Grub lua script to enable automatic creation of grub menu entries on zfs root. Download to /rpool/grub/zfsroot.lua

zfsroot.lua

-- Change this two variables with your actual setup
rpool="rpool"
zfs_rootdir="ROOT"
-- End of user-editable section

ds = ""
snap = ""
snap_dir = ""

function find_kernel_pair (name)
	kernel_ver = string.match (name, "vmlinuz%-(.+)")
	if (kernel_ver) then
		local kernel = snap_dir .. "/boot/vmlinuz-" .. kernel_ver
		local initrd = snap_dir .. "/boot/initrd.img-" .. kernel_ver
		local root = "root=ZFS=" .. rpool .. "/" .. zfs_rootdir .. "/" .. ds .. snap
	    local source = "linux " .. kernel .. " " .. root .. " ro boot=zfs" ..
			"\ninitrd " .. initrd
		grub.add_menu (source, "Boot linux " .. kernel_ver .. " on " .. rpool .. "/" .. zfs_rootdir .. "/" .. ds .. snap)
	end
end

function find_kernel_in_snapshot (name)
	snap = string.match (name, "(@.+)")
	if (snap) then
		snap_dir = "/" .. zfs_rootdir .. "/" .. ds .. "/" .. snap
		grub.enum_file (find_kernel_pair, snap_dir .. "/boot")
	end
end

function find_ds_with_cfg (name)
	ds = string.match (name, "(...+)")
	if (ds) then
		local ds_dir = "/" .. zfs_rootdir .. "/" .. ds
		local cfg = ds_dir .. "/@/boot/grub/grub.cfg"
		if (grub.file_exist(cfg)) then
			return ds,ds_dir,cfg
		end
	end
	return nil,nil,nil
end

function find_bootable_snapshot (name)
	ds,ds_dir,cfg = find_ds_with_cfg(name)
	if (ds) then
		grub.enum_file (find_kernel_in_snapshot, ds_dir)
	end
end

function find_bootable_ds (name)
	ds,ds_dir,cfg = find_ds_with_cfg(name)
	if (ds) then
		local source = "configfile " .. cfg
		grub.add_menu (source, "Boot menu from " .. rpool .. "/" .. zfs_rootdir .. "/" .. ds)
	end
end

grub.enum_file (find_bootable_ds, zfs_rootdir)
grub.enum_file (find_bootable_snapshot, zfs_rootdir)