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I installed 16.04 Server and I have had a similar message in my logs and this message when I upgrade initramfs packages through normal package upgrade.

...
Setting up initramfs-tools (0.122ubuntu8.3) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools (0.122ubuntu8.3) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-38-generic
W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.

Is this normal, or is Ubuntu expecting to find a RAID because of some misconfiguration somewhere?

Here is the contents of /etc/mdadm/mdadm.conf:

# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions containers

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays
Paul
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1 Answers1

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The error says W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.

I reckon that the warning is displayed whenever there's no ARRAY line in mdadm.conf.

The obvious solution would be to add one:

ARRAY <ignore> devices=/dev/sda

Worked for me...

Steffen Breitbach
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  • Thank you very much, Steffen. This has stopped the warnings. – Paul Jan 02 '17 at 19:29
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    What does it do? It wont show error? Or wont show and still will crash? Or it doesnt crash aalready but just shows error? If just showing then i dont care to add something if not fixing crashing. – Kangarooo Mar 05 '17 at 23:48
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    @Kangarooo There is no "crashing" problem reported anywhere in this question. The problem is just to make a warning go away. Steffen has provided a proper solution by telling mdadm that it should not expect there to be any arrays, which is all the warning was telling about. – Paul Mar 06 '17 at 01:01
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    Interesting: I have two instances of 16.04.4 installed at about the same time on similar hardware. The first has /etc/mdadm/mdadm.conf and therefore gives the error; the second does not even have that file. One wonders what triggers the installation of that file — maybe it figures out (wrongly?) that an array controller is present even if it is not being used? – Gwyneth Llewelyn Mar 02 '18 at 09:19
  • I can't reply to Steffen Breitbach because my "reputation on this website is too low". I followed his instructions about adding `ARRAY devices=/dev/sda` but I get this error -bash: ignore: No such file or directory – sumguy Aug 03 '19 at 20:30
  • @sumguy You should try asking a question about your problem to the site by clicking the "Ask Question" link at the top of the page. The way that the StackExchange Q&A sites work is that each question is narrowly focused only on the topic of the question. Given the popularity of this question, it seems likely you have some other issue preventing this solution from solving your problem. – Paul Aug 06 '19 at 01:59