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Introduction
The Kubernetes iSCSI implementation can connect to iSCSI devices via open-iscsi and multipathd on Linux. Currently supported features are
- Connecting to one portal
- Mounting a device directly or via multipathd
- Formatting and partitioning any new device connected
Prerequisites
This example expects there to be a working iSCSI target to connect to. If there isn't one in place then it is possible to setup a software version on Linux by following these guides
- Setup a iSCSI target on Fedora
- Install the iSCSI initiator on Fedora
- Install multipathd for mpio support if required
Creating the pod with iSCSI persistent storage
Once you have configured the iSCSI initiator, you can create a pod based on the example iscsi.yaml. In the pod YAML, you need to provide targetPortal (the iSCSI target's IP address and port if not the default port 3260), target's iqn, lun, and the type of the filesystem that has been created on the lun, and readOnly boolean. No initiator information is required.
If you want to use an iSCSI offload card or other open-iscsi transports besides tcp, setup an iSCSI interface and provide iscsiInterface in the pod YAML. The default name for an iscsi iface (open-iscsi parameter iface.iscsi_ifacename) is in the format transport_name.hwaddress when generated by iscsiadm. See open-iscsi or openstack for detailed configuration information.
Note: If you have followed the instructions in the links above you may have partitioned the device, the iSCSI volume plugin does not currently support partitions so format the device as one partition or leave the device raw and Kubernetes will partition and format it one first mount.
Once the pod config is created, run it on the Kubernetes master:
kubectl create -f ./your_new_pod.yaml
Here is the example pod created and expected output:
# kubectl create -f examples/volumes/iscsi/iscsi.yaml
# kubectl get pods
NAME READY STATUS RESTARTS AGE
iscsipd 2/2 RUNNING 0 2m
On the Kubernetes node, verify the mount output
For a non mpio device the output should look like the following
# mount |grep kub
/dev/sdb on /var/lib/kubelet/plugins/kubernetes.io/iscsi/10.0.2.15:3260-iqn.2001-04.com.example:storage.kube.sys1.xyz-lun-0 type ext4 (ro,relatime,data=ordered)
/dev/sdb on /var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-ro type ext4 (ro,relatime,data=ordered)
/dev/sdc on /var/lib/kubelet/plugins/kubernetes.io/iscsi/10.0.2.15:3260-iqn.2001-04.com.example:storage.kube.sys1.xyz-lun-1 type ext4 (rw,relatime,data=ordered)
/dev/sdc on /var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-rw type ext4 (rw,relatime,data=ordered)
And for a node with mpio enabled the expected output would be similar to the following
# mount |grep kub
/dev/mapper/mpatha on /var/lib/kubelet/plugins/kubernetes.io/iscsi/10.0.2.15:3260-iqn.2001-04.com.example:storage.kube.sys1.xyz-lun-0 type ext4 (ro,relatime,data=ordered)
/dev/mapper/mpatha on /var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-ro type ext4 (ro,relatime,data=ordered)
/dev/mapper/mpathb on /var/lib/kubelet/plugins/kubernetes.io/iscsi/10.0.2.15:3260-iqn.2001-04.com.example:storage.kube.sys1.xyz-lun-1 type ext4 (rw,relatime,data=ordered)
/dev/mapper/mpathb on /var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-rw type ext4 (rw,relatime,data=ordered)
If you ssh to that machine, you can run docker ps to see the actual pod.
# docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
f855336407f4 kubernetes/pause "/pause" 6 minutes ago Up 6 minutes k8s_iscsipd-ro.d130ec3e_iscsipd_default_f527ca5b-6d87-11e5-aa7e-080027ff6387_5409a4cb
3b8a772515d2 kubernetes/pause "/pause" 6 minutes ago Up 6 minutes k8s_iscsipd-rw.ed58ec4e_iscsipd_default_f527ca5b-6d87-11e5-aa7e-080027ff6387_d25592c5
Run docker inspect and verify the container mounted the host directory into the their /mnt/iscsipd directory.
# docker inspect --format '{{ range .Mounts }}{{ if eq .Destination "/mnt/iscsipd" }}{{ .Source }}{{ end }}{{ end }}' f855336407f4
/var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-ro
# docker inspect --format '{{ range .Mounts }}{{ if eq .Destination "/mnt/iscsipd" }}{{ .Source }}{{ end }}{{ end }}' 3b8a772515d2
/var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-rw