add `large_dnode=disabled` description

Debian-Stretch-Root-on-ZFS.md

@@ -71,7 +71,7 @@ Always use the long `/dev/disk/by-id/*` aliases with ZFS.  Using the `/dev/sd*`
 
 2.3  Create the root pool:
 
-    # zpool create -o ashift=12 \
+    # zpool create -o ashift=12 -o feature@large_dnode=disabled \
           -O atime=off -O canmount=off -O compression=lz4 -O normalization=formD \
           -O mountpoint=/ -R /mnt \
           rpool /dev/disk/by-id/scsi-SATA_disk1-part1
@@ -80,7 +80,7 @@ Always use the long `/dev/disk/by-id/*` aliases with ZFS.  Using the `/dev/sd*`
 * The use of `ashift=12` is recommended here because many drives today have 4KiB (or larger) physical sectors, even though they present 512B logical sectors.  Also, a future replacement drive may have 4KiB physical sectors (in which case `ashift=12` is desirable) or 4KiB logical sectors (in which case `ashift=12` is required).
 * Setting `normalization=formD` eliminates some corner cases relating to UTF-8 filename normalization. It also implies `utf8only=on`, which means that only UTF-8 filenames are allowed. If you care to support non-UTF-8 filenames, do not use this option. For a discussion of why requiring UTF-8 filenames may be a bad idea, see [The problems with enforced UTF-8 only filenames](http://utcc.utoronto.ca/~cks/space/blog/linux/ForcedUTF8Filenames).
 * Make sure to include the `-part1` portion of the drive path. If you forget that, you are specifying the whole disk, which ZFS will then re-partition, and you will lose the bootloader partition(s).
-* GRUB doesn't support all pool features of 0.7 release, if you install ZFS from backports or use Proxmox, disable them: `-o feature@large_dnode=disabled`
+* **[GRUB doesn't support all pool features](http://savannah.gnu.org/bugs/?func=detailitem&item_id=48885) of 0.7 release**, if you install ZFS from backports or use Proxmox, disable them: `-o feature@large_dnode=disabled`. If you use 0.6 release, remove this text from command.
 
 **Hints:**
 * The root pool does not have to be a single disk; it can have a mirror or raidz topology.  In that case, repeat the partitioning commands for all the disks which will be part of the pool. Then, create the pool using `zpool create ... rpool mirror /dev/disk/by-id/scsi-SATA_disk1-part1 /dev/disk/by-id/scsi-SATA_disk2-part1` (or replace `mirror` with `raidz`, `raidz2`, or `raidz3` and list the partitions from additional disks). Later, install GRUB to all the disks. This is trivial for MBR booting; the UEFI equivalent is currently left as an exercise for the reader.