Worker preparation

All of the worker nodes in the Kubernetes cluster need to be able to mount the volumes that users have provisioned for their pods.

If you are using the ontap-nas, ontap-nas-economy, ontap-nas-flexgroup driver for one of your backends, your workers will need the NFS tools. Otherwise they require the iSCSI tools.

Note

Recent versions of RedHat CoreOS have both installed by default. You must ensure that the NFS and iSCSI services are started up during boot time.

Note

When using worker nodes that run RHEL/RedHat CoreOS with iSCSI PVs, make sure to specify the discard mountOption in the StorageClass to perform inline space reclamation. Take a look at RedHat’s documentation here.

Warning

You should always reboot your worker nodes after installing the NFS or iSCSI tools, or attaching volumes to containers may fail.

NFS

Install the following system packages:

RHEL / CentOS

sudo yum install -y nfs-utils

Ubuntu / Debian

sudo apt-get install -y nfs-common

iSCSI

Warning

If using RHCOS >=4.5 or RHEL >=8.2 with the solidfire-san driver ensure that the CHAP authentication algorithm is set to MD5 in /etc/iscsi/iscsid.conf

sudo sed -i 's/^\(node.session.auth.chap_algs\).*/\1 = MD5/' /etc/iscsi/iscsid.conf

RHEL / CentOS

  1. Install the following system packages:

    sudo yum install -y lsscsi iscsi-initiator-utils sg3_utils device-mapper-multipath
    
  2. Check that iscsi-initiator-utils version is 6.2.0.874-2.el7 or higher:

    rpm -q iscsi-initiator-utils
    
  3. Set scanning to manual:

    sudo sed -i 's/^\(node.session.scan\).*/\1 = manual/' /etc/iscsi/iscsid.conf
    
  4. Enable multipathing:

    sudo mpathconf --enable --with_multipathd y
    
  5. Ensure that iscsid and multipathd are running:

    sudo systemctl enable --now iscsid multipathd
    
  6. Start and enable iscsi:

    sudo systemctl enable --now iscsi
    

Ubuntu / Debian

Note

For Ubuntu 18.04 you must discover target ports with iscsiadm before starting open-iscsi for the iSCSI daemon to start. You can alternatively modify the iscsi service to start iscsid automatically.

  1. Install the following system packages:

    sudo apt-get install -y open-iscsi lsscsi sg3-utils multipath-tools scsitools
    
  2. Check that open-iscsi version is 2.0.874-5ubuntu2.10 or higher (for bionic) or 2.0.874-7.1ubuntu6.1 or higher (for focal):

    dpkg -l open-iscsi
    
  3. Set scanning to manual:

    sudo sed -i 's/^\(node.session.scan\).*/\1 = manual/' /etc/iscsi/iscsid.conf
    
  4. Enable multipathing:

    sudo tee /etc/multipath.conf <<-'EOF'
    defaults {
        user_friendly_names yes
        find_multipaths yes
    }
    EOF
    
    sudo systemctl enable --now multipath-tools.service
    sudo service multipath-tools restart
    
  5. Ensure that open-iscsi and multipath-tools are enabled and running:

    sudo systemctl status multipath-tools
    sudo systemctl enable --now open-iscsi.service
    sudo systemctl status open-iscsi