4d11bb36ad
- 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>
Devmapper snapshotter
Devmapper is a containerd snapshotter plugin that stores snapshots in ext4-formatted filesystem images
in a devicemapper thin pool.
Setup
To make it work you need to prepare thin-pool in advance and update containerd's configuration file.
This file is typically located at /etc/containerd/config.toml.
Here's minimal sample entry that can be made in the configuration file:
[plugins]
...
[plugins.devmapper]
pool_name = "containerd-pool"
base_image_size = "128MB"
...
The following configuration flags are supported:
root_path- a directory where the metadata will be available (if empty default location forcontainerdplugins will be used)pool_name- a name to use for the devicemapper thin pool. Pool name should be the same as in/dev/mapper/directorybase_image_size- defines how much space to allocate when creating the base device
Pool name and base image size are required snapshotter parameters.
Run
Give it a try with the following commands:
ctr images pull --snapshotter devmapper docker.io/library/hello-world:latest
ctr run --snapshotter devmapper docker.io/library/hello-world:latest test
Requirements
The devicemapper snapshotter requires dmsetup (>= 1.02.110) command line tool to be installed and
available on your computer. On Ubuntu, it can be installed with apt-get install dmsetup command.