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setup_unix.go
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setup_unix.go
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// +build linux freebsd
package initlayer // import "github.com/docker/docker/daemon/initlayer"
import (
"os"
"path/filepath"
"strings"
"github.com/docker/docker/pkg/containerfs"
"github.com/docker/docker/pkg/idtools"
"golang.org/x/sys/unix"
)
// Setup populates a directory with mountpoints suitable
// for bind-mounting things into the container.
//
// This extra layer is used by all containers as the top-most ro layer. It protects
// the container from unwanted side-effects on the rw layer.
func Setup(initLayerFs containerfs.ContainerFS, rootIDs idtools.IDPair) error {
// Since all paths are local to the container, we can just extract initLayerFs.Path()
initLayer := initLayerFs.Path()
for pth, typ := range map[string]string{
"/dev/pts": "dir",
"/dev/shm": "dir",
"/proc": "dir",
"/sys": "dir",
"/.dockerenv": "file",
"/etc/resolv.conf": "file",
"/etc/hosts": "file",
"/etc/hostname": "file",
"/dev/console": "file",
"/etc/mtab": "/proc/mounts",
} {
parts := strings.Split(pth, "/")
prev := "/"
for _, p := range parts[1:] {
prev = filepath.Join(prev, p)
unix.Unlink(filepath.Join(initLayer, prev))
}
if _, err := os.Stat(filepath.Join(initLayer, pth)); err != nil {
if os.IsNotExist(err) {
if err := idtools.MkdirAllAndChownNew(filepath.Join(initLayer, filepath.Dir(pth)), 0755, rootIDs); err != nil {
return err
}
switch typ {
case "dir":
if err := idtools.MkdirAllAndChownNew(filepath.Join(initLayer, pth), 0755, rootIDs); err != nil {
return err
}
case "file":
f, err := os.OpenFile(filepath.Join(initLayer, pth), os.O_CREATE, 0755)
if err != nil {
return err
}
f.Chown(rootIDs.UID, rootIDs.GID)
f.Close()
default:
if err := os.Symlink(typ, filepath.Join(initLayer, pth)); err != nil {
return err
}
}
} else {
return err
}
}
}
// Layer is ready to use, if it wasn't before.
return nil
}