Hi guys,
I have an OpenMediaVault NAS configured with 4 WD Red 4TB in a RAID5 array.
I want to add 2 new disks to this array and unfortunately I cannot find how to do it.
I physically installed the disks in the server and start the NAS.
I click on Grow button in the RAID management tab but my disks were shown in spare in the details (below the details with one added disk, I decided to unplug the other one to perform the extension with one disk at a time...).
I have read several posts and it seems that a command line can solve this issue (mdadm --grow...) but I don't know where to enter this command.
If I connect a screen and a keyboard to my server I have a login line but if I enter my login and pswd the page actualize and ask me again login and pswd.
I am a complete beginner in NAS and Linux in general so I hope that someone can help me 
Thank you in advance!
Version : 1.2
Creation Time : Fri Dec 9 01:30:37 2016
Raid Level : raid5
Array Size : 8790405120 (8383.18 GiB 9001.37 GB)
Used Dev Size : 2930135040 (2794.39 GiB 3000.46 GB)
Raid Devices : 4
Total Devices : 5
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Sun Aug 27 01:12:16 2017
State : clean
Active Devices : 4
Working Devices : 5
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Name : NASnicoOMV:Cube2 (local to host NASnicoOMV)
UUID : f8b8f2fc:ef76fb8d:d603eeee:ca66164c
Events : 10022
Number Major Minor RaidDevice State
0 8 0 0 active sync /dev/sda
1 8 16 1 active sync /dev/sdb
2 8 32 2 active sync /dev/sdc
3 8 48 3 active sync /dev/sdd
4 8 64 - spare /dev/sde