I built some very small linux systems that I use to create virtual clusters in seconds. All the software has been compiled from source against the MUSL library and despite the small size they provide many features, tinyzfs for example is only 28MB but has:
QEMU, LXC, ZFS, http/s, vde2, wpa_supplicant, ddrescue, lynx, mdadm, iperf3, nfs, parted, stress, ntfs-3g, sysstats, etc. etc
Here is a screencast with migration between metal nodes: My Tiny Linux.
Last update on 13/09/2021 - kernel 5.14.3 changelog.