- reproducer
1. stop a container;
2. reboot, or dmsetup remove its corresponding dm device;
3. start the container, it will fail like:
"""
Error: failed to start containers: {"message":"failed to create container(4f33d2760760c41518a84821153ccdf7f80980b797b783cdd75178fc6ca0bf4b) on containerd: failed to create task for container(4f33d2760760c41518a84821153ccdf7f80980b797b783cdd75178fc6ca0bf4b): failed to mount rootfs component &{ext4 /dev/mapper/vg0-mythinpool-snap-2 []}: no such file or directory: unknown"}
"""
- how the fix works
activate the dm device if necessary, and give a warn msg:
"""
time="2019-08-21T22:44:08.422695797+08:00" level=warning msg="devmapper device \"vg0-mythinpool-snap-2\" marked as \"Activated\" but not active, activating it"
"""
Signed-off-by: Eric Ren <renzhen@linux.alibaba.com>
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