diff --git a/.gitignore b/.gitignore index 0930bb2..aeddf46 100644 --- a/.gitignore +++ b/.gitignore @@ -1,3 +1,4 @@ +/undocker /undocker-* coverage.html sha256sum.txt* diff --git a/main.go b/main.go index 661d3f0..472f763 100644 --- a/main.go +++ b/main.go @@ -2,6 +2,7 @@ package main import ( + "flag" "fmt" "io" "os" @@ -15,33 +16,56 @@ var Version = "unknown" var VersionHash = "unknown" const _usage = `Usage: - %s + %s [OPTION]... Flatten a Docker container image to a root file system. Arguments: - : Input Docker container. Tarball. - : Output tarball, the root file system. '-' is stdout. + Input Docker container. Tarball. + Output tarball, the root file system. '-' is stdout. + +Options: + --prefix= prefix all destination files with a given string. undocker %s (%s) Built with %s ` +func usage(pre string, out io.Writer) { + fmt.Fprintf(out, pre+_usage, + filepath.Base(os.Args[0]), + Version, + VersionHash, + runtime.Version(), + ) +} + +func usageErr(pre string) { + usage(pre, os.Stderr) + os.Exit(2) +} + func main() { runtime.GOMAXPROCS(1) // no need to create that many threads - if len(os.Args) != 3 { - fmt.Fprintf(os.Stderr, _usage, - filepath.Base(os.Args[0]), - Version, - VersionHash, - runtime.Version(), - ) - os.Exit(1) + var filePrefix string + fs := flag.NewFlagSet("undocker", flag.ExitOnError) + fs.Usage = func() { usageErr("") } + fs.StringVar(&filePrefix, "prefix", "", "prefix files in the tarball") + + if len(os.Args) == 1 { + usageErr("") + } + + _ = fs.Parse(os.Args[1:]) // ExitOnError captures it + + args := fs.Args() + if len(args) != 2 { + usageErr("invalid number of arguments\n") } c := &command{flattener: rootfs.Flatten, Stdout: os.Stdout} - if err := c.execute(os.Args[1], os.Args[2]); err != nil { + if err := c.execute(args[0], args[1], filePrefix); err != nil { fmt.Printf("Error: %v\n", err) os.Exit(1) } @@ -49,11 +73,11 @@ func main() { } type command struct { - flattener func(io.ReadSeeker, io.Writer) error + flattener func(io.ReadSeeker, io.Writer, ...rootfs.Option) error Stdout io.Writer } -func (c *command) execute(infile string, outfile string) (_err error) { +func (c *command) execute(infile, outfile, filePrefix string) (_err error) { rd, err := os.Open(infile) if err != nil { return err @@ -84,5 +108,5 @@ func (c *command) execute(infile string, outfile string) (_err error) { out = outf } - return c.flattener(rd, out) + return c.flattener(rd, out, rootfs.WithFilePrefix(filePrefix)) } diff --git a/main_test.go b/main_test.go index 020aea8..16d1568 100644 --- a/main_test.go +++ b/main_test.go @@ -9,6 +9,8 @@ import ( "path/filepath" "regexp" "testing" + + "git.sr.ht/~motiejus/undocker/rootfs" ) func TestExecute(t *testing.T) { @@ -17,7 +19,7 @@ func TestExecute(t *testing.T) { tests := []struct { name string fixture func(*testing.T, string) - flattener func(io.ReadSeeker, io.Writer) error + flattener func(io.ReadSeeker, io.Writer, ...rootfs.Option) error infile string outfile string wantErr string @@ -99,7 +101,7 @@ func TestExecute(t *testing.T) { inf := filepath.Join(dir, tt.infile) c := &command{Stdout: &stdout, flattener: tt.flattener} - err := c.execute(inf, tt.outfile) + err := c.execute(inf, tt.outfile, "") if tt.assertion != nil { tt.assertion(t, dir) @@ -135,11 +137,11 @@ func TestExecute(t *testing.T) { } } -func flattenPassthrough(r io.ReadSeeker, w io.Writer) error { +func flattenPassthrough(r io.ReadSeeker, w io.Writer, _ ...rootfs.Option) error { _, err := io.Copy(w, r) return err } -func flattenBad(_ io.ReadSeeker, _ io.Writer) error { +func flattenBad(_ io.ReadSeeker, _ io.Writer, _ ...rootfs.Option) error { return errors.New("some error") } diff --git a/rootfs/options.go b/rootfs/options.go new file mode 100644 index 0000000..f927911 --- /dev/null +++ b/rootfs/options.go @@ -0,0 +1,20 @@ +package rootfs + +type options struct { + filePrefix string +} + +type Option interface { + apply(*options) +} + +type filePrefixOption string + +func (p filePrefixOption) apply(opts *options) { + opts.filePrefix = string(p) +} + +// WithFilePrefixOption adds a prefix to all files in the output archive. +func WithFilePrefix(p string) Option { + return filePrefixOption(p) +} diff --git a/rootfs/rootfs.go b/rootfs/rootfs.go index f8aee15..4a017e7 100644 --- a/rootfs/rootfs.go +++ b/rootfs/rootfs.go @@ -35,7 +35,14 @@ type ( // Flatten flattens a docker image to a tarball. The underlying io.Writer // should be an open file handle, which the caller is responsible for closing // themselves -func Flatten(rd io.ReadSeeker, w io.Writer) (_err error) { +func Flatten(rd io.ReadSeeker, w io.Writer, opts ...Option) (_err error) { + options := options{ + filePrefix: "", + } + for _, o := range opts { + o.apply(&options) + } + tr := tar.NewReader(rd) var closer func() error var err error @@ -177,7 +184,8 @@ func Flatten(rd io.ReadSeeker, w io.Writer) (_err error) { if hdr.Typeflag != tar.TypeDir && file2layer[hdr.Name] != i { continue } - if err := writeFile(tr, tw, hdr); err != nil { + prefix := options.filePrefix + if err := writeFile(tr, tw, hdr, prefix); err != nil { return err } } @@ -188,10 +196,10 @@ func Flatten(rd io.ReadSeeker, w io.Writer) (_err error) { return nil } -func writeFile(tr *tar.Reader, tw *tar.Writer, hdr *tar.Header) error { +func writeFile(tr *tar.Reader, tw *tar.Writer, hdr *tar.Header, prefix string) error { hdrOut := &tar.Header{ Typeflag: hdr.Typeflag, - Name: hdr.Name, + Name: prefix + hdr.Name, Linkname: hdr.Linkname, Size: hdr.Size, Mode: int64(hdr.Mode & 0777), diff --git a/rootfs/rootfs_test.go b/rootfs/rootfs_test.go index df6b178..42f4514 100644 --- a/rootfs/rootfs_test.go +++ b/rootfs/rootfs_test.go @@ -34,6 +34,7 @@ func TestRootFS(t *testing.T) { tests := []struct { name string + opts []Option image tarball want []extractable wantErr string @@ -54,7 +55,7 @@ func TestRootFS(t *testing.T) { wantErr: "layer0/layer.tar defined in manifest, missing in tarball", }, { - name: "basic file overwrite, layer order mixed", + name: "ok: basic file overwrite, layer order mixed", image: tarball{ file{Name: "layer1/layer.tar", Contents: layer1.Buffer()}, file{Name: "layer0/layer.tar", Contents: layer0.Buffer()}, @@ -172,7 +173,7 @@ func TestRootFS(t *testing.T) { }, }, { - name: "archived layer", + name: "compressed layer", image: tarball{ file{Name: "layer1/layer.tar", Contents: layer1.Gzip()}, file{Name: "layer0/layer.tar", Contents: layer0.Gzip()}, @@ -183,6 +184,19 @@ func TestRootFS(t *testing.T) { file{Name: "/file", UID: 1, Contents: bytes.NewBufferString("from 1")}, }, }, + { + name: "ok: add a file prefix", + opts: []Option{WithFilePrefix("/opt")}, + image: tarball{ + file{Name: "layer1/layer.tar", Contents: layer1.Buffer()}, + file{Name: "layer0/layer.tar", Contents: layer0.Buffer()}, + manifest{"layer0/layer.tar", "layer1/layer.tar"}, + }, + want: []extractable{ + dir{Name: "/opt/", UID: 0}, + file{Name: "/opt/file", UID: 1, Contents: bytes.NewBufferString("from 1")}, + }, + }, } for _, tt := range tests { @@ -190,7 +204,7 @@ func TestRootFS(t *testing.T) { in := bytes.NewReader(tt.image.Buffer().Bytes()) out := bytes.Buffer{} - err := Flatten(in, &out) + err := Flatten(in, &out, tt.opts...) if tt.wantErr != "" { if err == nil { t.Fatal("expected error, got nil")