Improve os iscsi service

[niusmallnan]

If we want to use open-iscsi on RancherOS, we have two options:

1. Switch console to ubuntu, and install open-iscsi by apt.
2. Enable open-iscsi in the default console, just use ros service enable/up open-iscsi.

For the first option, it can work well. But some friends still want to use in the default console, so we need to improve the experience on os-services.

We may have the following tasks to be completed:

1. Keep the version of the open-iscsi service consistent with the version of the open-iscsi library, so that it will not bother users.
2. Support for enable open-iscsi service behind a proxy.
3. Open-isns is also built into the open-iscsi service, but it doesn't work due to issues with the related .so file version. We need to fix it or discard it.
4. Documentation, especially for documents used in conjunction with k8s, users are very concerned about this part.

gz#5556

[rajha-korithrien]

iSCSI support in Rancher OS would be very useful.
My team has a working Rancher OS cluster with Rancher v2.2.0 on top and we are very pleased with it.

Being able to correctly use iSCSI mounts from Rancher OS hosts (configured via ros as a service), as well as exposing iSCSI targets to Kubernetes (to be used as volumes) is a strong use case for my team.

[phoenix-bjoern]

It would be also great to run Longhorn directly on RancherOS, which requires open-iscsi as well AFAIK.

[Rancheroo]

Hello any progress with point 4
Documentation, especially for documents used in conjunction with k8s, users are very concerned about this part.

Thank you

[wsaca]

I'm testing rancher 2.3.4-rc4 and rancheros 1.5.5-rc1, but the second option "ros service enable/up open-iscsi" didn't work.

[hbudde]

Is there any progress related to this topic? Currently I am trying to install a CSI driver and enabled the open-iscsi service.
But the problem is that the iscsiadm script, which is mounted by the driver, can not execute the system-docker command.
Also the version of iscsiadm in the kubelet container (iscsiadm version 2.0-874) and the one of the open-iscsi container (iscsiadm version 2.0-873) are different.
I am using RancherOS 1.5.5 und Kubernetes 1.17.4

[k00p]

@hbudde Adding a bind mount to the system-docker command in the kubelet container allowed the iscsiadm script to run in my case.