64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
# Snapshotters
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Snapshotters manage the snapshots of the container filesystems.
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The available snapshotters can be inspected by running `ctr plugins ls` or `nerdctl info`.
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## Core snapshotter plugins
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Generic:
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- `overlayfs` (default): OverlayFS. This driver is akin to Docker/Moby's "overlay2" storage driver, but containerd's implementation is not called "overlay2".
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- `native`: Native file copying driver. Akin to Docker/Moby's "vfs" driver.
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Block-based:
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- [`blockfile`](./blockfile.md): A driver using raw block files for each snapshot. Block files are copied from a parent or base empty block file. Mounting requires a virtual machine or support for loopback mounts.
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- `devmapper`: ext4/xfs device mapper. See [`devmapper.md`](./devmapper.md).
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Filesystem-specific:
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- `btrfs`: btrfs. Needs the plugin root (`/var/lib/containerd/io.containerd.snapshotter.v1.btrfs`) to be mounted as btrfs.
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- `zfs`: ZFS. Needs the plugin root (`/var/lib/containerd/io.containerd.snapshotter.v1.zfs`) to be mounted as ZFS. See also https://github.com/containerd/zfs .
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[Deprecated](https://github.com/containerd/containerd/blob/main/RELEASES.md#deprecated-features):
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- `aufs`: AUFS. Deprecated since containerd 1.5. Removed in containerd 2.0. See also https://github.com/containerd/aufs .
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## Non-core snapshotter plugins
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- `fuse-overlayfs`: [FUSE-OverlayFS Snapshotter](https://github.com/containerd/fuse-overlayfs-snapshotter)
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- `nydus`: [Nydus Snapshotter](https://github.com/containerd/nydus-snapshotter)
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- `overlaybd`: [OverlayBD Snapshotter](https://github.com/containerd/accelerated-container-image)
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- `stargz`: [Stargz Snapshotter](https://github.com/containerd/stargz-snapshotter)
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## Mount target
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Mounts can optionally specify a target to describe submounts in the container's
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rootfs. For example, if the snapshotter wishes to bind mount to a subdirectory
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ontop of an overlayfs mount, they can return the following mounts:
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```json
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[
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{
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"type": "overlay",
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"source": "overlay",
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"options": [
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"workdir=...",
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"upperdir=...",
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"lowerdir=..."
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]
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},
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{
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"type": "bind",
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"source": "/path/on/host",
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"target": "/path/inside/container",
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"options": [
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"ro",
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"rbind"
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]
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}
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]
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```
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However, the mountpoint `/path/inside/container` needs to exist for the bind
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mount, so one of the previous mounts must be responsible for providing that
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directory in the rootfs. In this case, one of the lower dirs of the overlay has
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that directory to enable the bind mount.
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