245 lines
7.3 KiB
Go
245 lines
7.3 KiB
Go
// +build linux
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package mount
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import (
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"fmt"
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"os"
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"path/filepath"
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"syscall"
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"github.com/docker/docker/pkg/symlink"
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"github.com/docker/libcontainer/label"
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"github.com/docker/libcontainer/mount/nodes"
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)
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// default mount point flags
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const defaultMountFlags = syscall.MS_NOEXEC | syscall.MS_NOSUID | syscall.MS_NODEV
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type mount struct {
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source string
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path string
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device string
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flags int
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data string
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}
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// InitializeMountNamespace sets up the devices, mount points, and filesystems for use inside a
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// new mount namespace.
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func InitializeMountNamespace(rootfs, console string, sysReadonly bool, mountConfig *MountConfig) error {
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var (
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err error
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flag = syscall.MS_PRIVATE
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)
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if mountConfig.NoPivotRoot {
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flag = syscall.MS_SLAVE
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}
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if err := syscall.Mount("", "/", "", uintptr(flag|syscall.MS_REC), ""); err != nil {
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return fmt.Errorf("mounting / with flags %X %s", (flag | syscall.MS_REC), err)
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}
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if err := syscall.Mount(rootfs, rootfs, "bind", syscall.MS_BIND|syscall.MS_REC, ""); err != nil {
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return fmt.Errorf("mouting %s as bind %s", rootfs, err)
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}
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if err := mountSystem(rootfs, sysReadonly, mountConfig); err != nil {
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return fmt.Errorf("mount system %s", err)
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}
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if err := setupBindmounts(rootfs, mountConfig); err != nil {
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return fmt.Errorf("bind mounts %s", err)
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}
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if err := nodes.CreateDeviceNodes(rootfs, mountConfig.DeviceNodes); err != nil {
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return fmt.Errorf("create device nodes %s", err)
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}
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if err := SetupPtmx(rootfs, console, mountConfig.MountLabel); err != nil {
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return err
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}
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// stdin, stdout and stderr could be pointing to /dev/null from parent namespace.
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// Re-open them inside this namespace.
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if err := reOpenDevNull(rootfs); err != nil {
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return fmt.Errorf("Failed to reopen /dev/null %s", err)
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}
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if err := setupDevSymlinks(rootfs); err != nil {
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return fmt.Errorf("dev symlinks %s", err)
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}
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if err := syscall.Chdir(rootfs); err != nil {
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return fmt.Errorf("chdir into %s %s", rootfs, err)
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}
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if mountConfig.NoPivotRoot {
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err = MsMoveRoot(rootfs)
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} else {
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err = PivotRoot(rootfs)
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}
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if err != nil {
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return err
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}
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if mountConfig.ReadonlyFs {
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if err := SetReadonly(); err != nil {
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return fmt.Errorf("set readonly %s", err)
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}
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}
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syscall.Umask(0022)
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return nil
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}
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// mountSystem sets up linux specific system mounts like sys, proc, shm, and devpts
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// inside the mount namespace
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func mountSystem(rootfs string, sysReadonly bool, mountConfig *MountConfig) error {
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for _, m := range newSystemMounts(rootfs, mountConfig.MountLabel, sysReadonly, mountConfig.Mounts) {
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if err := os.MkdirAll(m.path, 0755); err != nil && !os.IsExist(err) {
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return fmt.Errorf("mkdirall %s %s", m.path, err)
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}
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if err := syscall.Mount(m.source, m.path, m.device, uintptr(m.flags), m.data); err != nil {
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return fmt.Errorf("mounting %s into %s %s", m.source, m.path, err)
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}
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}
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return nil
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}
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func createIfNotExists(path string, isDir bool) error {
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if _, err := os.Stat(path); err != nil {
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if os.IsNotExist(err) {
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if isDir {
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if err := os.MkdirAll(path, 0755); err != nil {
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return err
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}
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} else {
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if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
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return err
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}
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f, err := os.OpenFile(path, os.O_CREATE, 0755)
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if err != nil {
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return err
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}
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f.Close()
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}
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}
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}
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return nil
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}
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func setupDevSymlinks(rootfs string) error {
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var links = [][2]string{
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{"/proc/self/fd", "/dev/fd"},
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{"/proc/self/fd/0", "/dev/stdin"},
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{"/proc/self/fd/1", "/dev/stdout"},
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{"/proc/self/fd/2", "/dev/stderr"},
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}
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// kcore support can be toggled with CONFIG_PROC_KCORE; only create a symlink
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// in /dev if it exists in /proc.
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if _, err := os.Stat("/proc/kcore"); err == nil {
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links = append(links, [2]string{"/proc/kcore", "/dev/kcore"})
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}
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for _, link := range links {
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var (
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src = link[0]
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dst = filepath.Join(rootfs, link[1])
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)
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if err := os.Symlink(src, dst); err != nil && !os.IsExist(err) {
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return fmt.Errorf("symlink %s %s %s", src, dst, err)
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}
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}
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return nil
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}
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func setupBindmounts(rootfs string, mountConfig *MountConfig) error {
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bindMounts := mountConfig.Mounts
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for _, m := range bindMounts.OfType("bind") {
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var (
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flags = syscall.MS_BIND | syscall.MS_REC
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dest = filepath.Join(rootfs, m.Destination)
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)
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if !m.Writable {
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flags = flags | syscall.MS_RDONLY
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}
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stat, err := os.Stat(m.Source)
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if err != nil {
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return err
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}
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dest, err = symlink.FollowSymlinkInScope(dest, rootfs)
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if err != nil {
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return err
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}
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if err := createIfNotExists(dest, stat.IsDir()); err != nil {
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return fmt.Errorf("Creating new bind-mount target, %s", err)
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}
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if err := syscall.Mount(m.Source, dest, "bind", uintptr(flags), ""); err != nil {
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return fmt.Errorf("mounting %s into %s %s", m.Source, dest, err)
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}
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if !m.Writable {
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if err := syscall.Mount(m.Source, dest, "bind", uintptr(flags|syscall.MS_REMOUNT), ""); err != nil {
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return fmt.Errorf("remounting %s into %s %s", m.Source, dest, err)
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}
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}
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if m.Relabel != "" {
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if err := label.Relabel(m.Source, mountConfig.MountLabel, m.Relabel); err != nil {
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return fmt.Errorf("relabeling %s to %s %s", m.Source, mountConfig.MountLabel, err)
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}
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}
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if m.Private {
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if err := syscall.Mount("", dest, "none", uintptr(syscall.MS_PRIVATE), ""); err != nil {
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return fmt.Errorf("mounting %s private %s", dest, err)
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}
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}
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}
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return nil
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}
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// TODO: this is crappy right now and should be cleaned up with a better way of handling system and
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// standard bind mounts allowing them to be more dynamic
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func newSystemMounts(rootfs, mountLabel string, sysReadonly bool, mounts Mounts) []mount {
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systemMounts := []mount{
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{source: "proc", path: filepath.Join(rootfs, "proc"), device: "proc", flags: defaultMountFlags},
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{source: "tmpfs", path: filepath.Join(rootfs, "dev"), device: "tmpfs", flags: syscall.MS_NOSUID | syscall.MS_STRICTATIME, data: label.FormatMountLabel("mode=755", mountLabel)},
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{source: "shm", path: filepath.Join(rootfs, "dev", "shm"), device: "tmpfs", flags: defaultMountFlags, data: label.FormatMountLabel("mode=1777,size=65536k", mountLabel)},
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{source: "devpts", path: filepath.Join(rootfs, "dev", "pts"), device: "devpts", flags: syscall.MS_NOSUID | syscall.MS_NOEXEC, data: label.FormatMountLabel("newinstance,ptmxmode=0666,mode=620,gid=5", mountLabel)},
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}
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sysMountFlags := defaultMountFlags
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if sysReadonly {
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sysMountFlags |= syscall.MS_RDONLY
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}
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systemMounts = append(systemMounts, mount{source: "sysfs", path: filepath.Join(rootfs, "sys"), device: "sysfs", flags: sysMountFlags})
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return systemMounts
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}
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// Is stdin, stdout or stderr were to be pointing to '/dev/null',
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// this method will make them point to '/dev/null' from within this namespace.
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func reOpenDevNull(rootfs string) error {
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var stat, devNullStat syscall.Stat_t
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file, err := os.Open(filepath.Join(rootfs, "/dev/null"))
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if err != nil {
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return fmt.Errorf("Failed to open /dev/null - %s", err)
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}
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defer file.Close()
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if err = syscall.Fstat(int(file.Fd()), &devNullStat); err != nil {
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return fmt.Errorf("Failed to stat /dev/null - %s", err)
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}
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for fd := 0; fd < 3; fd++ {
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if err = syscall.Fstat(fd, &stat); err != nil {
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return fmt.Errorf("Failed to stat fd %d - %s", fd, err)
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}
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if stat.Rdev == devNullStat.Rdev {
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// Close and re-open the fd.
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if err = syscall.Dup2(int(file.Fd()), fd); err != nil {
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return fmt.Errorf("Failed to dup fd %d to fd %d - %s", file.Fd(), fd)
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}
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}
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}
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return nil
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}
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