I finally found a work around for using the 8 TB disk with the old u-boot which does not understand GPT: Normally, when a disk is partitioned with a GPT table, the first entry in the MBR table gets a so called "protective entry" allocating the maximum space of 2 TB of the old addressing scheme as a type "0xec". This entry also instructs Linux to use GPT instead of MBR partiby LinAdmin - Debian
Hybrid partitioning did not succeed and I have given up. So the question remains how WD MyCloud Gen2 (single drive) with only a small flash storage can boot with a GPT disk. In the GPL source from WD u-boot is not included, but I can not imagine how the Grub source included should do the job? So it still would be very helpful to know if NAS326 can boot on GPT?by LinAdmin - Debian
I have wiped the disk and using gparted created a single GPT-partition. It would have been too surprising if 'scsi init' would not hang as with every GPT :-( Questions regarding Zyxel NAS326: - With their u-boot and without anything on USB, what does 'scsi init' with 1 and 2 disk(s) partitioned with several GPT entries show? - If their u-boot does correctly handle itby LinAdmin - Debian
bodhi, the MBR of that disk was filled with zeros to make sure nothing was left from hybrid partitioning and then using gdisk one partition created.by LinAdmin - Debian
Conclusion about this u-boot and GPT: a) With GPT this u-boot does not work at all. b) With hybrid GPT, but without protective entry in the MBR table, this u-boot works. Linux however does not see the GPT and we need a trick to force Linux to use GPT although the protective entry in MBR table is missing. I did not find any such hints, but I still could imagine that some magic in the boot arby LinAdmin - Debian
I had described before that an old (750 G) disk partitioned with fdisk did work as excepted and when the partitioning was changed to GPT the 'scsi init' with the same disk hung. Other disks (small and up to 8 TB) partitioned with GPT show the same behavior. As said before, in part.h of WD u-boot there is no sign of GPT code visible. GPT is mentioned only in the context of efi and I dby LinAdmin - Debian
I have further investigated the problem: When u-boot waits on the serial console, the sata hardware is already powered up without giving any 'mw' command. However, 'scsi init' some times reports the disk id's with erroneous texts and and only after 'scsi reset' it eventually brings the correct text. After that, booting the small disk with partition table iby LinAdmin - Debian
Many thanks bodhi for your motivating reply. I built u-boot from latest WDMyCloud_Ex2Ultra_GPL_v2.30.193_20180502 running xbuild. This produces the file u-boot-a38x-GrandTeton_2014T3_PQ-nand-uart_512M which I renamed to u-boot.bin. The MyColud EX2 got one disk partitioned with fdisk holding a small bootP with stored uImage and initrd as used before on the USB stick. When giving the cby LinAdmin - Debian
Although there is some free space in the Nand flash I do not think that it is advisable to try to put your whole Debian in flash. The few GB you lose on the disk are not worth the effort. Someone has described in this forum how to encrypt the whole disk using luks and he stored the pwd in flash. Asking for the password at each boot is problematic because at this stage you have no ssh availableby LinAdmin - Debian
In this forum I have found several interesting threads about modifications of this NAS. I have an USB stick attached where initrd and kernel 4.9.y are stored and a serial cable connected where I can boot from USB with the rest of Debian in a file system on Disk. This system is pretty small and has excellent benchmarks for reading and writing via samba and nfs. The small footprint leaves enoby LinAdmin - Debian