mirror of https://github.com/containerd/containerd.git synced 2026-08-12 12:14:44 +00:00

Files

Andrew Halaney 9b50650d5c snapshots/erofs: Support idmap mounts

This disables the slow_chown feature (nobody in their right mind
is going to be choosing erofs and want to slowly chown each file),
indicates that we support idmaps if the kernel supports it, and makes
sure to chown the upperdir.

This is more or less exactly how the overlay snapshotter does things,
minus the slow_chown part (which has discussions about dropping
altogether at some point anyways).

Signed-off-by: Andrew Halaney <ahalaney@netflix.com>

2026-01-02 10:05:29 -06:00

blockfile.md

document usage and design of blockfile snapshotter

2024-04-28 11:44:03 +03:00

devmapper.md

update some devmapper docs

2022-07-11 15:49:54 +00:00

erofs.md

snapshots/erofs: Support idmap mounts

2026-01-02 10:05:29 -06:00

README.md

Add EROFS snapshotter documentation

2025-01-13 16:31:21 +08:00

README.md

Snapshotters

Snapshotters manage the snapshots of the container filesystems.

The available snapshotters can be inspected by running ctr plugins ls or nerdctl info.

Core snapshotter plugins

Generic:

overlayfs (default): OverlayFS. This driver is akin to Docker/Moby's "overlay2" storage driver, but containerd's implementation is not called "overlay2".
native: Native file copying driver. Akin to Docker/Moby's "vfs" driver.

Block-based:

blockfile: 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.
devmapper: ext4/xfs device mapper. See devmapper.md.

Filesystem-specific:

btrfs: btrfs. Needs the plugin root (/var/lib/containerd/io.containerd.snapshotter.v1.btrfs) to be mounted as btrfs.
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 .
erofs: EROFS. OverlayFS kernel module needs to be enabled for active snapshots. See also erofs.md.

Deprecated:

aufs: AUFS. Deprecated since containerd 1.5. Removed in containerd 2.0. See also https://github.com/containerd/aufs .

Non-core snapshotter plugins

fuse-overlayfs: FUSE-OverlayFS Snapshotter
nydus: Nydus Snapshotter
overlaybd: OverlayBD Snapshotter
stargz: Stargz Snapshotter

Mount target

Mounts can optionally specify a target to describe submounts in the container's rootfs. For example, if the snapshotter wishes to bind mount to a subdirectory ontop of an overlayfs mount, they can return the following mounts:

[
    {
        "type": "overlay",
        "source": "overlay",
        "options": [
            "workdir=...",
            "upperdir=...",
            "lowerdir=..."
        ]
    },
    {
        "type": "bind",
        "source": "/path/on/host",
        "target": "/path/inside/container",
        "options": [
            "ro",
            "rbind"
        ]
    }
]

However, the mountpoint /path/inside/container needs to exist for the bind mount, so one of the previous mounts must be responsible for providing that directory in the rootfs. In this case, one of the lower dirs of the overlay has that directory to enable the bind mount.