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What is this black magic?

(Birkelund) #1

Hi all,

I’m messing around with docker and I found this in my mounts:

/dev/mapper/vgroot-vgroot on /var/lib/docker/plugins type ext4 (rw,noatime,errors=remount-ro,data=ordered)
/dev/mapper/vgroot-vgroot on /var/lib/docker/overlay2 type ext4 (rw,noatime,errors=remount-ro,data=ordered)

/dev/mapper/vgroot-vgroot is my root block device. Is formatted with ext4 and mounted on /. Now, mount is telling me that that same block device is mounted on both /var/lib/docker/plugins and /var/lib/docker/overlay2. I would expect this to be mounted as some kind of overlay file system, but mount reports that it is mounted as an ext4 file system. I then expect to find the contents of my root file system in i.e. /var/lib/docker/plugins, but that is not the case.

Can anyone enlighten me as to what is going on here? It seems to be black magic to me. And I don’t like when stuff feels like black magic :wink: