This is trivial, but i keep forgetting it.

howto/raid.md

@@ -120,6 +120,28 @@ before reboot.
 TODO: consider ditching fstab in favor of whatever systemd is smoking
 these days.
 
+## Assembling an existing array
+
+This typically does the right thing:
+
+```
+mdadm --assemble --scan
+```
+
+Example run that finds two arrays:
+
+```
+# mdadm --assemble --scan
+mdadm: /dev/md/0 has been started with 2 drives.
+mdadm: /dev/md/2 has been started with 2 drives.
+```
+
+And of course, you can check the status with:
+
+``
+cat /proc/mdstat
+``
+
 # Hardware RAID
 
 Note: we do not have hardware RAID servers, nor do we want any in the