github.com/rish1988/moby@v25.0.2+incompatible/internal/testutils/specialimage/emptyfs.go (about)

     1  package specialimage
     2  
     3  import (
     4  	"io"
     5  	"os"
     6  	"path/filepath"
     7  )
     8  
     9  // EmptyFS builds an image with an empty rootfs.
    10  // Layout: Legacy Docker Archive
    11  // See https://github.com/docker/docker/pull/5262
    12  // and also https://github.com/docker/docker/issues/4242
    13  func EmptyFS(dir string) error {
    14  	if err := os.WriteFile(filepath.Join(dir, "manifest.json"), []byte(`[{"Config":"11f64303f0f7ffdc71f001788132bca5346831939a956e3e975c93267d89a16d.json","RepoTags":["emptyfs:latest"],"Layers":["511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158/layer.tar"]}]`), 0o644); err != nil {
    15  		return err
    16  	}
    17  
    18  	if err := os.Mkdir(filepath.Join(dir, "blobs"), 0o755); err != nil {
    19  		return err
    20  	}
    21  
    22  	blobsDir := filepath.Join(dir, "511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158")
    23  	if err := os.Mkdir(blobsDir, 0o755); err != nil {
    24  		return err
    25  	}
    26  
    27  	if err := os.WriteFile(filepath.Join(dir, "VERSION"), []byte(`1.0`), 0o644); err != nil {
    28  		return err
    29  	}
    30  	if err := os.WriteFile(filepath.Join(dir, "repositories"), []byte(`{"emptyfs":{"latest":"511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158"}}`), 0o644); err != nil {
    31  		return err
    32  	}
    33  	if err := os.WriteFile(filepath.Join(dir, "11f64303f0f7ffdc71f001788132bca5346831939a956e3e975c93267d89a16d.json"), []byte(`{"architecture":"x86_64","comment":"Imported from -","container_config":{"Hostname":"","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":null,"Image":"","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":null},"created":"2013-06-13T14:03:50.821769-07:00","docker_version":"0.4.0","history":[{"created":"2013-06-13T14:03:50.821769-07:00","comment":"Imported from -"}],"rootfs":{"type":"layers","diff_ids":["sha256:84ff92691f909a05b224e1c56abb4864f01b4f8e3c854e4bb4c7baf1d3f6d652"]}}`), 0o644); err != nil {
    34  		return err
    35  	}
    36  
    37  	if err := os.WriteFile(filepath.Join(blobsDir, "json"), []byte(`{"id":"511136ea3c5a64f264b78b5433614aec563103b4d4702f3ba7d4d2698e22c158","comment":"Imported from -","created":"2013-06-13T14:03:50.821769-07:00","container_config":{"Hostname":"","Domainname":"","User":"","Memory":0,"MemorySwap":0,"CpuShares":0,"AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"PortSpecs":null,"ExposedPorts":null,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":null,"Image":"","Volumes":null,"WorkingDir":"","Entrypoint":null,"NetworkDisabled":false,"OnBuild":null},"docker_version":"0.4.0","architecture":"x86_64","Size":0}`+"\n"), 0o644); err != nil {
    38  		return err
    39  	}
    40  
    41  	layerFile, err := os.OpenFile(filepath.Join(blobsDir, "layer.tar"), os.O_CREATE|os.O_WRONLY, 0o644)
    42  	if err != nil {
    43  		return err
    44  	}
    45  	defer layerFile.Close()
    46  
    47  	// 10240 NUL bytes is a valid empty tar archive.
    48  	_, err = io.Copy(layerFile, io.LimitReader(zeroReader{}, 10240))
    49  	if err != nil {
    50  		return err
    51  	}
    52  
    53  	return nil
    54  }
    55  
    56  type zeroReader struct{}
    57  
    58  func (_ zeroReader) Read(p []byte) (n int, err error) {
    59  	l := len(p)
    60  	for idx := 0; idx < l; idx++ {
    61  		p[idx] = 0
    62  	}
    63  	return l, nil
    64  }