Re: Recovering a mdadm raid after a stupid mistake
That's why you should NEVER be lazy, especially when we are talking about spending 5mins to create new partitions. There are tutorials to copy partition table with sfdisk but I wouldn't even do this.
Print the list of partitions of sda with parted, and create the same or similar on sdb. You need like 3mins having all data in front of you. Not you'll spend much more time trying to sort this out, plus your data is in danger.
Copying can often go wrong especially because of UUIDs.
I wonder if you zero the MBR on sdb again, will that make the system run fine degraded with only sda. After all, sda is fine including partition table and UUID. It should work with only sda.
Trying to use sda in read-only seems to be creating the issue, but you can always work in live mode, or try to remount as read-write. You can try working from live mode, creating a new blank partition table on sdb, creating the partitions, and try to add them to mdadm.
Darko.
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Ubuntu 18.04 LTS 64bit
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