====== Unique machine ID for nfs root systems ======

When multiple hosts running systemd share the same NFS root, they will also share the same machine-id.  This can cause issues, especially with journald.  Journald logging can be disabled by deleting ''/var/log/journal'' which solves most of the problems, but a better solution is to use unique machine-id values on all of the hosts.  Modern motherboards provide a unique UUID accessible via DMI, so a reasonable option is to write this out to /run during boot and point systemd at that as the machine-id.  Here is a simple way to set that up.

Create the file ''/etc/initramfs-tools/scripts/init-top/machineid'':

<code bash machineid>
#!/bin/sh -e

PREREQS=""

prereqs() { echo "$PREREQS"; }

case "$1" in
    prereqs)
    prereqs
    exit 0
    ;;
esac

# write sanitized motherboard UUID to /run/machine-id
sed 's/-//g' /sys/class/dmi/id/product_uuid > /run/machine-id

# requires the following symbolic links:
# ln -sf /run/machine-id /etc/machine-id
# ln -sf /run/machine-id /var/lib/dbus/machine-id

</code>

Rebuild the initramfs (for example ''update-initramfs -u'') and replace ''/etc/machine-id'' and ''/var/lib/dbus/machine-id'' with symlinks to ''/run/machine-id''.