diff --git a/xCAT-server/share/xcat/netboot/imgutils/imgutils.pm b/xCAT-server/share/xcat/netboot/imgutils/imgutils.pm
index 903baf453..5ef767964 100644
--- a/xCAT-server/share/xcat/netboot/imgutils/imgutils.pm
+++ b/xCAT-server/share/xcat/netboot/imgutils/imgutils.pm
@@ -11,6 +11,42 @@ use File::Path;
 use Cwd qw(realpath);
 use xCAT::SvrUtils;
 
+sub el_major_version {
+    my $version = shift;
+
+    return if !defined($version);
+
+    my ($os_family, $os_major) = xCAT::SvrUtils::parseosver($version);
+    return
+      if !defined($os_family)
+      || $os_family !~ /^(?:rhels?|rhelc|rhelhpc|centos(?:-stream)?|rocky|alma(?:linux)?|ol)$/;
+
+    return $os_major if length($os_major);
+    return;
+}
+
+sub rpm_installroot_command {
+    my ( $osver, $rootimg_dir, $non_interactive, $dnf_available ) = @_;
+    $non_interactive ||= "";
+    $dnf_available = -x "/usr/bin/dnf" unless defined($dnf_available);
+    my $majorrel = el_major_version($osver);
+    my $pkgmgr = "yum";
+
+    # EL8 and newer are dnf-native. Keep yum as the fallback for legacy
+    # systems and minimal environments that still provide only yum.
+    if (defined($majorrel) && $majorrel > 7 && $dnf_available) {
+        $pkgmgr = "dnf";
+    }
+
+    my $cmd = "$pkgmgr $non_interactive -c /tmp/genimage.$$.yum.conf --installroot=$rootimg_dir/ --disablerepo=* ";
+    if (defined($majorrel) && $majorrel > 7) {
+        $cmd .= "--releasever=" . $majorrel . " ";
+        $cmd .= "--setopt=module_platform_id=platform:el" . $majorrel . " ";
+    }
+
+    return $cmd;
+}
+
 sub varsubinline{
     my $line=shift;
     my $refvardict=shift;
diff --git a/xCAT-server/share/xcat/netboot/rh/genimage b/xCAT-server/share/xcat/netboot/rh/genimage
index 9e3ba2409..a648e65d8 100755
--- a/xCAT-server/share/xcat/netboot/rh/genimage
+++ b/xCAT-server/share/xcat/netboot/rh/genimage
@@ -92,38 +92,6 @@ sub majversion {
     return $majorrel;
 }
 
-sub el_major_version {
-    my $version = shift;
-
-    if (defined($version)
-        && $version =~ /^(?:rhels?|centos|rocky|alma(?:linux)?|ol)\D*(\d+)/)
-    {
-        return $1;
-    }
-
-    return;
-}
-
-sub rpm_installroot_command {
-    my $non_interactive = shift || "";
-    my $majorrel = el_major_version($osver);
-    my $pkgmgr = "yum";
-
-    # EL8 and newer are dnf-native. Keep yum as the fallback for legacy
-    # systems and minimal environments that still provide only yum.
-    if (defined($majorrel) && $majorrel > 7 && -x "/usr/bin/dnf") {
-        $pkgmgr = "dnf";
-    }
-
-    my $cmd = "$pkgmgr $non_interactive -c /tmp/genimage.$$.yum.conf --installroot=$rootimg_dir/ --disablerepo=* ";
-    if (defined($majorrel) && $majorrel > 7) {
-        $cmd .= "--releasever=" . $majorrel . " ";
-        $cmd .= "--setopt=module_platform_id=platform:el" . $majorrel . " ";
-    }
-
-    return $cmd;
-}
-
 sub mount_chroot {
     my $rootimage_dir = shift;
 
@@ -406,7 +374,9 @@ if($onlyinitrd){
     my $non_interactive;
     if (!$prompt) { $non_interactive = "-y"; }
 
-    my $yumcmd = rpm_installroot_command($non_interactive);
+    my $yumcmd = imgutils::rpm_installroot_command(
+        $osver, $rootimg_dir, $non_interactive
+    );
 
     foreach (0 .. $repnum) {
         $yumcmd .= "--enablerepo=$osver-$arch-$_ ";
@@ -572,7 +542,9 @@ if($onlyinitrd){
         }
         close($yumconfig);
         $index--;
-        my $yumcmd_base = rpm_installroot_command($non_interactive);
+        my $yumcmd_base = imgutils::rpm_installroot_command(
+            $osver, $rootimg_dir, $non_interactive
+        );
 
         #yum/rpm/zypper has defect on calculating diskspace usage when installing rpm on a NFS mounted installroot
         if (isNFSdir("$rootimg_dir")) {