Add support for PEBBLE_INIT_FROM.

`PEBBLE_INIT_FROM` allows `pebble run` to copy layers and state from
another directory when seeding a new `PEBBLE` directory.

go.mod

@@ -7,9 +7,10 @@ require (
 	github.com/canonical/x-go v0.0.0-20230522092633-7947a7587f5b
 	github.com/gorilla/mux v1.8.0
 	github.com/gorilla/websocket v1.4.2
+	github.com/otiai10/copy v1.14.0
 	github.com/pkg/term v1.1.0
 	golang.org/x/crypto v0.0.0-20220314234659-1baeb1ce4c0b
-	golang.org/x/sys v0.5.0
+	golang.org/x/sys v0.16.0
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c
 	gopkg.in/tomb.v2 v2.0.0-20161208151619-d5d1b5820637
 	gopkg.in/yaml.v3 v3.0.1
@@ -19,6 +20,7 @@ require (
 	github.com/kr/pretty v0.2.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	golang.org/x/net v0.7.0 // indirect
+	golang.org/x/sync v0.6.0 // indirect
 	golang.org/x/term v0.5.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 )

go.sum

@@ -13,16 +13,21 @@ github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/otiai10/copy v1.14.0 h1:dCI/t1iTdYGtkvCuBG2BgR6KZa83PTclw4U5n2wAllU=
+github.com/otiai10/copy v1.14.0/go.mod h1:ECfuL02W+/FkTWZWgQqXPWZgW9oeKCSQ5qVfSc4qc4w=
+github.com/otiai10/mint v1.5.1 h1:XaPLeE+9vGbuyEHem1JNk3bYc7KKqyI/na0/mLd/Kks=
 github.com/pkg/term v1.1.0 h1:xIAAdCMh3QIAy+5FrE8Ad8XoDhEU4ufwbaSozViP9kk=
 github.com/pkg/term v1.1.0/go.mod h1:E25nymQcrSllhX42Ok8MRm1+hyBdHY0dCeiKZ9jpNGw=
 golang.org/x/crypto v0.0.0-20220314234659-1baeb1ce4c0b h1:Qwe1rC8PSniVfAFPFJeyUkB+zcysC3RgJBAGk7eqBEU=
 golang.org/x/crypto v0.0.0-20220314234659-1baeb1ce4c0b/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/net v0.7.0 h1:rJrUqqhjsgNp7KqAIc25s9pZnjU7TUcSY7HcVZjdn1g=
 golang.org/x/net v0.7.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
+golang.org/x/sync v0.6.0 h1:5BMeUDZ7vkXGfEr1x9B4bRcTH4lpkTkpdh0T/J+qjbQ=
+golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20200909081042-eff7692f9009/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210320140829-1e4c9ba3b0c4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.5.0 h1:MUK/U/4lj1t1oPg0HfuXDN/Z1wv31ZJ/YcPiGccS4DU=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
+golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.5.0 h1:n2a8QNdAb0sZNpU9R1ALUXBbY+w51fCQDN+7EdxNBsY=
 golang.org/x/term v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

internals/cli/cli.go

@@ -375,6 +375,10 @@ func getEnvPaths() (pebbleDir string, socketPath string) {
 	return pebbleDir, socketPath
 }
 
+func getCopySource() string {
+	return os.Getenv("PEBBLE_INIT_FROM")
+}
+
 type cliState struct {
 	NoticesLastListed time.Time `json:"notices-last-listed"`
 	NoticesLastOkayed time.Time `json:"notices-last-okayed"`

internals/cli/cmd_run.go

@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/canonical/go-flags"
+	"github.com/otiai10/copy"
 
 	"github.com/canonical/pebble/client"
 	"github.com/canonical/pebble/cmd"
@@ -157,6 +158,11 @@ func runDaemon(rcmd *cmdRun, ch chan os.Signal, ready chan<- func()) error {
 			return err
 		}
 	}
+	err := maybeCopyPebbleDir(getCopySource(), pebbleDir)
+	if err != nil {
+		return err
+	}
+
 	dopts := daemon.Options{
 		Dir:        pebbleDir,
 		SocketPath: socketPath,
@@ -275,3 +281,35 @@ func convertArgs(args [][]string) (map[string][]string, error) {
 
 	return mappedArgs, nil
 }
+
+func maybeCopyPebbleDir(srcDir, destDir string) error {
+	if srcDir == "" {
+		return nil
+	}
+	dirEnts, err := os.ReadDir(destDir)
+	if err != nil {
+		return err
+	}
+	if len(dirEnts) != 0 {
+		return nil
+	}
+	err = copy.Copy(srcDir, destDir, copy.Options{
+		OnSymlink:         func(src string) copy.SymlinkAction { return copy.Shallow },
+		OnDirExists:       func(src, dest string) copy.DirExistsAction { return copy.Merge },
+		PermissionControl: copy.PerservePermission,
+		Skip: func(srcInfo os.FileInfo, src, dest string) (bool, error) {
+			if srcInfo.Mode()&os.ModeSetuid != 0 {
+				return true, fmt.Errorf("cannot copy file %q to %q with setuid bit", src, dest)
+			}
+			if srcInfo.Mode()&os.ModeSetgid != 0 {
+				return true, fmt.Errorf("cannot copy file %q to %q with setgid bit", src, dest)
+			}
+			return false, nil
+		},
+		PreserveOwner: false,
+	})
+	if err != nil {
+		return fmt.Errorf("cannot copy %q to %q: %w", srcDir, destDir, err)
+	}
+	return nil
+}