diff --git a/xCAT-server/share/xcat/netboot/ubuntu/genimage b/xCAT-server/share/xcat/netboot/ubuntu/genimage
index 17005cdb5..9fe0803b4 100755
--- a/xCAT-server/share/xcat/netboot/ubuntu/genimage
+++ b/xCAT-server/share/xcat/netboot/ubuntu/genimage
@@ -1827,8 +1827,11 @@ EOMS
         }
     }
 
-    if (-d "$rootimg_dir/lib/firmware/") {
-        system("cp -r $rootimg_dir/lib/firmware/* /tmp/xcatinitrd.$$/lib/firmware");
+    # The whole firmware tree is 666 MB on Ubuntu 26.04, and grub2 on a pseries node cannot
+    # load an initrd of that size. The initrd only has to reach the network.
+    foreach my $firmware (initrd_firmware_files($rootimg_dir, \@filestoadd)) {
+        copy_initrd_file("$rootimg_dir/lib/firmware/$firmware",
+            "/tmp/xcatinitrd.$$/lib/firmware/$firmware");
     }
 
     if (-d "$rootimg_dir/lib/modules/$kernelver/") {
@@ -1892,6 +1895,55 @@ sub isnetdriver {
     }
 }
 
+#-------------------------------------------------------------------------------
+
+=head3 initrd_firmware_files
+
+    Descriptions: Select the firmware that the drivers in the netboot initrd ask for.
+    Arguments:
+        rootimg_dir - the root image directory
+        filestoadd  - reference to the list of files that go into the initrd. A module
+                      is either a plain path or a [ source, destination ] pair.
+    Returns: the firmware files that exist, as paths below lib/firmware
+
+=cut
+
+#-------------------------------------------------------------------------------
+sub initrd_firmware_files {
+    my ($rootimg_dir, $filestoadd) = @_;
+
+    return () unless (-d "$rootimg_dir/lib/firmware");
+
+    my %wanted;
+    foreach my $entry (@$filestoadd) {
+        my $module = ref($entry) ? $entry->[0] : $entry;
+        next unless ($module =~ /\.ko(?:\.(?:gz|xz|zst))?$/);
+        next unless (-f "$rootimg_dir/$module");
+
+        my $out = `modinfo -F firmware "$rootimg_dir/$module" 2>/dev/null`;
+        if ($?) {
+            print "Warning: cannot read the firmware of $module\n";
+            next;
+        }
+        foreach my $name (split(/\n/, $out)) {
+            $name =~ s/^\s+|\s+$//g;
+            $wanted{$name} = 1 if (length $name);
+        }
+    }
+
+    my @files;
+    foreach my $name (sort keys %wanted) {
+
+        # Ubuntu keeps the firmware compressed and the kernel asks for the plain name.
+        foreach my $candidate ($name, "$name.zst", "$name.xz", "$name.gz") {
+            next unless (-e "$rootimg_dir/lib/firmware/$candidate");
+            push @files, $candidate;
+            last;
+        }
+    }
+    return @files;
+}
+
 sub find_rootimg_file {
     my ($file) = @_;