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mount.go
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mount.go
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package gokrazy
import (
"encoding/json"
"fmt"
"io/ioutil"
"log"
"os"
"path/filepath"
"strconv"
"strings"
"syscall"
"time"
"github.com/gokrazy/internal/config"
"github.com/gokrazy/internal/gpt"
"github.com/gokrazy/internal/rootdev"
)
// mountCompat deals with old FAT root file systems, to cover the case where
// users use an old gokr-packer with a new github.com/gokrazy/gokrazy package.
func mountCompat() error {
// Symlink /etc/resolv.conf. We cannot do this in the root file
// system itself, as FAT does not support symlinks.
if err := syscall.Mount("tmpfs", "/etc", "tmpfs", syscall.MS_NOSUID|syscall.MS_NODEV|syscall.MS_RELATIME, "size=1M"); err != nil {
return fmt.Errorf("tmpfs on /etc: %v", err)
}
if err := os.Symlink("/proc/net/pnp", "/etc/resolv.conf"); err != nil {
return fmt.Errorf("etc: %v", err)
}
// Symlink /etc/localtime. We cannot do this in the root file
// system, as FAT filenames are limited to 8.3.
if err := os.Symlink("/localtim", "/etc/localtime"); err != nil {
return fmt.Errorf("etc: %v", err)
}
if err := os.Mkdir("/etc/ssl", 0755); err != nil {
return fmt.Errorf("/etc/ssl: %v", err)
}
if err := os.Symlink("/cacerts", "/etc/ssl/ca-bundle.pem"); err != nil {
return fmt.Errorf("/etc/ssl: %v", err)
}
if err := ioutil.WriteFile("/etc/hosts", []byte("127.0.0.1 localhost\n::1 localhost\n"), 0644); err != nil {
return fmt.Errorf("/etc/hosts: %v", err)
}
return nil
}
func mountfs() error {
if err := syscall.Mount("tmpfs", "/tmp", "tmpfs", syscall.MS_NOSUID|syscall.MS_NODEV|syscall.MS_RELATIME, ""); err != nil {
return fmt.Errorf("tmpfs on /tmp: %v", err)
}
if err := os.Symlink("/proc/net/pnp", "/tmp/resolv.conf"); err != nil {
return fmt.Errorf("etc: %v", err)
}
if _, err := os.Lstat("/etc/resolv.conf"); err != nil && os.IsNotExist(err) {
if err := mountCompat(); err != nil {
return err
}
}
if err := syscall.Mount("devtmpfs", "/dev", "devtmpfs", 0, ""); err != nil {
if sce, ok := err.(syscall.Errno); ok && sce == syscall.EBUSY {
// /dev was already mounted (common in setups using nfsroot= or initramfs)
} else {
return fmt.Errorf("devtmpfs: %v", err)
}
}
if err := os.MkdirAll("/dev/pts", 0755); err != nil {
return fmt.Errorf("mkdir /dev/pts: %v", err)
}
if err := syscall.Mount("devpts", "/dev/pts", "devpts", 0, ""); err != nil {
return fmt.Errorf("devpts: %v", err)
}
if err := os.MkdirAll("/dev/shm", 0755); err != nil {
return fmt.Errorf("mkdir /dev/shm: %v", err)
}
if err := syscall.Mount("tmpfs", "/dev/shm", "tmpfs", 0, ""); err != nil {
return fmt.Errorf("tmpfs on /dev/shm: %v", err)
}
if err := syscall.Mount("tmpfs", "/run", "tmpfs", 0, ""); err != nil {
log.Printf("tmpfs on /run: %v", err)
}
// /proc is useful for exposing process details and for
// interactive debugging sessions.
if err := syscall.Mount("proc", "/proc", "proc", 0, ""); err != nil {
if sce, ok := err.(syscall.Errno); ok && sce == syscall.EBUSY {
// /proc was already mounted (common in setups using nfsroot= or initramfs)
} else {
return fmt.Errorf("proc: %v", err)
}
}
// /sys is useful for retrieving additional status from the
// kernel, e.g. ethernet device carrier status.
if err := syscall.Mount("sysfs", "/sys", "sysfs", 0, ""); err != nil {
if sce, ok := err.(syscall.Errno); ok && sce == syscall.EBUSY {
// /sys was already mounted (common in setups using nfsroot= or initramfs)
} else {
return fmt.Errorf("sys: %v", err)
}
}
dev := rootdev.Partition(rootdev.Perm)
for _, fstype := range []string{"ext4", "vfat", "bcachefs"} {
if err := syscall.Mount(dev, "/perm", fstype, 0, ""); err != nil {
log.Printf("Could not mount permanent storage partition %s as %s: %v", dev, fstype, err)
} else {
break
}
}
// Create /perm/var if needed so that the /var symlink resolves
if err := os.MkdirAll("/perm/var", 0755); err != nil {
log.Printf("mkdir /perm/var: %v", err)
}
if err := os.Symlink("/run", "/perm/var/run"); err != nil && !os.IsExist(err) {
log.Printf("symlink /perm/var/run to /run: %v", err)
}
if err := syscall.Mount("cgroup2", "/sys/fs/cgroup", "cgroup2", 0, ""); err != nil {
log.Printf("cgroup2 on /sys/fs/cgroup: %v", err)
}
if err := mountDevices(); err != nil {
log.Printf("mountDevices: %v", err)
}
return nil
}
func findGPTPartUUID(uuid string) (_ string, _ error) {
var dev string
uuid = strings.ToLower(uuid)
err := filepath.Walk("/sys/block", func(path string, info os.FileInfo, err error) error {
if err != nil {
log.Printf("findGPTPartUUID: %v", err)
return nil
}
if info.Mode()&os.ModeSymlink == 0 {
return nil
}
devname := "/dev/" + filepath.Base(path)
f, err := os.Open(devname)
if err != nil {
log.Printf("findGPTPartUUID: %v", err)
return nil
}
defer f.Close()
for idx, partUUID := range gpt.PartitionUUIDs(f) {
if strings.ToLower(partUUID) != uuid {
continue
}
dev = devname
if (strings.HasPrefix(dev, "/dev/mmcblk") ||
strings.HasPrefix(dev, "/dev/loop") ||
strings.HasPrefix(dev, "/dev/nvme")) &&
!strings.HasSuffix(dev, "p") {
dev += "p"
}
dev += strconv.Itoa(idx + 1)
// TODO: abort early with sentinel error code
return nil
}
return nil
})
if err != nil {
return "", err
}
if dev == "" {
return "", fmt.Errorf("PARTUUID=%s not found", uuid)
}
return dev, nil
}
func deviceForSource(source string) (string, error) {
if strings.HasPrefix(source, "PARTUUID=") {
return findGPTPartUUID(strings.TrimPrefix(source, "PARTUUID="))
}
return source, nil
}
func mountDevice(md config.MountDevice) error {
dev, err := deviceForSource(md.Source)
if err != nil {
return err
}
log.Printf("mounting %s on %s", dev, md.Target)
if err := syscall.Mount(dev, md.Target, md.Type, 0, ""); err != nil {
return err
}
return nil
}
// mountDevices mounts the user-specified devices. The packer persists them from
// the instance config to mountdevices.json.
func mountDevices() error {
b, err := os.ReadFile("/etc/gokrazy/mountdevices.json")
if err != nil {
if os.IsNotExist(err) {
return nil // packer too old
}
return fmt.Errorf("reading mountdevices.json: %v", err)
}
var mountdevices []config.MountDevice
if err := json.Unmarshal(b, &mountdevices); err != nil {
return err
}
// Start one goroutine per mount device
for _, md := range mountdevices {
md := md // remove once we are on Go 1.22
go func() {
for {
err := mountDevice(md)
if err == nil {
return
}
log.Printf("mounting %s: %v", md.Source, err)
time.Sleep(1 * time.Second)
}
}()
}
return nil
}