Make Alpine Linux VM Image

This project provides script for making customized Alpine Linux disk images for virtual machines. It’s quite simple (250 LoC of shell), fast (~40 seconds on Travis CI including Travis VM initialization) and requires minimum dependencies (QEMU and filesystem tools).

Tip	Don’t need VM, just want to chroot into Alpine Linux (e.g. on CI)? Try alpine-chroot-install!

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 (automatically installed by the script if running on Alpine)

• e2fsprogs (for ext4), btrfs-progs (for Btrfs), or xfsprogs (for XFS) (automatically installed by the script if running on Alpine)

Usage

Read documentation in alpine-make-vm-image. See .travis.yml for Travis example.

You can copy alpine-make-vm-image into your repository or download it on demand, e.g.:

wget https://raw.githubusercontent.com/alpinelinux/alpine-make-vm-image/v0.4.0/alpine-make-vm-image \
    && echo '5fb3270e0d665e51b908e1755b40e9c9156917c0  alpine-make-vm-image' | sha1sum -c \
    || exit 1

Pitfalls

Creating Image for VMware (ESXi)

VMware and disk images (virtual disks) is one big mess. You can find that VMware uses format VMDK, 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 created 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 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:

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.

Also note that VMware has some problem with hardened kernel, so you have to boot it with pax_nouderef (read more here).

License

This project is licensed under MIT License. For the full text of the license, see the LICENSE file.