title: How to get rid of "Some devices missing" in BTRFS after reuse of devices?
body: <p>I have been playing around with BTRFS on a few drives I had lying around. At first I created BTRFS using the entire drive, but eventually I decided I wanted to use GPT partitions on the drives and recreated the filesystem I needed on the partitions that resulted. (This was so I could use a portion of each drive as Linux swap space, FYI.)</p>
  
  <p>When I got this all done, BTRFS worked a treat. But I have annoying messages saying that I have some old filesystems from my previous experimentation that I have actually nuked. I worry this meant that BTRFS was confused about what space on the drives was available, or that some sort of corruption might occur.</p>
  
  <p>The messages look like this:</p>
  
  <pre><code>$ sudo btrfs file show
  Label: 'x'  uuid: 06fa59c9-f7f6-4b73-81a4-943329516aee
      Total devices 3 FS bytes used 159.20GB
      devid    3 size 931.00GB used 134.01GB path /dev/sde
      *** Some devices missing
  
  Label: 'root'  uuid: 5f63d01d-3fde-455c-bc1c-1b9946e9aad0
      Total devices 4 FS bytes used 1.13GB
      devid    4 size 931.51GB used 1.03GB path /dev/sdd
      devid    3 size 931.51GB used 2.00GB path /dev/sdc
      devid    2 size 931.51GB used 1.03GB path /dev/sdb
      *** Some devices missing
  
  Label: 'root'  uuid: e86ff074-d4ac-4508-b287-4099400d0fcf
      Total devices 5 FS bytes used 740.93GB
      devid    4 size 911.00GB used 293.03GB path /dev/sdd1
      devid    5 size 931.51GB used 314.00GB path /dev/sde1
      devid    3 size 911.00GB used 293.00GB path /dev/sdc1
      devid    2 size 911.00GB used 293.03GB path /dev/sdb1
      devid    1 size 911.00GB used 293.00GB path /dev/sda1
  </code></pre>
  
  <p>As you can see, I have an old filesystem labeled 'x' and an old one labeled 'root', and both of these have "Some devices missing". The real filesystem, the last one shown, is the one that I am now using.</p>
  
  <p>So how do I clean up the old "Some devices missing" filesystems? I'm a little worried, but mostly just OCD and wanting to tidy up this messy output.</p>
  
  <p>Thanks.</p>