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I have an 8Gig rpi 4b running Ubuntu 20.04.2 LTS that started from image ubuntu-20.04.1-preinstalled-server-arm64+raspi.img downloaded from the web site, and blown onto a microSD via Etcher. No problems booting or accessing. For comparison, I have an amd64 20.04.2 LTS install in a VM on my NAS server.

My goal is to boot the rpi from an iscsi target on my NAS. There are a couple of good walk-thrus on this, but assume Raspbian, not Ubuntu. So far the differences have been easy to reconcile.

First step seemed like it was to make sure I could attach the iscsi devices. After installing open-iscsi I do:

ubuntu@pi-1:~$ sudo iscsiadm --mode discovery --type sendtargets --portal 192.168.20.20
192.168.20.20:3260,1 iqn.1998-02.net.munged.nas1:pi-4-root-target
192.168.20.20:3260,1 iqn.1998-02.net.munged.nas1:pi-3-root-target
192.168.20.20:3260,1 iqn.1998-02.net.munged.nas1:pi-2-root-target
192.168.20.20:3260,1 iqn.1998-02.net.munged.nas1:pi-1-root-target

Then:

ubuntu@pi-1:~$ sudo iscsiadm --mode node --portal 192.168.20.20 --login --targetname iqn.1998-02.net.munged.nas1:pi-1-root-target
Logging in to [iface: default, target: iqn.1998-02.net.munged.nas1:pi-1-root-target, portal: 192.168.20.20,3260] (multiple)
Login to [iface: default, target: iqn.1998-02.net.munged.nas1:pi-1-root-target, portal: 192.168.20.20,3260] successful.

I do the exact same commands on the VM, and i get a new /dev/sdb device. I get nothing on the rpi itself. I was expecting an /dev/sda or something under /dev/mapper, maybe. I am careful not to try this on the rpi while the target is attached to the VM.

ubuntu@pi-1:~$ lsblk -f
NAME        FSTYPE   LABEL       UUID                                 FSAVAIL FSUSE% MOUNTPOINT
mmcblk0                                                                              
├─mmcblk0p1 vfat     system-boot B726-57E2                               134M    47% /boot/firmware
└─mmcblk0p2 ext4     writable    483efb12-d682-4daf-9b34-6e2f774b56f7   11.1G    18% /

and:

ubuntu@pi-1:~$ ls -al /dev/disk/by-id
lrwxrwxrwx 1 root root  13 Apr  1  2020 mmc-SC16G_0xc3294085 -> ../../mmcblk0
lrwxrwxrwx 1 root root  15 Apr  1  2020 mmc-SC16G_0xc3294085-part1 -> ../../mmcblk0p1
lrwxrwxrwx 1 root root  15 Feb  3 06:37 mmc-SC16G_0xc3294085-part2 -> ../../mmcblk0p2

and:

ubuntu@pi-1:~$ ls -al /dev/mapper
crw-------  1 root root 10, 236 Apr  1  2020 control

And dmesg shows only:

[40782.442776] Loading iSCSI transport class v2.0-870.
[40782.482588] iscsi: registered transport (tcp)
[40879.580046] scsi host0: iSCSI Initiator over TCP/IP

On the VM, dmesg shows the device actually being attached and such.

I've verified that the initiator iscsid.service is loaded, active, and running.

First question is what's next in troubleshooting this. I'm at the raw limits of my knowledge on this.

Second question I guess I need to ask, is would my experience be any different if I installed Ubuntu via the rpi imager program, rather than just using a downloaded image?

All help appreciated.

Wook
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1 Answers1

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Thought I'd covered all the bases on this, but I forgot a step on setting up the NAS side. I hadn't associated any extents to the target, so there was nothing for the rpi to connect to devices.

Once I'd associated pi-1-target to pi-1-extent, it worked perfectly, creating /dev/sda.

Sorry for the PEBCAK.

Wook
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