Describe layer_content_caches: what it replaces (a mkfs.erofs run per layer
on every node), how a hit is served, how multiple directories are searched,
and how to build a cache with ctr images build-erofs-cache. Call out that the
cached blob is symlinked rather than copied, so entries have to outlive the
snapshots referencing them, and that fsverity and IMMUTABLE_FL can't be used
alongside a cache.
Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>
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>
EROFS has supported a tiny metadata-only image to reference external
blobs since Linux 5.16. This eliminates the need to mount each EROFS
layer one by one and is also useful for VM-based containers (e.g.
nerdbox and Kata containers.)
Similar to LCOW/CimFS, `snapshots.UnpackKeyPrefix` is used to
trigger fsmerge generation (typically < 100 ms) on demand in Prepare().
In the future, we can also generate fsmeta in Commit() of the final
unpacking layer (by introducing an annotation to keep the chainID).
However, in the case of intermediate layer reuse, the Prepare() handling
will still be required.
```toml
[plugins."io.containerd.snapshotter.v1.erofs"]
max_unmerged_layers = 1 # enable fsmerge if image layers >= 2
```
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Enabling the IMMUTABLE_FL file attribute causes dirty data to be
flushed synchronously at least on EXT4, which can greatly impact
container launch performance. In contrast, the overlayfs snapshotter
does not use syncfs by default.
Most users may not need IMMUTABLE_FL, let's make IMMUTABLE_FL optional
to align with the behavior of the overlayfs snapshotter and recover the
original performance.
1. tensorflow
Test commands:
$ nerdctl image pull --snapshotter=X --unpack="false" tensorflow/tensorflow:2.19.0
$ time nerdctl container --snapshotter=X run -d tensorflow/tensorflow:2.19.0 /bin/sh
Results:
overlayfs | 0m18.748s
erofs (no IMMUTABLE_FL) | 0m10.090s
erofs (with IMMUTABLE_FL) | 0m21.074s
2. ubuntu 22.04
Test commands:
$ nerdctl image pull --snapshotter=X --unpack="false" ubuntu:22.04
$ time nerdctl container --snapshotter=X run -d ubuntu:22.04 /bin/sh
Results:
overlayfs | 0m1.147s
erofs (no IMMUTABLE_FL) | 0m0.795s
erofs (with IMMUTABLE_FL) | 0m1.094s
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Derive filesystem UUIDs (`lsblk -o +UUID`) from the OCI layer digests
(although diffIDs are better in principle, but they're unavailable by
differs in advance) rather than generating a random one. This allows
EROFS to uniquely identify each layer using the content-addressable
filesystem UUID.
It can also be used for reproducible builds. To achieve this, configure
`mkfs_options` with `-T0 --mkfs-time` (However, `--mkfs-time` requires
erofs-utils 1.8+; Otherwise, all inode timestamps will be reset w/o it):
``` toml
[plugins."io.containerd.differ.v1.erofs"]
mkfs_options = ["-T0 --mkfs-time"]
```
Fixes: c73c8e5d52 ("Introduce EROFS differ")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Currently, containerd cannot dynamically select between EROFS block
or file-based mounting approaches based on the specific runtime (or
the Linux kernel version of the runtime) due to its static mount
structure.
For example, the EROFS snapshotter fails on Linux 5.4 (Ubuntu 20.04)
with `bin/nerdctl run --net=host --snapshotter=erofs busybox:latest`:
FATA[0005] failed to mount {Type:erofs Source:/var/lib/containerd/
io.containerd.snapshotter.v1.erofs/snapshots/1/layer.erofs Target:
Options:[ro]} on "/tmp/initialC1374142795": block device required
Temporarily fix this by appending `-oloop` for single-layer images.
The upcoming mount manager will make it better [1].
[1] https://github.com/containerd/containerd/issues/11303
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
As documented in ioctl_iflags(2):
```
FS_IMMUTABLE_FL
The file is immutable: no changes are permitted to the file contents
or metadata (permissions, timestamps, ownership, link count, and so
on). (This restriction applies even to the superuser.)
```
For example, any user cannot delete/move layer blobs when
FS_IMMUTABLE_FL is set:
``` sh
# cd /var/lib/containerd/io.containerd.snapshotter.v1.erofs/snapshots/4
# mv layer{,1}.erofs
mv: cannot move 'layer.erofs' to 'layer1.erofs': Operation not permitted
# rm layer.erofs
rm: cannot remove 'layer.erofs': Operation not permitted
```
Note that it's a best-effort approach for data loss prevention. IOWs,
just warn out if FS_IMMUTABLE_FL cannot be set anyway (e.g., due to lack
of support in the underlying filesystem.)
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Add fsverity support to erofs snapshotter to enable data integrity
verification for erofs layers:
- Add an config option `EnableFsverity` for erofs snapshotter
- Add fsverity verification during mount operations
- Enable fsverity on erofs layers during commit
- Add documentation for fsverity support in erofs snapshotter.
- Add TestErofsFsverity to verify fsverity enablement and data protection
The feature can be enabled via config.toml, such as:
```toml
[plugins.'io.containerd.snapshotter.v1.erofs']
root_path = ''
ovl_mount_options = []
enable_fsverity = true
```
Signed-off-by: ChengyuZhu6 <hudson@cyzhu.com>
- Add Target to mount.Mount.
- Add UnmountMounts to unmount a list of mounts in reverse order.
- Add UnmountRecursive to unmount deepest mount first for a given target, using
moby/sys/mountinfo.
Signed-off-by: Edgar Lee <edgarhinshunlee@gmail.com>
Updated some documentation for devmapper snapshotter plugin.
Made consistent use of "thin-pool", "Device Mapper" when referring to
the volume management framework, and "devmapper" when referring to the
snapshotter plugin itself.
Also added some additional resources / reorg.
Signed-off-by: Gavin Inglis <giinglis@amazon.com>
Maksym Pavlenko