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83 lines
2.5 KiB
Go
83 lines
2.5 KiB
Go
// +build linux
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/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package fuseoverlayfs
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import (
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"fmt"
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"io/ioutil"
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"os"
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"os/exec"
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"path/filepath"
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"github.com/containerd/containerd/log"
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"github.com/containerd/containerd/mount"
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"github.com/pkg/errors"
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)
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// supportsReadonlyMultipleLowerDir checks if read-only multiple lowerdirs can be mounted with fuse-overlayfs.
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// https://github.com/containers/fuse-overlayfs/pull/133
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func supportsReadonlyMultipleLowerDir(d string) error {
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td, err := ioutil.TempDir(d, "fuseoverlayfs-check")
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if err != nil {
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return err
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}
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defer func() {
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if err := os.RemoveAll(td); err != nil {
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log.L.WithError(err).Warnf("Failed to remove check directory %v", td)
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}
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}()
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for _, dir := range []string{"lower1", "lower2", "merged"} {
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if err := os.Mkdir(filepath.Join(td, dir), 0755); err != nil {
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return err
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}
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}
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opts := []string{fmt.Sprintf("lowerdir=%s:%s", filepath.Join(td, "lower2"), filepath.Join(td, "lower1"))}
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m := mount.Mount{
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Type: "fuse3." + fuseoverlayfsBinary,
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Source: "overlay",
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Options: opts,
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}
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dest := filepath.Join(td, "merged")
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if err := m.Mount(dest); err != nil {
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return errors.Wrapf(err, "failed to mount fuse-overlayfs (%+v) on %s", m, dest)
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}
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if err := mount.UnmountAll(dest, 0); err != nil {
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log.L.WithError(err).Warnf("Failed to unmount check directory %v", dest)
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}
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return nil
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}
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// Supported returns nil when the overlayfs is functional on the system with the root directory.
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// Supported is not called during plugin initialization, but exposed for downstream projects which uses
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// this snapshotter as a library.
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func Supported(root string) error {
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if _, err := exec.LookPath(fuseoverlayfsBinary); err != nil {
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return errors.Wrapf(err, "%s not installed", fuseoverlayfsBinary)
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}
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if err := os.MkdirAll(root, 0700); err != nil {
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return err
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}
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if err := supportsReadonlyMultipleLowerDir(root); err != nil {
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return errors.Wrap(err, "fuse-overlayfs not functional, make sure running with kernel >= 4.18")
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}
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return nil
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}
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