diff --git a/disk/disk_linux.go b/disk/disk_linux.go
index 0bc6e2f..f5eb526 100644
--- a/disk/disk_linux.go
+++ b/disk/disk_linux.go
@@ -6,6 +6,7 @@ import (
 	"context"
 	"fmt"
 	"os/exec"
+	"path/filepath"
 	"strconv"
 	"strings"
 
@@ -289,6 +290,11 @@ func IOCountersWithContext(ctx context.Context, names ...string) (map[string]IOC
 	ret := make(map[string]IOCountersStat, 0)
 	empty := IOCountersStat{}
 
+	// use only basename such as "/dev/sda1" to "sda1"
+	for i, name := range names {
+		names[i] = filepath.Base(name)
+	}
+
 	for _, line := range lines {
 		fields := strings.Fields(line)
 		if len(fields) < 14 {
diff --git a/disk/disk_test.go b/disk/disk_test.go
index 436b8a5..269ca6c 100644
--- a/disk/disk_test.go
+++ b/disk/disk_test.go
@@ -25,6 +25,8 @@ func TestDisk_partitions(t *testing.T) {
 	if err != nil || len(ret) == 0 {
 		t.Errorf("error %v", err)
 	}
+	t.Log(ret)
+
 	empty := PartitionStat{}
 	if len(ret) == 0 {
 		t.Errorf("ret is empty")
@@ -46,6 +48,7 @@ func TestDisk_io_counters(t *testing.T) {
 	}
 	empty := IOCountersStat{}
 	for part, io := range ret {
+		t.Log(part, io)
 		if io == empty {
 			t.Errorf("io_counter error %v, %v", part, io)
 		}
diff --git a/docker/docker.go b/docker/docker.go
index 1d932cf..83716fd 100644
--- a/docker/docker.go
+++ b/docker/docker.go
@@ -1,6 +1,7 @@
 package docker
 
 import (
+	"encoding/json"
 	"errors"
 
 	"github.com/shirou/gopsutil/internal/common"
@@ -50,6 +51,11 @@ type CgroupMemStat struct {
 	MemFailCnt              uint64 `json:"memoryFailcnt"`
 }
 
+func (m CgroupMemStat) String() string {
+	s, _ := json.Marshal(m)
+	return string(s)
+}
+
 type CgroupDockerStat struct {
 	ContainerID string `json:"containerID"`
 	Name        string `json:"name"`
@@ -57,3 +63,8 @@ type CgroupDockerStat struct {
 	Status      string `json:"status"`
 	Running     bool   `json:"running"`
 }
+
+func (c CgroupDockerStat) String() string {
+	s, _ := json.Marshal(c)
+	return string(s)
+}
diff --git a/docker/docker_linux.go b/docker/docker_linux.go
index 8c722a0..c0724db 100644
--- a/docker/docker_linux.go
+++ b/docker/docker_linux.go
@@ -57,11 +57,6 @@ func GetDockerStatWithContext(ctx context.Context) ([]CgroupDockerStat, error) {
 	return ret, nil
 }
 
-func (c CgroupDockerStat) String() string {
-	s, _ := json.Marshal(c)
-	return string(s)
-}
-
 // GetDockerIDList returnes a list of DockerID.
 // This requires certain permission.
 func GetDockerIDList() ([]string, error) {
@@ -245,11 +240,6 @@ func CgroupMemDockerWithContext(ctx context.Context, containerID string) (*Cgrou
 	return CgroupMem(containerID, common.HostSys("fs/cgroup/memory/docker"))
 }
 
-func (m CgroupMemStat) String() string {
-	s, _ := json.Marshal(m)
-	return string(s)
-}
-
 // getCgroupFilePath constructs file path to get targetted stats file.
 func getCgroupFilePath(containerID, base, target, file string) string {
 	if len(base) == 0 {
diff --git a/host/host_linux.go b/host/host_linux.go
index 65f3b64..e0b4b60 100644
--- a/host/host_linux.go
+++ b/host/host_linux.go
@@ -104,7 +104,18 @@ func BootTimeWithContext(ctx context.Context) (uint64, error) {
 	if t != 0 {
 		return t, nil
 	}
-	filename := common.HostProc("stat")
+
+	system, role, err := Virtualization()
+	if err != nil {
+		return 0, err
+	}
+	statFile := "stat"
+	if system == "lxc" && role == "guest" {
+		// if lxc, /proc/uptime is used.
+		statFile = "uptime"
+	}
+
+	filename := common.HostProc(statFile)
 	lines, err := common.ReadLines(filename)
 	if err != nil {
 		return 0, err
diff --git a/host/host_test.go b/host/host_test.go
index c420580..87a6bd9 100644
--- a/host/host_test.go
+++ b/host/host_test.go
@@ -40,11 +40,13 @@ func TestBoot_time(t *testing.T) {
 	if v < 946652400 {
 		t.Errorf("Invalid Boottime, older than 2000-01-01")
 	}
+	t.Logf("first boot time: %d", v)
 
 	v2, err := BootTime()
 	if v != v2 {
 		t.Errorf("cached boot time is different")
 	}
+	t.Logf("second boot time: %d", v2)
 }
 
 func TestUsers(t *testing.T) {
diff --git a/process/process.go b/process/process.go
index 09b1e6a..e20742a 100644
--- a/process/process.go
+++ b/process/process.go
@@ -31,6 +31,8 @@ type Process struct {
 
 	lastCPUTimes *cpu.TimesStat
 	lastCPUTime  time.Time
+
+	tgid int32
 }
 
 type OpenFilesStat struct {
diff --git a/process/process_darwin.go b/process/process_darwin.go
index 005ae3c..97d1c49 100644
--- a/process/process_darwin.go
+++ b/process/process_darwin.go
@@ -96,6 +96,9 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 
 	return common.IntToString(k.Proc.P_comm[:]), nil
 }
+func (p *Process) Tgid() (int32, error) {
+	return 0, common.ErrNotImplementedError
+}
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())
 }
diff --git a/process/process_fallback.go b/process/process_fallback.go
index bc3bb1d..2f18afe 100644
--- a/process/process_fallback.go
+++ b/process/process_fallback.go
@@ -54,6 +54,9 @@ func (p *Process) Name() (string, error) {
 func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return "", common.ErrNotImplementedError
 }
+func (p *Process) Tgid() (int32, error) {
+	return 0, common.ErrNotImplementedError
+}
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())
 }
diff --git a/process/process_freebsd.go b/process/process_freebsd.go
index 7b85e8a..29a223a 100644
--- a/process/process_freebsd.go
+++ b/process/process_freebsd.go
@@ -63,6 +63,9 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 
 	return common.IntToString(k.Comm[:]), nil
 }
+func (p *Process) Tgid() (int32, error) {
+	return 0, common.ErrNotImplementedError
+}
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())
 }
diff --git a/process/process_linux.go b/process/process_linux.go
index a9aed88..14d151b 100644
--- a/process/process_linux.go
+++ b/process/process_linux.go
@@ -109,6 +109,16 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return p.name, nil
 }
 
+// Tgid returns tgid, a Linux-synonym for user-space Pid
+func (p *Process) Tgid() (int32, error) {
+	if p.tgid == 0 {
+		if err := p.fillFromStatus(); err != nil {
+			return 0, err
+		}
+	}
+	return p.tgid, nil
+}
+
 // Exe returns executable path of the process.
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())
@@ -985,6 +995,12 @@ func (p *Process) fillFromStatusWithContext(ctx context.Context) error {
 				return err
 			}
 			p.parent = int32(pval)
+		case "Tgid":
+			pval, err := strconv.ParseInt(value, 10, 32)
+			if err != nil {
+				return err
+			}
+			p.tgid = int32(pval)
 		case "Uid":
 			p.uids = make([]int32, 0, 4)
 			for _, i := range strings.Split(value, "\t") {
diff --git a/process/process_openbsd.go b/process/process_openbsd.go
index 2a8eec7..857bad0 100644
--- a/process/process_openbsd.go
+++ b/process/process_openbsd.go
@@ -66,6 +66,9 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 
 	return common.IntToString(k.Comm[:]), nil
 }
+func (p *Process) Tgid() (int32, error) {
+	return 0, common.ErrNotImplementedError
+}
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())
 }
diff --git a/process/process_windows.go b/process/process_windows.go
index c875ec2..f1fa1cb 100644
--- a/process/process_windows.go
+++ b/process/process_windows.go
@@ -170,6 +170,10 @@ func (p *Process) NameWithContext(ctx context.Context) (string, error) {
 	return name, nil
 }
 
+func (p *Process) Tgid() (int32, error) {
+	return 0, common.ErrNotImplementedError
+}
+
 func (p *Process) Exe() (string, error) {
 	return p.ExeWithContext(context.Background())
 }