Ansible Role: Multipath (DM Multipath)

This Ansible role is designed to properly install and configure the Linux multipathing software (DM Multipath) for either Boot from SAN or Local Boot.

Features of the Multipath Role:

• Configures DM Multipath following product guidelines and best practices.
• Adjusts driver settings.

Important Note

This role will overwrite existing DM Multipath settings.
Please check the multipath_backup_permanent variable in the Role Variables section.

This setup impacts the following directories and files:

• /etc/multipath/
• /etc/multipath.conf

Caution:
If there are issues after rebooting the host, you might encounter errors like Kernel panic on boot with "dracut Warning: LVM rootvg/rootlv not found".

In such cases, you should:

1. Boot the system using a Rescue ISO.
2. Restore the main files:
   • /boot/<original-initramfs>.img.ansible_multipath
   • /etc/fstab.ansible_multipath
   • /etc/lvm/lvm.conf.ansible_multipath

Tip: You can troubleshoot issues by changing kernel boot parameters to rdshell or rd.shell and removing rhgb and quiet.

How It Works

There are two main stages: pre-setup and setup.

Pre-setup: No system changes, except for installing packages if specified:

• Checks if the device-mapper-multipath package is installed.
• Gathers details about devices for /boot and /boot/efi.
• Loads necessary drivers based on the discovered boot disk.
• Determines if the configuration is for Boot from SAN.
• Retrieves GRUB's default kernel and initramfs.
• Sets up device names and LVM filters.

Setup: Makes system changes:

• Backs up files like /etc/fstab and the current initramfs.
• Removes the current DM Multipath configuration.
• Creates a new /etc/multipath.conf file and checks for errors.
• Configures /etc/fstab, LVM filters, modprobe files, and initramfs, checking for errors along the way.
• On errors, it cleans up and restores backup files.
• Reboots the system and deletes previous backups.

Requirements

• The playbook must use become: yes for root privileges and gather_facts: yes.
• Requires Ansible Engine version 2.7.1 or higher.

Role Variables

Variables for configuring the multipath role start with multipath_. Here are some key ones:

Variable	Type	Description
multipath_setup_pseudodevname	string (mandatory)	Sets the name for the boot disk managed by DM Multipath.
multipath_package_install	boolean (optional)	Installs the device-mapper-multipath package if missing.
multipath_package_upgrade	boolean (recommended)	Upgrades the device-mapper-multipath package if necessary.
multipath_preserve_currentfiles	boolean (recommended)	Backs up existing configuration files before setup.
multipath_reboot_allow	boolean (recommended)	Allows the role to reboot the managed node.
multipath_reboot_timeoutguest	integer (optional)	Maximum wait time (in seconds) for guests to reboot.
multipath_reboot_timeoutbaremetal	integer (optional)	Maximum wait time (in seconds) for bare metal systems to reboot.
multipath_debug_showvariables	boolean (recommended)	Displays role variables and their values.

Example Playbook

Here's what a simple playbook might look like:

- hosts: servers
  become: yes
  gather_facts: yes

  roles:
    - cdomingos.multipath

License

MIT

Author Information

Created by Cláudio Domingos in 2019.

Additional Information

Tested on:

• HP ProLiant BL460c Gen9 (UEFI)
• 3PAR Storage Array
• RHEL 6, 7, 8
• Fedora 31

This role is particularly useful for Bare Metal machines, as high-availability multipathing software needs to be at the hypervisor level.

For best practices in configuring DM Multipath with specific Storage Arrays, consult your Storage Array vendor or seek the Host Connectivity Guide for Linux.

TODO

• Resolve critical issues like dracut Warning: LVM rootvg/rootlv not found by implementing fallback scripts in case of system crashes during reboots.