Docker is in volume in use, but there aren't any Docker containers
<p>EDIT (2/19/21): A lot of time has elapsed since I asked this original question years ago and I've seen a flurry of activity since then. I re-selected an answer which I think is consistent with the most localized and safe option for solving this issue (which is typically associated with docker-compose). While docker did introduce the <code>prune</code> command, it is generally a dangerous operation and I would be cautious about using it as you may unintentionally impact other applications or setups you have on your machine</p>
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<p>I've been having issues with removing Docker volumes with Docker 1.9.1.</p>
<p>I've removed all my stopped containers so that <code>docker ps -a</code> returns empty.</p>
<p>When I use <code>docker volume ls</code>, I'm given a whole host of Docker containers:</p>
<pre><code>docker volume ls
DRIVER              VOLUME NAME
local               a94211ea91d66142886d72ec476ece477bb5d2e7e52a5d73b2f2f98f6efa6e66
local               4f673316d690ca2d41abbdc9bf980c7a3f8d67242d76562bbd44079f5f438317
local               eb6ab93effc4b90a2162e6fab6eeeb65bd0e4bd8a9290e1bad503d2a47aa8a78
local               91acb0f7644aec16d23a70f63f70027899017a884dab1f33ac8c4cf0dabe5f2c
local               4932e2fbad8f7e6246af96208d45a266eae11329f1adf176955f80ca2e874f69
local               68fd38fc78a8f02364a94934e9dd3b5d10e51de5b2546e7497eb21d6a1e7b750
local               7043a9642614dd6e9ca013cdf662451d2b3df6b1dddff97211a65ccf9f4c6d47
#etc x 50
</code></pre>
<p>Since none of these volumes contain anything important, I try to purge all the volumes with <code>docker volume rm $(docker volume ls -q)</code>.</p>
<p>In the process, the majority are removed, but I get back:</p>
<pre><code>Error response from daemon: Conflict: volume is in use
Error response from daemon: Conflict: volume is in use
Error response from daemon: Conflict: volume is in use
Error response from daemon: Conflict: volume is in use
Error response from daemon: Conflict: volume is in use
</code></pre>
<p>For a sizeable portion of them. If I don't have any containers existing in the first place, how are these volumes being used?</p>