Readme: Rewrite instructions for aarch64 regarding older Alpine

Author: jirutka

README.adoc

@@ -8,12 +8,10 @@ ifdef::env-github[]
 image:https://github.com/{gh-name}/workflows/CI/badge.svg["Build Status", link="https://github.com/{gh-name}/actions"]
 endif::env-github[]
 
-This project provides a script for making customized https://alpinelinux.org/[Alpine Linux] disk images for x86_64 and aarch64 virtual machines.
+This project provides a script for making customized https://alpinelinux.org/[Alpine Linux] disk images for x86_64 and aarch64 footnote:[Supported since Alpine Linux v3.19. See <<aarch64-old>>.] virtual machines.
 You can choose between BIOS mode (using https://syslinux.org/[Syslinux], only for x86_64) and UEFI mode (using Linux https://docs.kernel.org/admin-guide/efi-stub.html[EFI stub]).
 It’s quite simple (400 LoC of shell), fast (~32 seconds on GitHub Actions), requires minimum dependencies (QEMU and filesystem tools).
 
-IMPORTANT: aarch64 currently only works with the kernel (linux-virt or linux-lts) from Alpine edge! See <<aarch64-v3.18>> for more information and a workaround.
-
 TIP: Don’t need VM, just wanna chroot into Alpine Linux?
      Try https://github.com/alpinelinux/alpine-chroot-install[alpine-chroot-install]!
      Or do you want to create a custom rootfs?
@@ -51,29 +49,6 @@ Or, if you are on Alpine Linux, you can simply install the https://pkgs.alpineli
 
 == Howtos
 
-[[aarch64-v3.18]]
-=== Create Alpine v3.18 (latest-stable) image for aarch64
-
-The Linux kernel (_linux-virt_, _linux-lts_ or _linux-edge_ package) in Alpine v3.18 and earlier doesn’t have https://cateee.net/lkddb/web-lkddb/EFI_ZBOOT.html[EFI_ZBOOT] enabled, so EFI stub cannot load a compressed vmlinuz.
-We backported it to v3.18, but then we had to revert it due to a problem with Grub (see https://gitlab.alpinelinux.org/alpine/aports/-/issues/15263[alpine/aports#15263]).
-
-If you want to build an image with a stable branch of Alpine Linux, you can, but you must install the kernel from the edge branch.
-This is relatively safe because the kernel package doesn’t have any dynamic dependencies and the version in v3.18 and edge will be in sync at least until v3.19 is released.
-
-. Create a `repositories` file with a pinned main repository from edge, e.g.:
-+
-[source]
-----
-@edge https://dl-cdn.alpinelinux.org/alpine/edge/main
-https://dl-cdn.alpinelinux.org/alpine/v3.18/main
-https://dl-cdn.alpinelinux.org/alpine/v3.18/community
-----
-
-. Run {script-name} with the options `--repositories-file ./repositories` and `--packages linux-virt@edge` (or `linux-lts@edge` if you use `--kernel-flavor lts`).
-
-This will first install _linux-virt_ from v3.18, but in the later step it will reinstall it from the edge branch.
-
-
 === Create images for aarch64 on x86_64 host
 
 All you need to do is install the https://www.qemu.org/docs/master/user/main.html[QEMU User space emulator] for aarch64 and register it in https://docs.kernel.org/admin-guide/binfmt-misc.html[binfmt_misc] as the interpreter for aarch64 binaries.
@@ -110,6 +85,29 @@ See link:.github/workflows/ci.yml[] for a complete example.
 After that, run {script-name} with the option `--arch aarch64`.
 
 
+[[aarch64-old]]
+=== Create aarch64 image with Alpine v3.18 or older
+
+The Linux kernel (_linux-virt_, _linux-lts_ or _linux-edge_ package) in Alpine v3.18 and earlier doesn’t have https://cateee.net/lkddb/web-lkddb/EFI_ZBOOT.html[EFI_ZBOOT] enabled, so EFI stub cannot load a compressed vmlinuz.
+We backported it to v3.18, but then we had to revert it due to a problem with Grub (see https://gitlab.alpinelinux.org/alpine/aports/-/issues/15263[alpine/aports#15263]).
+
+If you want to build an image with an older branch of Alpine Linux, you can, but you must install the kernel from the v3.19 branch (or newer).
+This is relatively safe because the kernel package doesn’t have any dynamic dependencies.
+
+. Create a `repositories` file with a pinned main repository from v3.19, e.g.:
++
+[source]
+----
+@v319 https://dl-cdn.alpinelinux.org/alpine/v3.19/main
+https://dl-cdn.alpinelinux.org/alpine/v3.18/main
+https://dl-cdn.alpinelinux.org/alpine/v3.18/community
+----
+
+. Run {script-name} with the options `--repositories-file ./repositories` and `--packages linux-virt@v319` (or `linux-lts@v319` if you use `--kernel-flavor lts`).
+
+This will first install _linux-virt_ from v3.18, but in the later step it will reinstall it from the v3.19 branch.
+
+
 === Create image for VMware (ESXi)
 
 VMware and disk images (virtual disks) is one big mess.