medium type "dvddrive" cannot be used via a readonly iscsi target

[rshaw]

ISO mediums exposed in a dvddrive cannot be used over iSCSI when the target is readonly.

According to ​documentation, CD/DVD images are created read-only, but this doesn't seem to be the case, at least with iSCSI. I need access to a series of readonly iscsi targets that are exposing ISOs, but this does not seem possible unless I start snapshotting guests after the medium is added, and before it is turned on.

A sample target I am trying to connect to

ryan@TehDualLinux:~$ sudo tgtadm --lld iscsi --mode target --op show
Target 2: iqn.2001-04.com.TehDualLinux-2260f94a-90f3-4147-9e32-39c773f7095b
    System information:
        Driver: iscsi
        State: ready
    I_T nexus information:
    LUN information:
        LUN: 0
            Type: controller
            SCSI ID: IET     00020000
            SCSI SN: beaf20
            Size: 0 MB, Block size: 1
            Online: Yes
            Removable media: No
            Readonly: No
            Backing store type: null
            Backing store path: None
            Backing store flags: 
        LUN: 1
            Type: disk
            SCSI ID: IET     00020001
            SCSI SN: beaf21
            Size: 1013 MB, Block size: 512
            Online: Yes
            Removable media: No
            Readonly: Yes
            Backing store type: rdwr
            Backing store path: /usr/local/storage/linuxmint-14.1-mate-dvd32bit.iso
            Backing store flags: 
    Account information:
    ACL information:
        ALL

Adding the above target to VirtualBox

VBoxManage storageattach "NewPasswordWindowsReadOnly2" --storagectl "MyController" --port 1 --device 0 --type dvddrive --medium iscsi --server localhost --target "iqn.2001-04.com.TehDualLinux-2260f94a-90f3-4147-9e32-39c773f7095b" --lun 1 --tport 3260

It was added successfully.

vboxmanage list hdds

...
UUID:        2d4790e0-678b-4fc0-b529-32aebfec6f97
Parent UUID: base
Format:      iSCSI
Location:    localhost|iqn.2001-04.com.TehDualLinux-2260f94a-90f3-4147-9e32-39c773f7095b|1
State:       created
Type:        normal
Usage:       NewPasswordWindowsReadOnly2 (UUID: e86ffe75-2412-4aa6-9b36-3a0c0f3e4780)
...

After we try and turn the machine on, it fails with:

Failed to open a session for the virtual machine NewPasswordWindowsReadOnly2.
VD: error VERR_VD_IMAGE_READ_ONLY opening image file 'localhost|iqn.2001-04.com.TehDualLinux-2260f94a-90f3-4147-9e32-39c773f7095b|1' (VERR_VD_IMAGE_READ_ONLY).
Failed to open image 'localhost|iqn.2001-04.com.TehDualLinux-2260f94a-90f3-4147-9e32-39c773f7095b|1' in read-write mode rc=VERR_VD_IMAGE_READ_ONLY (VERR_VD_IMAGE_READ_ONLY).
Failed to attach driver below us! Image is read-only. (VERR_VD_IMAGE_READ_ONLY).
AHCI: Failed to attach drive to Port1 (VERR_VD_IMAGE_READ_ONLY).

Steps to replicate:

1. Make an iSCSI target with any iSCSI software and make it readonly
2. Add the target to your guest via vboxmanage stoargeattach and do not take snapshots
3. Turn on the guest.

Summary:

• If you remove the readonly flag on the iscsi target everything works perfectly (even through VirutalBox does not need write on this medium)
• If you take a snapshot (thus a differencing medium is created), everything works perfectly
• If you add the DVD as multiattach instead of "normal", it creates a differencing medium, and everything works perfectly.
• If you add the medium normally, even though VirtualBox's documentation claims it is readonly, it tries to access the medium as read/write.

[Squ!d]

I had the same VERR_VD_IMAGE_READ_ONLY with the following code: "VBoxManage.exe: error: Failed to open image FILE for writing due to wrong permissions (VERR_VD_IMAGE_READ_ONLY). VBoxManage.exe: error: AHCI: Failed to attach drive to Port0 (VERR_VD_IMAGE_READ_ONLY) VBoxManage.exe: error: Details: code E_FAIL (0x80004005), component ConsoleWrap, interface IConsole"

I am using Windows as the host computer so the modes/attributes came out to -arh--

Took the file off of readonly (changed modes/attributes to -a-h--) seems to boot up.

Thank you for your time.

Squ!d