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https://github.com/alpinelinux/alpine-make-vm-image

Make customized Alpine Linux disk image for virtual machines
https://github.com/alpinelinux/alpine-make-vm-image

alpine-linux ci deployment disk-image vm-images

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Make customized Alpine Linux disk image for virtual machines

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= Make Alpine Linux VM Image

:script-name: alpine-make-vm-image

:script-sha1: 0fe2deca927bc91eb8ab32584574eee72a23d033

:gh-name: alpinelinux/{script-name}

:version: 0.13.0



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 footnote:[Supported since Alpine Linux v3.19. See <>.] 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).



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?

     Then https://github.com/alpinelinux/alpine-make-rootfs[alpine-make-rootfs] is for you!



== Requirements



* Linux system with common userland (Busybox or GNU coreutils)

* POSIX-sh compatible shell (e.g. Busybox ash, dash, Bash, ZSH)

* `qemu-img` and `qemu-nbd` tools

* `rsync` (needed only for `--fs-skel-dir`)

* `sfdisk` (needed only for `--partition`, `--boot-mode UEFI` and non-x86 architectures)

* `mdev` or `udevadm` (needed only for `--partition`, `--boot-mode UEFI` and non-x86 architectures if device hotplug doesn’t work)

* `e2fsprogs` (for ext4), `btrfs-progs` (for Btrfs), or `xfsprogs` (for XFS)

* `dosfstools` (needed only for `--boot-mode UEFI` and non-x86 architectures)



All dependencies except the first two are automatically installed by the script when running on Alpine Linux.



== Usage



Read documentation in link:{script-name}[{script-name}].

See link:.github/workflows/ci.yml[] for GitHub Actions example.



You can copy link:{script-name}[{script-name}] into your repository or download it on demand, e.g.:



[source, sh, subs="+attributes"]

wget https://raw.githubusercontent.com/{gh-name}/v{version}/{script-name} \

    && echo '{script-sha1}  {script-name}' | sha1sum -c \

    || exit 1



Or, if you are on Alpine Linux, you can simply install the https://pkgs.alpinelinux.org/packages?name={script-name}[{script-name}] package.



== Howtos



=== 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.



On Alpine Linux::

+

[source, sh]

apk add qemu-aarch64 qemu-openrc

rc-service qemu-binfmt start



On Debian/Ubuntu::

+

[source, sh]

apt-get install -y --no-install-recommends binfmt-support qemu-user-static

update-binfmts --enable



On Fedora::

+

[source, sh]

dnf install qemu-user-static



On GitHub Actions::

+

[source, yaml]

----

- name: Install qemu-aarch64 and register in binfmt

  uses: jirutka/setup-alpine@v1

  with:

    arch: aarch64

----

+

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.

You can find that VMware uses the VMDK format, but the problem is that this is not a single format.

Actually it has many subformats with very different structure and various (in)compatibility with VMware hypervisors.



When I’ve created a disk image using `qemu-img create -f vmdk` or converted Qcow2 to VMDK using `qemu-img convert -O vmdk`, vSphere client loaded this image without any problem, but the data was corrupted.

Eventually I found in some old documentation that ESXi does not support “sparse” disks…



So after many trials I found out that the least bad and functional solution is to create Qcow2 image and then convert it to VMDK using:



[source, sh]

qemu-img convert -f qcow2 -O vmdk -o adapter_type=lsilogic,subformat=monolithicFlat alpine.qcow2 alpine.vmdk



Unfortunately, this creates a “thick” image, i.e. its size equals the “provisioned space”, not actually used space as in Qcow2.

However, you can compress it with gzip to avoid transferring multiple gigabytes of zeros over network.



== License



This project is licensed under http://opensource.org/licenses/MIT/[MIT License].

For the full text of the license, see the link:LICENSE[LICENSE] file.