Distrobuilder configuration for a "diskless mode" Alpine Linux UEFI VM image?

I want to build a custom VM image that boots an Alpine Linux VM in diskless mode. This basically means I need to create a rootfs.img that just contains an EFI partition with the required files (kernel, initramfs - possibly combined into a UKI image - and a directory with .apk packages).

Can I use distrobuilder for that kind of Alpine Linux setup? And are there any existing configurations to use as the starting point?

This is an interesting question. You are looking into PXE / iPXE booting, and by default the VMs will try to perform network booting if you do not provide them with a boot device. Then, you need to setup a PXE server to server the boot image. I do not know the specifics. See this relevant post, Trying to PXE Boot Netboot.xyz from an Incus VM

No, not really. Just standard UEFI boot from an EFI partition (with the UKI image as the EFI executable). But with Alpine “diskless mode”, that image then runs entirely in RAM (from the initramfs that is part of the UKI).

And what I’m looking for is not the boot setup, but rather if I can use distrobuilder to produce a VM rootfs image that either only has an EFI partition, or at least contains an EFI partition with a UKI image (that image is generated automatically by Alpine when you configure Alpine for direct UEFI boot and install the kernel package). I can live with an additional root partition in the image (which just won’t get used in that setup).

To finally answer my own question: Yes, it is possible, even if it is a bit hacky. Here is a proof of concept distrobuilder config that generates a diskless UKI-only version of https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml:

image:
  distribution: "alpinelinux"
  release: 3.22
  variant: uki-diskless

targets:
  incus:
    vm:

packages:
  manager: apk
  update: true
  cleanup: true
  sets:
  - packages:
    - acpi
    - linux-virt
    - zstd
    action: install
    types:
    - vm

  # same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
  - packages:
    - alpine-base
    - logrotate
    - doas
    action: install

actions:
- trigger: post-files
  types: 
  # - vm
  variants:
  # - uki-diskless
  action: |-
    #!/bin/sh
    set -eux
    
    # generate runlevel symlinks - for some reason, those are missing
    for SVC in devfs dmesg hwdrivers mdev udev udev-settle udev-trigger ; do
      ln -s /etc/init.d/$SVC /etc/runlevels/sysinit/
    done
    for SVC in acpid bootmisc hostname hwclock loadkmap modules networking swap sysctl syslog urandom ; do
      ln -s /etc/init.d/$SVC /etc/runlevels/boot/
    done
    
    # pack up the whole root filesystem as an initrd, with the exception of
    # - /boot/**
    #   --> not needed for UEFI boot directly from an UKI image
    # - /sbin/apk
    # - /etc/apk/**
    #   --> not needed because upgrades are done by installing a new UKI and rebooting
    find / -xdev -path /boot -prune -o -path /sbin/apk -prune -o -path /etc/apk -prune -o -print \
      | cpio --verbose --create --format=newc \
      | zstd > /boot/root.initramfs
    
    # install ukify and and EFI stub and build an UKI image.
    # Explicit install is done here to avoid getting ukify and its unique dependencies
    # into /boot/root.initramfs
    # The UKI image is installed to /boot/efi/EFI/BOOT/BOOTX64.EFI which causes it to end
    # up as the standard UEFI bootloader in the generated incus image
    apk add ukify systemd-efistub
    mkdir -p /boot/efi/EFI/BOOT
    FLAVOR=virt
    VERSION=$(cd /lib/modules && ls -d *-$FLAVOR)
    ukify build \
      --linux=/boot/vmlinuz-virt \
      --uname=$VERSION \
      --initrd=/boot/root.initramfs \
      --cmdline='rdinit=/sbin/init console=tty1 console=ttyS0' \
      --output=/boot/efi/EFI/BOOT/BOOTX64.EFI
files:
# same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
- path: /etc/hostname
  generator: hostname

# same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
- path: /etc/hosts
  generator: hosts

# same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
- generator: incus-agent
  types:
  - vm

# same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
- path: /etc/network/interfaces
  generator: dump
  content: |-
    auto eth0
    iface eth0 inet dhcp
    hostname $(hostname)

- path: /etc/inittab
  generator: dump
  name: inittab
  content: |-
    # /etc/inittab
    ::sysinit:/sbin/openrc sysinit
    ::sysinit:/sbin/openrc boot
    ::wait:/sbin/openrc default

    # Set up a couple of getty's
    ::respawn:/sbin/getty 38400 console

    # Stuff to do for the 3-finger salute
    ::ctrlaltdel:/sbin/reboot

    # Stuff to do before rebooting
    ::shutdown:/sbin/openrc shutdown


# same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
source:
  downloader: alpinelinux-http
  same_as: 3.12
  url: https://mirror.csclub.uwaterloo.ca/alpine/
  keys:
  # 0482D84022F52DF1C4E7CD43293ACD0907D9495A
  - |-
    -----BEGIN PGP PUBLIC KEY BLOCK-----

    mQINBFSIEDwBEADbib88gv1dBgeEez1TIh6A5lAzRl02JrdtYkDoPr5lQGYv0qKP
    lWpd3jgGe8n90krGmT9W2nooRdyZjZ6UPbhYSJ+tub6VuKcrtwROXP2gNNqJA5j3
    vkXQ40725CVig7I3YCpzjsKRStwegZAelB8ZyC4zb15J7YvTVkd6qa/uuh8H21X2
    h/7IZJz50CMxyz8vkdyP2niIGZ4fPi0cVtsg8l4phbNJ5PwFOLMYl0b5geKMviyR
    MxxQ33iNa9X+RcWeR751IQfax6xNcbOrxNRzfzm77fY4KzBezcnqJFnrl/p8qgBq
    GHKmrrcjv2MF7dCWHGAPm1/vdPPjUpOcEOH4uGvX7P4w2qQ0WLBTDDO47/BiuY9A
    DIwEF1afNXiJke4fmjDYMKA+HrnhocvI48VIX5C5+C5aJOKwN2EOpdXSvmsysTSt
    gIc4ffcaYugfAIEn7ZdgcYmTlbIphHmOmOgt89J+6Kf9X6mVRmumI3cZWetf2FEV
    fS9v24C2c8NRw3LESoDT0iiWsCHcsixCYqqvjzJBJ0TSEIVCZepOOBp8lfMl4YEZ
    BVMzOx558LzbF2eR/XEsr3AX7Ga1jDu2N5WzIOa0YvJl1xcQxc0RZumaMlZ81dV/
    uu8G2+HTrJMZK933ov3pbxaZ38/CbCA90SBk5xqVqtTNAHpIkdGj90v2lwARAQAB
    iH8EEhYKACcWIQRQQFYXHWwYKA6Ezfe2Zm2RwjfyiQUCWsf0cgWDAeEzgAMFATwA
    CgkQtmZtkcI38okvzwD+PFAaXtH+KkuIzYJPH1rlaswCx2ALFYUMR7ptsWNbQQwA
    /iaqtZns6UngP85uNyKNLjoxIWK3+WRQ8Cj3+pFBU58EtCVOYXRhbmFlbCBDb3Bh
    IDxuY29wYUBhbHBpbmVsaW51eC5vcmc+iH8EEhYKACcWIQRQQFYXHWwYKA6Ezfe2
    Zm2RwjfyiQUCWsf0cgWDAeEzgAMFATwACgkQtmZtkcI38okvzwD+PFAaXtH+KkuI
    zYJPH1rlaswCx2ALFYUMR7ptsWNbQQwA/iaqtZns6UngP85uNyKNLjoxIWK3+WRQ
    8Cj3+pFBU58EiMMEExMKACcWIQT64Bydmt13ap3e1NXkkuZkZCRt2AUCWsf4aAWD
    A8JnAAMFAXgACgkQ5JLmZGQkbdiYCwIJAURrcI3SntkkiwrvI8UjTiJ9+ZXRi7HF
    nAQCIXVBH5/p6KSXsEVKo2cr3uiJsXEWPQ1f4A4lmKre2e59kX+ABb2nAgkBLxsq
    gYTq0sj/SOO4+2rbDE0VzLhIEmiz63igk8CCkrQovKkwJ+cWz14pzGiojvbk85Mr
    xOlKlC3ThGE7xJVrgaqJARwEEAECAAYFAln4Pp4ACgkQOktclQn9UtFQ5Qf7BSqj
    vNhSbz88SGqL+ICOhJAEyMR8TKVqrm7MKEF4e/5GJ3f55mQxoFGQqHuPy3oxx5Gt
    MA5419HgSbUWE7AWoc+B6DoxoFguQv/yKvZnrZh0EiTRFQpTSZkcQUtepppKhAhN
    j6iuLMwOTeVnrNsmskrda72P7z/TM6z/DY3DHv5yWgRcQCBIKp8ZmC1oP2aFm0Y0
    uF7tAUbPcAtDk/93LgmJDB4x72+ac/rvFtUFLoUBIThm0CdLTfeKl7VRqSYS7GKE
    6Ih9wjXnP0Hn1do1K+MYvU8rjW6VhOmujX6K3nq8w6jv9EQ2bru0M7c0ev94ydjq
    hY7Wla+3nJS1mAW5/okBHAQQAQgABgUCVIlXRgAKCRBGcA6MYo+hzrNmCACOMe11
    SLVty3ptKA7qwkFzA1oXZJnBlDlO8H07cLIReFqxwkaa6tUC7C037B5Y9lEZ6jn0
    um9ohZETJrRZOwMGiuqThNgdwLlfOkcziRq5LFy4xexDEYhT4iydaH8E3rs7eQrU
    iEx/4gwgPkZ24nO+GMnLZzhdZ/OLQdZt4r0vRQWdtYvKhJYxB+CHsSs8nexJ5TAq
    RW4eYJEWMnGCPJpZ3lHcNQy1PacH8wWX4v24Q6CP4ZyY4+PTv/QHXJpYWMFikEVZ
    gbQCOL7rh5DiQHUOpFBtDvZ7EtAUWVY1QR3W8gQqOL9g8Y8e1OLzq3v1Jrtj+zC+
    XpZJWIRnHNIcelaTiQGcBBABCAAGBQJWOND9AAoJECWNqqKUWUkm25cL/3Rv652V
    ZpAvj+TwaY+Wv5Wj5pkY/cstM8212wgVdwLHb+bVVomVXY9Z55biFEFwLPnfG+U+
    OYnaDt4Wzd/s7Fl7/VXeg8TftwynH4PyDJ5cnrullJlVXUvD5bfzLlJ+kdFrC1UE
    DquuTVPW/UPbM4r5730VEBtYxtwUaZ69LSrOX0z9RemjWvylY47dVMNtJEWQkwzg
    6zCV8a6as4itN5xANMZyD4INZE41dWaCPTIAn6nADHHi5fL3IzA4Qt5aRnyXeQk0
    GI1WvN48gR6KdtEKyar5f04CpUlfmRIBoYBWBsruIlgsYe9WUpmrVm1YyKgD1iuO
    UTscLgrZ3owx6xCN1p1MyfU79iH5nGz/SuBeNsm7G2F/+eHidOqYh+Kh3+nWfZCH
    MSsk/4LUvHjMWbeZ07ih2UOcZ6lHIgX4Z+toSDh1HQkBkI8VhDssEFVhjgODsBwK
    ezZZA/h9kNKFA9b9KBeYCioR0pMSd2YYvQVUhRU7hh8Aoo6VyA1S8u0TyYkCHAQQ
    AQgABgUCVPTSVAAKCRB/lslknLy/URsqD/9I1rO3/qE96a2AWX5j817SOn3w6HZy
    9OD312erjBGdAJph6ZRc9GvMmPbMt4s6wh3cIodagqJ+LadocvQTzsWMMANIXTZW
    N0I5bjaRuQpZYYBpV6sQhPwdvj6E2RZ4eKeIFOsFc2VtqK2B+lMy4TGpmGCyZ68+
    maVO4VYpC7+j0S7G+8HEEmG0RX1erVrSoIyD8h8K49jdlGV6eS/rar/UBpKr6cSG
    5ghV9S+XrkleZeJLzzGD8Ff5lq/CmANmhGzAthXwgyweC1ozivg5Co1u8B5Esyi7
    /ImZCRlhVBrSK4YFdQ9+lKKsiV1MR+jaW2+KUxEYxmnOc9qfQZ5A9CyPd/YgsQip
    poexbMMOMgj8Wnyf+MuK/vYJp8b69R8GT+28iRiRwvzFw5X4XiEl8rqdjqlKLQpk
    yKLvff4pw9Oxjm6FfLMnAspsRQ+UEodyqQFklT0vnEqh8Ii9KXRaQ4cInSqsstcV
    Cbm/NG++ChpJSnP/CuRfnyzLqZm+1AbM+dZyyoAxd9k1HdAO0jiMx9AXlXHNwEfE
    aZ02YFQ5imIWpqZXBBImXjhGLu4/086E/AVFIFnJbj6iaxS1Qc4YE2H9ceo003sf
    tRdHuuAFUTRyQQMku6DAOcKUD4eQy5AlVKRjAzxiI80QihqjGuWRabHlAkc0Bhz3
    Svo0SLD95s09LYkCHAQQAQoABgUCVL403wAKCRAYhY1yfFeuYZV4D/93MISeIAIp
    Y/s1B2pHpxJxfYqR5HiMPq3hGjsUjIKmSXmaAkcnUqpFlrRDmU6Xerjsx16nIEsx
    u5JiyLeBfFO/UF92FcEPhbIzFFiBxxinB5nB2KYNl4SPHn2mXFgtrUDh0qHQyl5P
    LPYpiGq7WYOIIB6g+abJXTJH4Fsiv9UoVWpvPB+NW5eQXBpSS/a2SjwpfR5f172y
    4axPQd66ntDJXliN1R9upRLIlvB/KcbkLHVUvRemvph/30dix51z9hUz1TxDFHBV
    OdGODMljjDnSpS/ern1hO9tkelR5Ak/++p4oKwiEJD9PfZTpVruDWykJEZknED+I
    vfVd/5zFkBFd6RuJw+qQHsL/bSxFy80K81L9nKxE1ZLoEEEfGonYmQOGtCVpWRng
    Z6GyJbD19q9ZBVQOSemp4/6Vh5A3CwldXK0Hq8Mw159hkd5nsGVYmOOiFdnSwVVO
    SZaanh7iSHExxZjbhIQIbGblGPuPmFohTV2Sp67BPS+fUxFVG0j24d6CO2+qs5Q0
    gT6Uo8GkVD1gcemFe9IzJvCrA2ICPWyi3fmIRI0uucRATqTxlYNslaRqVffxSyDM
    tZLWXPIePPevwDQsouuwND4aytTaMRiFqqGiULn8dkOGDmAbSVPNHylewibrKdHC
    H91EVhOT3XY2Z2xPkW724RFgaG9ohLoHQYkCIgQSAQoADAUCWJ9UPgWDB4YfgAAK
    CRC5rer6U9uYHh5aEACcmUkR25IKDILZZWZ3Y+48wcAPbsQUQZE/+TnCo3D+F+be
    S0URApZROQri3QZ+9H3hPHxziv1l0sU/0IOGhFC6I7kSao4nNfOUe3OPZ3wm5o8l
    cULZNl2ChCMpbxn5GeQ5+LbyNpZpSjhZf2Xj3FqzacpLTVCg0UOpK+bF2CxRw8z1
    7eUL2sLldSsaRFWwDVAFIROS04yvfpGbAch9pKWAtJ2/VsrkTh+1/rl+EyGVynks
    TSkkx+pMsS/7HLCtxBiFKOy40FiL5QBOBkk/1g6sp2dvWCYzG7oGJeHr+TaDle0I
    +ynSulIDNZb1gsNpZk2wHZ6F7XcdIn9rD/LlHSlHeTnDaFudDw3wEuSRLpf/lQUF
    exXYZfOsazpORuz+fdDlpPMjL8XVocUW24XM3AGHdOlXpSdnGpWiaBYDEO7NmboH
    yn4hhBHs8ibTuxBBtzG7rq7f7n9EuEr7m7CfukGIZnT6aN6wVqFNa6nWsXOgzOCc
    +BPStTnUsBAliT22c5mzkPbrLZA5I3ydB/NrT0G0cWzYo1qESXJY2leVQkqzFIff
    CRC+7kKIJp00Uj5fjxhbrTZhJQGOHhlgkpfQL7mAC5rDNqn31yxve7+mgU6BbH7V
    nZmt8nqmCV9e7s2cbfbb5A5HWZ4TcHJ2KFKLKlSjyOsuQBFqQHVfDXYBmhFsbYkC
    MwQQAQgAHRYhBO22T6L3kGd6kKX9jjbDVqWm6mZ2BQJahiGaAAoJEDbDVqWm6mZ2
    pfkP/RFMkUCp4Gtv0g7RvhDkbybb6b2GiAS1bvmfSHYfZ8V4ZuQHYV6BM8g7SItq
    FOpsNADnb1LqTOKJFok1YCwjeN/YMNFExOqt/bE8w87rvj0UlxcRdbSM6cB4JxFo
    RAFjE23vJ0OZ/NujPLBnsVCD7Gk7wOTswR5nkhZ9usonpU1aaQUjEfmIiH2m0J+G
    84GXDqHofE13VeDApqPy3S/E2BxK8Td232bOYiU7s3mQuy1copaCDchXbWO5FaP5
    P+bhaUh4AS6a96v6FfYaZqj/0aUWOgwH5deFaU7Fch0C4xFejhvcq0r4YFmmY1T+
    R6aZu4VB69iNXeh9mcL9qnci0MxLa2I/VZn0oZ1nVoovaRYXRkMNx+VnEg57JVP3
    ap4MEwUZzhooN1RSNdsMnPK0nB2zYodbSvUe6ie5XstGtCRgLlFGzxoXwk9ZMO59
    ycVHnzgFA3AHKvKFuIP0YELRBOjvNoy9HLTYB9FY/xPCCf5+T5lzIwqv4qlDZfV/
    1rJJKPg5tijd5dXTlaoXtjGAixUYB8oFHJ/bl0fEMxUP1S1pE1t4DvIMNVUChUi0
    yL/OOX9RhDkzsVSGyvM53zAk9glvFAtg0pGbNXwu40lCZqvWGGmXLFi8P65KDnKC
    XpnUd45sNfwfMH6rGyhSLRqYZLETVsquMyGgsJZUW7KPva5ziQIzBBABCgAdFiEE
    UCa0fcAp7B2D76H27PE5p3fKNFQFAl0CRn0ACgkQ7PE5p3fKNFSDyBAAkhvoiSIf
    UhbsX82Hj/ESTOdEPPbC0bkzMdzhdYXdO/SteAfd09dpjtNuHkGsXXOGfw3iq7TG
    PwdfHgqtZDvu0ckQWqb2YC6CwhzFgl1ytrAKFfvwCmS3ftawSZA7bbE2q8q8+HLf
    KSeGFsRIOu2V0FG18WFatwyabxtP2y0lHMHoZDb7LOVBJ7NwQOwZsRKF7aQ7zQrT
    p15gFLx3BsD9uzsJN1SgrMRGiPBA3xeuQ4YHVaBlo3IQawR+vfaX6RIIECR6aGO0
    o6B539cyFBtp0D0lGbLaZ35xghXB1obpluR75R+AMl+dfWyAxRFK69R1ETtk0BZr
    2WQV2mn+/RINToQteeraRSMzkBGQ5r3n5O7QJcucn/EaeLmYDdh+pFAqRKtQQE+l
    q2xsH6XJdzmVLBrM7xB6zZNw9d1NORd6np4iTtuVOz0vyn6My0bfoXQf63x9cF5V
    HPHXhgvDkcSAPntGt79zunh5StRuX0RBejszYNyt7paFHgqh+pXbPi7dk1OdnEYz
    liMOibcqgvyL2gYyOQkYUpMCA1dz98w5uYGlkFrLsVKE6ySed8sRL+nTR3Y5zP0M
    Z6DVFLl5WF1fhFA2loxVFB4d0J8M/CX40OYjUceTHIiE3DjBsnSrvrURlf1YvtDf
    XX7g/Wdz9CrrC4WO4qn73blHiKtRgo5zewqJAjMEEAEKAB0WIQTU/3wdYJFfOEC/
    1Ysr6KOtDiGtnQUCW2QXrwAKCRAr6KOtDiGtna4xD/91HGyZhvQDY7gVYHejcE5w
    0gtSwGz/1PTIvFcJgAsBp6iFSWmqgqaz7KDoKC1bR/vR7Wp2apW3CSIqjBhb156H
    hX0fps9z6c80FvfcnJorYBpoSOJ0nDwgaQpbBxzCe9ddPgCduGPQUb89WasfyoG5
    /f/0SRPxr9jJr/qBEs0U6/bDhGOR+JOj9t/1bap2GbaTxBN5I6UxaE9ICu43C+/w
    DUap5co7071b58weVLSLhKEv/L0Tr1otx369MBiTiJJEESsIc3gsUpSIB9H9QFET
    Pqx+thxBGvo49GJxGbjIS5CC7jd4QUbTek0lks6o4UXv6Wg/LVQyZDXrSo0phTZY
    /j8cnjr8oZC/PO08GdaUUhXgNqp/gMm15bNNANfuNaUSeamIZsI9SVIQOPKGtznk
    M61jqu2ZRKFHiMFRSgzbRoqyL8rBLfmGkM83AcC+v6pPOf4s0ph5RZrC0VdeeAxF
    wCbfh8kYNTAeqaCOGw4JYfXfyqmDwBizrqYMGDDdxcFUIZ9sd5joZ4zezVdcfL1M
    amJiR4+0Debnxc+FGJPoGK/4pF5/BYmGvT/pYTFBmMgRno8fWNJQIPG7F9kTsE1t
    r1IxZttFycMlY/w+5eo9CoOUIPJunI5vtM/KP7xLaNz/6ec4lne2QASbS+FvjiCP
    SuMC8fi5PcH/ucxaU+Rpb4kCNgQTAQgAIAUCVIgQPAIbAwULCQgHAgYVCAkKCwID
    FgIBAh4BAheAAAoJECk6zQkH2Ula3DcQAJhM1/T0GnM85TwJQ3t5tQDdJT+hP9aW
    FiwRrOqhodfHFsXY8jlrDuO5wNT/nExkkgGHuJCDiMfZKdksTm3SnmU7mQgXVn0L
    v3LkRNdroEEBREZacFUTXejWLk91sme7/GV0cOH99xSLeAkq1tfwMjP76wPrVjaO
    228K/whWiHC/JCDT3HHRTqVodeHqzjXfzxG94DvNclyAOnNVZeJnHtiUtIXehBaI
    cUucjECTESEv2YPLn098hyVyGkpxvikT+1li0dGWi62gspGIvxFvZpkOPS8UKryj
    oI6UVvWjYAwPmqypdbpo6ZZABSNRmdP6gLICpuGoHbyxmYgmag13EVjaJRuT3jlF
    KYptX+faRp7qWd0W8+ARfOFPtbi/sndDkeWPfAMVhcqtHais/8xWMEJDFZ5fcltK
    ZCZj+6+jyo9G4VpLEF/kY2D6LI98MT2e4kijF+8WWqqJ/wh6R/f15vAmmxnAyE60
    uofofMdBRU/zFfyyoHN6vBOJpV3pXsNUbcSuIc1xaVypdFnEIOeH49VqsuOxZZAK
    xudHYtLrQgRpZlWUAPJ6hOaGJBS6aYhV89Ulwl6I33/12XTRdlnYFfGgyjmEytVg
    z1Ei5qmPqHzpEC+PWKmfTORUfITAG7y+nuAm8VVwpFiekPS4O/QM0t6bzlwifwlA
    0LOwd9L9NugWuQINBFSIEDwBEADB7jwL/wdCj/UhANT7F+ft+5OOpUz+5b+1RXe1
    Wg9awFDP2cg9n1oKyaa3AjxKXTH7rM3zh4xlUO9PFUPr5Q97xaDmRPioHip8wxvR
    c2F1z5sZFsxBKiNevGpnhfy0ITddlRdZquS27pIgCsdsrW9SPKJ7wrzSQ7x9Q/9w
    cUo+04VfWz/2xbn3DhxQTBcLcgZlGkeVsfegavuwxG068YbIaEIFKiCxLnVMoWWt
    Of066VLwuH/KnNHXmqiRTtcw+oLmcUVmXUliXXBc02ncoN+j+HshTMWtRbewZQyn
    SiwBZQhoEdI3zpykZnUShkTRUy0OvGgZXTeMMQbjMHtLZkcPc2MFsA+NwKvRNumL
    bsVUdcG981JovuO0B+ADQMzIqIphPTI+UqmK4M0CdCBsCIwbfhzcx72F/pMjLlRS
    uNZNlaOqFDlR7kDLt1IC70jzLMsOvXfiMCv667EMLrra7yfEHHWt63mtR71gVXGP
    7sqEbDrAku4rUujCuiikymlvIrJJhG9v4UNWQdUGlptrEPF3Jm90GYLcgX2Srgve
    U/5gFz09LhE+m06T+Q3RIt8BbPqsP3PRWUjQ2eIXzbktuHdrt0YfC1rf1PN4ngLr
    TZ7Tixob7mZtYy2Ldir81xPHC7d1e+f2RTvsRFe6y7jraxylpc4CUM7A6dYDOE8/
    VC3mOwARAQABiH8EEhYKACcWIQRQQFYXHWwYKA6Ezfe2Zm2RwjfyiQUCWsf0cgWD
    AeEzgAMFATwACgkQtmZtkcI38okvzwD+PFAaXtH+KkuIzYJPH1rlaswCx2ALFYUM
    R7ptsWNbQQwA/iaqtZns6UngP85uNyKNLjoxIWK3+WRQ8Cj3+pFBU58EiQIfBBgB
    CAAJBQJUiBA8AhsMAAoJECk6zQkH2UlayIAQAK4QnaNyLabhClnMcdtqDMA5vtHZ
    l5s6nD5wfMvU3zXKHE6CFz+Ox9flxHp2XU2GSTq3as6yumNT6ZcEL+oahU6MqYG0
    E3pJ62fEgg8hCnFOIndq+90x084DUoguEABNteIuZCnejzEJ+12FY7Mb4p92WpUt
    seJvFBWpdgvZ46PB6qE7AzkkctJs6KgKl5ngHt1/aWJnvwlMAOkfIRxIF+41IZvw
    K1VucGW6AIp8OQZigY1oiME9b8X78IGwtBANTtuBuM0KhCdiC5nDN0b1sLRRVmrE
    Kle6pynaQ/BCG6D2vDnJe46A3ObHivAc7CO7VzeGI8NGhwjpWdeX1hz2CoAxUUGk
    RX3zgzzW8UDYs2K7t6WxFgyyFKELScipfqNvvJuGlgmDcydVpBEI3vUWgaRzQ3Mn
    p+cgu97QhCbL02bjCOF6nOMYC7fMKK3ihOexkXYNnzvHzuNF90fyeWDOkqhu8trs
    I1QhxQXjtjZJK/Jzp6PkW59m9N3PTGqTE+JZfIyXbOMcIYaSI8zy1ndmXF/2Rqpr
    Jyj4q6HvadVT6JTe9joa/ZUvjl37zj1djfgK+awjm5oZ2G1xoFP6soZNapEbvsNm
    wWTjkCHWgn4eQB2592RhhkLJIFmQxT+MWdw1lxUljD7rxI25lJ9sa4faGLI7Dhsv
    bcgRRcklNr8mTzJH
    =ckew
    -----END PGP PUBLIC KEY BLOCK-----

# same as in  https://github.com/lxc/lxc-ci/blob/main/images/alpine.yaml
mappings:
  architecture_map: alpinelinux

Running sudo distrobuilder build-incus --vm alpine-uki.yaml --type=unified on that config will generate a working incus image that boots from UKI and runs entirely in RAM.

Note that the VM image generated by distrobuilder still contains a partition with a traditional root file system, even if it is not used (or needed) by the VM. To get a real minimal image, delete partition two from the generated rootfs.img and only keep partition 1 (the EFI partitition).