91 lines
5.3 KiB
Markdown
91 lines
5.3 KiB
Markdown
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## Introduction
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The Kubernetes iSCSI implementation can connect to iSCSI devices via open-iscsi and multipathd on Linux.
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Currently supported features are
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* Connecting to one portal
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* Mounting a device directly or via multipathd
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* Formatting and partitioning any new device connected
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## Prerequisites
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This example expects there to be a working iSCSI target to connect to.
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If there isn't one in place then it is possible to setup a software version on Linux by following these guides
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* [Setup a iSCSI target on Fedora](http://www.server-world.info/en/note?os=Fedora_21&p=iscsi)
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* [Install the iSCSI initiator on Fedora](http://www.server-world.info/en/note?os=Fedora_21&p=iscsi&f=2)
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* [Install multipathd for mpio support if required](http://www.linuxstories.eu/2014/07/how-to-setup-dm-multipath-on-rhel.html)
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## Creating the pod with iSCSI persistent storage
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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.
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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](http://www.open-iscsi.org/docs/README) or [openstack](http://docs.openstack.org/kilo/config-reference/content/iscsi-iface-config.html) for detailed configuration information.
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**Note:** If you have followed the instructions in the links above you
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may have partitioned the device, the iSCSI volume plugin does not
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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.
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Once the pod config is created, run it on the Kubernetes master:
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```console
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kubectl create -f ./your_new_pod.yaml
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```
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Here is the example pod created and expected output:
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```console
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# kubectl create -f examples/volumes/iscsi/iscsi.yaml
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# kubectl get pods
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NAME READY STATUS RESTARTS AGE
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iscsipd 2/2 RUNNING 0 2m
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```
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On the Kubernetes node, verify the mount output
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For a non mpio device the output should look like the following
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```console
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# mount |grep kub
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/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)
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/dev/sdb on /var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-ro type ext4 (ro,relatime,data=ordered)
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/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)
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/dev/sdc on /var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-rw type ext4 (rw,relatime,data=ordered)
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```
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And for a node with mpio enabled the expected output would be similar to the following
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```console
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# mount |grep kub
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/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)
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/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)
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/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)
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/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)
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```
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If you ssh to that machine, you can run `docker ps` to see the actual pod.
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```console
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# docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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f855336407f4 kubernetes/pause "/pause" 6 minutes ago Up 6 minutes k8s_iscsipd-ro.d130ec3e_iscsipd_default_f527ca5b-6d87-11e5-aa7e-080027ff6387_5409a4cb
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3b8a772515d2 kubernetes/pause "/pause" 6 minutes ago Up 6 minutes k8s_iscsipd-rw.ed58ec4e_iscsipd_default_f527ca5b-6d87-11e5-aa7e-080027ff6387_d25592c5
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```
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Run *docker inspect* and verify the container mounted the host directory into the their */mnt/iscsipd* directory.
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```console
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# docker inspect --format '{{ range .Mounts }}{{ if eq .Destination "/mnt/iscsipd" }}{{ .Source }}{{ end }}{{ end }}' f855336407f4
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/var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-ro
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# docker inspect --format '{{ range .Mounts }}{{ if eq .Destination "/mnt/iscsipd" }}{{ .Source }}{{ end }}{{ end }}' 3b8a772515d2
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/var/lib/kubelet/pods/f527ca5b-6d87-11e5-aa7e-080027ff6387/volumes/kubernetes.io~iscsi/iscsipd-rw
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```
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<!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
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[]()
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<!-- END MUNGE: GENERATED_ANALYTICS -->
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