[atomic-devel] Add iscsi-initiator-utils to Atomic host

[Radek Vykydal <rvykydal redhat com>]

The patch:
----------

https://rvykydal.fedorapeople.org/atomic/iscsi/0001-Add-iscsi-support-to-Atomic-Host.patch

Size increase:
--------------

- iscsi-intitiator-utils adds about 2 MB.
- iscsid dracut module (required for booting from iSCSI, or root 
partition on iSCSI) adds 380 KB to packed initramfs

Use cases:
----------

1) Boot Atomic Host from iSCSI

Requires adding iscsi dracut module to initramfs, it seems to pull 
iscsi-initiator-utils to the tree as compose dependency. It is possible 
that in this case we could use iscsid (insci-initiator-utils) in 
superprivileged container.

2) Installing Atomic Host with root partition on iSCSI

The same as 1) but additional fix is required in dracut: 
https://bugzilla.redhat.com/show_bug.cgi?id=1202405

3) docker images on iSCSI
- /var/lib/docker on iSCSI ... for overlayfs driver. Configure during 
installation?
- iSCSI device (configured in installer and) passed to 
docker-storage-setup (DEVS=) ... for devicemapper driver (direct-lvm)
Here SPC could be used but integration with startup services would be 
needed (and perhaps pulling the image during installation for some cases?)

4) docker persistent storage (volumes) on iSCSI. Business of kubernetes 
or other orchestration tool? SPC could be used here.


Why not using superprivileged container?
----------------------------------------

Using SPC would be possible for some of the cases above (with additional 
work of integrating it with host startup services). I got iscsid in SPC 
working:

https://github.com/rvykydal/dockerfile-iscsid

One reason for adding iscsid to the host seems to be ongoing work on 
adding iSCSI as persistent storage for Kubernetes and Docker: 
http://rootfs.github.io/iSCSI-Kubernetes/ where the tools are assumed to 
be on the host. It mentions performance reasons favouring tools on the 
host but they probably don't apply for SPC with --net=host?


Radek