|author||Sean Whitton <firstname.lastname@example.org>||2022-08-02 17:04:23 -0700|
|committer||Sean Whitton <email@example.com>||2022-08-02 17:04:23 -0700|
new blog entry
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+[[!meta title="Setting up a single-board desktop replacement with Consfigurator"]]
+The ThinkPad x220 that I had been using as an ssh terminal at home finally
+developed one too many hardware problems a few weeks ago, and so I ordered a
+Raspberry Pi 4b to replace it. Debian builds [minimal SD
+card](http://raspi.debian.net/) images for these machines already, but I
+wanted to use the usual ext4-on-LVM-on-LUKS setup for GNU/Linux workstations.
+So I used [Consfigurator](tech/code/consfigurator) to build a custom image.
+There are two key advantages to using Consfigurator to do something like this:
+1. As shown below, it doesn't take a lot of code to define the host, it's
+ easily customisable without writing shell scripts, and it's all
+ declarative. (It's quite a bit less code than [Debian's image-building
+ scripts](https://salsa.debian.org/raspi-team/image-specs), though I haven't
+ carefully compared, and they are doing some additional setup beyond what's
+ shown below.)
+2. You can do nested block devices, as required for ext4-on-LVM-on-LUKS,
+ without writing an intensely complex shell script to expand the root
+ filesystem to fill the whole SD card on first boot. This is because
+ Consfigurator can just as easily partition and install an actual SD card as
+ it can write out a disk image, using the same host definition.
+Consfigurator already had all the capabilities to do this, but as part of this
+project I did have to come up with the high-level wrapping API, which didn't
+exist yet. My first SD card write wouldn't boot because I had to learn more
+about kernel command lines; the second wouldn't boot because of a [minor bug
+in Consfigurator regarding
+and the third build is the one I'm using, except that the first boot runs into
+a bug in [cryptsetup-initramfs](https://bugs.debian.org/1016455). So as far
+as Consfigurator is concerned I would like to claim that it worked on my
+second attempt, and had I not been using LUKS it would have worked on the
+## The code
+(defhost erebus.silentflame.com ()
+ "Low powered home workstation in Tucson."
+ (os:debian-stable "bullseye" :arm64)
+ (timezone:configured "America/Phoenix")
+ (user:has-account "spwhitton")
+ (user:has-enabled-password "spwhitton")
+ :partition-typecode #x0700 :partition-bootable t :volume-size 512
+ (fat32-filesystem :mount-point #P"/boot/firmware/"))
+ :volume-size :remaining
+ :volume-label "erebus_crypt"
+ :cryptsetup-options '("--cipher" "xchacha20,aes-adiantum-plain64")
+ (lvm-physical-volume :volume-group "vg_erebus"))))))
+ :volume-group "vg_erebus"
+ :volume-label "lv_erebus_root" :volume-size :remaining
+ (ext4-filesystem :volume-label "erebus_root" :mount-point #P"/"
+ :mount-options '("noatime" "commit=120"))))
+ (apt:installed "linux-image-arm64" "initramfs-tools"
+ "raspi-firmware" "firmware-brcm80211"
+ "cryptsetup" "cryptsetup-initramfs" "lvm2")
+ (etc-default:contains "raspi-firmware"
+ "ROOTPART" "/dev/mapper/vg_erebus-lv_erebus_root"
+ "CONSOLES" "ttyS1,115200 tty0"))
+and then you just insert the SD card and, at the REPL on your laptop,
+CONSFIG> (hostdeploy-these laptop.example.com
+ (disk:first-disk-installed-for nil erebus.silentflame.com #P"/dev/mmcblk0"))
+There is more general information in the [OS installation
+in the Consfigurator user's manual.
+## Other niceties
+- Configuration management that's just as easily applicable to OS installation
+ as it is to the more usual configuration of hosts over SSH drastically
+ improves the ratio of cost-to-benefit for including small customisations one
+ is used to.
+ For example, my standard Debian system configuration properties (omitted
+ from the code above) meant that when I was dropped into an initramfs shell
+ during my attempts to make an image that could boot itself, I found myself
+ availed of my custom [Space Cadet-inspired keyboard
+ layout](blog/entry/spacecadetrebindings), without really having thought at
+ any point "let's do something to ensure I can have my usual layout while I'm
+ figuring this out." It was just included along with everything else.
+- As compared with the ThinkPad x220, it's nice how the Raspberry Pi 4b is
+ silent and doesn't have any LEDs lit by default once it's booted. A quirk
+ of my room is that one plug socket is controlled by a switch right next to
+ the switch for the ceiling light, so I've plugged my monitor into that
+ outlet. Then when I've finished using the new machine I can flick that
+ switch and the desk becomes completely silent and dark, without actually
+ having to suspend the machine to RAM, thereby stopping cron jobs, preventing
+ remote access from the office to fetch uncommitted files, etc..