Upgrade Proxmox that uses zectl to set boot environments (with ZFSBootMenu to pick amongst them)

upgrade_with_zectl.sh

#!/bin/bash

set -e

if [[ $# -ne 1 ]]; then
    echo 'Too many/few arguments, expecting one (new bootenv name)' >&2
    exit 1
fi

name=$1

#echo "***CREATING***"
zectl create "${name}"
#echo "***MOUNTING***"
mountpoint="$(zectl mount ${name})"
pushd "${mountpoint}" > /dev/null
mount -t proc /proc proc/
mount --rbind /dev dev/
mount --rbind /sys sys/
mount --make-rslave dev/
mount --make-rslave sys/
popd

#echo "***UPGRADING***"
chroot "${mountpoint}" apt dist-upgrade
#echo "***UNMOUNTING***"
umount -R "${mountpoint}"/proc
umount -R "${mountpoint}"/dev
umount -R "${mountpoint}"/sys
zectl unmount "${name}"
rmdir "${mountpoint}"
#echo "***DONE***"