pkg: Add extend for extending partitions

This was split out from pkg/format into its own package.
It has the ability to extend ext4, btrfs and xfs partitions.

Signed-off-by: Dave Tucker <dt@docker.com>

pkg/extend/Dockerfile

@@ -0,0 +1,33 @@
+FROM linuxkit/alpine:488aa6f5dd2d8121a3c5c5c7a1ecf97c424b96ac AS mirror
+
+RUN mkdir -p /out/etc/apk && cp -r /etc/apk/* /out/etc/apk/
+RUN apk add --no-cache --initdb -p /out \
+    alpine-baselayout \
+    busybox \
+    e2fsprogs \
+    e2fsprogs-extra \
+    btrfs-progs \
+    xfsprogs \
+    xfsprogs-extra \
+    musl \
+    sfdisk \
+    util-linux \
+    && true
+RUN rm -rf /out/etc/apk /out/lib/apk /out/var/cache
+
+FROM linuxkit/alpine:488aa6f5dd2d8121a3c5c5c7a1ecf97c424b96ac AS build
+
+RUN apk add --no-cache go musl-dev
+ENV GOPATH=/go PATH=$PATH:/go/bin
+
+COPY extend.go /go/src/extend/
+RUN go-compile.sh /go/src/extend
+
+FROM scratch
+ENTRYPOINT []
+CMD []
+WORKDIR /
+COPY --from=mirror /out/ /
+COPY --from=build /go/bin/extend usr/bin/extend
+CMD ["/usr/bin/extend"]
+LABEL org.mobyproject.config='{"binds": ["/dev:/dev"], "capabilities": ["CAP_SYS_ADMIN", "CAP_MKNOD"], "net": "new", "ipc": "new"}'

pkg/extend/Makefile

@@ -0,0 +1,4 @@
+IMAGE=extend
+DEPS=extend.go
+
+include ../package.mk

pkg/extend/extend.go

@@ -0,0 +1,290 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"sort"
+	"strings"
+	"syscall"
+	"time"
+)
+
+const timeout = 60
+
+var (
+	fsTypeVar string
+	driveKeys []string
+)
+
+// Fdisk is the JSON output from libfdisk
+type Fdisk struct {
+	PartitionTable struct {
+		Label      string `json:"label"`
+		ID         string `json:"id"`
+		Device     string `json:"device"`
+		Unit       string `json:"unit"`
+		FirstLBA   int    `json:"firstlba"`
+		LastLBA    int    `json:"lastlba"`
+		Partitions []Partition
+	} `json:"partitionTable"`
+}
+
+// Partition represents a single partition
+type Partition struct {
+	Node  string `json:"node"`
+	Start int    `json:"start"`
+	Size  int    `json:"size"`
+	Type  string `json:"type"`
+	UUID  string `json:"uuid"`
+	Name  string `json:"name"`
+}
+
+func autoextend(fsType string) error {
+	for _, d := range driveKeys {
+		err := exec.Command("sfdisk", "-d", d).Run()
+		if err != nil {
+			log.Printf("No partition table found on device %s. Skipping.", d)
+			continue
+		}
+		if err := extend(d, fsType); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func extend(d, fsType string) error {
+	mountpoint := "/mnt/tmp"
+
+	data, err := exec.Command("sfdisk", "-J", d).Output()
+	if err != nil {
+		log.Fatalf("Unable to get drive data for %s from sfdisk: %v", d, err)
+	}
+
+	f := Fdisk{}
+	if err := json.Unmarshal(data, &f); err != nil {
+		return fmt.Errorf("Unable to unmarshal partition table from sfdisk: %v", err)
+	}
+
+	if len(f.PartitionTable.Partitions) > 1 {
+		log.Printf("Disk %s has more than 1 partition. Skipping", d)
+		return nil
+	}
+
+	partition := f.PartitionTable.Partitions[0]
+	if partition.Type != "83" {
+		return fmt.Errorf("Partition 1 on disk %s is not a Linux Partition", d)
+	}
+
+	if partition.Start+partition.Size == f.PartitionTable.LastLBA {
+		log.Printf("No free space on device to extend partition")
+		return nil
+	}
+
+	switch fsType {
+	case "ext4":
+		if err := e2fsck(partition.Node, false); err != nil {
+			return fmt.Errorf("Initial e2fsck failed: %v", err)
+		}
+		// resize2fs fails unless we set force=true here
+		if err := e2fsck(partition.Node, true); err != nil {
+			return fmt.Errorf("e2fsck before resize failed: %v", err)
+		}
+
+		if err := createPartition(d, partition); err != nil {
+			return err
+		}
+
+		if err := exec.Command("resize2fs", partition.Node).Run(); err != nil {
+			return fmt.Errorf("Error running resize2fs: %v", err)
+		}
+
+		if err := e2fsck(partition.Node, false); err != nil {
+			return fmt.Errorf("e2fsck after resize failed: %v", err)
+		}
+	case "btrfs":
+		// We don't check btrfs before or after mount as it's less susceptible to consistency errors
+		// than it's extfs cousins.
+		if err := os.MkdirAll(mountpoint, os.ModeDir); err != nil {
+			return err
+		}
+		if err := createPartition(d, partition); err != nil {
+			return err
+		}
+		if out, err := exec.Command("mount", partition.Node, mountpoint).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error mounting partition: %s", string(out))
+		}
+		if out, err := exec.Command("btrfs", "filesystem", "resize", "max", mountpoint).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error resizing partition: %s\n%s", err, string(out))
+		}
+		if out, err := exec.Command("umount", mountpoint).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error unmounting partition: %s", string(out))
+		}
+	case "xfs":
+		// We don't check xfs before mounting as the xfs_check or xfs_repair utilities
+		// should be used only if we suspect a file system consistency problem.
+		if err := os.MkdirAll(mountpoint, os.ModeDir); err != nil {
+			return err
+		}
+		if err := createPartition(d, partition); err != nil {
+			return err
+		}
+		if out, err := exec.Command("mount", partition.Node, mountpoint).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error mounting partition: %s", string(out))
+		}
+		if out, err := exec.Command("xfs_growfs", mountpoint).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error resizing partition: %s\n%s", err, string(out))
+		}
+		if out, err := exec.Command("umount", mountpoint).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error unmounting partition: %s", string(out))
+		}
+		if out, err := exec.Command("xfs_repair", "-n", partition.Node).CombinedOutput(); err != nil {
+			return fmt.Errorf("Error checking filesystem: %s", string(out))
+		}
+
+	default:
+		return fmt.Errorf("%s is not a supported filesystem", fsType)
+	}
+
+	log.Printf("Successfully resized %s", d)
+	return nil
+}
+
+func createPartition(d string, partition Partition) error {
+	if err := exec.Command("sfdisk", "-q", "--delete", d).Run(); err != nil {
+		return fmt.Errorf("Error erasing partition table: %v", err.Error())
+	}
+
+	createCmd := exec.Command("sfdisk", "-q", d)
+	createCmd.Stdin = strings.NewReader(fmt.Sprintf("%d,,83;", partition.Start))
+	if err := createCmd.Run(); err != nil {
+		return fmt.Errorf("Error creating partition table: %v", err)
+	}
+
+	if err := exec.Command("sfdisk", "-A", d, "1").Run(); err != nil {
+		return fmt.Errorf("Error making %s bootable: %v", d, err)
+	}
+
+	// update status
+	if err := exec.Command("blockdev", "--rereadpt", d).Run(); err != nil {
+		return fmt.Errorf("Error running blockdev: %v", err)
+	}
+
+	exec.Command("mdev", "-s").Run()
+
+	// wait for device
+	var done bool
+	for i := 0; i < timeout; i++ {
+		stat, err := os.Stat(partition.Node)
+		if err == nil {
+			mode := stat.Sys().(*syscall.Stat_t).Mode
+			if (mode & syscall.S_IFMT) == syscall.S_IFBLK {
+				done = true
+				break
+			}
+		}
+		time.Sleep(100 * time.Millisecond)
+		exec.Command("mdev", "-s").Run()
+	}
+	if !done {
+		return fmt.Errorf("Error waiting for device %s", partition.Node)
+	}
+	// even after the device appears we still have a race
+	time.Sleep(1 * time.Second)
+	return nil
+}
+
+func e2fsck(d string, force bool) error {
+	// preen
+	args := []string{"-p"}
+	if force {
+		args = append(args, "-f")
+	}
+	args = append(args, d)
+	if err := exec.Command("e2fsck", args...).Run(); err != nil {
+		if exiterr, ok := err.(*exec.ExitError); ok {
+			status, ok := exiterr.Sys().(syscall.WaitStatus)
+			if !ok {
+				return fmt.Errorf("Unable to get status code from e2fsck")
+			}
+			switch status.ExitStatus() {
+			case 1:
+				return nil
+			case 2, 3:
+				return fmt.Errorf("e2fsck fixed errors but requires a reboot")
+			}
+		} else {
+			return fmt.Errorf("Unable to cast err to ExitError")
+		}
+	}
+
+	// exit code was > 4. try harder
+	args[0] = "-y"
+	if err := exec.Command("/sbin/e2fsck", args...).Run(); err != nil {
+		if exiterr, ok := err.(*exec.ExitError); ok {
+			status, ok := exiterr.Sys().(syscall.WaitStatus)
+			if !ok {
+				return fmt.Errorf("Unable to get status code from e2fsck")
+			}
+			switch status.ExitStatus() {
+			case 1:
+				return nil
+			case 2, 3:
+				return fmt.Errorf("e2fsck fixed errors but requires a reboot")
+			default:
+				return fmt.Errorf("e2fsck exited with fatal error: %v", err)
+			}
+		} else {
+			return fmt.Errorf("Unable to cast err to ExitError")
+		}
+	}
+	return nil
+}
+
+// return a list of all available drives
+func findDrives() {
+	driveKeys = []string{}
+	ignoreExp := regexp.MustCompile(`^loop.*$|^nbd.*$|^[a-z]+[0-9]+$`)
+	devs, _ := ioutil.ReadDir("/dev")
+	for _, d := range devs {
+		// this probably shouldn't be so hard
+		// but d.Mode()&os.ModeDevice == 0 doesn't work as expected
+		mode := d.Sys().(*syscall.Stat_t).Mode
+		if (mode & syscall.S_IFMT) != syscall.S_IFBLK {
+			continue
+		}
+		// ignore if it matches regexp
+		if ignoreExp.MatchString(d.Name()) {
+			continue
+		}
+		driveKeys = append(driveKeys, filepath.Join("/dev", d.Name()))
+	}
+	sort.Strings(driveKeys)
+}
+
+func init() {
+	flag.StringVar(&fsTypeVar, "type", "ext4", "Type of filesystem to create")
+}
+
+func main() {
+	flag.Parse()
+	findDrives()
+	if flag.NArg() == 0 {
+		if err := autoextend(fsTypeVar); err != nil {
+			log.Fatalf("%v", err)
+		}
+	} else {
+		for _, arg := range flag.Args() {
+			if err := extend(arg, fsTypeVar); err != nil {
+				log.Fatalf("%v", err)
+			}
+		}
+	}
+}