Using mdadm --examine to write mdadm.conf

Question

I'm trying to script the RAID setup for a (growing) number of identical servers. The advice I've seen for using mdadm suggests that once the RAID array has been created you can run mdadm --examine --scan >> /etc/mdadm.conf so that the array is initialised on bootup. But that doesn't seem to work for me - in particular the array is presented as /dev/md/<hostname>:pool, where the mdadm --examine outputs /dev/md/pool.

Am I doing something wrong? Is there something odd about my version of mdadm?

[root@positron /]# mdadm --create /dev/md0 --level=0 --name=pool --raid-devices=6 /dev/sda /dev/sdb /dev/sdc /dev/sdd /dev/sde /dev/sdf
[root@positron /]# mdadm --examine --scan
ARRAY /dev/md/pool metadata=1.2 UUID=567da122:fb8e445e:55b853e0:81bd0a3e name=positron:pool
[root@positron /]# ls /dev/md/*
/dev/md/md-device-map  /dev/md/positron:pool
[root@positron /]# cat /dev/md/md-device-map
md127 1.2 22a17d56:5e448efb:e053b855:3e0abd81 /dev/md/positron:pool
[root@positron /]# mdadm --version
mdadm - v3.1.3 - 6th August 2010

Answer 1

And here's the fix, I'm not entirely clear on why it works, but it does!

After updating your mdadm file following the RAID array creation - usually with something like mdadm --detail --scan >> /etc/mdadm/mdadm.conf

Simply run the following command update-initramfs -u

Then reboot, and everything will work as expected.

Voila ;)

Answer 2

I've found that I've had to manually edit both the mdadm.conf and udev.conf to get the manual device names to hold.

However, I've not found it to be an issue one LVM is layered on top.

Answer 3

I don't see what's the problem. Array will be assembled on boot okay, even if it would be only mentioned with its UUID.