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tech:linux:build_add_raid [2014/12/05 06:43] (current)
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 +====== Building an additional raid ======
 +My box already had two hard disks in raid10. ​ Wanted to add two more disks in a second raid.  Here is what I did.  This was on Ubuntu Trusty.
 +  * Boot with Ubuntu install CD
 +  * Go into recover mode
 +  * Navigate until you hit the partition disk option (had to go forward and backward in the wizard to end up here!)
 +  * Perform the partition as you would on a new system, except only do it for the two new disks and leave the existing untouched
 +  * When asked to specify mount point specify / (root)
 +    * Specifying root is not what I //​actually//​ wanted as this was a supplementary data disk (set)
 +    * The install (even recover mode) would not let me proceed if I did not have a root partition mount
 +  * Confirm the write to partition table
 +  * The system will start installing the OS on the new root partition! Not what we wanted of course.
 +  * Press reset (Ctl-Alt-Del) in the middle of the install to force reboot!
 +  * Boot back into the system (as before) with your regular boot disk
 +  * Run ''​fdisk -l''​ to check that disks are raid are all in place - should be or something went awry
 +  * Use ''​blkid''​ to determine the UUID of the new raid disk set
 +  * Update ''/​etc/​fstab''​ with mount point (create the mount-point directory first)
 +  * Issue a ''​mount -a''​ to mount the disks
 +  * Remove the frivolous install files that the Ubuntu installer started to copy in the new set of disks
 +  * Issue a ''​cat /​proc/​mdstat''​ to observe raid sync process
 +  * Issue a ''​mdadm --detail --scan''​ to get the new (and existing ARRAY) details
 +  * Update ''/​etc/​mdadm/​mdadm.conf''​ with the new ARRAY details
 +  * Run ''​update-initramfs -u''​ to add it to the initramfs image
 +I used the install CD as the process is standard and you can do it via a //tool// as opposed to commands, that I could not find a good comprehensive set of.  It is sort of imperfect in that you have to fool the installer into just creating your raid/​partitions and force abort the actual install. However it works and does not have any risk.

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