch Linux gets installed. Parallel to `zpool/root` it'll create `zpool/data` with a `zpool/data/home` child dataset that gets mounted at `/home`.

 # How to run this?

 - Boot an Arch Linux live CD ISO image
 - Run:
    ```
-    export SCRIPT_URL='https://quico.space/quico-os-setup/arch-zbm/raw/branch/main/setup.sh'
-    curl -s "${SCRIPT_URL}" | bash
+    export SCRIPT_URL='https://quico.space/quico-os-setup/arch-zbm/raw/branch/main/setup.sh' && curl -s "${SCRIPT_URL}" | bash
    ```
    During execution the script will call itself when it changes into its `chroot`, that's why we `export SCRIPT_URL`. Feel free to update `"${SCRIPT_URL}"` with whatever branch or revision you want to use from [quico.space/quico-os-setup/arch-zbm](https://quico.space/quico-os-setup/arch-zbm). Typically `.../branch/main/setup.sh` as shown above is what you want.

+## 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. 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.
+
+In cases where a variable is both exported prior to script execution and specified in `archzbm_settings.env` the latter will override the former.
+
+Known options are as follows.
+
+### Kernel downgrade
+
+By default we install newest `linux` and `linux-headers` packages into a `chroot`. Once we're in that `chroot` we then install newest [AUR zfs-dkms package](https://aur.archlinux.org/packages/zfs-dkms). You may want to override `linux` and `linux-headers` versions to ensure you end up with a compatible mix between them and `zfs-dkms`.
+
+For example:
+```
+export ARCHZBM_KERNEL_VER=6.5.9.arch2
+```
+
+In our `chroot` this will trigger execution of:
+```
+downgrade --ala-only 'linux=6.5.9.arch2' 'linux-headers=6.5.9.arch2' --ignore always
+```
+
+Where `downgrade` is the [AUR downgrade package](https://aur.archlinux.org/packages/downgrade). This will downgrade `linux` and `linux-headers` and will add a setting to your `/etc/pacman.conf`:
+```
+[options]
+IgnorePkg = linux linux-headers
+```
+
+Setting `ARCHZBM_KERNEL_VER` to an empty string `''` or keeping it undefined are both valid and will retain newest versions instead of downgrading.
+
+Also read [Kernel selection](#kernel-selection) for details.
+
+### Compression
+
+By default we create a zpool with ZFS property `compression=on`. If the `lz4_compress` pool feature is active this will by default enable `compression=lz4`. See `man 7 zfsprops` for example in ZFS 2.1.9 for details. See `zpool get feature@lz4_compress <pool>` to check this feature's status on your `<pool>`.
+
+To get a zpool with uncompressed datasets export the shell variable `ARCHZBM_ZFSPROPS_NO_COMPRESSION` with any value prior to running this script. Literally any value works as long as you're not setting this to an empty string:
+```
+export ARCHZBM_ZFSPROPS_NO_COMPRESSION=yesplease
+```
+
+### Encryption
+
+By default we encrypt the zpool with ZFS property `encryption=on`. In ZFS 2.1.9 this defaults to `encryption=aes-256-gcm`.
+
+To get a zpool with unencrypted datasets export the shell variable `ARCHZBM_ZFSPROPS_NO_ENCRYPTION` with any value prior to running this script:
+```
+export ARCHZBM_ZFSPROPS_NO_ENCRYPTION=yup
+```
+
+### Passwords
+
+By default both the zpool password and the account password for `root` are literally `password`. While you can certainly change these after initial system setup (see [Password change](#password-change)) you can also optionally set passwords before script execution as follows:
+
+```
+ARCHZBM_ZPOOL_PASSWORD='a fancy password'
+ARCHZBM_ROOT_PASSWORD='t0psecr3t!'
+```
+
+> While the `root` password is allowed to be weak and `chpasswd` won't care do make sure to set a zpool password that meets ZFS' complexity rules. Per `man 7 zfsprops` section `keyformat` the only requirement is a length "between 8 and 512 bytes" (as in minimum 8 characters). If you pick a password that's too weak ZFS will reject zpool creation and very ungracefully derail the rest of this script. The script doesn't check what you're setting.
+
+The script does create a second user named `build` but doesn't set a password on account creation. It's intended as a helper for system setup tasks such as `sudo -u build paru -S <package>` where an account password is irrelevant since `root` can always `sudo` whatever it wants. You will not be able to log in to the `build` account yourself although you certainly could set a password for it. Instead we suggest you create a proper user account for yourself. Your newly installed Arch Linux comes with an `/etc/motd` greeting that summarizes this as:
+
+```
+useradd --create-home --shell /bin/bash --user-group --groups wheel <user>
+passwd <user>
+```
+
+### Networking
+
+By default the script configures plain ZFSBootMenu without networking nor an SSH server. If you're interested in SSH-ing into your ZFSBootMenu boot loader you're going to want to specify some of the following variables.
+
+#### IP address
+
+> IPv6 addresses are untested. Script has been confirmed working with IPv4 addresses.
+
+```
+ARCHZBM_NET_CLIENT_IP=''
+ARCHZBM_NET_SERVER_IP=''
+ARCHZBM_NET_GATEWAY_IP=''
+ARCHZBM_NET_NETMASK=''
+ARCHZBM_NET_HOSTNAME=''
+ARCHZBM_NET_DEVICE=''
+ARCHZBM_NET_AUTOCONF=''
+```
+
+By default none of the variables are set to any value and no networking will be available in ZFSBootMenu. If you want networking as in an IP address bound to a network interface set at least one of these variables or one of the [SSH](#ssh) variables listed further down. Setting one or more `ARCHZBM_NET_*` variables to an empty string is valid. If at least one variable is given either from this paragraph or from [SSH](#ssh) we're assuming that you want networking. Unspecified values and values set to the empty string `''` use defaults.
+
+For networking we rely on the [mkinitcpio-nfs-utils](https://archlinux.org/packages/core/x86_64/mkinitcpio-nfs-utils/) package with its `net` hook. Please refer to its [initcpio-install-net](https://gitlab.archlinux.org/archlinux/packaging/packages/mkinitcpio-nfs-utils/-/blob/main/initcpio-install-net) script file for usage hints on above variables. The hook implements a subset of the [ip Kernel Command Line argument](https://docs.kernel.org/admin-guide/nfs/nfsroot.html).
+
+Mapping between `net` hook field names and our shell variables is straightforward. Fields 8, 9 and 10 (DNS and NTP server addresses) from the official `ip` docs are unsupported in `net` hook. As such our hook has a total of 7 fields available for you to configure.
+
+```
+-------------+------------------------+
+|  net hook   |       This script      |
+-------------+------------------------+
+| <client-ip> | ARCHZBM_NET_CLIENT_IP  |
+| <server-ip> | ARCHZBM_NET_SERVER_IP  |
+| <gw-ip>     | ARCHZBM_NET_GATEWAY_IP |
+| <netmask>   | ARCHZBM_NET_NETMASK    |
+| <hostname>  | ARCHZBM_NET_HOSTNAME   |
+| <device>    | ARCHZBM_NET_DEVICE     |
+| <autoconf>  | ARCHZBM_NET_AUTOCONF   |
+-------------+------------------------+
+```
+
+A valid example with a few fields populated may look like so:
+
+```
+ARCHZBM_NET_CLIENT_IP='10.10.10.2'
+ARCHZBM_NET_GATEWAY_IP='10.10.10.1'
+ARCHZBM_NET_NETMASK='255.255.255.0'
+ARCHZBM_NET_DEVICE='eth0'
+ARCHZBM_NET_AUTOCONF='none'
+```
+
+Note that in this example `ARCHZBM_NET_SERVER_IP` and `ARCHZBM_NET_HOSTNAME` are left unassigned.
+
+It'll add the following `ip=` instruction to your Kernel Command Line:
+```
+ip=10.10.10.2::10.10.10.1:255.255.255.0::eth0:none
+```
+
+This is also valid and will configure `eth0` via DHCP:
+
+```
+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.
+
+```
+ARCHZBM_SSH_PORT='22'
+ARCHZBM_SSH_KEEPALIVE_INTVL='1'
+ARCHZBM_SSH_AUTH_KEYS=''
+```
+
+In `ARCHZBM_SSH_PORT` you specify Dropbear's listening port, this defaults to `22` if unconfigured or set to an empty string. With `ARCHZBM_SSH_KEEPALIVE_INTVL` you define at which interval Dropbear will send keepalive messages to an SSH client through the SSH connection. This defaults to `1` as in every `1` second a keepalive message is sent. Per [man 8 dropbear](https://man.archlinux.org/man/extra/dropbear/dropbear.8.en) a value of `0` disables Dropbear sending keepalive messages. We suggest to leave this on and to keep the interval short, see [SSH in ZFSBootMenu](#ssh-in-zfsbootmenu) for how to work with this.
+
+Dropbear in this setup only supports key-based authentication, no password-based authentication. The value from `ARCHZBM_SSH_AUTH_KEYS` will be converted to a list of public SSH keys allowed to SSH into Dropbear as its default `root` user while ZFSBootMenu is running. The format of `ARCHZBM_SSH_AUTH_KEYS` is a single line where `authorized_keys` entries are split with double-commas:
+
+```
+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 questionnaire can guide you through settings and goes like this:
+
+![Command line setup questionnaire](https://i.imgur.com/OXG75GH.gif)
+
+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 scripts takes the following installation steps.
+The script takes the following installation steps.

 1. Install ZFS tools and kernel module with [github.com/eoli3n/archiso-zfs](https://github.com/eoli3n/archiso-zfs)
-1. Create one encrypted ZFS zpool on top of `BF00` partition, password `password`
+1. Create one ZFS zpool on top of zpool partition, encrypted and compressed datasets, password `password`
+    1. _See paragraph [Passwords](#passwords) to predefine your own passwords in a settings file_
+    1. _See paragraphs [Compression](#compression)/[Encryption](#encryption) to optionally disable properties_
 1. Create dataset for Arch Linux and `/home`
 1. Install Arch Linux into pool
-1. Add ZFSBootMenu to `EF00` partition if it doesn't exist already
+1. Add ZFSBootMenu to boot partition
+1. Configure boot method
+    - Either an EFI image with EFI boot order entries on a UEFI machine
+    - Or Syslinux with `extlinux` for a legacy BIOS computer
+1. If requested by user enable SSH in ZFSBootMenu. We then also add:
+    - [quico.space/quico-os-setup/mkinitcpio-dropbear-pacman-hook](https://quico.space/quico-os-setup/mkinitcpio-dropbear-pacman-hook)
+1. Add `pacman` hooks to keep ZFSBootMenu images (and `extlinux`) updated
+    - [quico.space/quico-os-setup/zbm-regen-pacman-hook](https://quico.space/quico-os-setup/zbm-regen-pacman-hook)
+    - [quico.space/quico-os-setup/zbm-syslinux-pacman-hook](https://quico.space/quico-os-setup/zbm-syslinux-pacman-hook)
 1. Exit into Arch Linux live CD ISO image shell for you to `reboot` and frolick

+# SSH in ZFSBootMenu
+
+Per [SSH](#ssh) and [Networking](#networking) this script will optionally add a Dropbear SSH daemon to ZFSBootMenu. While the mechanism of SSH-ing into a server isn't particularly noteworthy we humbly suggest that in this particular use case you let your SSH client listen for keepalive messages from the server.
+
+```
+ssh -o ServerAliveInterval=3 -o ServerAliveCountMax=0 root@<addr> -p <port>
+```
+
+A typical workflow with Dropbear is for you to SSH into it, issue `zfs` or `zfsbootmenu` commands and allow the Arch Linux boot process to commence. As soon as you're done Dropbear will terminate as ZFSBootMenu hands control off to your operating system's kernel. Without your client listening to keepalive messages it may not realize that the connection's gone for quite some time until you harshly interrupt it.
+
+The server defaults to sending keepalive messages to your client every second.
+
+With `-o ServerAliveInterval=3` you instruct your client to send an are-your-still-there message to the server if your client ever stops getting keepalive messages from the server for 3 seconds. The server defaults to sending 1 keepalive ping per second so even on a somewhat lossy connection we can reasonably expect to get one message through to us within 3 seconds.
+
+When it comes to the point that your SSH client sends an are-your-still-there message it expects a near-realtime response. It will accept `-o ServerAliveCountMax=0` failures from the server to comply.
+
+This effectively configures your SSH client to remain connected even through somewhat lossy hops to the Dropbear daemon; and to cleanly disconnect 3 seconds and some change after you've executed whatever you needed to do in ZFSBootMenu.
+
+# Kernel selection
+
+This script compiles ZFS via Arch Linux' [Dynamic Kernel Module Support](https://wiki.archlinux.org/title/Dynamic_Kernel_Module_Support) (DKMS). Not all kernels allow for successful compilation, in some instances a particularly recent kernel version may change APIs to such a degree that ZFS compilation simply fails.
+
+We strongly suggest to that you:
+
+- Firstly, refer to a resource such as the [Arch Linux Archive package version list](https://archive.archlinux.org/packages/l/linux/) to find out what newest kernel version this script will install.
+- Secondly, research if newest [AUR zfs-dkms package](https://aur.archlinux.org/packages/zfs-dkms) is compatible with that kernel. Two reasonable points of contact are AUR and its comments section for `zfs-dkms` where users quickly report issues; and the [github.com/openzfs/zfs issues list](https://github.com/openzfs/zfs/issues).
+
+An example for this is that `linux-6.6.1.arch1-1-x86_64` came out on Wednesday, November 8, 2023 at a time when newest `zfs-dkms` package version [was 2.2.0](https://aur.archlinux.org/cgit/aur.git/commit/?h=zfs-dkms&id=da1b6372c57b16f2781a7fda2b95971bb392c5ee) which did not compile against `linux` 6.6.x.
+
+You'd then set for example:
+```
+export ARCHZBM_KERNEL_VER=6.5.9.arch2
+```
+
+Where any 6.5.x version is known to work well with `zfs-dkms`. See also [Kernel downgrade](#kernel-downgrade) for details on how to configure this.
+
 # Flavor choices

 We make the following opinionated flavor choices. Feel free to change them to your liking.
@@ -52,14 +355,391 @@ We make the following opinionated flavor choices. Feel free to change them to yo
 After installation you're going to want to at least touch these points in your new Arch Linux install:

 - Package manager hook: `pacman` does not have a hook to do ZFS snapshots
-    - See [this GitHub gist](https://gist.github.com/Soulsuke/6a7d1f09f7fef968a2f32e0ff32a5c4c#file-arch_on_zfs-txt-L238) and [zfs-snapshotter.bash](https://github.com/Soulsuke/arch-zfs-tools/blob/master/zfs-snapshotter.bash) for inspiration
+    - See [quico.space/quico-os-setup/zfs-pacman-hook](https://quico.space/quico-os-setup/zfs-pacman-hook/src/branch/1-get-base-version-going) for an example you may want to install
 - Hostname: Installation chose a pseudo-randomly generated 8-character string with `pwgen`
    - Check `hostnamectl set-hostname <hostname>`
 - Unprivileged user accounts: The OS was installed with `root` and unprivileged `build` users
- Passwords
+- Unless you had a settings file or exported shell env vars per [Passwords](#passwords) you're going to want to change passwords now:
    - ZFS: The password for all datasets underneath `zpool` is `password`.
    - Local `root` account: The local `root` account's password is `password`.
- Arch User Repository (AUR) helper: We installed [paru](https://github.com/Morganamilo/paru) as our AUR helper, we installed from GitHub via `makepkg -si`.
+- Arch User Repository (AUR) helper: We installed [paru](https://github.com/Morganamilo/paru) as our AUR helper, we installed from AUR as [paru-bin](https://aur.archlinux.org/packages/paru-bin).
+- In `/etc/systemd/network/50-wired.network` instead of a DHCP-based network config you can get a static one. The DHCP-based one for reference looks like:
+    ```
+    ...
+
+    [Network]
+    DHCP=ipv4
+    IPForward=yes
+    Domains=~.
+
+    [DHCP]
+    UseDNS=yes
+    RouteMetric=10
+    ```
+    A static config does away with the `[DHCP]` section:
+    ```
+    ...
+
+    [Network]
+    Address=10.10.10.2/24
+    Gateway=10.10.10.1
+    DNS=10.10.10.1
+    IPForward=yes
+    Domains=~.
+    ```
+- In case you later want a graphical interface and specifically NetworkManager (via package `networkmanager`) consider telling it to keep its hands off of some of your network interfaces. The bullet point above adds a `systemd`-style config file that `systemd-networkd.service` will read and use. Should you ever install NetworkManager it will by default assume that it must manage all interfaces. It'll use its own DHCP client to try and get IP addresses for _managed interfaces_ in which case you'll end up with whatever addressing scheme you configured in a `.network` unit file plus NetworkManager's additional address. Create `/etc/NetworkManager/conf.d/99-unmanaged-devices.conf` for example to declare some interfaces as off-limits or _unmanaged_:
+    ```
+    [keyfile]
+    unmanaged-devices=mac:52:54:00:74:79:56;type:ethernet
+    ```
+    Check out [ArchWiki article "NetworkManager" section "Ignore specific devices"](https://wiki.archlinux.org/title/NetworkManager#Ignore_specific_devices) for more info.
+
+# Password change
+
+After installation you're going to want to change your ZFS encryption password (unless you preconfigured a good zpool password in a settings file per [Passwords](#passwords)). At any rate you still want to be familiar with the process and its caveat in case you ever need a zpool password change or want to do one now.
+
+## Steps
+
+In a running OS:
+
+1. Change password in `keylocation` file, e.g. `/etc/zfs/zpool.key` or whatever other `"${zpool_name}"'.key'` file you used during setup
+1. Set this key as the new encryption key:
+    ```
+    zfs change-key -l zpool
+    ```
+    Quoting `man 8 zfs-change-key` from `zfs-utils` version 2.1.9 for the `-l` argument: "Ensures the key is loaded before attempting to change the key." When successful the command will not output data, it'll just silently change your encryption key.
+1. Rebuild initramfs:
+    ```
+    mkinitcpio -P
+    ```
+    Here for example with `-P` (`--allpresets`) which processes all presets contained in `/etc/mkinitcpio.d`. This step puts the changed key file into your initramfs. During setup we've adjusted `/etc/mkinitcpio.conf` so that it contains `FILES=(/etc/zfs/zpool.key)` which causes the file to be added to initramfs as-is.
+
+## Boot flow
+
+With your password changed in two locations (key file and initramfs)  The boot process works as follows.
+
+At boot time ZFSBootMenu will scan all pools that it can import for a `bootfs` property. If it only finds one pool with that property the dataset given as `bootfs` will be selected for boot with a 10-second countdown allowing manual interaction. With `bootfs` set ZFSBootMenu will not actively search through datasets for valid kernel and initramfs combinations, it'll instead accept `bootfs` as the default boot entry without us entering the pool decryption passphrase.
+
+Upon loading into a given dataset ZFSBootMenu will attempt to auto-load the matching decryption key. In our setup this will fail because we purposely stored the encryption key inside our `zpool/root/archlinux` dataset. ZFSBootMenu will prompt us to type in the decryption key.
+
+Lastly ZFSBootMenu loads our OS' kernel and initramfs combination via `kexec`. For this step we don't need to enter the decryption key again. Our initramfs file contains the plain-text `/etc/zfs/zpool.key` file which allows it to seamlessly import the right dataset, load its key and mount it.
+
+## Caveats in a password change
+
+ZFS differentiates between user keys - also called wrapping keys - and the master key for any given encryption root. You never interact with the master key, you only pick your personal user key. Subsequently a user key change (in our use case we perceive this simply as a password change) has zero effect on data that's already encrypted. The operation is instant and merely reencrypts the already existing master key, the so-called _wrapped_ master key.
+
+ZFS generates the master key exactly once when you enable encryption on a dataset - technically when it becomes an encryption root. Among other inputs it uses your user key to encrypt (to _wrap_) the master key. When you change your user key it just means that the master key stays exactly the same and only the encrypted (_wrapped_) key changes.
+
+`man 8 zfs-change-key` from `zfs-utils` version 2.1.9 adds:
+> If the user's key is compromised, `zfs change-key` does not necessarily protect existing or newly-written data from attack. Newly-written data will continue to be encrypted with the same master key as the existing data. The master key is compromised if an attacker obtains a user key and the corresponding wrapped master key. Currently, `zfs change-key` does not overwrite the previous wrapped master key on disk, so it is accessible via forensic analysis for an indeterminate length of time.
+>
+> In the event of a master key compromise, ideally the drives should be securely erased to remove all the old data (which is readable using the compromised master key), a new pool created, and the data copied back. This can be approximated in place by creating new datasets, copying the data (e.g. using `zfs send | zfs recv`), and then clearing the free space with `zpool trim --secure` if supported by your hardware, otherwise `zpool initialize`.
+
+On one hand changing the ZFS encryption password is generally a good and useful thing to do. On the other hand changing your password does not currently overwrite previous wrapped master keys on disk. A sufficiently motivated party that gains access to a wrapped master key and the matching user key is able to decrypt the master key and use it to read all data encrypted with it.
+
+By extension this means after a password change your data remains at risk until you've copied it to a new dataset and erased previously used space thereby erasing any previous wrapped master keys.
+
+## Changing master key
+
+In order to generate a new master key after you've changed your user key as mentioned in `man 8 zfs-change-key` from `zfs-utils` version 2.1.9 one example workflow goes like this:
+
+1. Change user key
+    - Update `/etc/zfs/zpool.key`
+    - Update zpool with new key via `zfs change-key -l zpool`
+    - Generate new initramfs with `mkinitcpio -P`
+1. Create a snapshot from current system dataset
+    ```
+    # Assuming current system dataset is zpool/root/archlinux-sxu
+    # where '-sxu' is a random suffix to differentiate datasets
+    # and has no real meaning
+    zfs snapshot zpool/root/archlinux-sxu@rekey
+    ```
+1. Within same pool `send`/`receive` snapshot
+    ```
+    zfs send \
+        --large-block \
+        --compressed \
+        'zpool/root/archlinux-sxu@rekey' | \
+    \
+    zfs receive \
+        -Fvu \
+        -o 'encryption=on' \
+        -o 'keyformat=passphrase' \
+        -o 'keylocation=file:///etc/zfs/zpool.key' \
+        -o 'mountpoint=/' \
+        -o 'canmount=noauto' \
+        -o 'org.zfsbootmenu:commandline=rw nowatchdog rd.vconsole.keymap=de-latin1' \
+        'zpool/root/archlinux-frn'
+    ```
+    Explanation:
+    - We specifically don't `zfs send -R` (`--replicate`). While it would normally be nice to transfer all of a dataset's children at once such as all of its snapshots the `-R` argument conflicts with the `encryption` property. See [comment by Tom Caputi on GitHub openzfs/zfs issue 10507 from June 2020](https://github.com/openzfs/zfs/issues/10507#issuecomment-651162104) for details. Basically if `encryption` is set then `-R` doesn't work. We could transfer existing encryption properties with `-w`/`--raw` but we don't actually want to transfer encryption properties at all. We want them to change during transfer, see the bullet point four points down from here talking about `encryption`.
+    - We `zfs receive -F` destroying any target snapshots and file systems beyond the snapshot we're transferring. In this example the target `zpool/root/archlinux-frn` doesn't even exist so `-F` isn't necessary to clean anything up. It's just good practice.
+    - With `-v` we get verbose progress output
+    - Argument `-u` makes sure the dataset does not get mounted after transfer. ZFS would mount it into `/` which wouldn't be helpful since we're currently using that filesystem ourselves.
+    - We set encryption properties `keyformat`, `keylocation` and most importantly `encryption`. The latter will turn our transferred dataset into its own `encryptionroot` which in turn generates a new master key. The auto-generated new master key gets wrapped with our updated passphrase in `keylocation`. This basically reencrypts all data in this dataset during transfer.
+    - We set `mountpoint` and `canmount` as well as an `org.zfsbootmenu:commandline` as we would for any new system dataset.
+1. Change zpool's `bootfs` property to new system dataset
+    ```
+    zpool set bootfs=zpool/root/archlinux-frn zpool
+    ```
+1. Boot into new system dataset
+1. After reboot  and now that you're in the new system dataset change its `encryptionroot` by letting it inherit data from its parent:
+    ```
+    zfs change-key -i -l zpool/root/archlinux-frn
+    ```
+    The parent `zpool/root` is inheriting this property from `zpool` which will make sure that `zpool/root/archlinux-frn` essentially gets its key now from `zpool`. Both `zpool/root/archlinux-frn` and `zpool` use the same exact `keylocation` with identical content. This operation is instant.
+
+## Finishing touches
+
+### Confirm master key change
+
+Just to confirm that the master key has changed run this command. It takes a moment to output data:
+
+```
+zfs send --raw zpool/root/archlinux-frn@rekey | zstream dump | sed -n -e '/crypt_keydata/,/end crypt/p; /END/q'
+```
+
+Repeat for source dataset `zpool/root/archlinux-sxu@rekey`. You're particularly interested in parameters `DSL_CRYPTO_MASTER_KEY_1` and the initialization vector `DSL_CRYPTO_IV`. Notice that they differ between old and new dataset confirming that your new dataset has a new master key.
+
+### Clean-up
+
+Clean up:
+
+1. In newly keyed/reencrypted system dataset destroy its snapshot
+    ```
+    zfs destroy zpool/root/archlinux-frn@rekey
+    ```
+1. Recursively destroy source dataset
+    ```
+    zfs destroy -r zpool/root/archlinux-sxu
+    ```
+
+### Unmap/TRIM
+
+Next up unmap/TRIM unallocated disk areas. If your zpool runs on an entire disk and not just on a partition, and if your disk supports TRIM you're going to want to do:
+```
+zpool trim --secure zpool
+```
+
+The next best alternative is to instead do:
+```
+zpool initialize zpool
+```
+
+View status with either one of:
+```
+# With TRIM status
+zpool status -t zpool
+
+# Without TRIM status
+zpool status zpool
+```
+
+# ZFS setup explained
+
+## Overview
+
+The ZFS pool and dataset setup that makes this tick, explained in plain English.
+
+1. Create zpool with options:
+    1. `-R /mnt` (aka `-o cachefile=none -o altroot=/mnt`). The pool is never cached, i.e. it's considered temporary. All pool and dataset mount paths have `/mnt` prepended. From `man zpoolprops`:
+        > This can be used when examining an unknown pool where the mount points cannot be trusted, or in an alternate boot environment, where the typical paths are not valid. `altroot` is not a persistent property. It is valid only while the system is up.
+    1. `-O canmount=off`: Note the capital `-O` which makes this a file system property, not a pool property. File system cannot be mounted, and is ignored by `zfs mount -a`. This property is not inherited.
+    1. `-O mountpoint=none`: What it says on the tin, the pool has no mountpoint configured.
+    1. `-O encryption=on`: Makes this our `encryptionroot` and passes the `encryption` setting to all child datasets. Selecting `encryption=on` when creating a dataset indicates that the default encryption suite will be selected, which is currently `aes-256-gcm`.
+    1. `-O keylocation=file://...`: This property is only set for encrypted datasets which are encryption roots. Controls where the user's encryption key will be loaded from by default for commands such as `zfs load-key`.
+    1. `-O keyformat=passphrase`: Controls what format the user's encryption key will be provided as. Passphrases must be between 8 and 512 bytes long.
+1. At this time the newly created zpool is not mounted anywhere. Next we create the "root" dataset, that's an arbitary term for the parent dataset of all boot environments. Boot environments in your case may be for example different operating systems all of which live on separate datasets underneath the root.
+    1. `-o canmount=off`: Same as above, the root dataset can - just like the pool - not be mounted.
+    1. `-o mountpoint=none`: Same as above, the root dataset has - just like the pool - no mountpoint configured.
+    1. `zfs set org.zfsbootmenu:commandline=...`: Set a common kernel command line for all boot environments such as `"ro quiet"`.
+1. Neither the root dataset nor the pool are mounted at this time. We now create one boot environment dataset where we want to install Arch Linux.
+    1. `-o mountpoint=/`: Our Arch Linux dataset will be mounted at `/`.
+    1. `-o canmount=noauto`: When set to `noauto`, a dataset can only be mounted and unmounted explicitly. The dataset is not mounted automatically when the dataset is created or imported, nor is it mounted by the `zfs mount -a` command or unmounted by the `zfs unmount -a` command.
+    1. We then `zpool set bootfs="zpool/root/archlinux" zpool`: ZFSBootMenu uses the `bootfs` property to identify suitable boot environments. If only one pool has it - as is the case here - it identifies the pool's preferred boot dataset that will be booted with a 10-second countdown allowing manual interaction in ZFSBootMenu.
+    1. We explicitly mount the boot environment. Since the entire pool is still subject to our initial `-R /mnt` during creation a `zfs mount zpool/root/archlinux` will mount the Arch Linux dataset not into `/` but instead into `/mnt`.
+1. We also create a `data` dataset that - at least for now - we use to store only our `/home` data.
+    1. For `zpool/data`:
+        1. `-o mountpoint=/`: We use the `mountpoint` property here only for inheritance.
+        1. `-o canmount=off`: The `zpool/data` dataset itself cannot actually be mounted.
+    1. For a `zpool/data/home` child dataset:
+        1. We do not specify any properties. Since `canmount` cannot be inherited the parent's `canmount=off` does not apply, it instead defaults to `canmount=on`. The parent's `mountpoint=/` property on the other hand is inherited so for a `home` child dataset it conveniently equals `mountpoint=/home`.
+        1. In effect this `zpool/data/home` dataset is subject to `zfs mount -a` and will happily automount into `/home`.
+1. We export the zpool once, we then reimport it by scanning only inside `/dev/disk/by-partuuid`, again setting `-R /mnt` as we did during pool creation a moment ago and we do not mount any file systems.
+1. We `zfs load-key <encryptionroot>` which will load the key from `keylocation` after which the `keystatus` property for `<encryptionroot>` and all child datasets will change from `unavailable` to `available`.
+1. We mount our Arch Linux boot environment dataset. It automatically gets prefixed with `-R /mnt` since that's how we imported the pool.
+1. We `zfs mount -a` which automounts `zpool/data/home` into `/home`, which again gets auto-prepended by `/mnt`.
+1. We lastly mount our EFI partition into `/mnt/efi`.
+1. We instruct ZFS to save its pool configuration via `zpool set cachefile=/etc/zfs/zpool.cache zpool`.
+
+The complete ZFS structure now exists and is mounted at `/mnt` ready for any `pacstrap`, [debootstrap](https://wiki.debian.org/Debootstrap), `dnf --installroot` or other bootstrapping action.
+
+## Adding another boot environment-independent dataset
+
+Assume that in addition to your `/home` data which lives on `zpool/data/home` you want another dataset that is exempt from Arch Linux snapshots.
+
+Consider an example `/opt/git` directory where a bunch of Git repos are checked out on which you work. You don't want them to be snapshotted - and rolled back - when something goes sideways: they are decoupled from everything else that goes on on your machine so you can easily and safely have a static `/opt/git` directory available in all boot environments.
+
+Move your current `/opt/git` data out of the way for a moment:
+```
+mv '/opt/git'{,'.bak'}
+```
+Create datasets
+```
+zfs create -o canmount=off zpool/data/opt
+zfs create zpool/data/opt/git
+```
+Remember that the `zpool/data` dataset already exists and that it has both `mountpoint=/` and `canmount=off` set. It is not and cannot be mounted itself, it instead conveniently anchors datasets at `/`. Since the `canmount` dataset property cannot be inherited and defaults to `canmount=on` we have to manually specify `-o canmount=off`. Our new `zpool/data/opt` should not automatically mount into `/opt`.
+
+We then create the child dataset `zpool/data/opt/git`, it defaults to `canmount=on` thus immediately shows up at `/opt/git`.
+
+Move data back into place and clean up temp directory
+```
+rsync -av --remove-source-files '/opt/git'{'.bak',}'/'
+find '/opt/git.bak' -type d -empty -delete
+```
+
+An example `zpool/data` dataset may now look like so:
+```
+# zfs list -r -oname,mountpoint,canmount,mounted zpool/data
+NAME                MOUNTPOINT       CANMOUNT  MOUNTED
+zpool/data          /                off       no
+zpool/data/home     /home            on        yes
+zpool/data/opt      /opt             off       no
+zpool/data/opt/git  /opt/git         on        yes
+```
+
+## Nested environment-independent datasets
+
+### Caution
+
+If you want a dedicated dataset for a directory that lives deeper in your file system tree than just `/opt/git`, for example like `/var/lib/docker` make sure to not recursively create this structure in a single `zfs create` command.
+
+In [Adding another boot environment-independent dataset](#adding-another-boot-environment-independent-dataset) above you can safely do:
+```
+zfs create -o canmount=off zpool/data/opt
+```
+Here `zpool/data` already exists, you're only creating one child dataset `opt` and you're setting `-o canmount=off` so that it never mounts into your `/opt` directory.
+
+Now consider the same setup for `/var/lib/docker`. If you follow the exact same approach:
+```
+zfs create -o canmount=off zpool/data/var/lib
+```
+Docker will correctly report:
+```
+cannot create 'zpool/data/var/lib': parent does not exist
+```
+You might want to just create the parent then with `-p` argument:
+```
+zfs create -p -o canmount=off zpool/data/var/lib
+           ~~
+```
+Note, however, that `-o canmount=off` only applies to `lib` dataset and that `zpool/data/var` has just been auto-mounted into `/var`:
+```
+# zfs list -r -oname,mountpoint,canmount,mounted zpool/data
+NAME                MOUNTPOINT  CANMOUNT  MOUNTED
+zpool/data          /           off       no
+zpool/data/home     /home       on        yes
+zpool/data/opt      /opt        off       no
+zpool/data/opt/git  /opt/git    on        yes
+zpool/data/var      /var        on        yes  <---
+zpool/data/var/lib  /var/lib    off       no
+```
+
+### Advice
+
+Instead create nested parents in multiple steps where you set each one to `-o canmount=off`:
+```
+zfs create -o canmount=off zpool/data/var
+zfs create -o canmount=off zpool/data/var/lib
+```
+Lastly create the dataset you want mounted:
+```
+zfs create zpool/data/var/lib/docker
+```
+
+## Mounting zpool for maintenance
+
+In case you want to mount your zpool on an external operating system such as an Arch Linux live CD ISO image do it like so:
+
+```
+zpool import zpool -d /dev/disk/by-partuuid -R /mnt -f -N
+zfs load-key -L prompt zpool
+zfs mount zpool/root/archlinux
+zfs mount -a
+
+# UEFI system ...
+mount /dev/sda1 /mnt/efi
+
+# ... or legacy BIOS system
+mount /dev/sda1 /mnt/boot/syslinux
+
+arch-chroot /mnt /bin/bash
+```
+
+When done exit `chroot` and cleanly remove your work:
+
+```
+# UEFI system ...
+umount /mnt/efi
+
+# ... or legacy BIOS system
+umount /mnt/boot/syslinux
+
+zfs umount -a
+zpool export zpool
+```
+
+Explanation:
+
+- We always want to mount pools `by-partuuid` for consistency so we specifically only look for pools at `/dev/disk/by-partuuid`.
+- We mount our zpool with `-R /mnt` (aka `-o cachefile=none -o altroot=/mnt`). The pool is never cached, i.e. it's considered temporary. All pool and dataset mount paths have `/mnt` prepended. From `man zpoolprops`:
+    > This can be used when examining an unknown pool where the mount points cannot be trusted, or in an alternate boot environment, where the typical paths are not valid. `altroot` is not a persistent property. It is valid only while the system is up.
+- With `-f` and `-N` we force-mount our pool (`-f`) even if it previously wasn't cleanly exported; and we do not auto-mount any of its datasets (`-N`), not even the ones that have `canmount=on` set.
+
+    ```
+    # zfs list -oname,mountpoint,canmount,mounted
+    NAME                  MOUNTPOINT  CANMOUNT  MOUNTED
+    zpool                 none        off       no
+    zpool/data            /mnt        off       no
+    zpool/data/home       /mnt/home   on        no <-- Not immediately mounted
+    zpool/root            none        off       no
+    zpool/root/archlinux  /mnt        noauto    no <-- Not immediately mounted
+    ```
+- We load the decryption key by temporarily overriding the `keylocation` property to `-L prompt`. The default value is `file:///etc/zfs/zpool.key` which in all likelihood doesn't exist in this environment.
+- We mount our desired boot environment with `zfs mount zpool/root/archlinux`
+
+    ```
+    # zfs list -oname,mountpoint,canmount,mounted
+    NAME                  MOUNTPOINT  CANMOUNT  MOUNTED
+    zpool                 none        off       no
+    zpool/data            /mnt        off       no
+    zpool/data/home       /mnt/home   on        no
+    zpool/root            none        off       no
+    zpool/root/archlinux  /mnt        noauto    yes <-- Only boot env now mounted
+    ```
+- We mount all child datasets with `zfs mount -a` making `/mnt/home` available as well as any others you may have created yourself.
+
+    ```
+    # zfs list -oname,mountpoint,canmount,mounted
+    NAME                  MOUNTPOINT  CANMOUNT  MOUNTED
+    zpool                 none        off       no
+    zpool/data            /mnt        off       no
+    zpool/data/home       /mnt/home   on        yes <-- Now mounted
+    zpool/root            none        off       no
+    zpool/root/archlinux  /mnt        noauto    yes <-- Now mounted
+    ```
+- We lastly mount our EFI System Partition (ESP), in this example it's living at `/dev/sda1` so adjust this path accordingly.
+
+    ```
+    # df -hTP
+    Filesystem           Type      Size  Used Avail Use% Mounted on
+    ...                  ...       ...    ...   ...  ... ...
+    zpool/root/archlinux zfs       8.6G  2.5G  6.2G  29% /mnt
+    zpool/data/home      zfs       6.3G  161M  6.2G   3% /mnt/home
+    /dev/sda1            vfat      511M   31M  481M   6% /mnt/efi
+    ```
+- We're ready to `arch-chroot` into our boot environment.

 # Development

@@ -80,10 +760,10 @@ Commit _types_ besides `fix` and `feat` are:

 The following _scopes_ are known for this project. A Conventional Commits commit message may optionally use one of the following scopes or none:

- `iso`: Changing Arch Linux ISO CD
+- `iso`: Changing Arch Linux live CD ISO image
 - `zbm`: Adjusting ZFSBootMenu's behavior
 - `zfs`: A change to how ZFS interacts with the system, either a pool or a dataset
- `os`: Getting an perating system set up to correctly work in a ZFS boot environment
+- `os`: Getting an operating system set up to correctly work in a ZFS boot environment
 - `meta`: Affects the project's repo layout, readme content, file names etc.

 # Credits
--- a/setup.sh
+++ b/setup.sh