Booting ubuntu from ISCSI TARGET

[nxtu]

Hi everyone,
My RS818+Synology is running ISCSI target. I installed ubuntu on it but I have a issue. I'm using a intel NUC and only can boot ubuntu when it appear GNU GRUB menu. I observed that everytime even failed or succeed my intel NUC always can connect to ISCSI target. But it rarely can make GNU GRUB menu appear. I dont know why. Please help me with this issue.
Thanks for reading!

[dino99]

i have no experience with iscsi, but can point you to: https://help.ubuntu.com/lts/serverguide/iscsi-initiator.html

[nxtu]

i have no experience with iscsi, but can point you to: https://help.ubuntu.com/lts/serverguide/iscsi-initiator.html
Thank for your advice, But its guide how to mount a iscsi disk.