diff --git a/archive/changes.go b/archive/changes.go
index 4619a4c..76c36b5 100644
--- a/archive/changes.go
+++ b/archive/changes.go
@@ -173,7 +173,7 @@ func Changes(layers []string, rw string) ([]Change, error) {
 type FileInfo struct {
 	parent     *FileInfo
 	name       string
-	stat       *system.Stat_t
+	stat       *system.StatT
 	children   map[string]*FileInfo
 	capability []byte
 	added      bool
diff --git a/archive/changes_unix.go b/archive/changes_unix.go
index d780f16..a2ccbb2 100644
--- a/archive/changes_unix.go
+++ b/archive/changes_unix.go
@@ -8,10 +8,10 @@ import (
 	"github.com/docker/docker/pkg/system"
 )
 
-func statDifferent(oldStat *system.Stat_t, newStat *system.Stat_t) bool {
+func statDifferent(oldStat *system.StatT, newStat *system.StatT) bool {
 	// Don't look at size for dirs, its not a good measure of change
 	if oldStat.Mode() != newStat.Mode() ||
-		oldStat.Uid() != newStat.Uid() ||
+		oldStat.UID() != newStat.UID() ||
 		oldStat.Gid() != newStat.Gid() ||
 		oldStat.Rdev() != newStat.Rdev() ||
 		// Don't look at size for dirs, its not a good measure of change
diff --git a/archive/changes_windows.go b/archive/changes_windows.go
index 4809b7a..135db36 100644
--- a/archive/changes_windows.go
+++ b/archive/changes_windows.go
@@ -4,7 +4,7 @@ import (
 	"github.com/docker/docker/pkg/system"
 )
 
-func statDifferent(oldStat *system.Stat_t, newStat *system.Stat_t) bool {
+func statDifferent(oldStat *system.StatT, newStat *system.StatT) bool {
 
 	// Don't look at size for dirs, its not a good measure of change
 	if oldStat.ModTime() != newStat.ModTime() ||
diff --git a/stdcopy/stdcopy.go b/stdcopy/stdcopy.go
index 684b4d4..89c64ba 100644
--- a/stdcopy/stdcopy.go
+++ b/stdcopy/stdcopy.go
@@ -9,19 +9,24 @@ import (
 )
 
 const (
-	StdWriterPrefixLen = 8
-	StdWriterFdIndex   = 0
-	StdWriterSizeIndex = 4
+	stdWriterPrefixLen = 8
+	stdWriterFdIndex   = 0
+	stdWriterSizeIndex = 4
 )
 
-type StdType [StdWriterPrefixLen]byte
+// StdType prefixes type and length to standard stream.
+type StdType [stdWriterPrefixLen]byte
 
 var (
-	Stdin  StdType = StdType{0: 0}
-	Stdout StdType = StdType{0: 1}
-	Stderr StdType = StdType{0: 2}
+	// Stdin represents standard input stream type.
+	Stdin = StdType{0: 0}
+	// Stdout represents standard output stream type.
+	Stdout = StdType{0: 1}
+	// Stderr represents standard error steam type.
+	Stderr = StdType{0: 2}
 )
 
+// StdWriter is wrapper of io.Writer with extra customized info.
 type StdWriter struct {
 	io.Writer
 	prefix  StdType
@@ -36,10 +41,10 @@ func (w *StdWriter) Write(buf []byte) (n int, err error) {
 	binary.BigEndian.PutUint32(w.prefix[4:], uint32(len(buf)))
 	n1, err = w.Writer.Write(w.prefix[:])
 	if err != nil {
-		n = n1 - StdWriterPrefixLen
+		n = n1 - stdWriterPrefixLen
 	} else {
 		n2, err = w.Writer.Write(buf)
-		n = n1 + n2 - StdWriterPrefixLen
+		n = n1 + n2 - stdWriterPrefixLen
 	}
 	if n < 0 {
 		n = 0
@@ -61,7 +66,7 @@ func NewStdWriter(w io.Writer, t StdType) *StdWriter {
 	}
 }
 
-var ErrInvalidStdHeader = errors.New("Unrecognized input header")
+var errInvalidStdHeader = errors.New("Unrecognized input header")
 
 // StdCopy is a modified version of io.Copy.
 //
@@ -75,7 +80,7 @@ var ErrInvalidStdHeader = errors.New("Unrecognized input header")
 // `written` will hold the total number of bytes written to `dstout` and `dsterr`.
 func StdCopy(dstout, dsterr io.Writer, src io.Reader) (written int64, err error) {
 	var (
-		buf       = make([]byte, 32*1024+StdWriterPrefixLen+1)
+		buf       = make([]byte, 32*1024+stdWriterPrefixLen+1)
 		bufLen    = len(buf)
 		nr, nw    int
 		er, ew    error
@@ -85,12 +90,12 @@ func StdCopy(dstout, dsterr io.Writer, src io.Reader) (written int64, err error)
 
 	for {
 		// Make sure we have at least a full header
-		for nr < StdWriterPrefixLen {
+		for nr < stdWriterPrefixLen {
 			var nr2 int
 			nr2, er = src.Read(buf[nr:])
 			nr += nr2
 			if er == io.EOF {
-				if nr < StdWriterPrefixLen {
+				if nr < stdWriterPrefixLen {
 					logrus.Debugf("Corrupted prefix: %v", buf[:nr])
 					return written, nil
 				}
@@ -103,7 +108,7 @@ func StdCopy(dstout, dsterr io.Writer, src io.Reader) (written int64, err error)
 		}
 
 		// Check the first byte to know where to write
-		switch buf[StdWriterFdIndex] {
+		switch buf[stdWriterFdIndex] {
 		case 0:
 			fallthrough
 		case 1:
@@ -113,30 +118,30 @@ func StdCopy(dstout, dsterr io.Writer, src io.Reader) (written int64, err error)
 			// Write on stderr
 			out = dsterr
 		default:
-			logrus.Debugf("Error selecting output fd: (%d)", buf[StdWriterFdIndex])
-			return 0, ErrInvalidStdHeader
+			logrus.Debugf("Error selecting output fd: (%d)", buf[stdWriterFdIndex])
+			return 0, errInvalidStdHeader
 		}
 
 		// Retrieve the size of the frame
-		frameSize = int(binary.BigEndian.Uint32(buf[StdWriterSizeIndex : StdWriterSizeIndex+4]))
+		frameSize = int(binary.BigEndian.Uint32(buf[stdWriterSizeIndex : stdWriterSizeIndex+4]))
 		logrus.Debugf("framesize: %d", frameSize)
 
 		// Check if the buffer is big enough to read the frame.
 		// Extend it if necessary.
-		if frameSize+StdWriterPrefixLen > bufLen {
-			logrus.Debugf("Extending buffer cap by %d (was %d)", frameSize+StdWriterPrefixLen-bufLen+1, len(buf))
-			buf = append(buf, make([]byte, frameSize+StdWriterPrefixLen-bufLen+1)...)
+		if frameSize+stdWriterPrefixLen > bufLen {
+			logrus.Debugf("Extending buffer cap by %d (was %d)", frameSize+stdWriterPrefixLen-bufLen+1, len(buf))
+			buf = append(buf, make([]byte, frameSize+stdWriterPrefixLen-bufLen+1)...)
 			bufLen = len(buf)
 		}
 
 		// While the amount of bytes read is less than the size of the frame + header, we keep reading
-		for nr < frameSize+StdWriterPrefixLen {
+		for nr < frameSize+stdWriterPrefixLen {
 			var nr2 int
 			nr2, er = src.Read(buf[nr:])
 			nr += nr2
 			if er == io.EOF {
-				if nr < frameSize+StdWriterPrefixLen {
-					logrus.Debugf("Corrupted frame: %v", buf[StdWriterPrefixLen:nr])
+				if nr < frameSize+stdWriterPrefixLen {
+					logrus.Debugf("Corrupted frame: %v", buf[stdWriterPrefixLen:nr])
 					return written, nil
 				}
 				break
@@ -148,7 +153,7 @@ func StdCopy(dstout, dsterr io.Writer, src io.Reader) (written int64, err error)
 		}
 
 		// Write the retrieved frame (without header)
-		nw, ew = out.Write(buf[StdWriterPrefixLen : frameSize+StdWriterPrefixLen])
+		nw, ew = out.Write(buf[stdWriterPrefixLen : frameSize+stdWriterPrefixLen])
 		if ew != nil {
 			logrus.Debugf("Error writing frame: %s", ew)
 			return 0, ew
@@ -161,8 +166,8 @@ func StdCopy(dstout, dsterr io.Writer, src io.Reader) (written int64, err error)
 		written += int64(nw)
 
 		// Move the rest of the buffer to the beginning
-		copy(buf, buf[frameSize+StdWriterPrefixLen:])
+		copy(buf, buf[frameSize+stdWriterPrefixLen:])
 		// Move the index
-		nr -= frameSize + StdWriterPrefixLen
+		nr -= frameSize + stdWriterPrefixLen
 	}
 }
diff --git a/system/errors.go b/system/errors.go
index 6304518..2883189 100644
--- a/system/errors.go
+++ b/system/errors.go
@@ -5,5 +5,6 @@ import (
 )
 
 var (
+	// ErrNotSupportedPlatform means the platform is not supported.
 	ErrNotSupportedPlatform = errors.New("platform and architecture is not supported")
 )
diff --git a/system/events_windows.go b/system/events_windows.go
index 23f7c61..04e2de7 100644
--- a/system/events_windows.go
+++ b/system/events_windows.go
@@ -8,11 +8,6 @@ import (
 	"unsafe"
 )
 
-const (
-	EVENT_ALL_ACCESS    = 0x1F0003
-	EVENT_MODIFY_STATUS = 0x0002
-)
-
 var (
 	procCreateEvent = modkernel32.NewProc("CreateEventW")
 	procOpenEvent   = modkernel32.NewProc("OpenEventW")
@@ -21,13 +16,14 @@ var (
 	procPulseEvent  = modkernel32.NewProc("PulseEvent")
 )
 
+// CreateEvent implements win32 CreateEventW func in golang. It will create an event object.
 func CreateEvent(eventAttributes *syscall.SecurityAttributes, manualReset bool, initialState bool, name string) (handle syscall.Handle, err error) {
 	namep, _ := syscall.UTF16PtrFromString(name)
-	var _p1 uint32 = 0
+	var _p1 uint32
 	if manualReset {
 		_p1 = 1
 	}
-	var _p2 uint32 = 0
+	var _p2 uint32
 	if initialState {
 		_p2 = 1
 	}
@@ -40,9 +36,10 @@ func CreateEvent(eventAttributes *syscall.SecurityAttributes, manualReset bool,
 	return
 }
 
+// OpenEvent implements win32 OpenEventW func in golang. It opens an event object.
 func OpenEvent(desiredAccess uint32, inheritHandle bool, name string) (handle syscall.Handle, err error) {
 	namep, _ := syscall.UTF16PtrFromString(name)
-	var _p1 uint32 = 0
+	var _p1 uint32
 	if inheritHandle {
 		_p1 = 1
 	}
@@ -55,14 +52,17 @@ func OpenEvent(desiredAccess uint32, inheritHandle bool, name string) (handle sy
 	return
 }
 
+// SetEvent implements win32 SetEvent func in golang.
 func SetEvent(handle syscall.Handle) (err error) {
 	return setResetPulse(handle, procSetEvent)
 }
 
+// ResetEvent implements win32 ResetEvent func in golang.
 func ResetEvent(handle syscall.Handle) (err error) {
 	return setResetPulse(handle, procResetEvent)
 }
 
+// PulseEvent implements win32 PulseEvent func in golang.
 func PulseEvent(handle syscall.Handle) (err error) {
 	return setResetPulse(handle, procPulseEvent)
 }
diff --git a/system/filesys.go b/system/filesys.go
index e1f70e8..3e26e35 100644
--- a/system/filesys.go
+++ b/system/filesys.go
@@ -6,6 +6,8 @@ import (
 	"os"
 )
 
+// MkdirAll creates a directory named path along with any necessary parents,
+// with permission specified by attribute perm for all dir created.
 func MkdirAll(path string, perm os.FileMode) error {
 	return os.MkdirAll(path, perm)
 }
diff --git a/system/lstat.go b/system/lstat.go
index d0e43b3..bd23c4d 100644
--- a/system/lstat.go
+++ b/system/lstat.go
@@ -7,10 +7,10 @@ import (
 )
 
 // Lstat takes a path to a file and returns
-// a system.Stat_t type pertaining to that file.
+// a system.StatT type pertaining to that file.
 //
 // Throws an error if the file does not exist
-func Lstat(path string) (*Stat_t, error) {
+func Lstat(path string) (*StatT, error) {
 	s := &syscall.Stat_t{}
 	if err := syscall.Lstat(path, s); err != nil {
 		return nil, err
diff --git a/system/lstat_windows.go b/system/lstat_windows.go
index eee1be2..49e87eb 100644
--- a/system/lstat_windows.go
+++ b/system/lstat_windows.go
@@ -6,21 +6,17 @@ import (
 	"os"
 )
 
-// Some explanation for my own sanity, and hopefully maintainers in the
-// future.
-//
 // Lstat calls os.Lstat to get a fileinfo interface back.
 // This is then copied into our own locally defined structure.
 // Note the Linux version uses fromStatT to do the copy back,
 // but that not strictly necessary when already in an OS specific module.
-
-func Lstat(path string) (*Stat_t, error) {
+func Lstat(path string) (*StatT, error) {
 	fi, err := os.Lstat(path)
 	if err != nil {
 		return nil, err
 	}
 
-	return &Stat_t{
+	return &StatT{
 		name:    fi.Name(),
 		size:    fi.Size(),
 		mode:    fi.Mode(),
diff --git a/system/meminfo_linux.go b/system/meminfo_linux.go
index e2ca140..a07bb17 100644
--- a/system/meminfo_linux.go
+++ b/system/meminfo_linux.go
@@ -2,7 +2,6 @@ package system
 
 import (
 	"bufio"
-	"errors"
 	"io"
 	"os"
 	"strconv"
@@ -11,10 +10,6 @@ import (
 	"github.com/docker/docker/pkg/units"
 )
 
-var (
-	ErrMalformed = errors.New("malformed file")
-)
-
 // ReadMemInfo retrieves memory statistics of the host system and returns a
 //  MemInfo type.
 func ReadMemInfo() (*MemInfo, error) {
diff --git a/system/meminfo_unsupported.go b/system/meminfo_unsupported.go
index 604d338..82ddd30 100644
--- a/system/meminfo_unsupported.go
+++ b/system/meminfo_unsupported.go
@@ -2,6 +2,7 @@
 
 package system
 
+// ReadMemInfo is not supported on platforms other than linux and windows.
 func ReadMemInfo() (*MemInfo, error) {
 	return nil, ErrNotSupportedPlatform
 }
diff --git a/system/mknod.go b/system/mknod.go
index 26617eb..7395818 100644
--- a/system/mknod.go
+++ b/system/mknod.go
@@ -7,14 +7,16 @@ import (
 )
 
 // Mknod creates a filesystem node (file, device special file or named pipe) named path
-// with attributes specified by mode and dev
+// with attributes specified by mode and dev.
 func Mknod(path string, mode uint32, dev int) error {
 	return syscall.Mknod(path, mode, dev)
 }
 
+// Mkdev is used to build the value of linux devices (in /dev/) which specifies major
+// and minor number of the newly created device special file.
 // Linux device nodes are a bit weird due to backwards compat with 16 bit device nodes.
 // They are, from low to high: the lower 8 bits of the minor, then 12 bits of the major,
-// then the top 12 bits of the minor
+// then the top 12 bits of the minor.
 func Mkdev(major int64, minor int64) uint32 {
 	return uint32(((minor & 0xfff00) << 12) | ((major & 0xfff) << 8) | (minor & 0xff))
 }
diff --git a/system/mknod_windows.go b/system/mknod_windows.go
index 1811542..2e863c0 100644
--- a/system/mknod_windows.go
+++ b/system/mknod_windows.go
@@ -2,10 +2,12 @@
 
 package system
 
+// Mknod is not implemented on Windows.
 func Mknod(path string, mode uint32, dev int) error {
 	return ErrNotSupportedPlatform
 }
 
+// Mkdev is not implemented on Windows.
 func Mkdev(major int64, minor int64) uint32 {
 	panic("Mkdev not implemented on Windows.")
 }
diff --git a/system/stat.go b/system/stat.go
index e2ecfe5..7392c82 100644
--- a/system/stat.go
+++ b/system/stat.go
@@ -6,9 +6,9 @@ import (
 	"syscall"
 )
 
-// Stat_t type contains status of a file. It contains metadata
-// like permission, owner, group, size, etc about a file
-type Stat_t struct {
+// StatT type contains status of a file. It contains metadata
+// like permission, owner, group, size, etc about a file.
+type StatT struct {
 	mode uint32
 	uid  uint32
 	gid  uint32
@@ -17,30 +17,37 @@ type Stat_t struct {
 	mtim syscall.Timespec
 }
 
-func (s Stat_t) Mode() uint32 {
+// Mode returns file's permission mode.
+func (s StatT) Mode() uint32 {
 	return s.mode
 }
 
-func (s Stat_t) Uid() uint32 {
+// UID returns file's user id of owner.
+func (s StatT) UID() uint32 {
 	return s.uid
 }
 
-func (s Stat_t) Gid() uint32 {
+// Gid returns file's group id of owner.
+func (s StatT) Gid() uint32 {
 	return s.gid
 }
 
-func (s Stat_t) Rdev() uint64 {
+// Rdev returns file's device ID (if it's special file).
+func (s StatT) Rdev() uint64 {
 	return s.rdev
 }
 
-func (s Stat_t) Size() int64 {
+// Size returns file's size.
+func (s StatT) Size() int64 {
 	return s.size
 }
 
-func (s Stat_t) Mtim() syscall.Timespec {
+// Mtim returns file's last modification time.
+func (s StatT) Mtim() syscall.Timespec {
 	return s.mtim
 }
 
-func (s Stat_t) GetLastModification() syscall.Timespec {
+// GetLastModification returns file's last modification time.
+func (s StatT) GetLastModification() syscall.Timespec {
 	return s.Mtim()
 }
diff --git a/system/stat_freebsd.go b/system/stat_freebsd.go
index 4b2198b..d0fb6f1 100644
--- a/system/stat_freebsd.go
+++ b/system/stat_freebsd.go
@@ -5,8 +5,8 @@ import (
 )
 
 // fromStatT converts a syscall.Stat_t type to a system.Stat_t type
-func fromStatT(s *syscall.Stat_t) (*Stat_t, error) {
-	return &Stat_t{size: s.Size,
+func fromStatT(s *syscall.Stat_t) (*StatT, error) {
+	return &StatT{size: s.Size,
 		mode: uint32(s.Mode),
 		uid:  s.Uid,
 		gid:  s.Gid,
@@ -18,7 +18,7 @@ func fromStatT(s *syscall.Stat_t) (*Stat_t, error) {
 // a system.Stat_t type pertaining to that file.
 //
 // Throws an error if the file does not exist
-func Stat(path string) (*Stat_t, error) {
+func Stat(path string) (*StatT, error) {
 	s := &syscall.Stat_t{}
 	if err := syscall.Stat(path, s); err != nil {
 		return nil, err
diff --git a/system/stat_linux.go b/system/stat_linux.go
index 80262d9..8b1eded 100644
--- a/system/stat_linux.go
+++ b/system/stat_linux.go
@@ -5,8 +5,8 @@ import (
 )
 
 // fromStatT converts a syscall.Stat_t type to a system.Stat_t type
-func fromStatT(s *syscall.Stat_t) (*Stat_t, error) {
-	return &Stat_t{size: s.Size,
+func fromStatT(s *syscall.Stat_t) (*StatT, error) {
+	return &StatT{size: s.Size,
 		mode: s.Mode,
 		uid:  s.Uid,
 		gid:  s.Gid,
@@ -14,17 +14,17 @@ func fromStatT(s *syscall.Stat_t) (*Stat_t, error) {
 		mtim: s.Mtim}, nil
 }
 
-// FromStatT exists only on linux, and loads a system.Stat_t from a
+// FromStatT exists only on linux, and loads a system.StatT from a
 // syscal.Stat_t.
-func FromStatT(s *syscall.Stat_t) (*Stat_t, error) {
+func FromStatT(s *syscall.Stat_t) (*StatT, error) {
 	return fromStatT(s)
 }
 
 // Stat takes a path to a file and returns
-// a system.Stat_t type pertaining to that file.
+// a system.StatT type pertaining to that file.
 //
 // Throws an error if the file does not exist
-func Stat(path string) (*Stat_t, error) {
+func Stat(path string) (*StatT, error) {
 	s := &syscall.Stat_t{}
 	if err := syscall.Stat(path, s); err != nil {
 		return nil, err
diff --git a/system/stat_test.go b/system/stat_test.go
index 4534129..57121f1 100644
--- a/system/stat_test.go
+++ b/system/stat_test.go
@@ -22,7 +22,7 @@ func TestFromStatT(t *testing.T) {
 	if stat.Mode != s.Mode() {
 		t.Fatal("got invalid mode")
 	}
-	if stat.Uid != s.Uid() {
+	if stat.Uid != s.UID() {
 		t.Fatal("got invalid uid")
 	}
 	if stat.Gid != s.Gid() {
diff --git a/system/stat_unsupported.go b/system/stat_unsupported.go
index 5251ae2..381ea82 100644
--- a/system/stat_unsupported.go
+++ b/system/stat_unsupported.go
@@ -6,9 +6,9 @@ import (
 	"syscall"
 )
 
-// fromStatT creates a system.Stat_t type from a syscall.Stat_t type
-func fromStatT(s *syscall.Stat_t) (*Stat_t, error) {
-	return &Stat_t{size: s.Size,
+// fromStatT creates a system.StatT type from a syscall.Stat_t type
+func fromStatT(s *syscall.Stat_t) (*StatT, error) {
+	return &StatT{size: s.Size,
 		mode: uint32(s.Mode),
 		uid:  s.Uid,
 		gid:  s.Gid,
diff --git a/system/stat_windows.go b/system/stat_windows.go
index b1fd39e..39490c6 100644
--- a/system/stat_windows.go
+++ b/system/stat_windows.go
@@ -7,7 +7,9 @@ import (
 	"time"
 )
 
-type Stat_t struct {
+// StatT type contains status of a file. It contains metadata
+// like name, permission, size, etc about a file.
+type StatT struct {
 	name    string
 	size    int64
 	mode    os.FileMode
@@ -15,22 +17,27 @@ type Stat_t struct {
 	isDir   bool
 }
 
-func (s Stat_t) Name() string {
+// Name returns file's name.
+func (s StatT) Name() string {
 	return s.name
 }
 
-func (s Stat_t) Size() int64 {
+// Size returns file's size.
+func (s StatT) Size() int64 {
 	return s.size
 }
 
-func (s Stat_t) Mode() os.FileMode {
+// Mode returns file's permission mode.
+func (s StatT) Mode() os.FileMode {
 	return s.mode
 }
 
-func (s Stat_t) ModTime() time.Time {
+// ModTime returns file's last modification time.
+func (s StatT) ModTime() time.Time {
 	return s.modTime
 }
 
-func (s Stat_t) IsDir() bool {
+// IsDir returns whether file is actually a directory.
+func (s StatT) IsDir() bool {
 	return s.isDir
 }
diff --git a/system/umask.go b/system/umask.go
index fddbecd..c670fcd 100644
--- a/system/umask.go
+++ b/system/umask.go
@@ -6,6 +6,8 @@ import (
 	"syscall"
 )
 
+// Umask sets current process's file mode creation mask to newmask
+// and return oldmask.
 func Umask(newmask int) (oldmask int, err error) {
 	return syscall.Umask(newmask), nil
 }
diff --git a/system/umask_windows.go b/system/umask_windows.go
index 3be563f..13f1de1 100644
--- a/system/umask_windows.go
+++ b/system/umask_windows.go
@@ -2,6 +2,7 @@
 
 package system
 
+// Umask is not supported on the windows platform.
 func Umask(newmask int) (oldmask int, err error) {
 	// should not be called on cli code path
 	return 0, ErrNotSupportedPlatform
diff --git a/system/utimes_darwin.go b/system/utimes_darwin.go
index 4c6002f..9e3dcdd 100644
--- a/system/utimes_darwin.go
+++ b/system/utimes_darwin.go
@@ -2,10 +2,13 @@ package system
 
 import "syscall"
 
+// LUtimesNano is not supported by darwin platform.
 func LUtimesNano(path string, ts []syscall.Timespec) error {
 	return ErrNotSupportedPlatform
 }
 
+// UtimesNano is used to change access and modification time of path.
+// it can't be used for symbol link file.
 func UtimesNano(path string, ts []syscall.Timespec) error {
 	return syscall.UtimesNano(path, ts)
 }
diff --git a/system/utimes_freebsd.go b/system/utimes_freebsd.go
index ceaa044..15ce26f 100644
--- a/system/utimes_freebsd.go
+++ b/system/utimes_freebsd.go
@@ -5,6 +5,8 @@ import (
 	"unsafe"
 )
 
+// LUtimesNano is used to change access and modification time of the specified path.
+// It's used for symbol link file because syscall.UtimesNano doesn't support a NOFOLLOW flag atm.
 func LUtimesNano(path string, ts []syscall.Timespec) error {
 	var _path *byte
 	_path, err := syscall.BytePtrFromString(path)
@@ -19,6 +21,8 @@ func LUtimesNano(path string, ts []syscall.Timespec) error {
 	return nil
 }
 
+// UtimesNano is used to change access and modification time of the specified path.
+// It can't be used for symbol link file.
 func UtimesNano(path string, ts []syscall.Timespec) error {
 	return syscall.UtimesNano(path, ts)
 }
diff --git a/system/utimes_linux.go b/system/utimes_linux.go
index 8f90298..7909801 100644
--- a/system/utimes_linux.go
+++ b/system/utimes_linux.go
@@ -5,10 +5,12 @@ import (
 	"unsafe"
 )
 
+// LUtimesNano is used to change access and modification time of the speficied path.
+// It's used for symbol link file because syscall.UtimesNano doesn't support a NOFOLLOW flag atm.
 func LUtimesNano(path string, ts []syscall.Timespec) error {
 	// These are not currently available in syscall
-	AT_FDCWD := -100
-	AT_SYMLINK_NOFOLLOW := 0x100
+	atFdCwd := -100
+	atSymLinkNoFollow := 0x100
 
 	var _path *byte
 	_path, err := syscall.BytePtrFromString(path)
@@ -16,13 +18,15 @@ func LUtimesNano(path string, ts []syscall.Timespec) error {
 		return err
 	}
 
-	if _, _, err := syscall.Syscall6(syscall.SYS_UTIMENSAT, uintptr(AT_FDCWD), uintptr(unsafe.Pointer(_path)), uintptr(unsafe.Pointer(&ts[0])), uintptr(AT_SYMLINK_NOFOLLOW), 0, 0); err != 0 && err != syscall.ENOSYS {
+	if _, _, err := syscall.Syscall6(syscall.SYS_UTIMENSAT, uintptr(atFdCwd), uintptr(unsafe.Pointer(_path)), uintptr(unsafe.Pointer(&ts[0])), uintptr(atSymLinkNoFollow), 0, 0); err != 0 && err != syscall.ENOSYS {
 		return err
 	}
 
 	return nil
 }
 
+// UtimesNano is used to change access and modification time of the specified path.
+// It can't be used for symbol link file.
 func UtimesNano(path string, ts []syscall.Timespec) error {
 	return syscall.UtimesNano(path, ts)
 }
diff --git a/system/utimes_unsupported.go b/system/utimes_unsupported.go
index adf2734..cb614a1 100644
--- a/system/utimes_unsupported.go
+++ b/system/utimes_unsupported.go
@@ -4,10 +4,12 @@ package system
 
 import "syscall"
 
+// LUtimesNano is not supported on platforms other than linux, freebsd and darwin.
 func LUtimesNano(path string, ts []syscall.Timespec) error {
 	return ErrNotSupportedPlatform
 }
 
+// UtimesNano is not supported on platforms other than linux, freebsd and darwin.
 func UtimesNano(path string, ts []syscall.Timespec) error {
 	return ErrNotSupportedPlatform
 }
diff --git a/system/xattrs_linux.go b/system/xattrs_linux.go
index 00edb20..d2e2c05 100644
--- a/system/xattrs_linux.go
+++ b/system/xattrs_linux.go
@@ -5,7 +5,9 @@ import (
 	"unsafe"
 )
 
-// Returns a nil slice and nil error if the xattr is not set
+// Lgetxattr retrieves the value of the extended attribute identified by attr
+// and associated with the given path in the file system.
+// It will returns a nil slice and nil error if the xattr is not set.
 func Lgetxattr(path string, attr string) ([]byte, error) {
 	pathBytes, err := syscall.BytePtrFromString(path)
 	if err != nil {
@@ -36,6 +38,8 @@ func Lgetxattr(path string, attr string) ([]byte, error) {
 
 var _zero uintptr
 
+// Lsetxattr sets the value of the extended attribute identified by attr
+// and associated with the given path in the file system.
 func Lsetxattr(path string, attr string, data []byte, flags int) error {
 	pathBytes, err := syscall.BytePtrFromString(path)
 	if err != nil {
diff --git a/system/xattrs_unsupported.go b/system/xattrs_unsupported.go
index 0060c16..0114f22 100644
--- a/system/xattrs_unsupported.go
+++ b/system/xattrs_unsupported.go
@@ -2,10 +2,12 @@
 
 package system
 
+// Lgetxattr is not supported on platforms other than linux.
 func Lgetxattr(path string, attr string) ([]byte, error) {
 	return nil, ErrNotSupportedPlatform
 }
 
+// Lsetxattr is not supported on platforms other than linux.
 func Lsetxattr(path string, attr string, data []byte, flags int) error {
 	return ErrNotSupportedPlatform
 }