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--- raid:mdadm:add_a_disk_to_an_existing_array [2021/09/13 22:57] – created peter
+++ raid:mdadm:add_a_disk_to_an_existing_array [2021/09/26 12:17] (current) – peter
@@ Line 7: / Line 7: @@
 </code>
+----
+===== Add a disk using its UUID =====
+==== Check the UUIDs of the partitions ====
+<code bash>
+ls -l /dev/disk/by-partuuid/
+</code>
+returns:
+<code bash>
+lrwxrwxrwx 1 root root 10 Sep  4 14:49 526e2405-0124-4baa-805f-335369588ddd -> ../../sda1
+lrwxrwxrwx 1 root root 10 Sep  4 14:49 5d426ea0-5795-4165-863d-1ed947dc77fd -> ../../sda2
+lrwxrwxrwx 1 root root 10 Sep  4 14:49 8e53314c-0814-46cd-9f13-c2bb2b7a14b6 -> ../../sdb1
+lrwxrwxrwx 1 root root 10 Sep  4 14:49 90412d26-ebec-4996-96d6-a7a6c702e57e -> ../../sdc1
+</code>
+----
+==== Add /dev/sdc1 using its UUID ====
+<code bash>
+mdadm /dev/md0 --add /dev/disk/by-partuuid/90412d26-ebec-4996-96d6-a7a6c702e57e
+</code>
+returns:
+<code bash>
+mdadm: added /dev/disk/by-partuuid/90412d26-ebec-4996-96d6-a7a6c702e57e
+</code>
+----
+==== Check the details of the RAID array ====
+<code bash>
+mdadm --detail /dev/md0
+</code>
+returns:
+<code bash>
+</code>
+<WRAP info>
+**NOTE:**  It reports /dev/sdc1 instead of the UUID.
+This is not a problem.
+mdadm allows disks to be moved around freely in the machine, regardless of how you add the disk to the array.
+  * It tracks the disks by the RAID metadata (superblocks) stored on the disk.
+  * The default config, specified in /etc/mdadm/mdadm.conf, usually is normally DEVICE partitions, which means to look at all partitions (on all disks) checking for RAID superblocks.
+    * It checks for a match of the array name or UUID (depending on what is in that config file.
+</WRAP>