diff --git a/idtools/usergroupadd_linux.go b/idtools/usergroupadd_linux.go
index 86d9e21..4a4aaed 100644
--- a/idtools/usergroupadd_linux.go
+++ b/idtools/usergroupadd_linux.go
@@ -8,6 +8,7 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"sync"
 )
 
 // add a user and/or group to Linux /etc/passwd, /etc/group using standard
@@ -16,6 +17,7 @@ import (
 // useradd -r -s /bin/false <username>
 
 var (
+	once        sync.Once
 	userCommand string
 
 	cmdTemplates = map[string]string{
@@ -31,15 +33,6 @@ var (
 	userMod           = "usermod"
 )
 
-func init() {
-	// set up which commands are used for adding users/groups dependent on distro
-	if _, err := resolveBinary("adduser"); err == nil {
-		userCommand = "adduser"
-	} else if _, err := resolveBinary("useradd"); err == nil {
-		userCommand = "useradd"
-	}
-}
-
 func resolveBinary(binname string) (string, error) {
 	binaryPath, err := exec.LookPath(binname)
 	if err != nil {
@@ -94,7 +87,14 @@ func AddNamespaceRangesUser(name string) (int, int, error) {
 }
 
 func addUser(userName string) error {
-
+	once.Do(func() {
+		// set up which commands are used for adding users/groups dependent on distro
+		if _, err := resolveBinary("adduser"); err == nil {
+			userCommand = "adduser"
+		} else if _, err := resolveBinary("useradd"); err == nil {
+			userCommand = "useradd"
+		}
+	})
 	if userCommand == "" {
 		return fmt.Errorf("Cannot add user; no useradd/adduser binary found")
 	}