added option to change time zone

system.go

@@ -1,10 +1,14 @@
 package alpine_builder
 
 import (
+	"bufio"
 	"fmt"
 	"io/ioutil"
 	"os"
 	"os/exec"
+	"path"
+	"path/filepath"
+	"sort"
 	"strings"
 
 	"github.com/GehirnInc/crypt"
@@ -17,6 +21,8 @@ var systemDropbearConfig = "/data/etc/dropbear/dropbear.conf"
 var systemDropbearRestart = "rc-service dropbear restart"
 var systemShutdown = "poweroff"
 var systemReboot = "reboot"
+var systemZoneinfo = "/usr/share/zoneinfo/"
+var systemLocaltimeFile = "/data/etc/localtime"
 
 // SystemSetRootPassword update shadow file
 func SystemSetRootPassword(password string) error {
@@ -94,3 +100,52 @@ func SystemReboot() error {
 	}
 	return nil
 }
+
+// SystemListTimeZones available on system
+func SystemListTimeZones() ([]string, error) {
+	// load zone info tab
+	file, err := os.Open(path.Join(systemZoneinfo, "zone1970.tab"))
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	// parse file
+	zones := make([]string, 0)
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		lineSplit := strings.Split(line, "\t")
+		if len(lineSplit) < 3 {
+			continue
+		}
+
+		zones = append(zones, strings.TrimSpace(lineSplit[2]))
+	}
+	zones = append(zones, "Etc/UTC")
+
+	sort.Strings(zones)
+	return zones, nil
+}
+
+// SystemSetTimeZone for operating system
+func SystemSetTimeZone(name string) error {
+	if _, err := os.Stat(path.Join(systemZoneinfo, name)); err != nil {
+		return fmt.Errorf("invalid time zone given: %s", name)
+	}
+	_ = os.Remove(systemLocaltimeFile)
+	return os.Symlink(path.Join(systemZoneinfo, name), systemLocaltimeFile)
+}
+
+// SystemGetTimeZone currently set for operating system
+func SystemGetTimeZone() (string, error) {
+	link, err := os.Readlink(systemLocaltimeFile)
+	if err != nil {
+		return "", fmt.Errorf("failed to get local time zone")
+	}
+	return filepath.Rel(systemZoneinfo, link)
+}

system_test.go

@@ -3,6 +3,7 @@ package alpine_builder
 import (
 	"io/ioutil"
 	"os"
+	"path"
 	"strings"
 	"testing"
 
@@ -17,6 +18,9 @@ func init() {
 	systemDropbearRestart = "restart_dropbear_command"
 	systemReboot = "reboot_command"
 	systemShutdown = "shutdown_command"
+
+	systemZoneinfo = "zoneinfo/"
+	systemLocaltimeFile = "test_localtime"
 }
 
 func TestSystemSetRootPassword(t *testing.T) {
@@ -92,3 +96,74 @@ func TestSystemShutdown(t *testing.T) {
 	ass.EqualError(SystemShutdown(),
 		"failed to start system shutdown: exec: \"shutdown_command\": executable file not found in $PATH")
 }
+
+var zoneTab = `
+#
+#country-
+#codes	coordinates	TZ	comments
+AD	+4230+00131	Europe/Andorra
+AE,OM	+2518+05518	Asia/Dubai
+AQ	-6617+11031	Antarctica/Casey	Casey
+`
+
+func TestSystemListTimeZones(t *testing.T) {
+	ass := assert.New(t)
+
+	_, err := SystemListTimeZones()
+	ass.EqualError(err, "open zoneinfo/zone1970.tab: no such file or directory")
+
+	ass.NoError(os.MkdirAll(systemZoneinfo, os.ModePerm))
+	testZoneTab := path.Join(systemZoneinfo, "zone1970.tab")
+	ass.NoError(ioutil.WriteFile(testZoneTab, []byte(zoneTab), os.ModePerm))
+
+	zones, err := SystemListTimeZones()
+	ass.NoError(err)
+	ass.Equal([]string{
+		"Antarctica/Casey",
+		"Asia/Dubai",
+		"Etc/UTC",
+		"Europe/Andorra",
+	}, zones)
+
+	ass.NoError(os.Remove(testZoneTab))
+	ass.NoError(os.Remove(systemZoneinfo))
+}
+
+func TestSystemSetTimeZone(t *testing.T) {
+	ass := assert.New(t)
+
+	ass.NoError(os.MkdirAll(systemZoneinfo, os.ModePerm))
+	testZone := path.Join(systemZoneinfo, "test")
+	ass.NoError(ioutil.WriteFile(testZone, []byte(""), os.ModePerm))
+
+	ass.EqualError(SystemSetTimeZone("test2"),
+		"invalid time zone given: test2")
+
+	ass.NoError(SystemSetTimeZone("test"))
+	ass.NoError(SystemSetTimeZone("test"))
+
+	ass.NoError(os.Remove(systemLocaltimeFile))
+	ass.NoError(os.Remove(testZone))
+	ass.NoError(os.Remove(systemZoneinfo))
+}
+
+func TestSystemGetTimeZone(t *testing.T) {
+	ass := assert.New(t)
+
+	ass.NoError(os.MkdirAll(systemZoneinfo, os.ModePerm))
+	testZone := path.Join(systemZoneinfo, "test")
+	ass.NoError(ioutil.WriteFile(testZone, []byte(""), os.ModePerm))
+
+	_, err := SystemGetTimeZone()
+	ass.EqualError(err, "failed to get local time zone")
+
+	ass.NoError(os.Symlink(path.Join(systemZoneinfo, "test"), systemLocaltimeFile))
+
+	zone, err := SystemGetTimeZone()
+	ass.NoError(err)
+	ass.Equal("test", zone)
+
+	ass.NoError(os.Remove(systemLocaltimeFile))
+	ass.NoError(os.Remove(testZone))
+	ass.NoError(os.Remove(systemZoneinfo))
+}